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[AS] Remembering the Near-Mir Mission, 25 Years On
« dnia: Luty 06, 2020, 07:19 »
By Even A Centimeter: Remembering the Near-Mir Mission, 25 Years On (Part 1)
By Ben Evans, on February 2nd, 2020

The Mir space station, as viewed by the crew of STS-63. Photo Credit: NASA

A quarter-century ago this month, in February 1995, the astronauts (and a single cosmonaut) of shuttle Discovery roared into the night on a mission which performed the first rendezvous with Russia’s Mir space station. During their eight days in space, the men and women of STS-63—Commander Jim Wetherbee, Pilot Eileen Collins and Mission Specialists Bernard Harris, Mike Foale, Vladimir Titov and the late Janice Voss—approached to within 33 feet (10 meters) of the iconic orbital outpost, which would host several U.S. long-duration residents and no fewer than nine visiting shuttle crews between 1995 and 1998.

Yet STS-63 encompassed far more than that, with scientific research in a pressurized laboratory in Discovery’s payload bay, deployment and retrieval of a free-flying solar physics satellite, the first spacewalk by British and African-American astronauts and the first female pilot of the shuttle era.

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Video Credit: NASA

When the STS-63 crew was announced in late 1993, they could hardly have imagined that theirs was a voyage of destiny. Scheduled to launch in May 1994, the inclusion of Titov made this the second shuttle mission to include a Russian cosmonaut, part of a co-operative venture between the two former foes which would culminate in the construction of the International Space Station (ISS). But in September 1993, a series of high-level agreements between U.S. Vice President Al Gore and Russian Prime Minister Viktor Chernomyrdin led to STS-63 being selected to demonstrate the shuttle’s capacity to rendezvous with Mir and test radio communications and navigation equipment. At first, the plan was for Wetherbee and Collins to fly Discovery close to Mir and STS-63’s inclination was changed from 28.5 degrees to the 51.6-degree orbital “tilt” of the station.

By this time, STS-63 had slipped to early 1995, in part because the experiment load for its Spacehab-3 pressurized lab was relatively light. The Mir rendezvous commitment initially required Wetherbee to fly no closer than 1,100 feet (330 meters) from Mir, although U.S. and Russian trajectory specialists fine-tuned this to 400 feet (120 meters) and eventually just 110 feet (33 meters). But Wetherbee felt that the systems his crew needed to test—procedures, tracking radar, hand-held laser rangefinders and cameras—would be largely ineffective at great distance. “The first thing I noticed,” he recalled in an interview, “was that…the visual target that we used couldn’t be used accurately until we got to about 30 feet.” Wetherbee’s argument eventually won the backing of NASA management, but the Russians proved harder to convince, particularly as STS-63 offered little discernible benefit in terms of delivering crew or cargo to Mir. Eventually, it was agreed that Wetherbee would rendezvous to 33 feet (10 meters).

The STS-63 crew patch, bordered by the surnames of the six crew members, highlighted the Mir rendezvous commitment. Image Credit: NASA

It was made clear on both sides that he would approach no closer. “I was not going to violate that limit, by even a single centimeter,” said Wetherbee, “because I knew both space agencies in both countries were going to be watching as we approached on this flight.”

By the dawn of 1995, the launch of Wetherbee’s mission had slipped until no earlier than 2 February. Russian planners insisted that the rendezvous had to occur whilst Mir was in contact with Russian ground stations, which demanded that the shuttle’s final approach had to occur during orbital darkness. Although the rendezvous—which had by now earned the media moniker “Near-Mir”—on Flight Day Four was the most publicly visible part of STS-63, the mission also featured 20 experiments aboard the Spacehab-3 module, whose flat roof carried a pair of 12-inch-diameter (30 cm) windows, one of which housed a NASA docking camera to assist with proximity operations.

