Różne artykuły o Starlink

[Orionid]

SpaceX launches fourth batch of Starlink satellites, tweaks satellite design
by Caleb Henry — January 29, 2020 [SN]


SpaceX has launched 242 Starlink satellites, counting two demo spacecraft, but not all will be used for broadband service. Credit: SpaceX webcast

WASHINGTON — SpaceX completed its second Starlink launch of the month Jan. 29, conforming to a target cadence the company set last year to launch two dedicated Starlink missions monthly throughout 2020.

SpaceX’s Falcon 9 rocket lifted off at 9:07 a.m. Eastern from Cape Canaveral Air Force Station, Florida, with another 60 Starlink internet satellites. The rocket’s upper stage deployed the satellites into a 302-kilometer low Earth orbit about an hour after liftoff.

SpaceX said it will test its satellites around that low altitude, where it expects any failures would burn up in Earth’s atmosphere after a few months. After completing checkouts, SpaceX plans to raise the satellites to a 550-kilometer operational orbit.

The launch — SpaceX’s fourth for Starlink not counting two demonstration satellites launched in 2018 — carried an upgraded set of satellites designed for better spectral efficiency and throughput. Poor weather delayed the mission by about a week.

Falcon 9’s first-stage booster landed on the droneship “Of Course I Still Love You” in the Atlantic Ocean, completing its third trip to space. SpaceX previously used the booster to launch the company’s Crew Dragon capsule on a March 2019 demonstration mission for NASA, and to launch three Canadian radar satellites last June.

SpaceX successfully caught a payload fairing half with “Ms. Tree,” a boat equipped with a large net. Jessica Anderson, a SpaceX manufacturing engineer co-narrating the launch, said the second fairing half missed its recovery boat, “Ms. Chief,” but appeared to have a soft water landing.

“We will be pulling that fairing half out of the water and hopefully reusing it again in the future,” she said.

Changes to Starlink

SpaceX has now launched 242 Starlink broadband satellites, though not every satellite will be part of the constellation when it starts service, a milestone anticipated later this year in Canada and the United States.

Some 10 Starlink satellites have not raised their orbits, according to observations by Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics who tracks satellite movements.

SpaceX spokesman James Gleeson, when asked about the 10 satellites, said SpaceX is “performing a controlled de-orbit of several first iteration Starlink satellites,” using onboard propulsion. 

“While these satellites are operable and capable of providing service, the second iteration of Starlink satellites that SpaceX has started to deploy provide better spectrum efficiency, more capacity and optimized service to the end user,” he said.

SpaceX’s Starlink satellites launched Jan. 29 each weigh approximately 260 kilograms, an increase of 33 kilograms from the 60 satellites launched in May 2019.

SpaceX specified that the newest Starlink satellites have four phased array antennas. Previous satellites were described as having “multiple” phased array antennas.

SpaceX has been modifying Starlink’s design since early on in the program. The first 60 satellites were described as 95% demisable upon atmospheric reentry, meaning some components risked reaching the Earth’s surface. By the second dedicated launch in November, Starlink’s design featured fully demisable parts.

SpaceX is also experimenting with ways to lessen Starlink’s impact on astronomy. Earlier this month the company launched a satellite nicknamed “DarkSat” that features a darkening coating to make it less visible to stargazers and ground-based observatories.

SpaceX CEO Elon Musk said in May 2019 that later versions of Starlink would include inter-satellite links. He said then that the company would like to keep Starlink satellites in orbit for four to five years before deorbiting and replacing them with newer, more capable models.

Source: https://spacenews.com/spacex-launches-fourth-batch-of-starlink-satellites-tweaks-satellite-design/

[Orionid]

Understanding the impact of satellite constellations on astronomy
by Staff Writers  Garching, Germany (SPX) Feb 13, 2020 [SD]


Around 19 Starlink satellites were imaged shortly after launch in November 2019 by DECam on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) by astronomers Clara Martinez-Vazquez and Cliff Johnson. The gaps in the satellite tracks are due to the gaps between the DECam CCD chips.

In June 2019, the International Astronomical Union expressed concern about the negative impact that the planned mega-constellations of communication satellites may have on astronomical observations and on the pristine appearance of the night sky when observed from a dark region. We here present a summary of the current understanding of the impact of these satellite constellations.

Following the statement of June 2019, IAU's Commission B7 Protection of Existing and Potential Observatory Sites and the Executive Committee Working Group Dark and Quiet Sky Protection were asked by the IAU Executive Committee to assess the situation and to start discussions with the companies that are responsible for launching and operating the mega-constellations in order to study measures to mitigate their interference.

Commission B7 has requested the input of astronomers from different organisations (Vera C. Rubin Observatory, U. Michigan, CAHA, ESO and ESA) skilled in modeling the frequency, location and brightness of satellite mega-constellations. Some of those results are presented below. The results of the simulations, given the large number of parameters involved and the associated assumptions and uncertainties, are to be considered preliminary.

While there is large uncertainty about the future number of satellites, some simulations were conducted on the basis of a large sample of over 25 000 satellites from representative satellite constellations from different companies. With this sample, the number of satellites above the horizon at any given time would be between ~1500 and a few thousand, depending on the latitude.

Most of these will appear very close to the horizon, only a few of them passing directly overhead; for instance, about 250 to 300 would have an elevation of more than 30 degrees over the horizon (i.e. where the sky is clear from obstructions, and where most of the astronomical observations are performed). The vast majority of these will be too faint to be visible to the naked eye.

When the Sun is 18 degrees below the horizon (i.e. when the night becomes dark), the number of illuminated satellites above the horizon would be around 1000 (with around 160 at elevations higher than 30 degrees). The numbers decrease further towards the middle of the night, when more satellites are in the Earth's shadow (e.g., no reflected sunlight).

At the moment it is difficult to predict how many of the illuminated satellites will be visible to the naked eye, because of uncertainties in their actual reflectivity (also since experiments are being carried out by SpaceX to reduce the reflectivity of a Starlink satellite by adopting different coatings).

The appearance of the pristine night sky, particularly when observed from dark sites, will nevertheless be altered, because the new satellites could be significantly brighter than existing orbiting man-made objects. The interference with the uncontaminated view of the night sky will be particularly important in the regions of the sky close to the horizon and less evident at high elevation.

The prominent trains of satellites ("strings of pearls"), often seen in images and videos, are significant immediately after launch and during the orbit-raising phase when they are considerably brighter than they are at their operational altitude and orientation. The global effect depends on how long the satellites are in this phase and on the frequency of launches.

Apart from their naked-eye visibility, it is estimated that the trails of the constellation satellites will be bright enough to saturate modern detectors on large telescopes. Wide-field scientific astronomical observations will therefore be severely affected. For instance, in the case of modern fast wide-field surveys, like the ones to be carried out by the Rubin Observatory (formerly known as LSST), it is estimated that up to 30% of the 30-second images during twilight hours will be affected.

Instruments with a smaller field of view would be less affected. In theory, the effects of the new satellites could be mitigated by accurately predicting their orbits and interrupting observations, when necessary, during their passage. Data processing could then be used to further "clean" the resulting images. However, the large number of trails could create significant and complicated overheads to the scheduling and operation of astronomical observations.

A summary of the findings and of the actions that have so far been undertaken is presented in a specific IAU Theme.

The focus of this Statement has been on the optical wavelengths. This is not to underplay the effect on the radio and submillimetre wavelength ranges, which is still under investigation. The IAU considers the consequences of satellite constellations worrisome. They will have a negative impact on the progress of ground-based astronomy, radio, optical and infrared, and will require diverting human and financial resources from basic research to studying and implementing mitigating measures.

A great deal of attention is also being given to the protection of the uncontaminated view of the night sky from dark places, which should be considered a non-renounceable world human heritage. This is one of the main messages communicated on the dedicated IAU-UNESCO web site on astronomical heritage.

In order to mitigate the impacts of satellite constellations that may interfere with professional and amateur astronomical observations, the IAU, in close collaboration with the American Astronomical Society (AAS), will continue to initiate discussions with space agencies and private companies that are planning to launch and operate currently planned and future satellite constellations.

The IAU notes that currently there are no internationally agreed rules or guidelines on the brightness of orbiting manmade objects. While until now this was not considered a priority topic, it is now becoming increasingly relevant.

Therefore the IAU will regularly present its findings at the meetings of the UN Committee for Peaceful Uses of Outer Space (COPUOS), bringing the attention of the world Government representatives to the threats posed by any new space initiative on astronomy and science in general. In addition, the specific theme of the mega-satellites will be included in the Programme of the IAU/UNOOSA/IAC Conference Dark and Quiet Skies for Science and Society, which will be held in Santa Cruz de La Palma, Canary Islands, Spain, on 5-8 October 2020.

The IAU stresses that technological progress is only made possible by parallel advances in scientific knowledge. Satellites would neither operate nor properly communicate without essential contributions from astronomy and physics. It is in everybody's interest to preserve and support the progress of fundamental science such as astronomy, celestial mechanics, orbital dynamics and relativity.

A summary of the findings and of the actions that have so far been undertaken is presented in a specific IAU Theme here

Source: https://www.spacedaily.com/reports/Understanding_the_impact_of_satellite_constellations_on_astronomy_999.html

[Orionid]

SpaceX launches fifth batch of Starlink satellites, misses booster landing
by Caleb Henry — February 17, 2020 [SN]


SpaceX launched its fifth batch of Starlink satellites into a lower orbit than previous missions to reduce strain on the rocket. Credit: SpaceX webcast.

WASHINGTON — SpaceX completed its fifth dedicated Starlink launch Feb. 17, successfully sending 60 satellites into low Earth orbit while missing what would have been the company’s 50th booster recovery.

A Falcon 9 rocket lifted off at 10:05 a.m. Eastern from Cape Canaveral Air Force Station, Florida, on a mission profile that differed from past Starlink launches.

Instead of deploying the satellites into a circular orbit as it had done on all four dedicated Starlink launches, Falcon 9 released Starlink’s fifth batch of broadband satellites into the lower end of an elliptical orbit about 15 minutes after liftoff, eliminating the need to fire the rocket’s upper stage a second time.

SpaceX said all 60 satellites were deployed at an altitude of 227 kilometers and will use onboard electric propulsion to reach their target 550-kilometer circular orbit.

The lower deployment altitude SpaceX used Feb. 17 is about 70 kilometers below the drop-off point used for the three most recent missions and more than 200 kilometers below last May’s first dedicated Starlink deployment.

Future Starlink launches will continue to use the lower drop-off point in order to shorten the mission and ease the load on the rocket, Jessie Anderson, a lead manufacturing engineer at SpaceX, said while co-narrating the launch.

Despite the reduced workload, Falcon 9’s reusable first-stage booster missed the droneship “Of Course I Still Love You,” splashing down nearby in the Atlantic Ocean.

SpaceX used the same booster for three previous missions — two 2019 resupply missions to the International Space Station for NASA, and the December launch of the JCSAT-18/Kacific-1 communications satellite. Lauren Lyons, a Starlink satellite engineer co-narrating the launch, said reusing the booster for the Feb. 17 launch marked SpaceX’s “fastest turnaround to date.”

SpaceX has now launched 302 Starlink satellites, counting two prototypes launched in 2018. The company is targeting 24 Starlink launches this year, and plans on starting regional service in Canada and the northern United States later this year, with near global coverage by 2021.

