HUBBLE SPACE TELESCOPE STATUS REPORT

The new science instruments installed on the Hubble Space Telescope (HST) during the second servicing mission in February are performing normally. Activities being carried out as part of the Servicing Mission Orbital Verification (SMOV) continue to go well.

Scientists are entering an intensive calibration and science assessment phase for both the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS). During the next three weeks, scientists will obtain important calibrations for NICMOS, which include absolute photometry, aperture locations and extensive background measurements. Charged Couple Device (CCD) calibrations will continue on STIS and the Multi-Anode Microchannel Array (MAMA) detectors will be turned on and their performance verified.

The latest test on NICMOS camera 3 showed that the focus position remained constant between the last two measurements. This gives further indication that the instrument is very close to equilibrium. As reported in the previous status report (April 8), the NICMOS science program will be conducted assuming a 2-year life span for the instrument.

An HST safing event occurred last week when one of HST’s gyros failed. HST has six gyros, but only three are needed to point and track the telescope. Operations have returned to normal using three gyros. The loss of the gyro will not impact HST science operations.

Astronauts replaced two pairs of gyros on Hubble during the first servicing mission in 1993. Since then, NASA has had great success with HST’s gyros considering gyros are among the most commonly failed hardware on spacecraft. One gyro failed in December 1990, a second failed in June 1991, and a third in November 1992. None of the gyro failures affected HST’s performance; however, replacing the failed hardware increases system reliability. The latest gyro to fail will be replaced during the next servicing mission, targeted for 1999.