A German-built telescope is exposed during a flight of NASA's Stratospheric Observatory for Infrared Astronomy 747SP on Dec. 18, 2009. The telescope doors were fully opened, allowing engineers to understand how air flows in and around the telescope. (NASA Photo / Carla Thomas) NASA's Stratospheric Observatory for Infrared Astronomy – SOFIA – resumed flight envelope expansion test flights over the past two weeks. With its telescope cavity door both open and closed, the modified 747SP flew a variety of flight-test maneuvers to gauge its handling qualities and any potential problems with vibrations and buffeting.
As part of the tests, the SOFIA's pilots have been flying simulated landing approaches at 15,000, 25,000 and 35,000 feet altitude to evaluate aero-acoustic effects of having the 16-foot-high telescope door open while the aircraft is in landing configuration. Airspeeds during the test maneuvers have ranged from a low of about Mach .55 at the lower altitudes to a high of about Mach .84 at the higher altitude, with some additional test points at Mach .92 planned.
"These test flights are intended to verify that we can operate this airplane safely and have scientists on board to accommodate first light science flights," said NASA research pilot Tim Williams, one of the SOFIA pilots on the current series of test flights. "So far, we haven't seen any things that would alarm us."
When its initial science missions begin later this year, SOFIA will conduct world-class astronomical observations in the infrared while cruising at more than seven miles above ground.
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