As the hugely expensive Hubble Space Telescope continued to orbit Earth and capture the headlines this past year, the modest Kuiper Airborne Observatory--the world’s only airborne observatory--quietly finished a 21- year career as a workhorse of infrared astronomy. The Kuiper was a C-141 cargo plane retrofitted with a 450-pound telescope mounted on a vibration- shielding cushion of air. It flew countless missions at 41,000 feet, where its telescope could be above 99 percent of the atmosphere’s infrared- blocking water vapor. Since the observatory was mobile, it was able to chase the shadows that planets cast as they pass in front of stars and look for faint planetary features in the starlight. Such sightings revealed the rings of Uranus in 1977 and Pluto’s atmosphere in 1988. In its last year, researchers used the Kuiper to study Neptune’s moon Triton, among other things.
To replace the Kuiper, Congress seemed amenable to funding a plane called Sofia--the Stratospheric Observatory for Infrared Astronomy. Even if more space-based telescopes like the Hubble are launched, Sofia will retain two big advantages. For one, scientists will be able continually to update the telescope simply by carrying new equipment onto the plane. And, as Sofia project scientist Edwin Erickson says, the program’s cheap.