Launch on the 2nd was postponed by 24 hours, due to the failure of one of Discovery’s three Inertial Measurement Units (IMUs), which was replaced and tested. The launch window was particularly tight at just five minutes, and the precise launch time was decided relatively late in the countdown, based on new Mir state vectors for the shuttle rendezvous phasing requirements. These were updated about 60 minutes before launch, and the STS-63 crew rocketed away from Pad 39B at the Kennedy Space Center (KSC) at 12:22:03 a.m. EST on 3 February, turning night into day across the marshy Florida landscape.

“Pretty rough ride,” Wetherbee recounted at the post-flight press conference. “Seven and a half million pounds of thrust…and you can feel every one of those pounds.”

Commander Jim Wetherbee leads his crew out to Pad 39B on launch morning, 3 February 1995. Following are Pilot Eileen Collins and Mission Specialists Mike Foale, Janice Voss, Bernard Harris and Vladimir Titov. Photo Credit: NASA, via Joachim Becker/

Within nine minutes, Discovery reached her preliminary orbit, although not without incident, for one of her aft-mounted Reaction Control System (RCS) thrusters failed and another exhibited a minor, but persistent leak. As soon as the External Tank (ET) was jettisoned, Wetherbee and Collins were alerted by a “Jet Leak” and two “Jet Off” RCS messages. The shuttle was equipped with 44 primary and backup RCS thrusters on its nose and aft compartment, which were required primarily for orbital maneuvering. Two aft-mounted thrusters had failed, one on the port side (L2D) and one on the starboard (R1U). The former was “deselected” and remained off for the rest of the flight, but R1U was a primary thruster and critical for the Mir rendezvous commitment.

Wetherbee was dismayed, having trained for more than a year to prepare for STS-71, to see his flight potentially hamstrung within minutes of achieving orbit. “As the day wore on, I was pretty much convinced that we were not going to be able to rendezvous with Mir,” he said, “and it was pretty disappointing.” Although all of the thrusters were fully redundant, flight rules dictated that all aft-firing RCS needed to be operational for the orbiter to advance closer than 1,100 feet (330 meters) from Mir. Later that afternoon, Mission Control asked Wetherbee to position the shuttle to allow the Sun to shine onto the vehicle’s top side and hopefully warm up the leaking thruster, which was losing up to 2 pounds (0.9 kg) of oxidizer per hour. This was less than originally feared, and its temperature of 12.2 degrees Celsius (53.9 degrees Fahrenheit) was stable and well above the minimum redline of 4.4 degrees Celsius (40 degrees Fahrenheit), although if it dipped significantly it would be shut down and any chance of approaching Mir within 1,100 feet (330 meters) would evaporate.

In the meantime, the crew pressed on with their mission. By the time the six spacefarers turned in for bed, Discovery was trailing the station by about 7,000 miles (11,250 km) and closing this distance by about (330 km) per orbit. Over the next three days, Wetherbee and Collins would execute five maneuvers to position the shuttle at a point about 46 miles (75 km) “behind” Mir, ahead of the final manual rendezvous. Bernard Harris activated Spacehab-3—whose payloads included McDonnell Douglas’ Charlotte robot, capable of operating knobs, switches and buttons, as well as exchanging experiment samples and data cartridges, thereby freeing up valuable crew time—and Vladimir Titov grappled the SPARTAN-204 solar physics satellite with Discovery’s Remote Manipulator System (RMS) mechanical arm for a series of observations of the “shuttle glow” phenomenon.

Discovery springs away from Pad 39B a few minutes after midnight on 3 February 1995. Photo Credit: NASA, via Joachim Becker/

However, the RCS problems continued. The L2D aft thruster had been deselected, but its critical R1U counterpart maintained its minor leak. The problem worsened when one of the forward RCS thrusters in the shuttle’s nose (F1F) also began leaking during a two-part “hot-fire” test on 4 February. At one stage, its temperature fell below the minimum redline, forcing the crew to close its oxidizer supply line and maneuver Discovery into a nose-to-Sun orientation in an effort to warm it up. Efforts were also made to close and reopen its manifold, in the hope that the force of pressurization might push out any contaminants, and F1F was eventually revived.