Source: https://spacenews.com/spacex-launches-fifth-batch-of-starlink-satellites-misses-booster-landing/

[Orionid]

SpaceX delivers more Starlink satellites to orbit, booster misses drone ship landing
February 17, 2020 Stephen Clark [SFN]


A Falcon 9 rocket lifted off at 10:05:55 a.m. EST (1505:55 GMT) Monday with 60 more SpaceX Starlink satellites. Credit: SpaceX

Sixty more satellites for SpaceX’s Starlink broadband network launched Monday on a Falcon 9 rocket from Cape Canaveral, bringing the total number of Starlink platforms deployed in orbit since last May to 300.

More Starlink missions are on tap in the coming months, with the next slated to fly aboard another Falcon 9 launcher as soon as early March.

Monday’s mission began with a burst of flame from SpaceX’s Falcon 9 booster, followed by the release of hold-down clamps to allow the 1.2-million-pound Falcon 9 to climb into a partly cloudy sky over Cape Canaveral’s Complex 40 launch pad.

The 229-foot-tall (70-meter) rocket lifted off at 10:05:55 a.m. EST (1505:55 GMT) powered by thrust from nine kerosene-fueled Merlin 1D engines.

The Falcon 9 quickly cleared lightning towers at pad 40 and steered toward the northeast, sending a window-shaking roar across the Florida spaceport.

Two-and-a-half minutes into the mission, the Falcon 9’s first stage booster shut down its engines and separated, allowing a single Merlin engine on the launcher’s second stage to fire into orbit.

Seconds later, the Falcon 9’s payload shroud jettisoned as the rocket soared into space, revealing the launcher’s more than 34,000-pound (15.6-metric ton) payload package, comprised of 60 flat-panel signal relay nodes for SpaceX’s Starlink network.

While the second stage accelerated into orbit, the first stage of the Falcon 9 descended back through the atmosphere and attempted landing on SpaceX’s football field-sized drone ship “Of Course I Still Love You” holding position nearly 400 miles (630 kilometers) northeast of Cape Canaveral.

But the rocket missed the drone ship and appeared to make a soft landing in the water nearby, according to streaming video from the offshore vessel. The missed landing marked the first time a first stage booster on a Falcon 9 rocket has missed a landing attempt on a SpaceX drone ship since 2016.

The rocket used on Monday’s mission was a veteran of three previous launches and landings. It’s not likely to be reused after landing in sea water.

Two other SpaceX vessels were positioned in the Atlantic Ocean to try to catch the two halves of the Falcon 9’s payload shroud. SpaceX did not announce the results of the fairing recovery attempt, but a company employee said engineers are still experimenting with catching the aerodynamic shroud using fast-moving ships fitted with giant nets. Previous catch attempts have been hit or miss.

Around the same time as the first stage reached the ocean, a SpaceX launch controller announced that the Falcon 9 upper stage had arrived in orbit and was poised to release the 60 Starlink satellites, the mission’s primary objective.

After firing thrusters to enter a controlled spin, the upper stage released retention rods holding the Starlink satellites to the rocket. That allowed the spacecraft — each weighing about a quarter-ton — to fly away from the Falcon 9 as the vehicles soared over the North Atlantic Ocean.

One change introduced Monday different from past Starlink missions was the release of the Starlink payloads into an elliptical transfer orbit, instead of a circular orbit.

SpaceX did not respond to questions from Spaceflight Now on the reason for the change in launch profile, but a host on the company’s webcast Monday said all future Starlink missions will use the new trajectory to inject the satellites into an elliptical orbit after a single upper stage burn.

“We are executing a direct inject of the Starlink satellites into an elliptical, or oval-shaped, orbit,” said Jessica Anderson, a manufacturing engineer at SpaceX. “In prior Starlink missions, we deployed the satellites into a 290-kilometer (180-mile) circular orbit, which required two burns of the Merlin vacuum engine on the second stage.

“Keep in mind the stack of 60 Starlink satellites combined is one of the heaviest payloads we fly, so putting them directly into this orbit requires more vehicle performance and makes recovery more challenging,” she said. “Going forward, and starting with today, we will deploy the satellites shortly after the first burn of the second stage, putting the Starlink satellites into an elliptical orbit.


A stack of 60 Starlink satellites. Credit: SpaceX

“Once checkouts are complete, the satellites will then use their on-board ion thrusters to move into their inteded orbits at an operational altitude of 550 kilometers (341 miles).”

According to preflight predictions, the Starlink craft on Monday were programmed for deployment in an elliptical, or egg-shaped, orbit ranging between 131 miles (212 kilometers) and 239 miles (386 kilometers) in altitude, with an inclination of 53 degrees to the equator.

As a result of the orbit change, the Falcon 9’s second stage remained in orbit after release the Starlink satellites Monday. It is expected to passively re-enter the atmosphere in the coming months, instead of performing a controlled de-orbit burn, as the stage did after previous Starlink launches.

Like SpaceX’s previous Starlink launches, the satellites deployed in a tight cluster. SpaceX ground teams will activate krypton ion thrusters and other systems on the satellites to maneuver them into a higher orbit, targeting an altitude of 341 miles for operational service broadcasting signals in Ku-band.

The first phase of SpaceX’s Starlink program, which aims to beam consumer broadband to customers around the world, will include 1,584 of the flat-panel satellites — including spares — in orbit 341 miles above Earth.

SpaceX has approval from the Federal Communications Commission to operate nearly 12,000 Starlink satellites in Ku-band, Ka-band and V-band frequencies, with groups of spacecraft flying at different altitudes with various orbital tilts, or inclinations.

Last year, SpaceX signaled to the International Telecommunication Union that it may seek authority to operate up to 30,000 additional broadband satellites in low Earth orbit, potentially bringing the total Starlink fleet to 42,000 platforms.

But SpaceX says the fleet’s growth will hinge on demand, and the company must launch roughly 20 more missions before completing the first phase of its Starlink network.


Artist’s illustration of a Starlink satellite. Credit: SpaceX

SpaceX also needs to test the network and begin selling the Starlink service, and work continues on user terminals to link customers on the ground with the satellite network in space. The company has not announced a price or Internet speeds for its consumer-grade service.

The rapid-fire deployment of Starlink satellites — coupled with plans for other large satellite fleets — has astronomers worried that the proliferation of small spacecraft could impact observations by ground-based telescopes.

The Starlink satellites are brighter than predicted, sometimes reflecting sunlight and becoming as bright as the most luminous stars in the night sky. But the brightest sightings occur only soon after a launch, when the satellites are flying at lower altitudes and are clumped close together.

The satellites are harder to spot as they spread out in the weeks after a launch and begin raising their orbits to their 341-mile-high operating altitude. But scientists caution they will pose a threat to high-power telescopes, such as the U.S. government-funded Vera C. Rubin Observatory under construction in Chile.

The International Astronomical Union — a global body chartered in 1919 to “promote and safeguard the science of astronomy” — said last week that it “considers the consequences of satellite constellations worrisome.”

“They will have a negative impact on the progress of ground-based astronomy, radio, optical and infrared, and will require diverting human and financial resources from basic research to studying and implementing mitigating measures,” the IAU said in a press release.

“A great deal of attention is also being given to the protection of the uncontaminated view of the night sky from dark places, which should be considered a non-renounceable world human heritage,” the IAU said.

At the request of the IAU, scientists from the Vera Rubin Observatory, the University of Michigan, the Centro Astronómico Hispano-Alemán, the European Southern Observatory and the European Space Agency modeled the frequency, location and brightness of satellites in planned “mega-constellations” flying in low Earth orbit.

The IAU said the results of the simulations are preliminary. Some of the simulations assumed more than 25,000 broadband satellites could be deployed in low Earth orbit, in which case between 1,500 and a few thousand spacecraft could be above the horizon at any given time, depending on the observer’s latitude.

The “vast majority” of those satellites would not be visible to the naked eye, according to the IAU. The simulations showed that around 250 to 300 of the spacecraft above the horizon at any given time would have an elevation of more than 30 degrees, the region of the sky where astronomers perform most of their observations.

At astronomical dawn and dusk — when the sun is 18 degrees below the horizon — simulations suggest around 1,000 satellites could be illuminated by sunlight and above the horizon. Around 160 of the illuminated spacecraft could be higher than 30 degrees in the sky at one time, and those are the satellites that pose the greatest threat to astronomical research.

The numbers of illuminated satellites will decrease in the middle of the night, according to the IAU.


This 333-second exposure taken last year by the Dark Energy Camera on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory shows 19 streaks attributed to Starlink satellites passing through the camera’s field-of-view shortly after their launch Nov. 11 from Cape Canaveral. Credit: NSF’s National Optical-Infrared Astronomy Research Laboratory/NSF/AURA/CTIO/DELVE

In response to astronomers’ concerns, SpaceX launched one satellite in early January with an experimental darker coating. The long-term effectiveness of the external treatment will not be known until the satellite reaches the Starlink fleet’s operational altitude.

Gwynne Shotwell, SpaceX’s president and chief operating officer, said in December the company was in dialog with astronomers about the issue.

“Astronomy is one of a few things that gets little kids excited about space,” Shotwell said. “There are a lot of adults that get excited, too, who either depend on it for their living or for entertainment. But we want to make sure we do the right thing, to make sure little kids can look through their telescopes. It’d be cool for them to see a Starlink. I think that’s cool. But they should be looking at Saturn and the moon.”

The other company on the cusp of launching hundreds, and perhaps thousands, of broadband satellites is London-based OneWeb.

OneWeb has launched 40 satellites to date, with plans to launch roughly 32 to 36 more every month to deploy an initial fleet of nearly 650 spacecraft. But like SpaceX, OneWeb has plans to grow from there.

The satellites owned by OneWeb are smaller than the Starlink spacecraft, and they orbit higher, allowing the company to provide global coverage with fewer satellites than SpaceX. The higher altitude also means they will be dimmer to ground observers, the company says.

“We’re going to do the most we can to mitigate (astronomers’ concerns),” said Adrian Steckel, OneWeb’s CEO. “We’re not visible to the naked eye. We are visible to telescopes. It’s hard to get around some of those facts.”

Scientists have also questioned whether constellations of thousands of satellites broadcasting broadband data will interfere with radio astronomy, which uses giant antennas to listen to faint radio signals generated from distant stars and galaxies.

“With respect to radio frequency … we’ll try,” Steckel said earlier this month. “We’re going to do the most we can. I don’t know if there will be a solution that will make everybody happy. At least we’re in dialog, and we’re trying to get feedback on what can we do.”

The IAU said there is still uncertainty in the eventual impacts of huge flocks of satellites on astronomy.

“At the moment it is difficult to predict how many of the illuminated satellites will be visible to the naked eye, because of uncertainties in their actual reflectivity,” the IAU said, referencing the unknown outcome of SpaceX’s experiments with darker coatings.


The Vera Rubin Observatory is under construction in Chile. Credit: Vera Rubin Observatory

“The appearance of the pristine night sky, particularly when observed from dark sites, will nevertheless be altered, because the new satellites could be significantly brighter than existing orbiting man-made objects,” the IAU said. “The interference with the uncontaminated view of the night sky will be particularly important in the regions of the sky close to the horizon and less evident at high elevation.”

The IAU said astronomical impacts during the period of time when Starlink satellites are brightest — soon after a launch — depend on how long the spacecraft are flying at lower altitudes, and the frequency of launches.

