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ngc3314
2006-Jan-13, 06:01 PM
Hubble made a transition in late August designed to extend its useful life. After feasibility tests, in entered "2-gyro mode", in which all but two of the gyroscopes needed for pointing information were turned off (giving two spares). The remaining pointing information comes from the two star trackers which point backward from the telescope's optical axis by about 135 degrees. This imposes serious constraints on the area of sky accessible at any time, although the accuracy of pointing actually maintained within that area is almost equal to the 3-gyro mode. Statistics suggested that this mode could extend the usability of HST by perhaps a year, in the absence of an additional servicing mission.

At the end of an article by Roger Doxsey describing this transition (latest STScI newsletter (http://sco.stsci.edu/newsletter/PDF/2005/fall_05.pdf), pages 4-5), there is some added news that extends the unserviced ilfe of HST perhaps further. At the end, he writes, "Havng entered the operaional aera for 2GM, the engineering staffs at GSFC and the Institute have beguin investigating the possibility of a One-Gyro Mode (1GM). Based on the initial evaluation, and with relatively few changes to the current mode, PCS engineers believe that 1GM is feasible." In this mode, additional pointing information would come from the magnetometers' interaction with the geomagnetic field - an interaction used by FUSE and MOST not only for orientation information but for actual contol of their pointings.

So this gives hope for a longer lifetime for the telescope in the worst-case Shuttle schedule. Still, it sure would be nice to have a new set of batteries and gyros plus COS and WFC3...

Wolverine
2006-Jan-14, 04:56 AM
So this gives hope for a longer lifetime for the telescope in the worst-case Shuttle schedule. Still, it sure would be nice to have a new set of batteries and gyros plus COS and WFC3...

Indeed.