Endeavour flew the second Space Radar Laboratory in September 1994, returning the imaging radar to orbit to photograph the same regions its April flight had mapped, now in a different season. The paired missions let scientists see how landscapes, wetlands and vegetation changed through the year, a powerful demonstration of monitoring the environment from space.
The crew of six, working around the clock, captured a striking bonus when a volcano in Russia's Kamchatka erupted during the flight, giving the radar a rare chance to watch an eruption unfold. The eleven-day mission had nearly been lost weeks earlier to a pad abort when the engines shut down after ignition, but once flying it delivered a rich record of a changing planet.
The Space Radar Laboratory flew a second time in the autumn of 1994 to photograph the same sites in a different season — the whole point of the pairing being to see how landscapes change between spring and autumn, when the ground is wetter or drier and the vegetation has grown.
Fortune supplied a spectacular bonus. The Kliuchevskoi volcano on Kamchatka erupted while the mission was in progress, and the radar imaged the ash plume and the fresh lava flows in a way optical instruments never could have, since the whole region was under cloud. The images ran worldwide and demonstrated the practical case for radar observation better than any brochure.
The flight had begun with drama of its own. An August launch attempt was halted 1.9 seconds before liftoff when the engines, already running, were shut down after a temperature sensor detected an overheating turbopump — the fifth and final on-pad abort of the programme. The engines were replaced and Endeavour flew six weeks later.