“Apart from their naked-eye visibility, it is estimated that the trails of the constellation satellites will be bright enough to saturate modern detectors on large telescopes,” the IAU concluded. “Wide-field scientific astronomical observations will therefore be severely affected. For instance, in the case of modern fast wide-field surveys, like the ones to be carried out by the Rubin Observatory (formerly known as LSST), it is estimated that up to 30 percent of the 30-second images during twilight hours will be affected.”

Formerly known as the Large Synoptic Survey Telescope, the Vera Rubin Observatory will capture deep, wide-field images of the entire available sky, allowing astronomers to learn more about dark energy and dark matter, and detect potentially hazardous asteroids with orbits near Earth, among other objectives.

“Instruments with a smaller field of view would be less affected,” the IAU continued. “In theory, the effects of the new satellites could be mitigated by accurately predicting their orbits and interrupting observations, when necessary, during their passage. Data processing could then be used to further ‘clean’ the resulting images. However, the large number of trails could create significant and complicated overheads to the scheduling and operation of astronomical observations.”

The IAU’s statement last week focused on optical astronomy. Astronomers continue studying the possible interference that signals transmitted by broadband satellites in low Earth orbit will have on radio astronomy.<

The IAU said there are no internationally-agreed rules of guidelines on the brightness of satellites. The group said it will present its findings to the United Nations to bring the attention of world government representatives on the issue.

“The IAU stresses that technological progress is only made possible by parallel advances in scientific knowledge,” the group said. “Satellites would neither operate nor properly communicate without essential contributions from astronomy and physics. It is in everybody’s interest to preserve and support the progress of fundamental science such as astronomy, celestial mechanics, orbital dynamics and relativity.”

SpaceX’s next launch is scheduled for 1:45 a.m. EST (0545 GMT) March 2, again from pad 40 at Cape Canaveral, when a Falcon 9 rocket will loft a Dragon cargo capsule into orbit on a resupply mission to the International Space Station.

Another Starlink launch on a Falcon 9 rocket is also scheduled as soon as March 4 from nearby pad 39A at the Kennedy Space Center.

Source: https://spaceflightnow.com/2020/02/17/spacex-delivers-more-starlink-satellites-to-orbit-booster-misses-drone-ship-landing/

[Orionid]

SpaceX launches Starlink satellites, misses booster landing for second time
by Caleb Henry — March 18, 2020


SpaceX CEO Elon Musk said one of the nine engines on Falcon 9's first stage shut down early during ascent. Credit: SpaceX webcast.

WASHINGTON — SpaceX successfully launched 60 satellites for its Starlink broadband constellation March 18, but failed to recover the rocket’s first stage, marking the company’s second consecutive booster miss.

The Falcon 9 rocket lifted off at 8:16 a.m. Eastern from Cape Canaveral Air Force Station in Florida and deployed the satellites into a 221-kilometer low Earth orbit about 15 minutes later. One of the nine engines on the rocket’s first stage shut down prematurely during ascent, SpaceX CEO Elon Musk tweeted after the mission.

The engine shut down didn’t affect orbital insertion, he said. Musk did not address if the engine outage was influential in SpaceX’s inability to recover the booster, which was completing its fifth reflight — the highest SpaceX has attempted. Musk said a “thorough investigation” will be needed before SpaceX’s next mission.

SpaceX previously planned to launch its latest Starlink satellites on March 15, but aborted the launch immediately after engine ignition due to what SpaceX described as “out of family data” during an engine power check.

The launch Wednesday was SpaceX’s first to use the same Falcon 9 booster for a fifth time. SpaceX used the same booster to launch 10 Iridium Next satellites in July 2018, Argentina’s Saocom-1A satellite in October 2018, the Indonesian Nusantara Satu satellite in February 2019, and the second dedicated Starlink mission in November. The company has designed Falcon 9 first-stage boosters to complete 10 flights each.

SpaceX tweaked the mission profile for Starlink launches starting with its Feb. 17 mission, dropping off 60 satellites in an elliptical orbit rather than a circular one, to reduce the load on the rocket and ease booster recovery. Neither mission using that modified profile has been successful, however.

SpaceX’s March 18 launch did successfully reuse payload fairing halves from a Starlink mission last May. The company is attempting to recover the fairing halves again using the boats “Ms. Chief” and “Ms. Tree,” which are outfitted with large catcher’s nets.

SpaceX has now launched 362 Starlink satellites, counting two demonstration spacecraft in 2018. The company said it will test the latest 60 satellites at their drop off altitude before using electric propulsion to raise them to their target 550-kilometer orbit.

SpaceX is building and launching a constellation of up to 12,000, and potentially even 42,000, satellites for global internet connectivity. Musk said at the Satellite 2020 conference that Starlink is designed to serve the 3-4% of the population that is most difficult to reach. Musk said SpaceX is not thinking about spinning off Starlink as a separate business.

Source: https://spacenews.com/spacex-launches-starlink-satellites-misses-booster-landing-for-second-time/

[Orionid]

SpaceX claims some success in darkening Starlink satellites
by Jeff Foust — March 18, 2020 [SN]


SpaceX says that an experimental Starlink satellite has demonstrated a "notable reduction" in its brightness, but that may not be enough to assuage astronomers concerned the constellation could adversely affect their observations. Credit: Victoria Girgis/Lowell Observatory

WASHINGTON — SpaceX says it will take more steps to reduce the impact of its Starlink satellite constellation on astronomy, although astronomers disagree with statements by Elon Musk that the system will have “zero” effect on their work.

SpaceX launched its latest set of Starlink satellites March 18, the fourth such launch this year and sixth overall. The company has placed 362 Starlink satellites into orbit, counting two experimental satellites launched in 2018, and nearly all of them remain in orbit.

Since large-scale Starlink launches started in May 2019, astronomers have warned that the satellites, far brighter than expected, could interfere with their observations, particularly if SpaceX proceeds with plans to launch 12,000 or more such satellites in the next several years. In response to those concerns, SpaceX included an experimental “DarkSat” among the 60 Starlink satellites launched Jan. 6, with portions of the satellite darkened to reduce its reflectivity and hence brightness.

During the company’s webcast of the latest Starlink launch, SpaceX claimed some success with that effort. “Preliminary results show a notable reduction,” said Jessica Anderson, one of the hosts of the webcast. She added that the company had “a couple of other ideas that we think could reduce the reflectivity even further.”

One of those, she said, was a “sunshade” that would deploy like a patio umbrella from the satellite. That will be tested on a future Starlink mission, but she didn’t give more details about either the sunshade itself or when it would be flown.

SpaceX Chief Executive Elon Musk also mentioned the sunshade option during an onstage interview at the Satellite 2020 conference here March 9. “We are working with senior members of the science community and senior astronomers to minimize the potential for reflection from the satellites,” he said. “We’re running a bunch of experiments.” That includes a sunshade and other steps “to minimize the potential for any impact.”

However, the company’s claim that DarkSat has achieved a “notable reduction” in brightness is not necessarily supported by recent observations. In a paper posted to the online preprint server arXiv March 17, astronomers using a small telescope in Chile measured the brightness of DarkSat and compared it to another Starlink satellite without darkening treatments. They found DarkSat was about 0.88 magnitudes, or 55%, dimmer than the ordinary DarkSat.

That falls far short of what many astronomers are seeking. In a March 11 panel discussion organized by the American Astronomical Society, Tony Tyson, chief scientist for the Vera Rubin Observatory under construction in Chile, said that simulations of the Starlink satellites showed that not only would the satellites make bright streaks on images taken by the telescope, but create other image artifacts by saturating pixels in the detector.

“If we could make those particular spacecraft, the Starlinks, darker by 10 to 20 times, it may remove many of these artifacts,” he said. “It won’t remove the main trail — it will always be there — but it would remove the artifacts so that we might be able to get the science out of the data.”

At the time of that event, there was still little information available about how much dimmer DarkSat was than the rest of the Starlink constellation. While launched in early January, the spacecraft reached its operational orbit only in late February, allowing for accurate comparisons of its brightness.

“This is a continuing experiment,” Tyson said of the DarkSat observations, noting that measurements of its brightness were taken just the night before. The data from the small Chilean telescope analyzed in the arXiv preprint came primarily from a single night of observations in early March after DarkSat reached its operational orbit.

Tyson, though, emphasized the cooperation between SpaceX and the astronomy community to reduce the brightness of future Starlink satellites. “We’ve had a really delightful collaboration going now for a couple months with SpaceX engineers,” he said. “There are a lot of ideas on the table for darkening their satellites. This is just the first.”

Musk, in his Satellite 2020 appearance, claimed that the Starlink constellation will ultimately have no effect on ground-based astronomy. “I am confident that we not cause any impact whatsoever in astronomical discoveries,” he said. “Zero. That’s my prediction. We will take corrective action if it’s above zero.”

Astronomers like Tyson, though, would not go so far to say that Starlink will have “zero” effect on their observations. “My hope in the future is that they will be darkened sufficiently, just as I mentioned, just to get out of this region where our detectors are impacted very negatively,” he said. “The trail will always be there, of course, but maybe we can salvage some of the science.”

Source: https://spacenews.com/spacex-claims-some-success-in-darkening-starlink-satellites/

[Orionid]

Falcon 9 rocket overcomes engine failure to deploy Starlink satellites
March 18, 2020 Stephen Clark [SFN]


A Falcon 9 rocket takes off from pad 39A Wednesday morning at NASA’s Kennedy Space Center in Florida. Credit: SpaceX

A SpaceX Falcon 9 rocket overcame a rare in-flight engine failure soon after launch from Florida’s Space Coast Wednesday to place 60 satellites in orbit for the company’s Starlink Internet network.

One of the rocket’s nine first stage engines shut down prematurely around 2 minutes, 22 seconds, after liftoff from pad 39A at NASA’s Kennedy Space Center in Florida, an event visible in a view from a camera streaming live video from the Falcon 9 as it climbed into the upper atmosphere.

Elon Musk, SpaceX’s founder and CEO, confirmed in a tweet that the Falcon 9 experienced an “early engine shutdown on ascent, but it didn’t affect orbit insertion.”

The rocket’s other Merlin engines fired a little longer to compensate for the loss of thrust. The rest of the Falcon 9’s climb into orbit appeared to go according to plan, and the upper stage deployed the 60 Starlink satellites into orbit around 15 minutes after liftoff.

“Shows value of having 9 engines!” Musk wrote on Twitter.

The first stage missed a landing attempt on SpaceX’s drone ship parked in the Atlantic Ocean northeast of Cape Canaveral, the second time SpaceX has missed a rocket landing in the company’s last three missions. It was not immediately clear whether the engine shutdown on ascent affected the recovery attempt.

There are nine kerosene-fueled Merlin 1D engines on the Falcon 9’s first stage, each generating 190,000 pounds of thrust at sea level when firing at full power. The Falcon 9 is designed to persevere through a booster engine failure and still deliver its payload to orbit.

The in-flight engine failure on Wednesday’s launch marked the second time a Merlin engine has prematurely shut down on a Falcon 9 flight.

In October 2012, a Merlin 1C engine — a predecessor to the Merlin 1D — failed during the launch of a Dragon supply ship on the way to the International Space Station. The Falcon 9 was still able to deliver the Dragon spacecraft into orbit, but the failure resulted in the loss of an Orbcomm data relay satellite riding as a secondary payload.

Musk promised a “thorough investigation” of Wednesday’s early engine shutdown before the next Falcon 9 launch, and it was not immediately clear whether the inquiry might prompt launch delays.

