The detection of weak, longer-wavelength infrared light requires the instruments to be kept at extremely low temperatures. The liquid helium aboard Spitzer was expected to last for two and a half years, but NASA officials say the "efficient design and careful operations" allowed that to more than double to five and a half years.
But the end of the liquid helium doesn't mean an end to Spitzer's operation.
Although the longer wavelength multiband imaging photometer and the infrared spectrograph will no longer be able to detect cool objects, the two shorter wavelength detectors will still function properly at the relatively warm temperature of -242 Celsius (-404 Fahrenheit).
"They will still pick up the glow from a range of objects: asteroids in our solar system, dusty stars, planet-forming disks, gas-giant planets and distant galaxies. In addition, Spitzer still will be able to see through the dust that permeates our galaxy and blocks visible-light views," said NASA officials.
Among the projects still planned for Spitzer include refining estimates of the rate at which the universe is expanding, searching for extremely distant galaxies, and examining the atmospheres of the gas giant planets expected to be found by Kepler.
"We will do exciting and important science with these two infrared channels," said Spitzer project scientist Michael Werner. "Our new science program takes advantage of what these channels do best. We're focusing on aspects of the cosmos that we still have much to learn about."