Almost a quarter-century since its launch, and more than two decades since shuttle astronauts triumphantly snatched it from an unusable low-Earth orbit and successfully reboosted it to its intended geostationary altitude, more than 22,300 miles (35,900 km) above the Home Planet, the historic Intelsat 603 communications satellite has reached the end of its operational lifetime. According to its owner, the Luxembourg-headquartered International Telecommunications Satellite Organisation, the final commands to dispose of “this famous bird” occurred on 23 January 2015 and were executed from Intelsat’s East Coast Operations Center in Tysons Corner, Va. Although Intelsat announced that it would “deorbit” Intelsat 603, the aging satellite was actually moved to a graveyard orbit, thereby preventing it from posing a collision hazard or adding to the existing orbital debris field.
At the time of its launch in March 1990, Intelsat 603 formed part of the sixth generation of geostationary communications satellites, designed by Hughes Aircraft Company on behalf of Intelsat. The latter began its life as a 11-nation Inter-Governmental Organization (IGO) in August 1964, but received its present name in 1973 and most recently became a private company, Intelsat, Ltd., in July 2001. During more than five decades of operations, its fleet of satellites—led by the trailblazing Intelsat-1, or “Early Bird,” launched in April 1965—have provided the first-ever direct and near-instantaneous contact between the United States and Europe and enabled trans-Pacific communications in January 1967 and across the breadth of the Indian Ocean in July 1969, as well as returning images from the Moon during Neil Armstrong’s historic first steps on the lunar surface. Since then, Intelsat also provided the earliest demonstrations of the Internet in July 1978, as well as global coverage of Live Aid and the wedding of Prince Charles and Diana, Princess of Wales, in the 1980s.
Five Intelsat 6 satellites were built between 1983 and 1991 and a half-scale model today hangs in the lobby of Intelsat’s Washington, D.C. headquarters. The 9,260-pound (4,200-kg) wide-body satellites were spin-stabilized at 30 revolutions per minute, with a “de-spun” element to accommodate their communications payloads and direct their antennas toward desired locations on Earth. In the pre-Challenger era, at least one member of the Intelsat 6 family was earmarked to fly aboard the shuttle, with the 601 satellite assigned in June 1984 to travel into orbit on Mission 61E in the spring of 1986, co-manifested with the ASTRO-1 payload. However, in the era of payload-juggling which characterized the early shuttle era, Intelsat 601 was subsequently dropped in favor of another satellite and the loss of Challenger led it to be reassigned to fly aboard an expendable booster.
Measuring 11.8 feet (3.6 meters) in diameter and 17 feet (5.2 meters) tall, expanding to a height of 38.4 feet (11.7 meters) when its concentric solar arrays and communications payload was fully deployed in orbit, the Intelsat 6 satellite “bus” carried a bi-propellant system of nitrogen tetroxide and monomethyl hydrazine, which fed radial and axial thrusters for station-keeping and attitude control. The outer surfaces of the satellites were coated with photovoltaic solar cells for electrical power, whilst nickel-hydrogen pressure vessel batteries supported operations in Earth eclipse. The communications payload carried 38 C-band and 10 Ku-band transponders.
Several years later than intended, Intelsat 603 was lofted atop the second flight of Martin Marietta’s Commercial Titan III vehicle from Space Launch Complex (SLC)-40 at Cape Canaveral Air Force Station, Fla., on 14 March 1990. However, the rocket’s second stage failed to separate properly and the payload could only be released by means of jettisoning its attached Orbus-21 perigee kick motor. This rendered it incapable of conducting a “burn” to achieve geostationary transfer orbit and the $157 million satellite—which was not insured, but instead had been “self-insured” by Intelsat, from its own funds—was left stranded and inoperable in low-Earth orbit.
In the weeks and months following the malfunction, Hughes entered into a contract with NASA, worth in excess of $90 million, for a shuttle flight to reboost Intelsat 603. Two possible options quickly gained prominence: either to carry a new perigee kick motor into orbit and attach it to the satellite to reboost it into geostationary transfer orbit or retrieve Intelsat and bring it back to Earth for refurbishment. Concerns about the extent to which the satellite’s surfaces might degrade over two years were allayed by the test flight of several solar array sample “coupons,, attached to the Remote Manipulator System (RMS) mechanical arm during shuttle mission STS-41 in October 1990. These were exposed to the harsh atomic oxygen environment for a minimum of 23 hours, with few ill-effects. Two months later, in December, the seven-member STS-49 crew—Commander Dan Brandenstein, Pilot Kevin Chilton, and Mission Specialists Rick Hieb, Bruce Melnick, Pierre Thuot, Kathy Thornton, and Tom Akers—was named to conduct the audacious retrieval mission, with launch aboard the maiden voyage of Shuttle Endeavour targeted for May 1992.
