NASA seems reluctant to point out that this is not really "1 gyro mode" but actually "2 FGS mode". The Perkin-Elmer Fine Guidance Sensors on HST were always intended to provide absolute pointing knowledge when teamed with guide star positions from the Guide Star Catalog. Technically, the gyros provided smooth pointing with the FGSs constantly removing any rate bias by providing a pointing error update 40 times per sec. Now it appears the LMSC Pointing Control System is running algorithms which use the FGS error signals more directly in the sensor mix. This is not 'rocket science' or a technology miracle, but straightforward control practice. Given how well the basic FGS design, created in the 1970s, has worked over the decades, it would be nice if NASA credited the folks who designed and built them with flexibility to adjust to new application. Also the LMSC and Bendix teams who devloped the original system concepts that have been so resilient.
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