NASA has switched the launches of the STS100 Endeavour Shuttle Radar Topography and the STS103 Discovery Hubble servicing missions while inspection and repair work continues on the orbiter's electrical wiring (Flight International, 8-14 September).

The tentative launch date for STS103 is 28 October, while STS101 is targeted for a 19 November lift-off. The STS101 Atlantis mission to the International Space Station (ISS) had already been put off until 22 January next year and NASA has warned that each mission could be subject to further delays as wiring inspections continue.

STS103 is one of the most rapidly prepared missions in Shuttle history. It was originally scheduled for next June as a comprehensive service of the Hubble space telescope. However, when the telescope's gyros began to fail it was decided to split the mission, flying the first expedition in October and the second in September next year.

The preparation time for the STS103 "is very short; we can feel the rush", says mission specialist Jean-Francois Clervoy, the French European Space Agency astronaut and the robot arm operator for the mission. Clervoy and the four-man spacewalk team are making extensive use of virtual reality to prepare for the four spacewalks, including developing techniques for arm movements and attitudes.

The first will fit new gyros and a new voltage kit, while the second will be used to install a new computer and fine guidance sensor. The third spacewalk will install radio transmitters and a data recorder, and the fourth will install thermal blankets.

Spacewalks one and three will be made by Hubble veteran Steve Smith, and John Grunsfield, while two and four will be made by Michael Foale and Claude Nicollier.

Meanwhile, Mark Lee, a veteran NASA astronaut spacewalker, has been dropped from the STS98 Atlantis mission to the International Space Station. The reasons have not been disclosed. The mission is set for April, but could be delayed until next December. Lee has been replaced in a four-spacewalker team by Robert Curbeam, who had been training for spacewalks on the STS100 Endeavour mission in July.

Source: Flight International