NASA鈥檚 attempt to resurrect the Hubble Space Telescope hit a roadblock on Thursday, further delaying an attempt to resume its science observations.
Engineers successfully bypassed a faulty computer on Wednesday in order to wake an 18-year-old onboard spare from hibernation.
But the telescope re-entered a standby, or 鈥渟afe鈥�, mode on Thursday, when the telescope鈥檚 science instruments were turned on for calibration.
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Software on the telescope鈥檚 Advanced Camera for Surveys (ACS), which until recently served as the telescope鈥檚 main camera, detected an anomalously low voltage level in the ACS and shut off the instrument at about 1330 EDT (1830 GMT), NASA announced on Friday.
A second glitch, which affected the telescope鈥檚 main control unit for its science instruments, sent the entire telescope into safe mode hours later.
The cause of the two problems is still unknown, and it is unclear whether they are related, Hubble manager Art Whipple of NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland told reporters.
鈥淲e鈥檙e in the early stage of going through a mountain of data that has been downloaded over the last 24 hours,鈥� Whipple said.
NASA had hoped to resume most science observations aboard the telescope on Friday, but now it is not clear when the telescope might begin working again.
Hubble has been down since late September, when a device needed to collect and process data from the telescope鈥檚 science instruments failed.
Star tracking
The glitch prompted NASA to postpone a long-awaited space shuttle mission to service the telescope.
The flight has been rescheduled for February, when the crew will attempt to replace the failed computer. But officials say that timeline could be optimistic, as the replacement part may not be ready to fly immediately.
Since the outage nearly three weeks ago, Hubble鈥檚 scientific activities have been limited to tracking the positions of stars using the telescope鈥檚 precision pointers, or Fine Guidance Sensors.
If the reboot is successful, Hubble will have three operational science instruments: the telescope鈥檚 Wide Field Planetary Camera 2; its Fine Guidance Sensors; and an ultraviolet sensor on the Advanced Camera for Surveys (ACS).
The ultraviolet sensor, called the Solar Blind Channel, is the only one that still works on the ACS 鈥� power problems knocked out the camera鈥檚 two other channels in 2007. The agency plans to send a new ACS power supply aboard the upcoming servicing mission.
Hubble鈥檚 infrared camera, called NICMOS (Near Infrared Camera and Multi-Object Spectrometer), may also come online several weeks after the telescope is rebooted, says Goddard spokesperson Susan Hendrix.
The instrument, used to observe faint, distant galaxies, has been incapacitated since September, when problems turned up in the spectrometer鈥檚 cooling unit.