The first stage flown on Monday’s mission was making its fifth trip to space, after flawless performance on four previous missions since 2018. It was the first time SpaceX has launched a Falcon 9 booster on a fifth flight.

The launch was previously scheduled for Sunday, but computers ordered a last-second abort after ignition of the rocket’s Merlin main engines. Musk tweeted that the launch attempt was aborted due to “slightly high power” detected in the Falcon 9’s propulsion system, adding that the event was “possible, but not obviously, related to today.”

Spaceflight Now@SpaceflightNow 2:11 PM - Mar 18, 2020
Elon Musk, SpaceX’s founder and CEO, confirms one of the Falcon 9’s first stage engines shut down prematurely during today’s launch.

Although the rocket achieved the planned orbit, Musk says a thorough investigation is needed before the next mission. https://spaceflightnow.com/2020/03/13/falcon-9-starlink-5-mission-status-center/ …

Twitter

“This vehicle has seen a lot of wear, so today isn’t a big surprise,” Musk tweeted. “Life leader rockets are used only for internal missions. Won’t risk non-SpaceX satellites.”

SpaceX says Falcon 9 boosters are designed for 10 missions without major work, although technicians routinely perform inspections and some refurbishment on the vehicles between flights.

The 229-foot-tall (70-meter) Falcon 9 rocket took off at 8:16:39 a.m. EDT (1216:39 GMT) Wednesday from pad 39A at the Florida spaceport, then turned northeast to soar into space over the Atlantic Ocean.

The Falcon 9’s first stage continued firing more than around 15 seconds after the engine failure, then separated to allow the rocket’s second stage to ignite its single Merlin engine to accelerate into orbit with the 60 Starlink satellites.

The bulbous aerodynamic shroud on the nose of the Falcon 9 rocket jettisoned moments later. Like the first stage, the two halves of the clamshell-like fairing were recycled from a previous mission.

SpaceX later confirmed the two fairing halves descended to parachute-assisted water landings in the Atlantic Ocean, where two recovery ships were on station to retrieve the parts and return them to port.

The Falcon 9’s booster reignited its engines for an entry burn to begin slowing down for landing on SpaceX’s football field-sized landing platform, but the video feed from the first stage cut off soon after the maneuver. SpaceX later confirmed the booster was unable to land on the drone ship.

A Falcon 9 first stage also missed landing on the drone ship after a Feb. 17 launch, but the booster on a March 6 launch made a successful onshore landing at Cape Canaveral Air Force Station.

SpaceX is the only company that currently recovers and reuses orbital-class rocket boosters.

While recovering the booster helps reduce costs and maintain a rapid launch cadence, the first stage landing is always a secondary objective on SpaceX missions.

The rocket’s upper stage shut down its engine around nine minutes after liftoff Wednesday, then fired thrusters to enter a spin before releasing the 60 flat-panel Starlink satellites. Live video beamed back to ground controllers from the Falcon 9 showed the Starlink payloads flying away from the rocket as the vehicle soared over the North Atlantic Ocean.

Spaceflight Now@SpaceflightNow 1:37 PM - Mar 18, 2020
Sixty Starlink broadband relay satellites have deployed from SpaceX’s Falcon 9 rocket in orbit. With this launch, SpaceX has launched 360 Starlink stations since last May. https://spaceflightnow.com/2020/03/13/falcon-9-starlink-5-mission-status-center/ …

Twitter

The 60 Starlink spacecraft were to be released in an elliptical, or egg-shaped, transfer orbit ranging between 130 miles (210 kilometers) and 227 miles (366 kilometers) above Earth, with an inclination of 53 degrees to the equator.

Each of the quarter-ton Starlink satellites was expected to unfurl a solar array wing and activate a krypton ion propulsion drive to begin climbing to an operational orbit 341 miles (550 kilometers) in altitude.

The Starlink network is designed to beam Internet signals to most of the world’s population, targeting hard-to-reach consumers and users on the go. With Wednesday’s launch, SpaceX has added 360 satellites to the Starlink fleet since beginning dedicated missions last May.

SpaceX has become a leader in the commercial launch market with its Falcon 9 and Falcon Heavy rockets, thanks in large part to the company’s ability to cut the cost of access to space. The company is developing a pair of next-generation vehicles called the Starship and the Super Heavy booster to replace the Falcon rocket family.

Musk has said revenue from SpaceX’s business, including launch contracts and Starlink services, will help fund development of the Starship and other future technology needed to carry people to Mars and other planetary destinations.

“The whole purpose of SpaceX is really to help make life multi-planetary, but the revenue potential of launching satellites, servicing the space station and whatnot, that taps out about $3 billion a year,” Musk said March 9 in a talk at the Satellite 2020 conference in Washington. “But I think providing broadband is more like an order of magnitude beyond that, probably $30 billion a year as a rough approximation. And we’re still probably below 5 percent (market share) at that point.”

Musk said the Starlink network will reach the “hardest to serve” Internet customers, and will not be a major threat to established telecom operators.

“It’s not like Starlink is some real threat to teclos,” he said.

The first phase of the Starlink network will include more than 1,500 satellites — including spares — orbiting 341 miles above Earth on tracks inclined 53 degrees to the equator. But SpaceX has regulatory authority from the Federal Communications Commission to operate up to 12,000 communications and data relay spacecraft.

“5G is great for high-density situations like being here in D.C. or New York, San Francisco, that kind of thing,” Musk said. “But it’s actually not great for the countryside. For rural areas, it’s not great. You need range. So any kind of sparse environment, 5G is really not well-suited, but it’s great for dense city situations.

“So Starlink will effectively service the 3 or 4 percent hardest to reach customers for telcos, or people who simply have no connectivity right now, or the connectivity is really bad,” Musk said. “So I think it will be actually helpful and take a significant load off the traditional telcos.”

The U.S. military could also be a major customer for Starlink services.


Artist’s concept of a Starlink satellite with its solar array wing unfurled. Credit: SpaceX

SpaceX has not publicized connectivity speeds or prices for consumer-grade connectivity through the Starlink network. But Musk gate prospective customers a taste of what they could expect.

“It will be very low latency, and we’re targeting latency below 20 milliseconds, so somebody could play a fast response video game at a competitive level,” he said. “That’s the threshold for latency. And bandwidth? The bandwidth is a very complex question. Let’s just say somebody will be able to watch high-definition movies, play video games, and do all the things they want to do without noticing speed.”

Musk said user ground terminals will “look like a UFO on a stick,” and the first version of the Starlink ground antenna will have actuators to point the transmitter and receiver.

“It’s very important that you don’t need a specialist to install,” Musk said. “The goal is that (on) the instructions on the box, there are just two instructions, and they can be done in either order: Point at sky and plug in.”

Many astronomers are worried that the launch of thousands of satellites, such as those planned by SpaceX and competitors like OneWeb and Amazon, will impact observations of the night sky.

SpaceX’s Starlink satellites are brighter than expected, particularly soon after a launch when the spacecraft are clumped together in clusters at lower altitudes. Reflective surfaces on the satellites glint sunlight back to Earth’s surface near dawn and dusk.

The European Southern Observatory reported March 5 that its Very Large Telescope and future Extremely Large Telescope in Chile will be ‘moderately affected’ by the satellite constellations under development. About 3 percent of long exposures from the telescopes could be ruined at twilight, the scientists concluded in a study accepted for publication in the scientific journal Astronomy & Astrophysics.

But other facilities may not be so fortunate.

“The study also finds that the greatest impact could be on wide-field surveys, in particular those done with large telescopes,” ESO said in a statement. “For example, up to 30 percent to 50 percent of exposures with the U.S. National Science Foundation’s Vera C. Rubin Observatory … would be ‘severely affected,’ depending on the time of year, the time of night, and the simplifying assumptions of the study.

“Mitigation techniques that could be applied on ESO telescopes would not work for this observatory although other strategies are being actively explored,” ESO said.

Musk dismissed those concerns March 9.

“I’m confident that we will not cause impact whatsoever in astronomical discoveries,” he said. “Zero. That’s my prediction. We’ll take corrective action if it’s above zero.

“When the satellites are first launched, they’re tumbling a little bit, so they’re going to glint because they haven’t stabilized. And they are raising their orbits, so they’re lower than you’d expect, and they reflect in ways that is not the case when they’re on orbit.”

SpaceX and OneWeb are working with scientists to mitigate the effects of satellite constellations on astronomical observations.

“So we’re running a bunch of experiments to, for example, paint the phased array antenna black instead of white,” Musk said. “And we’re working on a sunshade because there are certain angles if the sun get just right and there’s not, like, a little sunshade — we’re not talking about a lot here — then you can get a reflection. So we’re launching sunshade, changing the color of the satellites, and otherwise minimizing the potential for any impact.”

SpaceX said last month it was considering spinning off the Starlink business into a separate company, and potentially launch a public stock offering in the project, in the next several years.

Musk said March 9 that SpaceX is focused on making Starlink successful first.

“We’re thinking about that zero,” he said. “We need to make the thing work.”

Guess how many LEO (low Earth orbit) constellations didn’t go bankrupt? Zero. Iridium’s doing OK (now), but Iridium 1 went bankrupt. Orbcomm went bankrupt. Globalstar, bankrupt. Teledesic, bankrupt.”

Musk said there’s room for other companies in the market to provide Internet services from space, and SpaceX is happy to launch satellites for competitors. SES, a longtime SpaceX customer, announced last year it would launch seven high-power broadband satellites for its O3b mPower network on two Falcon 9 rocket flights.

“If you want to launch a constellation on SpaceX, that sounds good to me,” he said. “The world seems to have an insatiable appetite for bandwidth … We don’t think Starlink is going to destroy all other satellites, or something like that.”

The next launch on SpaceX’s schedule is slated for no earlier than March 30 from pad 40 at Cape Canaveral. A Falcon 9 rocket is being readied to carry Argentina’s SAOCOM 1B radar observation satellite into a polar sun-synchronous orbit, flying on a southerly trajectory just offshore roughly parallel with Florida’s East Coast.

The last time Cape Canaveral was the departure point for mission into a polar orbit was in 1960.

Another Falcon 9 launch with Starlink satellites is scheduled from pad 40 in April, and a U.S. military GPS navigation satellite is set to take off on a Falcon 9 rocket April 29, also from pad 40.

SpaceX’s first mission with astronauts could launch as soon as May from pad 39A at the Kennedy Space Center. NASA astronauts Doug Hurley and Bob Behnken are training for a test flight to the International Space Station aboard SpaceX’s Crew Dragon spaceship.

That flight will be the first human space mission to launch into orbit from U.S. soil since the retirement of the space shuttle in 2011.

But launch dates hinge on numerous factors, including the growing coronavirus pandemic, which has prompted NASA to mandate telework for non-essential employees at all the agency’s facilities, including the Kennedy Space Center.

NASA Administrator elevated the agency to Stage 3 of NASA’s Response Framework late Tuesday, triggering new limits on travel and access to NASA centers. But critical work needed to maintain safety, security, launch dates and mission operations continues.

In Stage 4 of the Response Framework, NASA centers would effectively be shut down entirely, except for workers required to protect “life and critical infrastructure.”

There’s some added uncertainty about SpaceX’s upcoming launch schedule as engineers begin their investigation into the early engine shutdown on Wednesday’s mission.

