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Falcon 9 launches Sentinel-6 Michael Freilich ocean science satellite
by Jeff Foust — November 21, 2020

Sentinel-6 Michael Freilich, launched Nov. 21, is the latest in a series of satellites going back nearly three decades to track rising sea levels. Credit: NASA

WASHINGTON — A SpaceX Falcon 9 successfully launched Nov. 21 the latest in a series of satellites developed by the United States and Europe to track rising sea levels.

The Falcon 9 lifted off from Space Launch Complex (SLC) 4 East at Vandenberg Air Force Base in California at 12:17 p.m. Eastern. Its payload, the Sentinel-6 Michael Freilich satellite, separated from the rocket’s upper stage nearly an hour later, after a brief second burn of the upper stage. The rocket’s first stage landed on a pad back at SLC-4.

Sentinel-6 Michael Freilich is the first of two satellites jointly developed by a group of agencies in the United States and Europe, including NASA, NOAA, the European Space Agency, Eumetsat and the European Commission, to provide precise measurements of rising sea levels.

The spacecraft will ensure a continuity of measurements dating back nearly three decades, starting with the TOPEX/Poseidon satellite launched in 1992 and followed by the three Jason spacecraft launched in 2001, 2008 and 2016. Those earlier spacecraft were joint projects of NASA, NOAA, Eumetsat and the French space agency CNES, while Sentinel-6 Michael Freilich is considered part of the Copernicus program of Earth observation satellites by ESA and the EU.

“It’s the first time that ESA and NASA have really collaborated in such an integrated way on an Earth observation satellite,” said Pierrik Vuilleumier, Sentinel-6 project manager at ESA, during a Nov. 20 pre-launch briefing. NASA and ESA are each spending about half a billion dollars on the total program, which includes a second Sentinel-6 satellite that will launch in the middle of the decade.

The spacecraft itself, weighing 1,192 kilograms at launch, was built by Airbus Defence and Space in Germany. It has a distinctive appearance with two body-mounted solar panels that look like the roof of a house. That design is intended to maximize the power they can provide without requiring the use of deployable arrays and motors than can induce vibrations in the spacecraft.

The spacecraft’s main instrument is a radar altimeter provided by ESA, which bounces radio pulses off the ocean to measure sea level as well as wave height and ocean speed. It is supported by a microwave radiometer developed at NASA’s Jet Propulsion Laboratory, which measures water vapor in the atmosphere to providing timing corrections for the radar altimeter.

Also on Sentinel-6 Michael Freilich is a global navigation satellite system radio occultation (GNSS-RO) instrument to provide measurements of the atmospheric temperature and moisture by measuring signals from GPS and other navigation satellites. That instrument is similar to those on the six COSMIC-2 satellites launched in June 2019. In addition to measuring atmospheric conditions, data from the GNSS-RO instrument will be used with that from three other sensors to precisely measure the spacecraft’s orbit, at an altitude of 1,336 kilometers and an inclination of 66 degrees.

Sentinel-6 Michael Freilich will operate in the same orbit as Jason-3, with the two satellites about 30 seconds apart. That will assist in the commissioning of the new spacecraft, a process that will take about a year, said Remko Scharroo, project scientist for the mission at Eumetsat. “They will basically see the same ocean conditions, and that, of course, makes comparing the measurements much better,” he said at a pre-launch briefing.

While the spacecraft features improved resolution and precision compared to its predecessors, scientists emphasized the importance of continuing a series of measurements of sea level height dating back nearly three decades. Sentinel-6 Michael Freilich “will continue our record of sea surface height observations well into the next decade,” said Karen St. Germain, director of NASA’s Earth science division.

“It’s a critical observation for a number of reasons, but its power is really unleashed when we combine our altimetry observations of the sea surface height measurements with the observations we get from the other satellites in the NASA fleet and the international fleet,” she continued. “We can see not only that the sea level is rising but we can also tell how much of that change is coming from melting ice sheets and glaciers, and how much of that change is coming from thermal expansion of the oceans themselves.”

