Hub­ble tele­scope spins round, fixes self

Calgary Herald - - NEWS - Amy B. Wang

It hasn’t been the best month for the Hub­ble Space Tele­scope.

Dur­ing the first week of Oc­to­ber, one of the space­craft’s three gy­ro­scopes failed. The gi­ant tele­scope needs the de­vices to mea­sure turn­ing speeds and to zero in on the things in space it ob­serves and pho­to­graphs.

In a state­ment, NASA re­as­sured the pub­lic that the break­down was ex­pected, say­ing the gyro “had been ex­hibit­ing end-of-life be­hav­iour for ap­prox­i­mately a year” and, in any case, “two other gy­ros of the same type had al­ready failed.”

To re­place it, NASA en­gi­neers pow­ered up a backup gy­ro­scope that had been dor­mant since early 2011. They were heart­ened, at first. The gy­ro­scope be­gan spin­ning de­spite not be­ing used for 71/2 years. How­ever, it sent back read­ings that were clearly too high.

The dis­crep­ancy was “sim­i­lar to a speedome­ter on your car con­tin­u­ously show­ing that your speed is 100 miles per hour faster than it ac­tu­ally is,” NASA said. “It prop­erly shows when your car speeds up or slows down, and by how much, but the ac­tual speed is in­ac­cu­rate.”

En­gi­neers con­cluded the prob­lem must have been some kind of me­chan­i­cal ob­struc­tion. Vow­ing to fix it, NASA kept the tele­scope in “safe mode,” lim­it­ing its op­er­a­tions in the same way a com­puter in that mode op­er­ates at bare-bones set­tings.

Keep­ing the tele­scope in safe mode also meant “we were not do­ing science,” Hub­ble Op­er­a­tions project man­ager Pa­trick Crouse told The Wash­ing­ton Post. Days passed.

NASA teams ran tests, re­viewed the flight soft­ware and con­sid­ered what they could do to rem­edy the prob­lem with as lit­tle dam­age as pos­si­ble to their prized (and ex­pen­sive) tele­scope.

On Oct. 16, the Hub­ble team even at­tempted a “run­ning restart,” turn­ing the prob­lem­atic gy­ro­scope off for one sec­ond, then back on again. Un­for­tu­nately, the “have you tried pow­er­ing it off and on?” ap­proach — long favoured as a first-re­sort by tech­ni­cal sup­port staff on Earth — didn’t work in space. Would that it were that easy, Crouse said.

In­stead, what ap­peared to work was re­peat­edly turn­ing the en­tire Hub­ble space­craft to see if it would “dis­lodge” any­thing that was block­ing the gy­ro­scope in ques­tion.

The re­peated ma­noeu­vres seemed to work, with the gyro re­port­ing ro­ta­tion rates that were back to nor­mal — much to the re­lief of Hub­ble en­gi­neers, Crouse said.


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