During one of three planned EVAs, Thuot and Hieb would seize Intelsat 603 with a “capture bar,” designed and built by engineers in the Crew and Thermal Systems Division at NASA’s Johnson Space Center (JSC) in Houston, Texas. Weighing 160 pounds (73 kg), it measured 15 feet (4.6 meters) long and about 3.3 feet (1 meter) wide and included detachable beam extensions and a steering wheel. As Thuot rode on the end of Endeavour’s RMS arm, he would be positioned close to the base of Intelsat 603 and after grappling the giant satellite would lower it delicately into a Hughes-built cradle in the payload bay. “There was a lot of analysis done,” recalled Brandenstein in his NASA oral history, “and we were assured that because it was spinning slightly and it had a lot of mass, we could bump it and it would stay pretty much in place and wasn’t going to be a problem.”
Throughout 1991, Thuot and Hieb trained underwater and on the air-bearing table for the delicate procedure, but as described in a previous AmericaSpace history article the actual retrieval in May 1992 proved far from straightforward. On no fewer than two EVAs, the spacewalkers were unable to grapple Intelsat 603—hampered by failed latches, an inability of the capture bar to “sit” correctly, and oscillations within the satellite itself—and were faced with the very real possibility of failure. At length, it was decided to stage a never-before-tried three-person EVA, with Akers joining Thuot and Hieb to stabilize Intelsat 603. “A big mental switch flipped over for me,” Hieb recalled later. “In my mind, having a third set of hands out there meant that we would be successful, although we weren’t yet sure how.”
In spite of concerns about even fitting three fully-suited spacewalkers into Endeavour’s tiny airlock—a concern allayed by ground tests, involving fellow astronauts Story Musgrave, Jim Voss, and Michael “Rich” Clifford—the idea proved to be a spectacular success. With Hieb close to the starboard wall of the payload bay, Akers in the center, and Thuot on the tip of the RMS at the port side, they grabbed the satellite and held it firmly. “I actually thought the other two guys had stopped it from rotating,” Thuot said later, “so little force had I applied. Very gently, the thing came to a stop.”
With Intelsat 603 snared, the astronauts removed the steering wheel and installed an extension to the capture bar, which Melnick then grappled using the RMS. The satellite was then positioned above its Orbus-21 perigee kick motor, which sat vertically in its cradle. After closing four docking clamps to secure the pair, and attaching two electrical umbilicals between Intelsat and the motor itself, the spacewalkers set a pair of deployment timers and retreated to Endeavour’s airlock.
Meanwhile, Kathy Thornton prepared to activate the springs to deploy the payload. At first, it did not move. “They had made a change in the wiring of the deploy system,” recalled Brandenstein, “and the change never made it through the process [and] never got into the checklist. Fortunately, somebody in Mission Control apparently knew about it. They just quickly called up a different switch sequence and she did that sequence and it went.” Deployment occurred at 12:53 a.m. EDT on 14 May, and the satellite vacated the payload bay at a little under 0.6 feet/sec (0.2 m/sec). Less than an hour later, the three spacewalkers repressurized the airlock and returned inside the cabin.
Early the following morning, the Orbus-21 ignited to successfully boost Intelsat 603 into geostationary orbit, which it reached by 21 May. Initially positioned at 34.5 degrees West longitude, over the Atlantic Ocean, in July 1992 the satellite carried television coverage of the Barcelona Olympics in Spain, which saw the last performance of the member states of the Soviet Union as a unified team and the first performance of a united Germany in almost three decades. It was moved to 24.5 degrees West in October 1997 and to 19.95 degrees West in August 2002 and finally to 11.5 degrees East in May 2010. The satellite was reportedly deactivated in January 2013 and last month Intelsat announced that it had “been sending the sequence of commands to deorbit this famous bird,” as part of efforts to “deorbit” it.
However, “deorbit” may appear to be an imprecise descriptor, since Intelsat 603 has been deactivated for emplacement in a “graveyard orbit.” Mr. Jason Bates, Intelsat’s Media Communications Manager, confirmed that the satellite was removed from geostationary altitude at 6:04:14 p.m. UTC on 23 January and was moved to a new location, about 221 x 225 miles (355 x 362 km) above its previous position. Although it is possible to deorbit a satellite from geostationary altitude, the large delta-V requirement of so doing—about 4,900 feet/sec (1,500 meters/sec)—is substantially higher than moving it to a graveyard orbit. Such orbits typically require the movement of the satellite to an altitude a few hundred miles above its operational position. This reduces the likelihood of creating a collision hazard with other operational satellites, as well as cutting the risk of generating further orbital debris. As of yesterday (Monday), Intelsat 603 was identified as being resident at a mean altitude of 22,383 miles (36,022 km), inclined 10.6 degrees to the equator, and completing one orbit of Earth every 24.1 hours.