That satellite data has shown that sea levels are not only rising, but also that the rate of increase is accelerating. Sea levels were rising at the rate of about two millimeters per year in the 1990s, said Josh Willis, project scientist for the mission at JPL, but are now increasing at four to five millimeters per year. “We’re watching the rate of sea-level rise increase right before our very eyes, and it’s satellites like this that allow us to do it,” he said.

“We cannot ignore that our planet is changing,” said Pierre Delsaux, deputy director general for space for the European Commission, at a briefing about the mission in October. “The climate is changing. Nobody can deny it. From that point of view, we need to understand why the climate is changing, what are the factors, and we need to monitor the situation.”

NASA and ESA named the spacecraft after Michael Freilich, a former director of NASA’s Earth science division, during a ceremony early this year. Freilich, who retired from NASA in 2019 after leading NASA’s Earth science programs for more than a decade, died of cancer in August.

“This partnership is very much aligned with what Mike Freilich’s passion has been,” said Thomas Zurbuchen, NASA associate administrator for science, at the pre-launch briefing, noting Freilich’s research in ocean sciences before taking the NASA position. “I want to tell you how honored I feel, and how it still moves me today, that the name of Michael Freilich is, in fact, on this spacecraft.”

“It’s an extra special day when we will see this satellite launch, the satellite that he worked so hard to put in place,” said St. Germain.


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International satellite launches to extend measurements of sea level rise
November 21, 2020 Stephen Clark [SFN]

A Falcon 9 rocket lifts off from Vandenberg Air Force Base with the Sentinel-6 Michael Freilich oceanography satellite. Credit: SpaceX

A European-built satellite with the unusual shape of a house launched into orbit Saturday aboard a SpaceX Falcon 9 rocket from California’s Central Coast, carrying a sophisticated radar altimeter to measure rising sea levels on our home planet.

The Sentinel-6 Michael Freilich observation satellite lifted off at 9:17:08 a.m. PST (12:17:08 p.m. EST; 1717:08 GMT) Saturday from Space Launch Complex 4-East at Vandenberg Air Force Base around 140 miles (225 kilometers) northwest of Los Angeles.

Flying toward the south-southeast, the 229-foot-tall (70-meter) Falcon 9 rocket hauled the satellite into orbit on SpaceX’s first mission from the West Coast launch site since June 2019.

Less than two-and-a-half minutes into the flight, the Falcon 9’s first stage booster detached and fired cold gas thrusters to flip around and fly tail first. A boost-back burn and entry burn by a subset of the rocket’s Merlin engines guided the Falcon 9 booster back toward Vandenberg.

The supersonic return maneuvers culminated in a landing burn by the rocket’s center engine. Four landing legs unfurled just before touchdown as the 15-story booster settled to a bullseye landing at SpaceX’s rocket recovery facility at Vandenberg Air Force Base about eight-and-a-half minutes after liftoff.

The successful landing marked the third time SpaceX has returned a Falcon 9 booster to the onshore landing site at Vandenberg, and the 66th recovery of a Falcon booster overall.

Here’s a replay of the Falcon 9 rocket’s launch from SLC-4E at Vandenberg Air Force Base, California, with the Sentinel-6 Michael Freilich oceanography satellite.
Continuing coverage:
— Spaceflight Now (@SpaceflightNow) November 21, 2020

The rocket’s upper stage continued firing its single Merlin to reach a parking orbit around Earth, then reignited the engine for about 10 seconds to circularize its orbit before separation of the Sentinel-6 Michael Freilich satellite around 58 minutes after launch.

Live video from the Falcon 9’s upper stage showed the 2,628-pound (1,192-kilogram) spacecraft flying free of the rocket over the Indian Ocean.

The Sentinel-6 Michael Freilich satellite was built by Airbus in Germany and is the size of a small pickup truck. Sentinel-6 Michael Freilich carries a radar altimeter, a microwave radiometer, and instruments to precisely locate the satellite in orbit. Working together, the instruments will track changes in sea level down to a few centimeters.

