CAPE CANAVERAL, Fla. A mid-February mission to service the Hubble Space Telescope might be delayed to give engineers time to put in place a plan to replace a balky pointing device aboard NASAs flagship observatory.
At present shuttle Columbia is scheduled for launch on Feb. 14, but the flight could be pushed back until late February or early March, a NASA Hubble project official said Tuesday.
One of the telescopes two reaction wheels devices that enable the observatory to be accurately pointed at celestial targets recently suffered a seven-minute glitch that prompted concern among project managers.
Data beamed back from the telescope showed that the wheel was spinning, but an associated tachometer indicated that the device was not rotating. The device since has been operating properly, but the glitch raised questions about its reliability.
Only one of the reaction wheels is needed to point the telescope, but project managers decided that it would be prudent to replace the balky device on the upcoming servicing mission.
Doing so, however, will require astronauts involved in the mission to undergo additional training to carry out the spacewalking replacement work.
A spare reaction wheel also will have to be readied for flight and delivered to Kennedy Space Center so it can be loaded aboard Columbia.
"Were now thinking of a two-week slip," NASA Hubble project manager Frank Cepollina said. "At least thats what were asking for."
Ceppolina said plans now are being put in place to conduct the change-out on the second of five back-to-back spacewalks to be carried out by the Columbia crew, which is headed up by veteran shuttle astronaut Scott Altman.
Mission specialists Jim Newman and Michael Massimino would likely carry out the work in that case. Fellow spacewalkers John Grunsfeld and Richard Linnehan also will be conducting servicing jobs on the telescope during the 11-day flight.
In what promises to be one of NASAs most complex servicing missions ever, the spacewalkers aim to replace the telescopes power-producing solar arrays and outfit the observatory with an advanced planetary camera.
A power control unit that distributes electricity from the solar wings to telescope batteries and other parts of the observatory also will be changed out, and the spacewalkers will retrofit a dormant infrared camera with a new experimental cooling system.
The mission will be the fourth of five planned servicing trips to the observatory, which was launched aboard shuttle Discovery in 1990. The telescope is expected to operate through 2010.
Made by Lockheed Martin, the observatory has no onboard steering thrusters, exhaust from which could foul sensitive telescope instruments. Consequently, plans now call for a shuttle crew to return the 13.5-ton observatory to Earth to avoid an uncontrolled atmospheric reentry.
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