The Stellar Reference System - Bench Checkout Equipment (SRS-BCE) is used to test and calibrate the star tracker and stellar reference system on the GLAS instrument prior to launch. The stellar reference system compares the stars it views to a database of star fields. This permits extremely accurate altimetry measurements of the polar ice caps.
The SRS-BCE is used to test and calibrate the SRS. Therefore, it must be more accurately aligned and more stable than the flight instrument. This system feeds a star pattern into the GLAS SRS via a 257 fiber optic (16 x 16 with 1 reference fiber) array. The SRS-BCE also monitors this star pattern in relation to the GLAS Laser.
The entire system must be thermal vacuum compatible. Therefore, it must not out gas when subjected to vacuum levels of 10-7 Torr.