Speaking of Hubble...

Archive: August 2009

Back to Cool

August 20, 2009 by Frank Summers

It’s the third week of August and already some of my friends on Facebook are talking about their kids going back to school. It struck me as weird because I don’t have my summer vacation until next week. My kids start school the following week. Seems those times of school starting after Labor Day (3 weeks away) are long gone.

Here at Space Telescope, August has been a month for getting back to work with Hubble. Servicing Mission Observatory Verification (SMOV) has been progressing all summer long with very good results. We even got a bonus: NICMOS is back to cool!

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The NICMOS Cryocooler System in the clean room.

NICMOS Anomaly
NICMOS is an instrument on Hubble whose acronym stands for Near Infrared Camera and Multi-Object Spectrograph. The important word here is “infrared.” Since infrared light is emitted by anything warm, infrared instruments like NICMOS must be cooled down to very low temperatures so that they can detect the emissions of astronomical objects and not their own hardware.

In September 2008, the NICMOS cooling system had to be shut down during a spacecraft computer update. Attempts to restart the cooling system after the update resulted in problems. In NASA-speak, these are called anomalies. The team made several attempts at restarting before work was discontinued in preparation for the October 2008 servicing mission.

As everyone knows, the October 2008 servicing mission was delayed until May 2009. During the winter, a few more attempts were made to restart NICMOS cooling, trying different solutions and encountering some different problems. In late January 2009, the restart attempts were deferred until after the servicing mission.

At this point, it has been almost a year since NICMOS was operational.

NICMOS Recovery
During Servicing Mission 4 in May 2009, NICMOS was not serviced. The problem was one for engineers, not astronauts, to solve. The SMOV plans for summer 2009 were chock full of tasks for both the two new instruments (WFC3 and COS) as well as the two repaired instruments (ACS and STIS). Still, it was important to get back to the work of recovering NICMOS as soon as feasible.

In late July, the first attempt at restart failed. New startup procedures were devised to work around the problems. It reminds me of the scenes in the movie “Apollo 13″ where Rusty Schweickart works through all sorts of variations of power startup in the ground simulator to find one that will work in space.

On August 1, the cooling system restarted and got past all the previous problems. NICMOS began cooling efficiently, and actually faster than expected. Note that when we say “cool,” we really mean “cold.” Really cold. Beyond Arctic, mind-numbing, freezingly cold. NICMOS is cooled to -321 degrees Fahrenheit. That’s the temperature needed for infrared observations.

It takes NICMOS more than a week to achieve that temperature. Then the instrument must show stability at those temperatures for science to be possible. After that comes a period of taking calibration data and determining how the instrument is functioning. Only then can science observations begin again.

Back to Business
We are not there yet, but we are past the major hurdle. It is a cause of many smiles in our building. Beyond that, SMOV is going well all around. Hubble looks to have five fully functional science instruments. The observatory will be the best it has ever been. And that, above all, is really cool.