Source: https://spaceflightnow.com/2020/03/18/falcon-9-rocket-overcomes-engine-failure-to-deploy-starlink-

[Orionid]

Starlink passes 400 satellites with seventh dedicated launch
by Caleb Henry — April 22, 2020 [SN]


SpaceX now has 422 Starlink satellites in orbit. Credit: SpaceX webcast

WASHINGTON — SpaceX launched its seventh batch of Starlink satellites on a Falcon 9 rocket April 22, growing its internet constellation to 422 satellites in low Earth orbit.

The Falcon 9 lifted off at 3:30 p.m. Eastern from Cape Canaveral Air Force Station in Florida, releasing its payload of 60 satellites 15 minutes later at an altitude of 224 kilometers above the Earth. There the 260-kilogram satellites will complete testing before climbing to an operational altitude of 550-kilometers using their onboard propulsion.

SpaceX landed the Falcon 9’s first stage almost nine minutes after lift off. The same booster had completed three earlier launches, all to low Earth orbit. SpaceX also reused the payload fairings from an August launch carrying the Amos-17 telecommunications satellite for Spacecom.

SpaceX now has enough Starlink satellites orbiting to start limited service in northern geographies, according to a teleconference SpaceX CEO Elon Musk gave in May 2019. Musk said Starlink needed at least 400 satellites to start partial geographic service.

SpaceX did not respond to SpaceNews inquiries April 13 and April 20 about when it will start service. The company reiterated in a mission overview document for its April 22 launch that service in Canada and the Northern U.S. should start this year, followed by near-global coverage in 2021.

SpaceX has FCC permission to operate nearly 1,600 Ku- and Ka-band satellites at 550 kilometers. Recently the company asked the FCC for authorization to fly another 2,800 at that altitude. SpaceX is planning a constellation of up to 12,000, or potentially 42,000 internet satellites, according to filings with U.S. and international regulators.

Source: https://spacenews.com/starlink-passes-400-satellites-with-seventh-dedicated-launch/

[Orionid]

SpaceX’s Starlink network surpasses 400-satellite mark after successful launch
April 22, 2020 Stephen Clark [SFN]


A Falcon 9 rocket streaks into the sky over Cape Canaveral in this long exposure photo. Credit: SpaceX

SpaceX launched 60 more spacecraft Wednesday to join the Starlink fleet beaming broadband signals around the world, while the company’s engineers move closer to debuting a sunshade that could reduce the satellites’ impacts on ground-based astronomy.

Riding 1.7 million pounds of thrust from nine Merlin main engines, a Falcon 9 rocket took off at 3:30:30 p.m. EDT (1930:30 GMT) Wednesday from pad 39A at NASA’s Kennedy Space Center in Florida.

The Falcon 9 launcher, standing 229 feet (70 meters) tall, tilted on a track northeast from Florida’s Space Coast and rocketed through a thin layer of high clouds on the way to orbit.

Two-and-a-half minutes after liftoff, the Falcon 9’s first stage booster shut down and separated to begin a controlled descent back into the atmosphere. The rocket’s single-engine upper stage ignited seconds later, and the Falcon 9 released its clamshell-like payload fairing more than three minutes into the mission.

Flying into space for the fourth time, the reusable first stage nailed a pinpoint landing on SpaceX’s drone ship in the Atlantic Ocean east of Charleston, South Carolina. Two recovery ships were stationed in the Atlantic to retrieve the rocket’s two-piece payload shroud, which was also recycled from a previous flight.

Spaceflight Now @SpaceflightNow 9:54 PM - Apr 22, 2020
Here’s a replay of today’s launch from the Kennedy Space Center — the 84th by a SpaceX Falcon 9 rocket since 2010.

That makes the Falcon 9 the most-flown orbital-class US launch vehicle currently operational. https://spaceflightnow.com/2020/04/22/falcon-9-starlink-6-mission-status-center/ …

Twitter

The Falcon 9 rocket released retention rods holding the Starlink satellites to the upper stage around 15 minutes after launch. Video from camera on the rocket showed the 60 flat-panel satellites — each with mass of about a quarter-ton — receding into space over the North Atlantic Ocean.

The satellites were each expected to extend their power-generating solar panel wing go through an activation sequence. Krypton ion thrusters on the spacecraft will boost them from their preliminary elliptical transfer orbit to an operational altitude of 341 miles (550 kilometers) over the coming weeks and months.

The successful launch Wednesday marked the 84th flight of a Falcon 9 rocket since June 2010. That makes SpaceX’s Falcon 9 the most-flown orbital-class U.S. launcher currently in operation, exceeding the 83 missions performed by the Atlas 5 rocket built by rival United Launch Alliance.

Wednesday’s launch was SpaceX’s seventh Falcon 9 mission of the year.

It was the first Falcon 9 launch since March 18, when one of the Falcon 9’s nine Merlin booster engines shut down prematurely. The rocket was able to recover from the engine failure, and still placed its payload of 60 Starlink satellites into the planned orbit.

Elon Musk, SpaceX’s founder and CEO, said Wednesday the engine problem was caused by a “small amount of isopropyl alcohol (cleaning fluid)” that was trapped in a “sensor dead leg,” or an area where it couldn’t flow through. The fluid ignited in flight, causing the engine to automatically shut down.

Lauren Lyons, a SpaceX engineer hosting the company’s launch webcast, said ground crews did not perform that particular cleaning procedure on the Falcon 9 rocket used Wednesday.

Spaceflight Now@SpaceflightNow 9:48 PM - Apr 22, 2020
SpaceX’s next 60 Starlink satellites have deployed in orbit after a successful launch aboard a Falcon 9 rocket.

This gives SpaceX more than 400 satellites for its broadband Internet project. https://spaceflightnow.com/2020/04/22/falcon-9-starlink-6-mission-status-center/ …
Twitter

With Wednesday’s launch, SpaceX has delivered 422 Starlink satellites to space, including two prototypes that are now being deorbited. Since last May, SpaceX has orbited 420 Starlink spacecraft. Three of those relay stations are no longer in orbit, according to publicly-available U.S. military tracking data.

SpaceX’s next Starlink launch after Wednesday could happen as soon as early May on another Falcon 9 rocket mission from Cape Canaveral.

That will be followed by SpaceX’s first launch with astronauts on-board — scheduled for May 27 — to begin a test flight of the company’s Crew Dragon spaceship to the International Space Station.

SpaceX seeks to modify Starlink regulatory license

SpaceX has regulatory approval from the Federal Communications Commission to eventually field a fleet of up to 12,000 small Starlink broadband stations.

Officials say 24 launches are needed to provide global broadband service through the Starlink service. But the company could provide an interim level of service over parts of the Earth — such as Canada and northern parts of the United States — later this year, once SpaceX has launched around 720 satellites on 12 Falcon 9 flights.

SpaceX has modified the architecture of the Starlink network several times. Most recently, SpaceX submitted an application to the Federal Communication Commission on Friday proposing to operate more satellites in lower orbits than the FCC previously authorized.

The first phase of the Starlink network will include 1,584 satellites orbiting 341 miles (550 kilometers) above Earth in planes inclined 53 degrees to the equator. That part of the constellation, which SpaceX intends to launch through the end of the year, remains unchanged in SpaceX’s application.

SpaceX previously had regulatory approval from the FCC to operate another 2,825 satellites in higher orbits between 690 miles (1,110 kilometers) and 823 miles (1,325 kilometers) in altitude, in orbital planes inclined 53.8, 70, 74 and 81 degrees to the equator.


Artist’s illustration of the distribution of satellites in SpaceX’s Starlink network. Credit: SpaceX

The modified plan submitted to the FCC by SpaceX foresees Ku-band and Ka-band satellites in the next phase of the Starlink network all operated at altitudes between 335 miles (540 kilometers) and 354 miles (570 kilometers) at inclinations of 53.2, 70 and 97.6 degrees.

The application covers 4,408 Starlink satellites, one fewer than SpaceX envisioned under the previous architecture.

In documentation submitted Friday to the FCC, SpaceX said lower altitude will put the satellites closer to Starlink consumers and allow the network “to provide low-latency broadband to unserved and underserved Americans that is on par with service previously only available in urban areas.”

The change will also improve Starlink service for U.S. government users in polar regions and allow for more rapid deployment of the network, SpaceX said.

Flying Starlink satellites in lower orbits will help ensure they re-enter the atmosphere a shorter time in case of failure. And the spacecraft will broadcast signals at reduced power levels because they are closer to Earth, which SpaceX said will allow the Starlink fleet to be compliant with limits to reduce radio interference with other satellite and terrestrial wireless networks.

Last week’s application to modify SpaceX’s FCC license is the latest in a series of adjustments to the Starlink architecture. Before the first launch of 60 Starlink satellites last year, SpaceX received FCC approval to migrate the positions of the fleet’s first 1,584 satellites from 714 miles (1,150 kilometers) to 341 miles (550 kilometers).

In December, the FCC granted a SpaceX request to reconfigure the distribution of the Starlink satellites in different orbital planes. SpaceX said that request was intended to expand Starlink coverage faster around the United States without the need for more satellites.

SpaceX working on sunshade for future Starlink satellites

At lower altitudes, the Starlink satellites will fly in a region with busier space traffic. SpaceX says its Starlink spacecraft can maneuver to avoid collisions with other objects in orbit, and it releases orbital data on the Starlink satellites so other operators can also perform evasive maneuvers.

Astronomers have also raised concerns about the brightness of the Starlink satellites, which could interfere with ground-based telescope images, particularly around sunrise and sunset.

The Starlink satellites reflect more sunlight than SpaceX or astronomers anticipated before the first dedicated Starlink launch last year. The American Astronomical Society and other groups are working with SpaceX to try and limit the satellites’ impacts on astronomy.

One of the ground-based facilities most at risk of interference from the Starlink satellites is the U.S. government-funded Vera Rubin Observatory, formerly known as the Large Synoptic Survey Telescope. The observatory under construction in Chile will capture deep, wide-field images of the entire southern sky, allowing astronomers to learn more about dark energy and dark matter, and detect potentially hazardous asteroids with orbits near Earth, among other objectives.

Steve Kahn, director of the Vera Rubin Observatory, said Wednesday that SpaceX is responsive to astronomers’ concerns.

“They’ve been quite cooperative in working with us,” Kahn told Spaceflight Now in an interview.

“SpaceX is committed to promoting all forms of space exploration, which is why it has already taken a number of proactive steps to ensure it does not materially impact optical astronomy,” the company wrote in Friday’s application to the FCC, which does not have regulatory authority over the brightness of satellites. “SpaceX is working with U.S. and international astronomy organizations and observatories to measure scientifically the actual impact of its satellites.”

Flying more Starlink satellites at lower altitudes could make the relay nodes appear brighter from the ground, but there will be fewer Starlink satellites visible in the sky at one time. The spacecraft at lower altitudes will also spend less time illuminated by sunlight.

“In some respects, that’s good for astronomy because the Earth’s shadow is a cone,” said Pat Seitzer, an astronomer and orbital debris expert at the University of Michigan. “So the satellites at higher altitude will be visible longer into the darkest part of the night, but because they’re closer now, they’ll be brighter. So we’ll just have to sort out and see how that works.”

Seitzer agreed with SpaceX that the lower operating altitude for the Starlink satellites “really helps them for space safety, in terms of space debris or orbital debris considerations.”


