Back To Flight: The SOFIA Flies And Is Poised To Reach Milestone
NASA's Stratospheric Observatory for Infrared Astronomy, or SOFIA, took to the air for the second time in less than a week Dec. 14 for the first flight tests with both the internal and external doors that cover its large infrared telescope opened.
The highly modified Boeing 747SP lifted off from U.S. Air Force Plant 42 in Palmdale, Calif., just five days after a Dec. 9 check flight. During that test, the external telescope cavity door was opened for the first time in flight, although the inner door that covers the telescope remained closed. The SOFIA's test missions are conducted in restricted airspace near Dryden over Edwards Air Force Base.
On the Dec. 14. mission, test engineers opened the telescope cavity doors to 10 percent of their maximum range to evaluate the effects of airflow on the structural integrity of the telescope, the cavity and the airframe.
A third flight, a major milestone for the SOFIA development program in which the two doors will be fully opened using the cavity door drive system to expose the telescope, is scheduled for the near future. During both test flights, the telescope's primary mirror is covered to protect it from unexpected debris.
The flights this month were the first since January 2008. The 747SP carries a German-built telescope that will be used for infrared astronomy research.
The Dec. 9 check flight evaluated the aircraft's performance, handling characteristics and flight systems, including engines, flight controls and communication. The cavity door drive system, the mechanism that controls the doors covering the telescope cavity, was engaged without exposing the telescope.
Modifications that have been made to the aircraft and telescope since previous test flights include:
- The telescope's primary mirror was removed, coated and reinstalled.
- Upgrades were completed on the telescope's gyros, fine drive brakes, vibration isolation system and cooling supply unit.
- The upper rigid door covering the telescope cavity was instrumented and reinstalled with the lower flexible door and aperture.
- The telescope cavity door drive system was installed.
- Test instrumentation equipment was added throughout the aircraft.
- The basic mission command and control computer equipment to move the telescope during flight was built and installed.
- Routine 747SP maintenance was completed.
While the aircraft was undergoing maintenance at NASA's Dryden Aircraft Operations Facility in Palmdale, three nighttime telescope operational checkouts were conducted with several of the SOFIA's unique instruments, including the Focal Plane Imager, the High-speed Imaging Photometer for Occultations and the Fast Diagnostic Camera.
The SOFIA program is a partnership between NASA and the DLR (German Aerospace Agency). The program is managed at Dryden, with the related science project managed at NASA's Ames Research Center near Moffett Field, Calif. The SOFIA is based at the DAOF.
By Beth Hagenauer
Dryden Public Affairs