US space agency reverses earlier decision and will send Shuttle to service telescope

NASA's overwhelmingly popular decision to mount a Space Shuttle mission to repair the Hubble Space Telescope will affect the agency's plans for the Orion crew exploration vehicle (CEV).

Expected in 2008, the SM-4 servicing mission by orbiter Discovery will require a second Shuttle to be ready to launch a rescue attempt. This will affect plans to hand over Pad 39B to the Constellation exploration programme for flight testing of the Ares I crew launch vehicle, says NASA administrator Michael Griffin.

The manned CEV, being designed by Lockheed Martin, will also have to be capable of reaching the Hubble in the 2020-25 timeframe to attach a solid rocket motor with which to de-orbit the massive telescope safely at the end of its life. Plans to attach a de-orbit stage during the SM-4 mission have been dropped. "We will build the CEV with the capability of going to Hubble, so we don't need to worry right now," says Griffin.

The servicing mission - the fifth since Hubble was launched by a Shuttle 16 years ago - will see the replacement of batteries, attitude-control gyros and a guidance sensor and the installation of two new scientific instruments, the Cosmic Origins Spectrograph and Wide Field Camera 3, potentially extending Hubble's life for at least five more years.

Speaking at NASA Goddard Space Flight Center in Maryland last week, Griffin's announcement that "we are going to add a Hubble servicing mission to the manifest before the Shuttle fleet retires" drew a standing ovation and meant victory for the campaign to overturn the agency's decision, in the wake of the Columbia disaster, not to risk a mission that would preclude using the International Space Station as a safe haven in the event of damage to the orbiter's thermal protection.

Griffin says the last three successful Shuttle missions proved the orbiter could reach the Hubble and perform the repair mission despite the additional requirements of inspecting, and potentially repairing, the thermal protection system without help from the ISS. "We have a couple of techniques to effect small repairs that would survive re-entry," he says, and the ability to use the extended orbiter boom sensor system as a work platform for in-orbit repairs has been proved.

In the absence of the ISS safe haven, Discovery's time in orbit "can be extended to 25 days without extreme measures", says Griffin. Meanwhile, a scheduled ISS assembly mission will be timed so that a second Shuttle is on the pad throughout the Hubble flight ready to launch a rescue. The crew for the servicing is mission commander Scott Altman, pilot Greg Johnson and mission specialists Andrew Feustel, Mike Good, John Grunsfeld, Mike Massimino and Megan McArthur.

Following the 2003 Columbia disaster, Hubble faced being abandoned and de-orbited in 2013. But pressure from the scientific community, and a report by the National Academy of Sciences that concluded Hubble's continued operation was highly advisable, changed NASA's decision. The repair mission will keep Hubble operational until its successor, the James Webb Space Telescope, is launched by expendable booster in 2013.

Additional reporting by Graham Warwick

Source: Flight International