By Patricia Daukantas
No sooner did we report on the progress toward the next Hubble Space Telescope repair mission than we have to note that the repair mission has been postponed for several months.
NASA officials, including Preston Burch, the Hubble program manager at NASA’s Goddard Space Flight Center, today announced the delay after a serious communications glitch developed within the orbiting telescope. The shuttle mission, known as STS-125, may launch next February.
The glitch – which has nothing to do with Hubble’s optical systems – developed over the past weekend in the orbiting observatory’s science instrument command and data handling unit. An undetermined error caused “side A” of the unit to put itself into safe mode, thus interrupting the flow of science data from the optical instruments to researchers on Earth.
The Hubble team will try to activate “side B” of the data handling unit, which, like “side A,” has been in orbit since the telescope’s launch in 1990. Over the next few days, the team will assess whether that activation will pose any large risk to the telescope, and test out their theories using the Vehicle Electrical System Test (VEST), a copy of the Hubble support system bay that resides in the huge NASA Goddard clean room in Greenbelt, Maryland, USA. If “side B” can turn itself on, astronomers can resume observations with the existing Hubble instruments.
According to Burch, NASA has a backup copy of the dual-sided data handling unit here on the ground, and Goddard researchers will start testing it for flight qualification. If the unit passes the severe vibration, thermal vacuum and acoustical tests, the fresh unit will be added to the STS-125 payload and the spacewalking astronauts will have to make time (up to two hours) to install it on the telescope. Of course, the backup unit is as old as the one in Earth orbit, but the space agency expects that tests will show that it still works.
Leaving only “side B” on the telescope would leave Hubble with several potential single points of failure, while the complete replacement of the data handling unit will bring Hubble’s communications systems back to full redundancy, said Ed Weiler, associate administrator of NASA’s science mission directorate.
The VEST unit inside NASA Goddard’s clean room. (Photo by Patricia Daukantas)
2008-09 September, Astronomy