159. GP-B Aft Power Unit
View of a flight Gravity Probe-B Aft Power Unit (APU) built for Stanford
University. The APU contains 5 individual ultra-low noise
(sub-microvolt) power supplies (both high voltage and low voltage) for
providing power to the GP-B gyroscope suspension system. The unit is
approximately 11 inches by 17 inches. The compartments provide both
structural rigidity as well as noise isolation. Four APU units are
operating on-orbit as part of the GP-B mission launched in April 2004.