Servicing Hubble
Making
house calls
to Hubble
Servicing Mission 1
STS-61 Endeavour • December 2-13, 1993
Servicing Mission 1, launched in December 1993, was the first opportunity to conduct planned maintenance on the telescope. In addition,
new instruments were installed and the optics of the flaw in Hubble’s
primary mirror was corrected.
After Hubble’s deployment in 1990, scientist realized that the telescope’s primary mirror had a flaw called spherical aberration. The
outer edge of the mirror was ground too flat by a depth of 2.2 microns
(roughly equal to one-fiftieth the thickness of a human hair). This aberration resulted in images that were fuzzy because some of the light
from the objects being studied was being scattered.
COSTAR (the Corrective Optics Space Telescope Axial Replacement) was developed as an effective means of countering the effects
of the flawed shape of the mirror. COSTAR was a telephone boothsized instrument which placed 5 pairs of corrective mirrors, some as
small as a nickel coin, in front of the Faint Object Camera, the Faint
Object Spectrograph and the Goddard High Resolution Spectrograph.
The new Wide Field Planetary Camera (WFPC2) significantly improved ultraviolet performance over WFPC1, the original instrument.
In addition to having more advanced detectors and more stringent
contamination control, it also incorporated built-in corrective optics.
In addition, SM1 included the installation and replacement of other
components including the solar arrays, Solar Array Drive Electronics
(SADE), magnetometers, coprocessors for the flight computer, two rate
sensor units, two gyroscope electronic control units, and GHRS redundancy kit.