Tim Furniss/LONDON

DETAILED PLANS for the second Space Shuttle mission to service the Hubble Space Telescope (HST) in February 1997 cover three space walks during which two new instruments and new equipment will be fitted. The STS82/Discovery mission will cost about $260 million to fly.

NASA has already selected four space walkers, (Mark Lee, Gregory Harbaugh, Steven Smith and Joe Tanner), who will make three space walks to install new digital data recorders, a data-interface unit and the two new instruments, the Space Telescope Imaging Spectrograph (STIS) and the Near Infrared Camera Multi-Object Spectrograph (NICMOS), both built by Ball Aerospace.

The NICMOS, which is cooled by solid nitrogen and carbon dioxide, will replace the Goddard High Resolution Spectrograph. The STIS replaces the High Resolution Spectrometer and Faint-Object Spectrograph.

Lee will be the payload commander of the STS82 mission, the ground-based director of which will be former astronaut Richard Richards.

The commander pilot and remote manipulator system operator-mission specialist will be selected later.

NASA has also established an independent review team for the second Hubble mission, led by former astronaut Rick Hauck and including STS61 commander Richard Covey, who has retired from the astronaut corps. The team will be involved in mission-planning, risk-assessment and flight-readiness issues.

One added risk to the STS82 mission is the plan to test a reboost manoeuvre planned for the 1999 HST servicing mission during which the solar panels will remain fully deployed.

During a series of short thruster firings, any movement of the panels will be monitored carefully to ensure that it will be safe to leave them deployed during the actual manoeuvre in 1999. By then, the HST's altitude will be too low to ensure full control over pointing capability.

Originally, it was planned to retract the arrays for the manoeuvre, but the risk of not being able to redeploy them afterwards was considered greater than leaving them extended.

Additional servicing missions are planned for 1999, 2002 and 2005. The Hubble Advanced Camera for Exploration will be installed during November 1999.

Astronomers using the HST's images of Saturn have discovered two "probable" moons in addition to 18 already discovered by Earth observations and by the Voyager 1 and 2 spacecraft, which flew past the planet in 1980-1.

Source: Flight International