An astronaut on the International Space Station captured this view of a string of Starlink satellites April 13. Credit: NASA

One of 60 Starlink satellites launched Jan. 6 carried a new darker coating intended to reduce the spacecraft’s reflectivity. SpaceX said last month that preliminary data indicated a “notable reduction” in the brightness of that satellite, which has been dubbed “DarkSat.”

“The darkening that they did on DarkSat is about a factor of two-and-a-half fainter — so about 1 magnitude in astronomical units — and it’s still visible to the unaided eye under excellent conditions,” Seitzer said. “That is you’re a person with great vision sitting on top of a mountaintop faraway from the city lights.”

Kahn agreed, adding that the darker coating was a step in the right direction for astronomers.

“Beyond this (darkening) treatment, SpaceX is developing new mitigation efforts that it plans to test in the coming months,” SpaceX wrote in Friday’s FCC filing. “Additionally, SpaceX will make satellite tracking data available so astronomers can better coordinate their observations with our satellites.”

One change SpaceX is studying is the addition of a sunshade, or visor, to unfurl like an umbrella on Starlink satellites to reduce the amount of sunlight glinting off the spacecraft.

Musk tweeted Wednesday that SpaceX is taking “key steps to reduce satellite brightness.” He wrote that the satellites “should be much less noticeable” when they’re flying at lower altitudes soon after launch.

He said SpaceX is changing the angle of each satellite’s solar panel, and all of the Starlink satellites will have sunshades beginning with the fleet’s ninth launch. That launch is expected in a couple of months.

Beyond the 4,400 Ku-band and Ka-band satellites covered in Friday’s application for a modified FCC license, SpaceX plans to launch another 7,500 V-band data relay stations into orbits around 214 miles (345.6 kilometers) in altitude. The FCC has already approved SpaceX to operate the V-band network.

Source: https://spaceflightnow.com/2020/04/22/spacexs-starlink-network-surpasses-400-satellite-mark-after-successful-launch/

[Orionid]

SpaceX to add sunshades to all future Starlink satellites
by Caleb Henry — May 27, 2020 [SN]


SpaceX's VisorSat will use sunshades modeled on sun visors in a car windshield to keep sunlight from reflecting off the satellite's antennas, reducing its brightness as seen from the ground. Credit: SpaceX

WASHINGTON — SpaceX has decided to add sunshades to future Starlink satellites to reduce their impact on astronomy, having opted for constellation-wide implementation of the reflective hardware.

Patricia Cooper, SpaceX’s vice president of satellite government relations, said May 26 that SpaceX has another 80 or so Starlink satellites it is preparing to launch based on their current design before regularly incorporating sunshades that block sunlight from hitting reflective parts of each satellite.

“We would have about 500 satellites at their current brightness, and then all satellites beyond that would have these sunshades,” Cooper said during a webinar hosted by the American Astronomical Society and the Satellite Industry Association. “That is the ratio we would be looking at.”

SpaceX has launched 422 Starlink satellites, including two prototypes, since 2018. The company is building and launching an initial constellation of roughly 4,400 satellites, though regulatory filings indicate the company could grow Starlink to 12,000 or even 42,000 satellites.

SpaceX’s first visor-equipped satellite, dubbed VisorSat, was expected to launch May 17, but was delayed because of Tropical Storm Arthur until after the company’s highly anticipated Crew Demo 2 mission, scheduled for May 27 at 4:33 p.m. Eastern. Cooper said SpaceX has yet to announce a date for its next Starlink mission.

SpaceX typically launches Starlink satellites in batches of 60 on Falcon 9 rockets, a rate that would suggest one or two more launches would occur without Starlink satellites routinely equipped with sunshades. Cooper said SpaceX will likely retire early Starlink satellites more quickly to reduce their impact on astronomy.

“The earlier version of our satellites that we’ve launched, we don’t expect them to have a complete five-year life span,” she said. “We are expecting to cut in the VisorSat mitigation at the point that we are launching still in the 500s of satellites.”

Tony Tyson, chief scientist for the Vera Rubin Observatory, said Starlink satellites need to be dimmed to an apparent magnitude of seven so that astronomers can work around them using image processing. Recent observations show Starlink satellites at around magnitude five. DarkSat, a Starlink satellite treated with an experimental darkening coating, was observed at roughly magnitude six, he said.

“Progress is being made, [but] we still have to get to seventh magnitude somehow,” Tyson said. SpaceX is working with astronomers on reducing the impact of Starlink, he said.

Cooper, when asked if SpaceX had the same goal of lowering Starlink’s brightness to magnitude seven, said it is an “interesting threshold,” but did not commit to meeting that target.

Source: https://spacenews.com/spacex-to-add-sunshades-to-all-future-starlink-satellites/

[Orionid]

SpaceX to debut satellite-dimming sunshade on Starlink launch next month
April 28, 2020 Stephen Clark [SFN]


SpaceX plans to debut a new sunshade structure on its future Starlink satellites. Credit: SpaceX

A new sunshade, or visor, designed to reduce the brightness of SpaceX’s Starlink broadband Internet satellites will debut on the company’s next launch, a measure intended to alleviate astronomers’ concerns about impacts on observations through ground-based telescopes, SpaceX founder Elon Musk said Monday.

Beginning with the next launch of Starlink satellites — scheduled as soon as May 7 from Cape Canaveral — SpaceX will try out a new light-blocking panel to make the spacecraft less visible to skywatchers and astronomers.

“We have a radio-transparent foam that will deploy nearly upon the satellite being released (from the rocket),” Musk said Monday in a virtual meeting of the National Academies’ Decadal Survey on Astronomy and Astrophysics 2020 panel, a committee charged with setting the top priorities for U.S. astronomy for the next decade.

Musk said the new material will block sunlight from reaching the satellites’ antennas, comparing it to a sun visor in a car’s windshield. Reflected sunlight at dawn and dusk is what makes the satellites visible from the ground.

The sunshade is transparent to radio signals. SpaceX has nicknamed the new Starlink satellite design “VisorSat.”

On seven launches since last May, SpaceX has deployed 420 Starlink satellites to begin building out the Starlink network. The satellites are designed to provide global broadband Internet service, and SpaceX eventually plans to launch thousands of the quarter-ton, flat-panel data relay stations to orbits below an altitude of about 354 miles (570 kilometers).

“Using our low orbital altitude and flat satellite geometry to our advantage, we designed an RF-transparent deployable visor for the satellite that blocks the light from reaching most of the satellite body and all of the diffuse parts of the main body,” SpaceX wrote in an update posted on the company’s website this week. “This visor lays flat on the chassis during launch and deploys during satellite separation from Falcon 9. The visor prevents light from reflecting off of the diffuse antennas by blocking the light from reaching the antennas altogether.”

SpaceX says that every future Starlink satellite will be fitted with the sun visor beginning with a subsequent launch in June.

Five Falcon 9 rocket launches so far this year have carried 300 Starlink satellites into orbit — 60 at a time — most recently on April 22. The next Falcon 9 launch for the Starlink network is set for May 7 at approximately 7:30 a.m. EDT (1130 GMT).

The sunshade is the latest change SpaceX has introduced on Starlink satellites in response to complaints from astronomers about the network’s impacts on observations from ground-based telescopes.


This 333-second exposure taken last year by the Dark Energy Camera on the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory shows 19 streaks attributed to Starlink satellites passing through the camera’s field-of-view shortly after their launch Nov. 11 from Cape Canaveral. Credit: NSF’s National Optical-Infrared Astronomy Research Laboratory/NSF/AURA/CTIO/DELVE

The first 60 Starlink satellites launched last May were much brighter than SpaceX or astronomers anticipated, prompting a series of discussions between the aerospace company and the astronomy community.

SpaceX launched a satellite with a darker coating in January, and astronomers noticed an improvement. SpaceX said last month that preliminary data indicated a “notable reduction” in the brightness of that satellite, which has been dubbed “DarkSat.”

“The darkening that they did on DarkSat is about a factor of two-and-a-half fainter — so about 1 magnitude in astronomical units — and it’s still visible to the unaided eye under excellent conditions,” said Pat Seitzer, an astronomer and orbital debris expert at the University of Michigan.. “That is you’re a person with great vision sitting on top of a mountaintop faraway from the city lights.”

But the darker coating has drawbacks, SpaceX said. Black surfaces in space get hot, so the company is moving forward with the sun visor solution instead.

“This avoids thermal issues due to black paint, and is expected to be darker than DarkSat since it will block all light from reaching the white diffuse antennas,” SpaceX said.

The Starlink satellites are brightest soon after a launch, when they are flying at an altitude of around 200 miles (300 kilometers). Once deployed from the Falcon 9 rocket, the spacecraft unfurl their solar array wings to generate electricity, then activate krypton ion thrusters to begin climbing into their higher operational orbit some 341 miles (550 kilometers) above Earth.

SpaceX commands the satellites to fly in a special attitude, or orientation, during the orbit-raising maneuvers. This minimizes drag on the satellites.

“This low-drag and thrusting flight configuration resembles an open book, where the solar array is laid out flat in front of the vehicle,” SpaceX said. “When Starlink satellites are orbit-raising, they roll to a limited extent about the velocity vector for power generation, always keeping the cross sectional area minimized while keeping the antennas facing Earth enough to stay in contact with the ground stations.”


Credit: SpaceX

After the satellites reach their operational orbit, SpaceX flies the spacecraft in a different configuration called the “shark-fin” attitude. In this orientation, the solar panel points away from the Earth.

When the satellites are in the “open book” configuration at lower altitudes, sunlight reflects off the craft’s solar arrays, making them more visible from the ground.

The sun visor is designed to reduce brightness while the Starlink satellites are on station at their operational altitude. SpaceX is debuting a different technique to address brightness concerns during the early weeks of each satellite’s life, when the spacecraft are flying closer to Earth.

“We’re taking several steps to reduce brightness in orbit-raising, which has definitely startled a lot of people around the world,” Musk said Monday. “I’ve gotten quite a lot of feedback on that front. So we’re changing the angles. That should be something that happens even this week — the satellites being commanded to a different angle that is less bright.”

“We’re currently testing rolling the satellite so the vector of the sun is in-plane with the satellite body, i.e. so the satellite is knife-edge to the sun,” SpaceX said. “This would reduce the light reflected onto Earth by reducing the surface area that receives light.”

The new roll maneuver can be implemented when the satellites are climbing to higher altitude, and when they pause in an intermediate orbit to align with their operational planes within the Starlink network.

SpaceX said the new “orientation roll” maneuver will diminish the amount of power generated by each satellite’s solar panel, and reduce contact time between the spacecraft and ground controllers. The change also points star tracker cameras at the Earth and the sun, reducing the satellite’s attitude knowledge, according to SpaceX.

“There will be a small percentage of instances when the satellites cannot roll all the way to true knife edge to the sun due to one of the aforementioned constraints,” SpaceX said. “This could result in the occasional set of Starlink satellites in the orbit raise of flight that are temporarily visible for one part of an orbit.”

Musk described the changes as “quite simple.”

“I think, with the benefit of hindsight, the changes seem quite simple, which is to make sure that the orientation of the satellites is not such that we’re reflecting the sun,” he said. “And to either darken the specular surfaces or the white surfaces, or shade them, is really quite simple actually. It’s a little bit silly in hindsight. It’s not that hard.

“Our objectives, generally, are to make the satellites invisible to the naked eye within a week, and to minimize the impact on astronomy, especially so that we do not saturate observatory detectors and inhibit discoveries,” Musk said.