The mission is a partnership between NASA, the European Space Agency, Eumetsat, and NOAA. The European Commission — the EU’s executive arm — and the French space agency CNES also provided support to the mission.

The Sentinel-6 Michael Freilich satellite is named for the former head of NASA’s Earth science division, who died of cancer earlier this year.

“Congratulations to everyone that made today’s launch of the Sentinel-6 Michael Freilich satellite possible!” NASA Administrator Jim Bridenstine tweeted. “A fitting tribute to an incredible trailblazer in Earth science.”

Ground teams at the European Space Operations Center in Germany received the first signals from the new oceanography satellite about an hour-and-a-half after liftoff, while the spacecraft sailed over a ground station in Alaska. Controllers confirmed the satellite extended its power-generating solar panels, and the spacecraft appeared to be in good shape in a first-look health assessment.

Initial data showed the Falcon 9 rocket placed the satellite into an orbit very close to the mission’s target altitude of 830 miles (1,336 kilometers). The launcher aimed to inject the spacecraft in an orbit inclined about 66 degrees to the equator, the same orbital plane where a predecessor oceanography satellite named Jason 3 flies.

Falcon 9 has landed! The brand new booster that launched the Sentinel-6 Michael Freilich oceanography satellite has returned to a bullseye landing on California’s Central Coast.
This marks the third landing of a Falcon 9 booster at Vandenberg.
— Spaceflight Now (@SpaceflightNow) November 21, 2020

Rising sea levels are one consequence of climate change. Data from previous satellites show the rate of sea level rise is accelerating, according to mission scientists.

Sentinel-6 Michael Freilich is the next in a series of oceanography missions tracking sea level rise, beginning with the U.S.-French Topex/Poseidon mission that launched in 1992. The Jason 1, Jason 2, and Jason 3 satellites followed Topex/Poseidon, and an identical satellite to Sentinel-6 Michael Freilich named Sentinel-6B is planned for launch in 2025 to further extend the data record of sea level rise.

The Topex/Poseidon and Jason satellites have charted about 3.5 inches (9 centimeters) of global sea level rise over the last 30 years, said Remko Scharroo, Sentinel-6 project scientist at Eumetsat.

The cost of the two Sentinel-6 missions is roughly $1 billion, and was evenly divided between the U.S. and European partner agencies, according to Thomas Zurbuchen, head of NASA’s science mission directorate.

“It’s the satellite so nice we built it twice,” said Josh Willis, Sentinel-6 project scientist at NASA’s Jet Propulsion Laboratory.

“The record of global sea level rise actually goes back to the early ’90s,” Willis said. “What’s interesting about it is that you can see the rate of rise is actually increasing. In the ’90s, sea level was rising at about 2 millimeters per year. In the 2000s, it was more like 3 millimeters per year, and now it’s more like 4 or close to 5 millimeters per year. So we’re watching the rate of sea level rise increase right before our very eyes, and it’s satellites like this that allow us to do it.”

Artist’s concept of the Sentinel-6 Michael Freilich satellite. Credit: ESA/ATG medialab

Craig Donlon, Sentinel-6 mission scientist at ESA, said rising sea levels “threaten major cities with increased flooding, including New York, London, Amsterdam, Tokyo, and more. It’s estimated that about 2 to 3 million more people are exposed for every 1 millimeter rise in sea level.”

Sentinel-6 Michael Freilich is the eighth satellite to launch for the European Copernicus constellation, a fleet of orbiting sentinels observing Earth’s land surfaces, oceans, ice sheets, and atmosphere with radar, optical, microwave, altimetry, and spectral instruments. The European Commission manages the Copernicus program, with ESA providing technical expertise and coordinating development of the Sentinel satellites.

A primary goal of the Copernicus satellites is to collect data on Earth’s changing climate. The fleet is the most capable satellite program focused on Earth observation. Data from the Sentinel satellites are distributed worldwide free of charge.

“We see evidence of this dramatic change in many different measurements and events around the world, but they all point in the same direction — the Earth is warming,” Donlon said in a pre-launch news conference. “And the greatest indicator of this Earth system imbalance is sea level rise. That’s because it integrates the total impact of global warming. That’s dominated by the ice sheets melting, the thermal expansion of the sea water, and changes in terrestrial water storage.”

