ESA Science & Technology - PR 55-1999: European astronaut duo on their way to Hubble Space Telescope

They are on a 8-day mission to service the orbiting Hubble Space Telescope. The European scientific community is waiting anxiously for the telescope to be returned to full operation. Nicollier is set to become the first European to walk in space from the Space Shuttle. On Thursday 23 December, Nicollier will step out of the Shuttle's airlock, help fit a new main computer, a replacement fine guidance sensor which will allow fine pointing and keep Hubble stable. Clervoy will operate the Shuttle's robotic arm during demanding phases of the mission, including initial capture of the satellite and for the spacewalks.

Nicollier is on his fourth flight into space. Among them he took part in the first Hubble servicing mission in 1993, controlling the Shuttle's robotic arm while astronauts outside performed repairs to the telescope. This time Clervoy, on his third flight, will have the lead role in the operation of the robotic arm.

A vital part of the mission is to replace the telescope's six gyroscopes which help stabilise the giant observatory during observations of distant astronomical objects.

Hubble requires three of its six gyroscopes to operate properly for accurate stabilisation but a fourth failed in November posing no long term threat to the telescope but meaning observations had to be suspended until replacements are fitted. Discovery's mission is scheduled to last almost 9 days with a landing targeted to occur at the Kennedy Space Centre Shuttle Landing Facility on Monday 27 December 22:24 UT.

Hubble was launched in 1990 with an expected orbital lifetime of 20 years. ESA contributed a 15 percent share to its development and in return European astronomers receive a guaranteed 15 percent share of observing time but in reality this has averaged 20 percent because of the high quality of proposals from scientists in Europe.

The new shortened schedule for the Servicing Mission is:

• Launch: Monday Dec. 20, 1999 at 00:50 UT
• Grappling of Hubble: Wednesday Dec. 22 at 00:41 CET
• First Spacewalk: Wednesday Dec. 22 at 19:40 UT (gyro replacement)
• Second Spacewalk: Thursday Dec. 23 at 19:50 UT (replace computer and fine guidance sensor)
• Third spacewalk: Friday Dec. 24 at 19:50 UT (replace recorder and repair insulation)
• Release of Hubble: Saturday Dec. 25 at 23:03 UT
• Landing: Monday Dec. 27, 1999 22:24 UT

To ESA's Hubble Project Scientist Piero Benvenuti the launch was definitely a milestone: "The successful launch of Discovery this morning, after so many postponements, was a big relief to us all. Although Hubble is safe, the interruption of normal operations for so long is having a serious effect on the planned science program. It would have been especially disappointing had the launch been delayed unit January. We are now looking forward to a successful Servicing Mission and we are eager to enter the second decade of Hubble observations with a refurbished telescope."