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19 July 1999
For Immediate Release

Fuse Satellite Tracks First Star Image

On July 18, 1999, the Far Ultraviolet Spectroscopic Explorer (FUSE) successfully acquired and tracked its first star image as part of the initial calibration testing using the Instrument Data System (IDS) that controls instrument functions. The IDS, developed by The Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Md., acquired an image of a star field from the instrument's Fine Error Sensor supplied by the Canadian Space Agency, identified specific stars in the image, and began controlling the satellite attitude using those stars as a reference. The IDS flight software allows the satellite to achieve and hold a pointing accuracy of 0.5 arcseconds (1/7200 of a degree). This high-accuracy pointing will be required to collect the FUSE mission science data.

The IDS flight software allows the FUSE satellite to operate autonomously for periods of more than 24 hours. IDS is programmed from the ground with instructions on what celestial objects to observe and the duration of those observations. The flight software then sequences through the observations automatically, finds the specific targets, configures and aligns the instrument, and then acquires the data. IDS also implements an active thermal control system that is necessary to achieve and maintain the precise optical alignment required for successful acquisition of the spectroscopic data. This software was developed in conjunction with Interface & Control Systems, Inc., of Columbia, Md., and Melbourne, Fla.

"The IDS software is some of the most complex flight software developed at APL and for spacecraft in general," states Larry Frank, APL's mission system engineer for FUSE. "It integrates command and data handling, high-accuracy attitude determination, and active thermal control." Adds Ted Mueller, the APL project manager, "This significant event for FUSE indicates that our flight software is ready to support science data collection scheduled to begin in Fall 1999."

Along with software development and hardware procurement for IDS, APL procured the FUSE spacecraft system. APL's other contributions included mission system engineering, the instrument's Power Switching and Distribution Unit, and the instrument's Electrical Ground Support System, which included database management, flight part procurement for common buys, component engineering, mirror development, and integration and test facilities.

Launched on June 24, 1999, from Cape Canaveral, Fla., FUSE is a NASA mission developed and managed by the Center for Astrophysical Sciences at The Johns Hopkins University in collaboration with APL and other universities, contractors, and international partners. The three-year mission will probe the chemical composition and evolution of the universe using the technique of high-resolution spectroscopy in the far-ultraviolet spectral region. FUSE is operated from a control center on The Johns Hopkins University Homewood campus in Baltimore. The satellite will continue to be calibrated over the next few months in preparation for routine operations.

The Applied Physics Laboratory (APL) is a not-for-profit laboratory and independent division of The Johns Hopkins University. APL conducts research and development primarily for national security and for nondefense projects of national and global significance. APL is located midway between Baltimore and Washington, D.C., in Laurel, Md.

For more information, contact:

JHU Applied Physics Laboratory
Helen Worth
Laurel, MD 20723
Phone: 240-228-5113