The Sentinel-6 Michael Freilich spacecraft carries a European dual-frequency Poseidon 4 radar altimeter that transmits signals toward the ocean surface more than 800 miles below the satellite. A receiver measures the time it takes for the signal to bounce off the ocean and return to the satellite.

A microwave radiometer provided by NASA measures atmospheric properties that can introduce minuscule effects on the travel time of the radar altimeter signal, allowing scientists to correct for the perturbations and obtain a more precise measurement of sea level.

Sentinel-6 Michael Freilich also carries instruments to help determine its exact location using GPS navigation signals, Doppler measurements, and laser tracking.

This chart illustrates the sea level rise observed by satellites since the early 1990s. Credit: NASA

The satellite will also measure wave height and derive wind speed estimates by observing the roughness of the ocean surface. It will cover about 95 percent of the world’s oceans every 10 days.

The unusual house-like shape of the spacecraft itself is also an important factor in its performance. Engineers designed it for simplicity, and its lack of articulating solar array wings and other structures “makes for a very stable satellite design, which is really important for a satellite altimeter mission,” Donlon said.

Sentinel-6 Michael Freilich will take its measurements with higher resolution than earlier satellites looking at sea level rise. That means the new satellite will be able to better see how rising sea levels are impacting coastlines.

Eumetsat will take over regular operations of Sentinel-6 Michael Freilich for its planned five-and-a-half year mission after it completes a three-day activation timeline.

Ground teams will maneuver Sentinel-6 Michael Freilich into position flying about 140 miles, or 230 kilometers, behind the Jason 3 satellite — which launched in 2016 — for about a year’s worth of cross-calibration to ensure the new spacecraft provides the same reliable data as its predecessor.

Sentinel-6B will replace Sentinel-6 Michael Freilich after it launches in 2025, extending the sea level rise data record through at least 2030.

SpaceX tentatively plans to reuse first stage that flew with the Sentinel-6 Michael Freilich mission Saturday on the company’s next launch of a NASA spacecraft from Vandenberg next July, NASA launch director Tim Dunn said in a recent interview with Spaceflight Now.

On that flight, a Falcon 9 rocket will launch NASA’s Double Asteroid Redirection Test, or DART, mission from Vandenberg. It will mark the first time a NASA science mission has launched on a previously-flown Falcon 9 booster.

DART is scheduled for launch in a window opening July 2021, allowing the probe to reach its asteroid target in late 2022. DART will intentionally crash into a tiny moonlet orbiting asteroid Didymos to test out deflection techniques that scientists could use to move an asteroid off a collision course with Earth.

Dunn said NASA’s Launch Services Program, which manages launch procurement and preparations for NASA science missions, has approved the rocket reuse plan for the DART mission, pending post-flight inspections and refurbishment on the booster after the Sentinel-6 Michael Freilich mission.

NASA has already approved launches of SpaceX’s Dragon space station cargo ships on previously-flown Falcon 9 boosters, and the agency earlier this year agreed to launch Crew Dragon astronaut missions on reused rockets beginning with the next SpaceX crew flight in March 2021.

One caveat to the booster’s future is its possible use as a backup for the SpaceX Crew-2 mission in March. Kathy Lueders, head of NASA’s human spaceflight directorate, said last week that the Falcon 9 first stage from the Sentinel-6 Michael Freilich mission could be a backup for the Crew-2 launch if problems arise with the primary rocket assigned to astronaut mission.

NASA and SpaceX have agreed to use the same booster for the Crew-2 launch that sent the Crew-1 mission toward the International Space Station on Nov. 15. That stage landed on a SpaceX drone ship in the Atlantic Ocean and returned to Cape Canaveral on Thursday with a lean after it apparently slid across the deck of the vessel in high winds or rough seas.

The booster otherwise appeared to be in good shape, and SpaceX offloaded the rocket from the drone ship for transport to a hangar at Cape Canaveral for inspection and refurbishment.

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