May 15 2009
From The Space Library
After the SST entered standby mode at 3:11 p.m. (PDT), NASA announced the end of its primary mission and the start of its “warm” mission. NASA had designed SST to conduct a two- and-a-half-year mission to detect infrared light from cool cosmic objects, a mission that required maintaining the telescope’s three instruments at -456°F (-271°C), the coldest temperature theoretically attainable. SST’s liquid helium, used as cryogen, had lasted twice as long as projected—more than five-and-a-half years—but Spitzer’s supply of the coolant had finally depleted. The telescope would remain cold, at -404°F (-242°C), but that temperature would be too warm to allow Spitzer’s infrared spectrograph and its longer wavelength, multiband imaging photometer to detect cool objects in space. SST Project Manager Robert K. Wilson at NASA’s JPL remarked that, with its coolant depleted, Spitzer would be “reborn,” with a mission to tackle new scientific pursuits. During its so-called warm mission, Spitzer would continue to see through the dust that permeates our galaxy, blocking visible-light views, and two channels of one of its instruments would continue to operate at full capacity. Spitzer’s two infrared-array camera detectors with short wavelengths would continue to function as designed, picking up the glow from a range of objects, such as asteroids, dusty stars, planet-forming discs, gas-giant planets, and distant galaxies. Spitzer’s new projects would include refining estimates of Hubble’s constant; searching for galaxies at the edge of the universe; assessing how often potentially hazardous asteroids might impact Earth; and characterizing the atmospheres of gas-giant planets that astronomers expected NASA’s Kepler mission would discover.
NASA, “NASA’s Spitzer Telescope Warms Up to New Career,” news release 09-099, 6 May 2009, http://www.nasa.gov/home/hqnews/2009/may/HQ_09-099_Spitzer_Warms_Up.html (accessed 20 June 2011); NASA Jet Propulsion Laboratory, “Spitzer Space Telescope Mission Status,” JPL news release 15 May 2009, http://www.jpl.nasa.gov/news/news.cfm?release=2009-086 (accessed 30 June 2011).
Astronauts Michael J. Massimino, a mechanical and robotics engineer on this third spacewalk, and Michael T. Good, a former U.S. Air Force test pilot on his first space mission, undertook the second of five planned spacewalks to repair the HST. The spacewalk agenda consisted of the most important task of the 11-day mission—to replace the gyroscopes that kept the telescope pointed in the correct direction—and to replace three batteries. Working from inside the telescope, Good and Massimino had difficulty installing the second set of new gyroscopes and resorted to using a spare that did not initially fit either. The extra work extended the spacewalk to 8 hours—1.5 hours longer than scheduled—making it the tenth longest spacewalk on record.
Dennis Overbye, “Astronauts Work on Replacing Hubble’s Gyroscopes,” New York Times, 16 May 2009.
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