An $85 million NASA satellite carrying five instruments designed and built at the University of Colorado at Boulder to study how and why variations in the sun affect Earth聮s atmosphere and climate is slated for launch on Jan 25.
The mission, known as the Solar Radiation and Climate Experiment, or SORCE, is a free-flying satellite that will launch from Florida聮s Kennedy Space Center. CU-Boulder聮s Laboratory for Atmospheric and Space Physics designed and built the instruments and contracted Orbital Sciences Corp. of Dulles, Va., to build the satellite bus. The project is part of NASA聮s Earth Observing System.
聯We need a long-term record of the natural variation in Earth聮s climate, including changes in the sun, land and sea surfaces to hang our hat on in order to model future climate change,聰 said Gary Rottman, a LASP senior research scientist and principal investigator on the SORCE project. 聯Precisely measuring changes in solar radiation is a large key to this challenge.聰
Rottman also is the principal investigator on an instrument dubbed SOLSTICE, which launched on NASA聮s Upper Atmosphere Research Satellite in 1991. Originally scheduled to orbit Earth for three years, SOLSTICE is still orbiting and functioning and has given researchers a full 11-year solar cycle. An article that appeared in the Dec. 20, 2002 issue of Science magazine 聳 a highly respected weekly science journal -- cited the sun-Earth connection as one of five key areas to watch in 2003.
聯From a financial standpoint, SORCE is the largest single project LASP ever has been involved in,聰 said Rottman. 聯Ultraviolet radiation in Earth聮s atmosphere influences many of the chemical processes, including the natural production and destruction of ozone.聰
The SORCE spacecraft will be launched from a Pegasus expendable-launch vehicle built by Orbital Sciences. 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 accelerate in front of the jet, and begin ascending, placing the SORCE satellite in a circular orbit about 400 miles above Earth within 10 minutes.
聯The SORCE spacecraft specifically will study solar variability and its influence on climate change,聰 said Rottman. 聯We are interested in understanding the sun聮s influence on Earth聮s atmosphere and climate so that we can more reliably determine how humans are changing the environment.聰
According to Tom Sparn, the SORCE project manager, understanding the sun is crucial to evaluating its influence on Earth. 聯Everything about climate, from droughts and ozone loss to human health problems like eye cataracts and skin cancer, revolve around our understanding of the sun,聰 he said. 聯We need to integrate our long-term solar data with supercomputers that model Earth聮s climate system to see what is occurring in the big picture.聰
Two nearly identical copies of SOLSTICE will be flying on SORCE, which will be controlled at LASP聮S CU Research Park facility.
SORCE also will include the Total Irradiance Monitor, or TIM, to monitor changes in the total amount of sunlight reaching Earth. The spacecraft 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.
聯Because SOLSTICE has been flying on UARS for so long, we have the calibration to match up with our new data sets,聰 said Sparn. We finally have an anchor point.聰
Evidence indicates the release of man-made chlorofluorocarbons, or CFCs, were largely responsible for the decline in stratospheric ozone levels in the 1990s, said Rottman. "There really doesn't seem to be any doubt that significant changes are occurring in stratospheric ozone levels," said Rottman. 聯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."
SORCE research and education efforts benefit the scientific community and the general public, said LASP Director Daniel Baker. 聯Understanding fluctuations in the sun has become crucial in the last several years, fluctuations ranging from space weather to the sun聮s impact on our everyday lives. We want to share this information with the top solar scientists as well as K-12 students, college students and the general public, and we now have the NASA mission to do it.聰