Credit: SpaceX

The satellites that launched without the brightness mitigations will likely be retired and will re-enter the atmosphere and burn up within three or four years, Musk said. They will be replaced with improved satellites.

SpaceX has regulatory approval from the Federal Communications Commission to eventually field a fleet of up to 12,000 small Starlink broadband stations.

Officials say 24 launches are needed to provide global broadband service through the Starlink service. But the company could provide an interim level of service over parts of the Earth — such as Canada and northern parts of the United States — later this year, once SpaceX has launched around 720 satellites on 12 Falcon 9 flights.

Musk tweeted last week that SpaceX aims to begin private “beta testing” of the Starlink service within about three months, followed by a public trial period in six months.

SpaceX has modified the architecture of the Starlink network several times. Most recently, SpaceX submitted an application to the Federal Communication Commission on Friday proposing to operate more satellites in lower orbits than the FCC previously authorized.

Rather than launching more than 2,800 of the Starlink satellites to higher orbits between 690 miles (1,110 kilometers) and 823 miles (1,325 kilometers) in altitude, SpaceX will instead deploy the spacecraft closer to Earth. The change allows the network to provide consumers with better Internet service, and also reduces the number of Starlink satellites that might be visible in the sky at any one time.

“We think, for a lot of reasons, that 550 (kilometers) and below is the right approach for a LEO (Low Earth Orbit) broadband situation,” Musk said. “Your data rate is going to be four times better than say at 1,100 kilometers. That’s a close approximation. It’s also better for astronomy.”

The lower orbit also ensures atmospheric drag will cause dead satellites to re-enter the atmosphere more quickly, SpaceX said.


This diagram illustrates when the Starlink satellites are most visible, shortly after sunset and shortly before sunrise. Credit: SpaceX

Musk said 20,000 to 30,000 Starlink satellites may be needed to provide the level of Internet service envisioned by SpaceX, which aims to provide connectivity to the “3 or 4 percent of the least-served portion of the Earth.”

“So it’s not a huge percentage, but it’s for those that have the least service,” Musk said Monday. “You do want to have probably on the order of 20,000 to 30,000 satellites, something like that. But not 200,000, I don’t think.”

SpaceX has filed documentation with the International Telecommunication Union for up to 30,000 additional Starlink satellites beyond the 12,000 spacecraft already authorized by the FCC.

It’s the large number of Internet satellites planned by SpaceX and other companies, such as Amazon, that worries astronomers.

“SpaceX is committed to the progress of science, both in the United States and elsewhere,” Musk said. “So we’ll do our best to ensure that we’re not going to interfere with any facilities anywhere in the world.”

One of the ground-based facilities most at risk of interference from the Starlink satellites is the U.S. government-funded Vera Rubin Observatory, formerly known as the Large Synoptic Survey Telescope. The observatory under construction in Chile will capture deep, wide-field images of the entire southern sky, allowing astronomers to learn more about dark energy and dark matter, and detect potentially hazardous asteroids with orbits near Earth, among other objectives.

Steve Kahn, director of the Vera Rubin Observatory, said last week that SpaceX is responsive to astronomers’ concerns.

“They’ve been quite cooperative in working with us,” Kahn told Spaceflight Now in an interview.

Scientists will measure the brightness of the new VisorSat spacecraft after launch to gauge the effectiveness of the sunshade. If it works as advertised, the sun visor could limit the impacts of the Starlink satellites on the Vera Rubin Observatory.

Musk pitches astronomers on Starship’s ability to launch giant space telescopes

Toward the end of Monday’s virtual meeting, Musk expressed interest in building and launching a new space-based observatory using SpaceX’s next-generation Starship launch vehicle.

“I’d be pretty interested in trying to figure out how to help launch and possibly build a big satellite, a big observatory in space,” Musk said. “Maybe … we can get together and talk about what would be a really exciting space observatory, like a planet imager or something like that.”

The decadal survey panel was chartered to prioritize which space-based observatories NASA should pursue after the launch of the James Webb Space Telescope and the Wide Field Infrared Survey Telescope.

“I’m really interested in the advancement of science, and to understand what the heck is going on in this universe,” Musk said.

SpaceX says from the Starlink Internet business will help fund development of the Starship. When coupled with a new first stage booster SpaceX calls the Super Heavy, the Starship will be able to loft more than 100 metric tons, or 220,000 pounds, of cargo to low Earth orbit.

“Starship has the capability to transport satellites, payloads, crew, and cargo to a variety of orbits and Earth, lunar, or Martian landing sites,” SpaceX wrote in a Starship user’s guide released last month.

The Starship’s payload envelope is also significantly larger than any other existing rocket. Its diameter will measure around 30 feet, or 9 meters, allowing the Starship to launch big telescopes without requiring the mirrors be folded to fit inside a payload fairing.

“The launch situation has changed quite dramatically from where it was in 2010,” Musk said. “It will be very much changed, I think, in even five years. I think Starship … will be flying quite soon. I think you’ll see regular flights within a couple of years, and that’s a very big rocket.

“It allows for space telescopes to be at least transported to orbit at probably an order of magnitude lower cost than in the past,” Musk said. “So that’s pretty important to factor into future plans.”

Source: https://spaceflightnow.com/2020/04/28/spacex-to-debut-satellite-dimming-sunshade-on-starlink-launch-next-month/

[Orionid]

SpaceX launches eighth Starlink mission, first VisorSat satellite
by Caleb Henry — June 3, 2020 [SN]


SpaceX launched its eighth batch of 60 Starlink satellites June 3.

WASHINGTON — SpaceX launched a batch of 60 Starlink broadband satellites June 3, including one with a deployable sunshield meant to test out a new way to reduce the brightness of future satellites.

The Falcon 9 rocket lifted off at 9:25 p.m. Eastern from Cape Canaveral Air Force Station in Florida, and deployed the satellites into low Earth orbit 15 minutes later.

The rocket’s first stage landed on SpaceX’s drone ship “Just Read the Instructions” about nine minutes after lift off. The launch marked the fifth use of that booster, which previously flew one mission to geostationary transfer orbit and three missions to low Earth orbit, the latest being in January, also for Starlink. The launch was also the first time SpaceX successfully recovered a first-stage booster after five flights.

SpaceX has launched 482 Starlink satellites, counting Wednesday’s launch and two prototypes launched in 2018. The company had planned its latest Starlink mission for May, but was delayed by Tropical Storm Arthur until after the company’s Demo-2 Crew Dragon mission to the International Space Station, which took place May 30.

May was the first month this year SpaceX did not conduct a Starlink launch. The company had averaged one Starlink launch a month before the delay. SpaceX was originally targeting two Starlink launches a month throughout 2020.

SpaceX is building and launching a constellation of up to 12,000, and potentially 42,000 satellites in low Earth orbit to support a global satellite internet service. The company expects to start service late this year in Canada and parts of the United States.

SpaceX plans to add deployable visors to all future Starlink satellites after launching around 500 with their current design, Patricia Cooper, SpaceX’s vice president of satellite government relations, said during a webinar last week.

“We would have about 500 satellites at their current brightness, and then all satellites beyond that would have these sunshades,” Cooper said during a webinar hosted by the American Astronomical Society and the Satellite Industry Association. “That is the ratio we would be looking at.”

SpaceX is seeking to lessen the brightness of Starlink satellites to reduce their impact on astronomy.

Source: https://spacenews.com/spacex-launches-eighth-starlink-mission-first-visorsat-satellite/

[Orionid]

SpaceX sets new mark in rocket reuse 10 years after first Falcon 9 launch
June 4, 2020 Stephen Clark [SFN]


A SpaceX Falcon 9 rocket lifts off at 9:25 p.m. EDT Wednesday (0125 GMT Thursday) from pad 40 at Cape Canaveral Air Force Station with 60 more Starlink Internet satellites. Credit: Stephen Clark / Spaceflight Now

On the eve of the 10th anniversary of the Falcon 9 rocket’s debut flight, SpaceX launched a Falcon 9 from Cape Canaveral with a reused booster Wednesday, then landed the previously-flown booster for a record fifth time after sending 60 more Starlink Internet satellites into space.

The 229-foot-tall (70-meter) Falcon 9 rocket lifted off from pad 40 at Cape Canaveral Air Force Station at 9:25 p.m. EDT Wednesday (0125 GMT Thursday).

Nine Merlin 1D engines lit the sky orange as the Falcon 9 rocket climbed into an overcast sky over Florida’s Space Coast with 1.7 million pounds of ground-shaking thrust. Two-and-a-half minutes later, the first stage turned off its engines and dropped away to head for a pinpoint touchdown on SpaceX’s offshore landing platform, or drone ship.

The rocket’s upper stage fired into orbit with the 60 Starlink satellites, and then released all of the flat-panel spacecraft at one time around 15 minutes after liftoff in a preliminary elliptical orbit. The satellites were expected to deploy their solar arrays and spread out before beginning orbit-raising maneuvers to enter SpaceX’s Starlink constellation around 341 miles (550 kilometers) above Earth.

The launch Wednesday came a little more than four days after SpaceX’s previous launch from the Florida spaceport.

A different Falcon 9 rocket took off Saturday from pad 39A at the Kennedy Space Center — a few miles north of pad 40 — with SpaceX’s Crew Dragon spacecraft carrying NASA astronauts Doug Hurley and Bob Behnken to the International Space Station. The launch Saturday was the first time astronauts flew into orbit from U.S. soil since the final liftoff of the space shuttle program July 8, 2011.

Hurley and Behnken docked with the space station aboard their Crew Dragon capsule Sunday, and the Falcon 9 booster that carried them aloft returned to Port Canaveral Tuesday after landing on SpaceX’s ocean-going rocket recovery vessel named “Of Course I Still Love You.”

SpaceX’s other rocket retrieval drone ship, named “Just Read the Instructions,” was dispatched into the Atlantic Ocean before the other landing platform made it back to the Florida Coast with the booster from the Crew Dragon launch.

The drone ship Just Read the Instructions, or JRTI, was used for a rocket landing off Florida’s coast for the first time Wednesday night, following a transit from California after supporting a series of Falcon 9 missions from Vandenberg Air Force Base, the primary launch site on the U.S. West Coast.

After detaching from the Falcon 9’s upper stage and the rocket’s payload stack of 60 Starlink spacecraft, the 15-story-tall first stage booster maneuvered using thrusters to fly tail first, extended four stabilizing aerodynamic grid fins, and plunged back into the thick, lower atmosphere.

An entry burn using three of the first stage’s Merlin engines helped target the booster for landing on the drone ship, positioned in the Atlantic Ocean roughly 230 miles (370 kilometers) east of Charleston, South Carolina. The rocket’s center engine fired just before reaching the vessel, and four carbon fiber landing legs extended as the booster touched down on the drone ship.

With the entry into service of a second drone ship in Florida, SpaceX can remove one hurdle to achieving a faster cadence of missions from its two launch pads on the Space Coast.

Spaceflight Now@SpaceflightNow
The Falcon 9 rocket's first stage used on tonight’s launch has landed on SpaceX’s drone ship “Just Read the Instructions” in the Atlantic Ocean. https://spaceflightnow.com/2020/06/03/falcon-9-starlink-7-mission-status-center/
3:37 AM · Jun 4, 2020 Twitter

This marks the first time a Falcon 9 booster has successfully launched and landed five times

Wednesday night’s launch of 60 more Starlink satellites was delayed from last month after Tropical Storm Arthur brought high winds and rough seas to the downrange recovery area northeast of Cape Canaveral in the Atlantic Ocean, where SpaceX’s drone ship needed to be positioned for landing of the Falcon 9’s first stage booster.

