In the summer of 1990, everything seemed to conspire to prevent the launch of the Astro-1 mission. Originally set for a 16 May launch, a faulty orbiter coolant system
valve caused a delay until 30 May. Then the launch was scrubbed due to a major hydrogen leak in the 43-cm orbiter/ET disconnect umbilical during tanking operations and a minor leak in one of the Mobile Launch Platform's two tail service masts. The crew was not on board during this incident, but they were awakened in the crew quarters at the Cape and promptly told to go back to sleep because they were not going to launch that day.
After the stack had been returned to the VAB to replace the umbilical, the launch was reset for September, only for another hydrogen leak to be revealed during tanking in Columbia's aft compartment. More pumps and seals in the SSME system had to be replaced, and the launch was rescheduled yet again, this time to 18 September. A third hydrogen leak was recorded during the next tanking and the delay forced NASA to move the vehicle to Pad B to make way for STS-38. It was then returned to the VAB again due to tropical storm Klaus.
STS-35 was finally launched on 2 December 1990, nearly five years after it was originally scheduled to fly. It carried the Astro-1 payload of telescopes, mounted on a pallet in the payload bay, which would be operated on a two-shift system. The crew experienced further difficulties with the computer consoles, due to the failure of the visual display units which aimed the telescope mounts and the instruments. Within twenty-four hours, the ground team came up with procedures to guide the telescopes and allow the collection of data from the instruments. On top of all this, there was also a clogged drain which prevented waste water dumps during the mission. Still, the crew
Parker (left) and Durrance conduct a simulation of Astro-1 payload activities during training for STS-35 (formerly STS 61-E).
were able to present a "Classroom in Space'', in which the astronomer-astronauts (Parker and Hoffman - who had taught in class before coming to NASA) put together a small field lesson from space demonstrating what astronomy is all about. Parker really enjoyed this, especially the interaction with several children in a school near Goddard and a second near the Marshall Space Flight Center. After a flight of 8 days 23 hours 5 minutes 8 seconds and 144 orbits, STS-35 at least managed to land without incident. The mission had been scheduled for a further twenty-four hours in flight but, in keeping with the pattern of the rest of the mission, impending bad weather at Edwards AFB in California had caused the crew to return a day earlier than planned.
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