Scientists in SwRI's Space Instrumentation and Research Division, in collaboration with NASA's Dryden Flight Research Center, have just completed a successful, groundbreaking proof-of-concept program that takes astronomy and astronomers into the backseat of high performance, two seater military jet aircraft used by NASA for flight testing. The test program culminated on January 9th with the successful observation from a NASA F-18 of an asteroid occulting a star using SwRI's SWUIS-A airborne astronomical imager. According to SwRI's Dr. Alan Stern, the project's Principal Investigator, "This observation will reveal the size of the asteroid, 308 Polyxo, which (like most asteroids) is too small for even the Hubble Space Telescope to resolve." Dr. Daniel Durda, the SWUIS flight astronomer for the just completed asteroid occultation mission adds, "Our observation with SWUIS-A, obtained from above the high clouds that obscured the sky over Dryden during the event, will be combined with three ground-based observations from other locations to deduce the shape of 308 Polyxo as well."
Click here to see an mpeg animation (1612K) of the 308 Polyxo occultation reconstructed from SWUIS-A flight data. First, you will see a star chart showing HIP 49999, the 8.5 magnitude star occulted by 308 Polyxo. The chart then disolves to SWUIS-A images of the star field taken before, during, and after the occultation event. If you look carefully at the image taken during the event itself, when the star has been occulted by Polyxo, you may note the faint image of the asteroid itself, at magnitude 12.7.
Click here to see an mpeg movie (1878K) of the actual SWUIS-A flight data of the 308 Polyxo occultation.
For decades, airborne astronomy and geophysical observations have proven useful adjuncts to groundbased and spacebased instrumentation, particularly for optical and infrared studies. Compared to groundbased instruments, airborne research platforms offer superior atmospheric transmission, the mobility to reach remote and often otherwise unreachable locations over the Earth where no observatories exist, including over the oceans. Airborne platforms also offier virtually guaranteed good weather for observing the sky, and they are far less expensive to operate than spacecraft.
A key advantage of the small, high performance platforms like the F-18s over larger, more conventional airborne platforms is the even greater cost savings they generate. For example, an F-18 is about 10 times less expensive to operate per hour than the KC-135/Boeing 707s and Boeing 747s used for most airborne astronomy missions. Other key advantages include worldwide basing (obviating the need for expensive, campaign-style movement of specialized large aircraft and their logistics support teams), and ultimately faster reaction times to transient astronomical events.
Although small, high-performance aircraft cannot carry as large a payload or as sophisticated telescopes as larger airborne observatories, the SwRI/NASA demonstration program has shown that astronomers can fly with their instruments in these aircraft, thereby providing Space Shuttle-like "payload specialist" capability to "close the loop" in real time during the flights. Flight training for the two SWUIS-A flight astronomers (PI Stern, and CoI Durda), funded largely through the SwRI internal research program, has included intensive FAA and NASA flight physicals, various aircraft systems training courses, altitude chamber training, aircraft egress and ejection seat training, water survival school, and aircraft certification check rides.
To date 14 successful SwRI/NASA airborne astronomy missions missions have now been flown, all using the sensitive but rugged SWUIS-A airborne imager. These missions included five high-altitude flights with Dr. Stern in a NASA/WB-57 to observe comet Hale-Bopp in mid-1997, and nine missions with Drs. Stern and Durda in NASA/F-18 aircraft to perfect techniques for observing asteroid and planetary occultations over oceans where groundbased facilities cannot be based.
Future SWUIS-A airborne missions aboard high-altitude aircraft, such as two-seater U-2s flying at up to 75,000 feet, will take advantage of the ability of the instrument to look near (and soon, even at) the Sun to search for Vulcanoids (a putative population of small asteroids circling the Sun inside Mercury's orbit) and to observe breakup mechanics in Sun-grazing comets. On the horizon there is also the possibility of using SWUIS-A to detect and track space debris that might pose a hazard to satellites, the Space Shuttle, and the International Space Station, and the application of SWUIS-A to the study of a variety of terrestrial aeronomical phenomena, including lightning and sprites, aurora, and ozone studies, and future studies of meteoroid showers, missile tests, and other phenomena of interest.
Few institutions can now match the capabilities that have been developed at SwRI for airborne, scientist-in-the-loop research missions using comparatively inexpensive, high-performance aircraft. For more information on the SWUIS-A system, contact PI Stern at SwRI in Boulder, CO, or visit the SWUIS-A web site at http://www.boulder.swri.edu/swuis/swuis.instr.html.