STS-51-A (Discovery)

Background

By the autumn of 1984, two commercial communications satellites were drifting uselessly in low Earth orbit, casualties of a shared malfunction. Palapa B2, owned by Indonesia, and Westar 6, operated by Western Union, had both been released from Space Shuttle *Challenger* during mission STS-41-B in February of that year. In each case the Payload Assist Module upper stage, intended to boost the spacecraft to geostationary transfer orbit, fired incorrectly, leaving the satellites stranded in orbits too low to be commercially useful. The financial and diplomatic stakes were substantial: insurers faced enormous payouts, and the owners faced the prospect of losing major communications infrastructure permanently.

The solution proposed was audacious. Rather than simply write off the hardware, NASA and the insurance underwriters devised a plan to retrieve both satellites and return them to Earth, where they could be refurbished and relaunched. No crewed spacecraft had ever attempted to capture and bring home a free-flying satellite. STS-51-A, assigned to orbiter *Discovery*, would be the mission to try it — and to finance the effort, the flight would also deliver two entirely different satellites to orbit first.

The crew selected for this dual mandate was experienced and capable. Commander Frederick Hauck and Pilot David Walker would manage the orbiter, while mission specialists Joseph Allen, Anna Fisher, and Dale Gardner would handle the complex EVA and robotics work at the heart of the retrieval operations. Allen and Gardner had trained extensively with the Manned Maneuvering Unit, the self-contained nitrogen-propelled jetpack that would allow an astronaut to fly untethered away from the orbiter and approach a slowly tumbling satellite.

Launch and Satellite Deployments

*Discovery* lifted off from Kennedy Space Center on November 8, 1984. The ascent was nominal, and the vehicle reached orbit approximately eight and a half minutes after liftoff. Among the first order of business was fulfilling the delivery half of the mission's contract. Within the first day and a half of flight, the crew successfully deployed both Anik D2 and Leasat 1 from the payload bay, completing that phase of the mission cleanly and on schedule. The deployments demonstrated that the shuttle remained a reliable satellite ferry even as the crew prepared for the far more novel work ahead.

The Retrievals

Rendezvous with the two stranded satellites began in earnest at approximately three days into the mission. The capture operations themselves required a combination of precise orbital mechanics, careful maneuvering by the orbiter crew, and remarkable physical improvisation by the EVA astronauts.

The fundamental challenge was that Palapa B2 and Westar 6 were not designed to be grabbed. They were spinning slowly and had no grapple fixtures that the shuttle's robotic arm could engage directly. The solution was to have a spacewalking astronaut fly out on the MMU, match the satellite's slow rotation, and physically stop it by hand before attaching a specially designed capture bar. Once stabilized, the satellite could be grasped by the robotic arm, operated from inside the cabin by Anna Fisher, and berthed in the payload bay.

Joseph Allen made the first retrieval, flying out to Palapa B2 on the MMU and manually arresting its spin before the capture bar was attached. Dale Gardner retrieved Westar 6. The operations were meticulous and demanding, requiring the astronauts to manage their own momentum while handling large, unwieldy spacecraft in the unforgiving environment of open space. At one point during the Westar retrieval, Gardner held the satellite steady while Allen assisted from below, standing on a foot restraint in the payload bay — a striking image of two people physically wrestling a communications satellite into submission. Both retrievals were completed successfully, and Palapa B2 and Westar 6 were secured in *Discovery*'s payload bay. The mission thus accomplished what had never been done before: the capture and return of failed satellites to Earth.

Reentry and Landing

With both recovered satellites safely stowed, *Discovery* completed its remaining time on orbit before the deorbit burn fired on flight day eight, committing the vehicle to reentry. The orbiter landed at Kennedy Space Center, closing out a mission of just under eight days. The two retrieved satellites were subsequently returned to their manufacturers, refurbished, and eventually relaunched — a remarkable second life for hardware that had once seemed lost.

Legacy

STS-51-A occupies a singular place in the history of human spaceflight. It remains the only mission on which failed satellites were captured and brought back to Earth. The flight demonstrated in the most practical terms imaginable that the Space Shuttle was not merely a delivery vehicle but a genuine orbital service and recovery platform — capable of complex in-space operations that no previous spacecraft could have attempted.

The mission also showcased the Manned Maneuvering Unit at the height of its operational utility. The combination of untethered EVA capability, a robotic arm, and a large pressurized payload bay created a system whose flexibility exceeded what most planners had initially envisioned. Anna Fisher became the first mother to fly in space on this mission, adding another note of historic significance to a flight already rich with firsts.

For the insurance industry, the financial logic of the retrieval was straightforwardly compelling: recovering expensive hardware for refurbishment was preferable to total loss. For NASA, the mission was a demonstration of confidence in human spaceflight operations at their most demanding. And for the five crew members who pulled it off — deploying two satellites, then hunting down and hand-catching two more — STS-51-A represented an operational tour de force that has never been repeated.