The ailing R1U in the aft compartment was not so fortunate, however, with no fewer than four fruitless attempts made to bring it back online. By 5 February, the day before the Mir rendezvous, it was still leaking. “You could look out the back window and you could see the propellant going up for miles,” Wetherbee recalled. “It kind of goes in a cone-shaped pattern, because there’s no atmosphere to attenuate its motion, and it just goes up pretty straight and it just continues, like a snowstorm.” The risk of contaminating Mir was very real, not only in terms of the station’s fragile solar arrays, but also the delicate optical sensors of the Soyuz TM-20 spacecraft, which would ferry cosmonauts Aleksandr Viktorenko, Yelena Kondakova and Valeri Polyakov back to Earth in late March.

Although the rendezvous to 33 feet (10 meters) was still officially on, Wetherbee remained uneasy. He pulled Titov to one side. “You know, if this leak doesn’t get any smaller, I will not bring our vehicle close to Mir,” he told the cosmonaut, “even if they give us a Go, because I don’t want to cause any problems for the cosmonauts when they’re coming back.” Indeed, 6 February 1995 would be a day of truth for both the shuttle, Mir, and the new partnership between the two nations.


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Odp: [AS] Remembering the Near-Mir Mission, 25 Years On
« Odpowiedź #1 dnia: Luty 10, 2020, 06:00 »
We Will Shake Your Hand: 25 Years Since STS-63’s Near-Mir Mission (Part 2)
By Ben Evans, on February 9th, 2020 [AS]

Valeri Polyakov, pictured at Mir’s windows during the STS-63 shuttle rendezvous mission in February 1995, is the incumbent record-holder for the longest single spaceflight. Photo Credit: NASA, via Joachim Becker/

Last week, U.S. astronaut Christina Koch returned safely to Earth, wrapping up the longest single space mission ever accomplished by a woman; an astonishing 328 days, easily surpassing the previous record-holder, Peggy Whitson, and coming less than two weeks shy of exceeding the 340-day mission of Scott Kelly in 2015-2016 . Women have been setting records off-Earth for almost six decades, ever since Soviet cosmonaut Valentina Tereshkova became the first female spacefarer in June 1963. Since then, women have spacewalked, they have worked for hundreds of days aboard space stations and—25 years ago, this week—they entered the spacecraft’s “front seat” for the first time. In February 1995, Eileen Collins became the first woman to serve as a Space Shuttle pilot. In time, her career would also see her command two missions, including the first flight after the Columbia tragedy.

The STS-63 crew. Front row (left to right) are Janice Voss, Eileen Collins, Jim Wetherbee and Vladimir Titov. Back row are Bernard Harris (left) and Mike Foale. Photo Credit: NASA/Ben Evans personal collection

As detailed in last weekend’s AmericaSpace history article, STS-63 was a remarkable shuttle flight, not only because of Collins’ presence, but also the multi-faced smorgasbord of activities performed during its eight days in orbit. Joining Collins were Commander Jim Wetherbee and Mission Specialists Bernard Harris, British-born Mike Foale, Russian cosmonaut Vladimir Titov and Janice Voss. Twenty-three biomedical and technology experiments were performed inside the Spacehab-3 pressurized lab in shuttle Discovery’s payload bay, the free-flying SPARTAN-204 satellite was deployed and retrieved to conduct two days of intensive solar research, the first British and African-American spacewalkers strutted their stuff in the void…and, for the first time, the shuttle performed a rendezvous with another inhabited spacecraft in orbit: Russia’s Mir space station.

But STS-63 hit a serious obstacle almost as soon as the shuttle reached orbit, when two of the 44 Reaction Control System (RCS) thrusters—principally required for orbital maneuvering—began to exhibit irregularities. The two troubled thrusters were situated on Discovery’s aft end, one on her port side (L2D) and one on the starboard (R1U). The former was “deselected” and remained out of use for the rest of the mission, but R1U was classified as a primary thruster for the Mir rendezvous and its full functionality was paramount if the STS-63 crew were to be permitted to advance closer than about 1,100 feet (330 meters) from Mir. Matters worsened when a nose-mounted RCS thruster (F1F) also began leaking. Although the nose thruster issue was later resolved, that of R1U continued to linger.

