For immediate release
San Antonio, Texas The NASA Johnson Space Center and the Southwest Research Institute in San Antonio, along with scientific collaborators from the Jet Propulsion Laboratory (JPL), Applied Physics Laboratory (APL), and the University of Maryland, will be flying an innovative, wide-field ultraviolet (UV) imager to observe comet Hale-Bopp from the space shuttle Discovery, to be launched in early August.
"The research goals of the instrument, termed the Southwest Ultraviolet Imaging System, or SWUIS, are to obtain image sequences of Hale-Bopp to study its coma and tail morphology and its response to solar wind conditions during its turn-off phase as the comet moves outbound beyond 2 AU (astronomical units)," says Dr. Alan Stern, SWUIS principal investigator and assistant director of SwRI's Space Science Department. Observations are scheduled on four days during the 11-day STS-85 Discovery mission; each observation period will last approximately three hours, and SWUIS will gather approximately 100,000 images in up to six ultraviolet and visible spectral bands to isolate various emissions from molecules in the comet.
SWUIS was conceived and developed under the direction of Stern. After laboratory development in 1992, SWUIS was flight tested in 1993 aboard a NASA SR-71 Blackbird aircraft flying at Mach 3.3 and at an altitude of 86,000 feet. In 1996, NASA accepted proposals to fly the low-cost imager on three flights of the shuttle, beginning with the August 1997 Discovery mission. SwRI Senior Research Scientist Dr. David Slater is the SWUIS project manager. Stern and Slater have teamed with Dr. Michael A'Hearn (University of Maryland), Dr. Paul Weissman (JPL), and Dr. Larry Paxton (APL) for the Hale-Bopp mission.
Weighing only 55 pounds, the instrument package is based around a rugged, 18-cm diameter Maksutov-design UV telescope and a UV-sensitive, image-intensified charged-coupled device camera that frames at video rates. By combining the video data in a computer on the ground, scientists can obtain sensitive measurements of astronomical targets observed by SWUIS; the video-rate framing also freezes out the motion of the shuttle.
The SWUIS experiment operates from inside the shuttle mid-deck cockpit and looks out of the shuttle through an optical-quality quartz window on the port side of the Orbiter. In contrast to the Hubble Space Telescope and most other space telescopes whose optics do not allow the instruments to view closer than 45 degrees to the Sun, SWUIS can observe as close as 20 degrees to the Sun. Although less sensitive than Hubble, SWUIS has more than 500 times the sky coverage area of Hubble. These capabilities make SWUIS ideal for studying comets, the inner planets, and a variety of other phenomena.
Discovery Mission Specialist Dr. Steve Robinson will operate SWUIS while Mission Commander Col. Curt Brown points the shuttle to view the comet. In a daring move to shield from the Sun the shuttle window through which SWUIS will view Hale-Bopp, Mission Specialist Dr. Jan Davis will position the shuttle's Remote Manipulator System arm to cast a shadow over the observing window to reduce scattered light and glare off the window.
SwRI personnel on the ground at Mission Control in Houston, assisted by JPL personnel, will advise Discovery astronauts on the quality of the data being obtained and make recommendations to optimize each of the four planned comet observing runs.
During the mission, Stern will be taking an infrared-sensitive version of SWUIS to altitudes as high as 50,000 feet aboard a NASA high-performance WB-57 aircraft operated out of the Johnson Space Center's Ellington Field to make additional observations that will complement the shuttle's UV measurements during its flight.
"We are very grateful to NASA for providing us this opportunity to conduct an important observational campaign with SWUIS, which will provide the only wide-field UV images of comet Hale-Bopp," says Dr. James Burch, vice president of SwRI's Instrumentation and Space Research Division. Additional flights of SWUIS to observe other solar system and astronomical targets are planned for 1998 and 1999 shuttle missions.