Note to Editors: LASP will hold an open house at its East Campus facility Friday, Feb. 22, at 3 p.m. on Colorado Avenue east of 30th Street featuring scientists, students and instruments involved in SORCE.
Five space instruments developed and built at the University of Colorado at Boulder are being shipped to a spacecraft manufacturing plant in Dulles, Va., next week in preparation for a November 2002 launch to measure solar radiation.
The mission, known as the Solar Radiation and Climate Experiment, or SORCE, is a small, free-flying satellite built by Orbital Sciences Corp. for CU-Boulder's Laboratory for Astrophysics and Space Astronomy. Sponsored by NASA, the $85 million project is part of NASA's Earth Observing System.
"From a financial standpoint, SORCE is the largest project LASP ever has been involved in," said Gary Rottman, a LASP senior research associate who is spearheading the project. Ultraviolet radiation in Earth's atmosphere influences a wide variety of chemical processes, including the natural production and destruction of ozone.
The SORCE spacecraft will be launched from a Pegasus expendable-launch vehicle, also built by Orbital Sciences Corp. The Pegasus will be carried to an altitude of 40,000 feet by a jet aircraft and dropped in a five-second free-fall. It will then ignite horizontally and begin ascending, placing SORCE in a circular orbit about 400 miles above Earth within 10 minutes.
"The SORCE spacecraft specifically will study solar variability and its influence on climate change," said Rottman. "We are interested in understanding the sun's influence on Earth's atmosphere and climate so that we can more reliably determine how humans are changing the environment."
Rottman also is the principal investigator on an instrument known as SOLSTICE flying aboard NASA's Upper Atmosphere Research Satellite, launched in 1991. Two nearly identical copies of that ultraviolet radiation-measuring instrument will be flying on SORCE to continue the UARS observations.
SORCE also will include a Total Irradiance Monitor, or TIM, said Rottman. TIM will monitor changes in the total amount of sunlight reaching Earth. Measurements made in the last 20 years indicate total solar radiation has changed only 0.1 percent over the 11-year solar cycle, with somewhat greater variations on a day-to-day basis.
The spacecraft also will carry a Spectral Irradiance Monitor, or SIM, a prism-like device to gather visible and infrared data, said Rottman.
The fifth CU-Boulder-built instrument is the X-ray Photometer System, or XPS, a package of 12 photodiodes to measure extreme ultraviolet sunlight, he said.
For example, strong evidence indicates the release of man-made chlorofluorocarbons, or CFCs, are largely responsible for the decline in stratospheric ozone levels in the 1990s, most markedly over the Antarctic and Arctic. Used in the manufacture of refrigerants, cleaners and foaming agents, CFCs' migrations into the upper atmosphere decompose under ultraviolet sunlight, freeing chlorine atoms to act as catalysts in the destruction of ozone molecules.
"There really doesn't seem to be any doubt that significant changes are occurring in stratospheric ozone levels," said Rottman. "By understanding and removing the natural variability due to variations of solar radiation, we can more accurately establish how much of the change is the result of human activity."