June 23, 2006N
ASA scientists have no explanation for Hubble's Advanced Camera for Surveys' (ACS) unexpected shutdown June 19. At 1:15 P.M.
EDT, peak power-supply voltages in the camera's charge-coupled device (CCD) Electronics Box (CEB) exceeded limits. As a result, the camera suspended activity and automatically went into safe mode.
Preliminary analysis of technical information from the camera's components reveals no anomalies. Tests focusing on the camera's low-voltage power supply and analog-to-digital converters are now under way. One possibility being considered for the camera's shutdown includes a cosmic-ray strike that damaged its electronics.
The ACS team is considering switching to the camera's backup electronics, although they have never before been used. The switch, which could take place as early as next week, would also involve recalibrating the ACS. Scientists estimate ACS' recalibration could take several weeks.
Max Mutchler, an astronomer and science-instrument analyst at the Space Telescope Science Institute (STSCI) in Baltimore, told ScienceNOW Daily News,
"It's a serious situation." Mutchler knows firsthand how valuable the Hubble cameras are: He was the first person to use Hubble images to identify Pluto's second and third satellites, Nix and Hydra.
For now, no science observations can be carried out with the ACS — Hubble's most-used camera — and time reserved for ACS observations will have to be filled with non-ACS observations. Hubble's other instruments include: the Near Infrared Camera and Multi-Object Spectrometer (NICMOS); Space Telescope Imaging Spectrograph (STIS); and the Wide Field Planetary Camera 2 (WFPC).