When the crew bedded down for the night on 5 February 1995, the evening before the Mir rendezvous, Discovery trailed the Russian space station by 1,150 miles (1,850 km) and was closing on its quarry by about 80 miles (130 km) per orbit. Early next morning, STS-63 Commander Jim Wetherbee was awakened to encouraging news: the R1U leak had slowed and stabilized, but had not yet stopped. From the shuttle’s aft flight deck windows, Wetherbee could see that its conical plume was less pronounced and U.S. and Russian flight controllers reached agreement on two possible forward plans. The first called for Discovery to maneuver, as planned, to 33 feet (10 meters), whilst the second adopted a more conservative approach, reaching no nearer than 400 feet (120 meters).

Kicking off the final stage of the rendezvous, Wetherbee fired the RCS at 9:16 a.m. EST and again at 10:02 a.m. to decrease his rate of closure along the so-called “V-Bar,” approaching Mir from “behind,” along its velocity vector, or direction of travel, toward the station’s Kristall module. Later, at 11:37 a.m., at a distance of 9.2 miles (14.8 km), he would perform the Terminal Initiation (TI) burn, to bring the shuttle to a halt 400 feet (120 meters) “ahead” of Mir, about one orbit later at 1:16 p.m. At this stage, the shuttle’s rendezvous radar would begin to provide range and range-rate data, and Wetherbee would take manual control just after passing about a half-mile (0.8 km) below Mir.

In their seminal work Shuttle-Mir: The United States and Russia Share History’s Highest Stage, Clay Morgan noted that STS-63 Flight Director Bill Reeves struggled to explain the effect of the RCS problems to his Russian counterparts.

After one presentation, they asked him a rather odd question: “We understand what you’re saying, but what about the 180-gram snowball?”

Reeves stared blankly at them. “What are you talking about?” “The 180-gram snowball in your fax.”

It transpired that a team of NASA engineers had produced an extremely remote, worst-case plan for an RCS thruster freezing and becoming packed with ice. Communications links between Moscow and Houston were relatively poor and the fax was mistakenly sent directly to the Russians, bypassing Reeves, and thereby leaving in the unenviable position of having to explain that the RCS issue aboard STS-63 was by no means a critical problem.

During the final rendezvous, the decision point was approaching about whether Discovery would perform a flyaround of Mir at 400 feet (120 meters) or continue to 33 feet (10 meters). That decision was relayed to the crew, not by Capcom Story Musgrave, but by Russian cosmonauts Aleksandr Viktorenko, Yelena Kondakova and Valeri Polyakov, aboard the space station itself. “We were testing out a new VHF radio that…all the crews used to talk directly with Mir,” Wetherbee later recalled. “You need to have an ability for the crew members to talk to each other, to co-ordinate things separately from the air-to-ground voice loop, from the ground control center in Moscow and from the orbiter to the control center in Houston. We had a separate communication, directly with Mir. The two mission control centers were co-ordinating the approach and they finally had agreed that they were going to let us make the final approach, but Houston didn’t tell us right away. We heard from Mir, from the Russian cosmonauts, that they were going to give us a Go.”

Unfortunately, the actions of the STS-63 crew were being recorded and broadcast live in Houston, although without audio, and there was some surprise when Mission Control saw the astronauts and Titov cheering and clapping. Viktorenko, Kondakova, and Polyakov had stolen their thunder, and Wetherbee had to tell his crew to calm down until they were given a definitive Go. Finally, Musgrave’s voice crackled across the airwaves: “We think you know this, because of the reaction we saw, but you do have a final Go to approach to 10 meters!” As if to echo Musgrave’s words, the STS-63 “simulated” their profound euphoria for the second time.

Flying the orbiter from instruments on the aft flight deck, Wetherbee intersected the V-Bar and after passing within 1,100 feet (330 meters) began executing RCS firings in a so-called “Low-Z” mode, whereby he employed thrusters which were slightly offset to the space station, rather than those which pointed directly at Mir. This helped to eliminate the possibility of contamination. Additional laser ranging data was provided by the Trajectory Control System (TCS), mounted in Discovery’s payload bay, and Wetherbee made use of the centerline camera in the roof window of Spacehab-3. At 400 feet (120 meters), he halted Discovery to await permission to advance closer. At 200 feet (60 meters), VHF ship-to-ship radio communications was initiated between the shuttle and Mir’s crews, and, by 2:23:20 pm, Discovery reached a distance of 37 feet (12 meters) from the station.

