HOUSTON A 2001 mission to the Hubble Space Telescope will finish the job that will be started by Discoverys spacewalkers this year.
NASA officials originally planned to accomplish all the tasks with a mission planned for 2000, but a series of gyroscope failures forced the space agency to launch earlier and split the repairs between two flights.
Dr. John Campbell, the telescopes project manager, said flight rules dictated an earlier mission after a third gyroscope failure. The telescope has six gyros and must have three operating to continue the science mission.
"Since we were already involved in preparations for the servicing mission next year," Campbell said, "we essentially decided to divide the planned mission into two flights and reduce the workload on each."
Another gyro failed over the weekend ending the science mission until Discoverys crew replaces the units in December. The telescope is now in a "safe" mode and being directed by ground controllers.
The June 2001 mission focuses more on adding and improving scientific instruments aboard the telescope in addition to replacing solar arrays and continuing repair work on the Hubbles insulating blanket.
Space walkers will add an advanced camera to Hubbles scientific package that is 10 times more powerful than ones currently on board.
Additionally, astronauts will add a cooling unit to the Near Infrared Camera and Multi-Object Spectrograph (NICMOS) installed in 1997. Unfortunately, the unit ran out of coolant in 1999 has not been used since.
"If it works, it will restore a dead instrument back to life," said Dr. Edward Weiler, the space agencys associate administrator for space science.
The cooling package should keep NICMOS operating until the end of Hubbles mission in 2010.
Hubble managers have also decided to install a cooling package in the telescopes aft area for the other scientific instruments.
Swapping solar arrays will also allow use of up to four instruments at once. The new panels produce about 30 percent more power than the old ones.
Campbell said the improved cooling and power would allow scientists to use multiple instruments at once.
Astronauts will also continue repairs to the telescopes insulating blanket. The insulation protects the telescope from severe and rapid temperature changes as it makes the 90-minute orbit around the Earth.
During the 1997 mission to Hubble, astronauts discovered tears and breaks in the insulation.
Hubble managers will have a last chance to fix any problems or make changes with the final servicing mission to the telescope in 2003.
Current plans include changing all of the telescopes batteries and gyros. Project managers are keeping their options open though.
"Roughly a year or so before the 2003 final servicing mission, well take a close look at every piece of hardware on there," Weiler said. "After 2003, there will be no more servicing missions and what [we] have is what we have."
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