Retrieving the lost satellites

NASA mounted an ambitious rescue mission on STS-51A in November 1984. After it had deployed another HS-376 and an HS-381, Discovery was to retrieve the satellites stranded in elliptical orbits with 1,000-kilometre apogees in February.17 After jettisoning their stages, these satellites had used their thrusters to lower themselves, and were now in similar orbits and spaced several hundred kilometres apart. Their retrieval would involve considerably more orbital manoeuvring than on any previous Shuttle mission. Discovery drew to a halt barely 10 metres from Palapa B2. The satellite's 60-rpm spin had been virtually eliminated, leaving only a slow residual roll for stability. Since the HS-376 had not been designed to be manipulated in orbit, and did not have a trunnion pin, recovering it would be more difficult than in the case of SolarMax. To capture it without damaging the conformal solar cells on its drum, a device had been produced to engage the ring at the base that had mated with the PAM stage. Although the designers referred to this as the capture device, its shape had inevitably resulted in the astronauts dubbing it the 'stinger'. It was really several devices in one. Like the TPAD, it had a clamp to attach to the arms of the MMU. A long rod projecting out in front (the stinger itself) was to be inserted into the throat of the satellite's apogee motor. A ring at the base of the stinger was to connect with that on the satellite. There was also a trunnion pin on the side of the device to enable the remote manipulator to take over once the satellite had been stabilised.

Joe Allen manoeuvred into position aft of the satellite, and then eased forward. The stinger's success was evident even before Allen reported it, because he adopt the satellite's spin. Once this motion had been cancelled by the thrusters on the MMU, he manoeuvred into a convenient orientation and Anna Fisher brought the arm in over his shoulder to snare the trunnion pin. With Allen still attached, Fisher eased the satellite into the bay, where Dale Gardner was waiting with shears to remove the rod-like omni antenna that projected from the top of the satellite. The satellite had then Dale Gardner manoeuvres to raptae Westar 6.

to be turned upside down for stowage. A bracket had been built to run over the top of the drum, but this could not be attached. It had been tested on similar satellites at Hughes, but the model was tailored to its customer's requirements, and the feed horn of the folded antenna on top of this one projected a little further than the tool's designers had been told, preventing the clamps from engaging. In the original plan, Gardner was to affix the bracket, Fisher was to raise Allen back out of the bay and release him, Allen would flip the satellite to enable Fisher to grip the trunnion pin on the bridge that Gardner had fitted, Allen would disengage the stinger, and Fisher would line up the satellite and lower it onto the waiting mount. Given that the common bracket clamp (as the bridging bracket was formally known) would not fit, the astronauts set out to improvise. In the revised plan, Allen disengaged, leaving the arm grasping the satellite via the stinger. While Allen stowed the MMU, Gardner placed a portable foot restraint on the sidewall. Allen then stood on this restraint and took hold of the satellite by its still-folded main antenna. When Fisher withdrew the arm, Allen did his best to hold the satellite steady while Gardner disengaged the stinger. Gardner placed a 'shower cap' over the motor nozzle to prevent flakes of solid propellant falling out into the bay when Discovery landed. Gardner then disconnected the A-frame carriage mount from the bay floor and mated it to the ring on the base of the satellite. Throughout this activity (which lasted well over an hour) Allen held the satellite steady. With the mount attached, they pitched Palapa down into the bay and Gardner reconnected the A-frame to the bay floor. In all, the retrieval had taken six hours.

Two days later, Discovery drew up alongside Westar 6, and Allen and Gardner went out to retrieve it. It had been decided to use a revision of the impromptu procedure. This time Gardner donned the MMU and the stinger, and Allen installed a foot restraint on the arm and mounted it. Gardner captured the satellite and flew it to Allen, who grasped it by the antenna. This time, the stinger was promptly disengaged and stowed, together with the MMU. With Gardner on the bay floor, Fisher slowly brought Allen and the satellite down. The fact that Allen had to hold the satellite by its antenna meant that this time the satellite arrived conveniently for fitting the A-frame. With the satellite in place, the omni antenna was cut off to prevent it interfering with the closing of the bay doors. Before they came in, the two men perched on the arm and displayed a placard to a camera advertising two satellites for sale. In recognition that their ''extraordinary exertions contributed to the preservation of property'', Lloyds of London gave the astronauts its Silver Medal. Both satellites were subsequently sold and relaunched under new names.

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