At least, that was the detail in the issued press releases. “The closest point of approach between structure was 33 feet,” said Wetherbee in his NASA oral history. “The number that was reported in the press was 37 feet, because that was the distance between the laser system and the target on Mir. You had to triangulate and that’s the longer hypotenuse of the triangle. Not that that matters; it was just interesting to see that when we came back it was reported, and is still reported, as 37 feet, but it really was 33 feet and not one centimeter closer. We did not get a single inch closer to Mir.” True to his word, Wetherbee had flown the first-ever rendezvous between a shuttle and a space station perfectly and with precision.

The STS-63 crew consisted of (front left, from left) Eileen Collins, Jim Wetherbee and Bernard Harris and (back row, from left) Vladimir Titov, Mike Foale and Janice Voss. Photo Credit: NASA

In the hours before the event, he had another issue on his mind: the right words to say over the space-to-ground communications loop when U.S. and Russian piloted spacecraft reached their closest point in orbit for almost 20 years. Wetherbee knew that the rendezvous would be watched by both a U.S. audience and a Russian audience and he was determined to deliver his message in both languages. That proved easier said than done, for although he had studied a little Russian, his powers of translation were poorer, and he approached Vladimir Titov for help. He wrote down what he wanted to say, showed none of his other crewmates, and passed it to Titov, who read it and translated it on his kneeboard. Armed with the translation, Wetherbee practiced a handful of times until he was satisfied that he could deliver the message and properly pronounce the words. As the point of closest approach neared, the time to speak those words finally came.

“As we are bringing our space ships closer together, we are bringing our nations closer together,” Wetherbee told Viktorenko, via the VHF radio link. “The next time we approach, we will shake your hand and together we will lead our world into the next millennium.”

“We are one. We are human,” came Viktorenko’s heartfelt reply.

Astronauts Bernard Harris and Mike Foale, during their EVA on STS-63. Photo Credit: NASA

For the three cosmonauts aboard Mir, there was no noticeable vibration or movement in the station’s solar arrays and its attitude-control system performed normally. Wetherbee held Discovery at 37 feet (12 meters) for about 15 minutes, before withdrawing to a distance of 400 feet (120 meters) by 3:00 p.m. He then completed a slow, quarter-loop flyaround of Mir and conducted a final separation manoeuvre at shortly after 4 p.m. This positioned the orbiter “ahead” of Mir and began their departure, opening up the distance between them with each successive orbit. Fortunately, no other RCS issues arose during the rendezvous. During a subsequent ship-to-ship communications session, relayed through an interpreter in Houston, Wetherbee and Viktorenko shared their personal perspectives of the historic operation. For Wetherbee, the high point was when Mir maneuvered into a new attitude as Discovery performed the quarter-loop flyaround around the station. “It was like dancing in the cosmos,” he told Viktorenko. “It was great.” The two commanders pledged to meet on Earth after their respective missions were over.

With the Near-Mir operations behind them, the STS-63 crew turned their attention to the deployment of the SPARTAN-204 astronomy satellite on 7 February. It spent two days in free flight, utilizing the Naval Research Laboratory’s Far Ultraviolet Imaging Spectrograph (FUVIS) for astronomical observations, before being retrieved and returned to its berth in the payload bay. It was also used during a five-hour EVA by STS-63 Mission Specialists Bernard Harris and Mike Foale—who became, respectively, the first African-American and first British-born spacewalkers—on the 9th, during which they evaluated new garments and tools to handle the deep cold of working in orbital darkness. After a troubled, but ultimately triumphant eight days in space, Discovery returned to Earth on 11 February, having played an enormous and critical part in making the shuttle-Mir and International Space Station (ISS) programs possible.