SpaceX decided to use the drone ship Of Course I Still Love You — originally deployed into the Atlantic for the Starlink launch — to recover the Falcon 9 first stage from the Crew Dragon mission.

With a single operational drone ship, SpaceX would require more than a week between Falcon 9 flights from different pads at Cape Canaveral, and still be able to retrieve both boosters for future flights. With two drone ships, SpaceX has demonstrated the capability to launch two Falcon 9 rockets from Florida and recover both boosters in a span of four days.

Two additional SpaceX vessels were in the Atlantic Ocean for Wednesday night’s launch to attempt to catch the two halves of the Falcon 9 rocket’s payload fairing, the aerodynamic shroud the shields satellites during the first few minutes of flight. Once in space, the Falcon 9 sheds the fairing halves to fall back to Earth with the aid of parafoils.

SpaceX has two ships equipped with giant nets to try to catch the fairings as they come back to Earth.

The booster and fairing recovery efforts pursued by SpaceX are unique the launch industry, and SpaceX made it a reality after a series of trial-and-error experiments and step-by-step redesigns of the Falcon 9 rocket.

SpaceX launched its first Falcon 9 rocket on a test flight 10 years ago Thursday from pad 40, the same launch complex that served as the departure point for Wednesday night’s mission.

Spaceflight Now covered the first Falcon 9 launch in 2010. Read our story from that day.


SpaceX’s first Falcon 9 rocket took off from pad 40 at Cape Canaveral Air Force Station on June 4, 2010, carrying a mock-up of the company’s Dragon cargo capsule. Credit: SpaceX

The launch Wednesday night marked the 86th flight of a Falcon 9 rocket since its debut in June 2010, and the ninth Falcon 9 launch so far in 2020.

While the Falcon 9 still uses the same fundamental launch architecture as the first version of the rocket in 2010, SpaceX has revamped numerous technological details. For example, the Falcon 9’s Merlin engines have gone through multiple upgrades to produce more thrust, and SpaceX stretched the length of the rocket’s kerosene and liquid oxygen propellant tanks to gain performance.

When those upgrades proved not enough, SpaceX began loading liquid propellants into the Falcon 9 that are chilled closer to their freezing temperature. The change, known as propellant densification, allowed engineers to cram more propellants into the Falcon 9 to further improve its lift capacity.

There have also been changes to make the Falcon 9 reliable enough to carry astronauts, as the rocket did for the first time Saturday. And SpaceX has redesigned parts of the rocket’s helium pressurization system to address the causes of two catastrophic failures — one in flight in 2015 and another on the launch pad in 2016 — that destroyed a pair of Falcon 9 rockets and their payloads.

But the most dramatic change to the Falcon 9’s design since 2010 has been in how SpaceX lands and reuses the first stage boosters.

SpaceX originally hoped to use a parachute to slow down returning rocket boosters for a gentle splashdown at sea. When that didn’t work, engineers devised a way to land the rocket vertically using variable thrust from the booster’s throttleable Merlin engines.

In some cases, when a satellite payload is light enough, the Falcon 9 first stage carries enough reserve propellant to reverse course and return to an onshore landing pad near the launch site. In cases where a payload is heavier, or if a satellite needs more energy from the Falcon 9 to go to a more distant orbit, the Falcon 9 booster arcs toward a landing on a downrange drone ship after releasing the rocket’s upper stage to continue the push into space.

Avoiding a splashdown in the ocean ensures sensitive engine components are not exposed to corrosive salt water, easing refurbishment and reuse.

SpaceX installed landing lets, aerodynamic fins and a heat shield on Falcon 9 boosters to make the recovery experiments a success. The company first recovered a Falcon 9 first stage intact on a land-based pad in December 2015, then successfully landed on a drone ship at sea for the first time in April 2016.

With Wednesday night’s booster landing, SpaceX has recovered 53 Falcon rockets, including boosters used on the company’s triple-body Falcon Heavy launcher.

The achievements have allowed SpaceX to reduce its launch costs — in some cases below $50 million — and caused rival launch providers to change plans, cut prices, and develop new rockets to try to compete with the Falcon 9.

SpaceX has won commercial business that previously went to international launch companies, and the company is now certified to launch NASA astronauts and sensitive U.S. military satellites.

Although SpaceX’s relatively low launch prices compared to competitors has lured customers from around the world, the bulk of the Falcon 9 flights in recent months have been dedicated to the company’s own satellite constellation.

The Starlink fleet could eventually number tens of thousands of satellites to beam broadband Internet services to customers lacking reliable, high-speed connectivity via terrestrial networks. Designed for low-latency broadband links, the Starlink network could be used by rural customers, support schools, hospitals and businesses in developing countries, and provide service to the U.S. military.

Spaceflight Now@SpaceflightNow
Starlink deployment confirmed! This video from aboard the Falcon 9 upper stage shows the release of retention rods holding the Starlink broadband satellites on the rocket.
https://spaceflightnow.com/2020/06/03/falcon-9-starlink-7-mission-status-center/
3:45 AM · Jun 4, 2020 Twitter

That allowed the 60 flat-panel satellites to fly free of the launcher in orbit.

With Wednesday’s flight, SpaceX has launched 480 Starlink satellites on eight dedicated Falcon 9 missions since May 2010.

SpaceX aims to launch around 1,000 more Starlink satellites later this year and next year to begin offering worldwide Internet service. Initial beta testing of the Starlink network could begin later this year, beginning in higher latitude regions like Canada and the northern United States, the company says.

Thousands more Starlink spacecraft could launch in the coming years to meet global demand, according to SpaceX.

A new sunshade to reduce the brightness of the Starlink satellites was also due to be demonstrated on one of the spacecraft on Wednesday night’s launch. The umbrella-like visor will block sunlight from reaching the shiniest parts of the flat-panel spacecraft, making them less visible from the ground.

Scientists have raised concerns that thousands of Starlink satellites — as envisioned by SpaceX — could impact astronomical observations through ground-based telescopes. So far, SpaceX has answered with an experimental darkening treatment that offered some reduction in visibility, and the company says it is changing the orientation of the Starlink satellites during the period shortly after launch to turn their solar panels away from the sun.

The sunshade should provide a more significant dimming effect, SpaceX says.

With Wednesday night’s mission in the books, SpaceX plans two more Falcon 9 launches later this month from pad 40 and pad 39A to deliver more Starlink satellites into orbit from Cape Canaveral. SpaceX is also gearing up for the launch of a U.S. military GPS navigation satellite from pad 40 no earlier than June 30.

Source: https://spaceflightnow.com/2020/06/04/spacex-sets-new-mark-in-rocket-reuse-10-years-after-first-falcon-9-launch/

[Orionid]

SpaceX to add sunshades to all future Starlink satellites
by Caleb Henry — May 27, 2020 [SN]


SpaceX's VisorSat will use sunshades modeled on sun visors in a car windshield to keep sunlight from reflecting off the satellite's antennas, reducing its brightness as seen from the ground. Credit: SpaceX

WASHINGTON — SpaceX has decided to add sunshades to future Starlink satellites to reduce their impact on astronomy, having opted for constellation-wide implementation of the reflective hardware.

Patricia Cooper, SpaceX’s vice president of satellite government relations, said May 26 that SpaceX has another 80 or so Starlink satellites it is preparing to launch based on their current design before regularly incorporating sunshades that block sunlight from hitting reflective parts of each satellite.

“We would have about 500 satellites at their current brightness, and then all satellites beyond that would have these sunshades,” Cooper said during a webinar hosted by the American Astronomical Society and the Satellite Industry Association. “That is the ratio we would be looking at.”

SpaceX has launched 422 Starlink satellites, including two prototypes, since 2018. The company is building and launching an initial constellation of roughly 4,400 satellites, though regulatory filings indicate the company could grow Starlink to 12,000 or even 42,000 satellites.

SpaceX’s first visor-equipped satellite, dubbed VisorSat, was expected to launch May 17, but was delayed because of Tropical Storm Arthur until after the company’s highly anticipated Crew Demo 2 mission, scheduled for May 27 at 4:33 p.m. Eastern. Cooper said SpaceX has yet to announce a date for its next Starlink mission.

SpaceX typically launches Starlink satellites in batches of 60 on Falcon 9 rockets, a rate that would suggest one or two more launches would occur without Starlink satellites routinely equipped with sunshades. Cooper said SpaceX will likely retire early Starlink satellites more quickly to reduce their impact on astronomy.

“The earlier version of our satellites that we’ve launched, we don’t expect them to have a complete five-year life span,” she said. “We are expecting to cut in the VisorSat mitigation at the point that we are launching still in the 500s of satellites.”

Tony Tyson, chief scientist for the Vera Rubin Observatory, said Starlink satellites need to be dimmed to an apparent magnitude of seven so that astronomers can work around them using image processing. Recent observations show Starlink satellites at around magnitude five. DarkSat, a Starlink satellite treated with an experimental darkening coating, was observed at roughly magnitude six, he said.

“Progress is being made, [but] we still have to get to seventh magnitude somehow,” Tyson said. SpaceX is working with astronomers on reducing the impact of Starlink, he said.

Cooper, when asked if SpaceX had the same goal of lowering Starlink’s brightness to magnitude seven, said it is an “interesting threshold,” but did not commit to meeting that target.

Source: https://spacenews.com/spacex-to-add-sunshades-to-all-future-starlink-satellites/

[Orionid]

Army’s evaluation of Starlink broadband to focus on reliability, vulnerability
by Sandra Erwin — May 27, 2020 [SN]


The Army is interested in commercial LEO broadband to supplement existing satcom and terrestrial systems. Credit: U.S. Army

Gen. Murray: “It’s about figuring out what capabilities they can provide, and what vulnerabilities do they have?"

WASHINGTON — The upcoming evaluation of SpaceX’s Starlink broadband by the U.S. Army will look primarily at the reliability of the service and potential vulnerabilities of the satellites to hostile attacks, a senior Army official said May 27.

The Army on May 20 signed a three-year agreement with SpaceX to experiment using Starlink broadband to move data across military networks.

“I would view this as exploratory,” Gen. John Murray, commander of the U.S. Army Futures Command, told reporters on Wednesday on a Defense Writers Group conference call.

“It’s about figuring out what capabilities they can provide, and what vulnerabilities do they have?” said Murray.

The Army Futures Command advises Army leaders on what investments the service should make to modernize weapons and information systems. One of the priorities identified by Futures Command is high capacity, low latency communications for units in the field that need to move large amounts of data.

A space internet service from low Earth orbit like Starlink would be used by the Army to supplement geosynchronous satellite-based and terrestrial communications.

Murray said the Army has signed exploratory agreements with SpaceX and other companies to make sure the product works before it buys it. The Army wants to try it “before we lock ourselves into a multibillion dollar acquisition program,” he said.

“Yes, we are interested in commercial broadband capability from space, and from low Earth orbit,” said Murray. “But I would be lying to you if I said there were absolutely zero concerns.”

Making sure the service is reliable is one concern, he said. Security is another. The Army will want to assess the cyber security of the data moving through the network and also will examine the risks that an adversary could target low altitude satellites with weapons from the ground.

Source: https://spacenews.com/armys-evaluation-of-starlink-broadband-to-focus-on-reliability-vulnerability/