Saint-Hubert, Quebec and Ottawa, Ontario – July 21, 2003 -The Far Ultraviolet Spectroscopic Explorer (FUSE) satellite has been given a new lease on life following the successful implementation of new software in three on-board computers controlling the precision pointing of the telescope.
“As a research tool, FUSE has been used by more than 50 Canadian astronomers to date,” said Dr. John Hutchings, Principal Research Officer at NRC’s Herzberg Institute of Astrophysics, and Canadian FUSE project scientist. “I am delighted that we have helped extend the lifetime of this unique space telescope. Science results from all investigations by FUSE will be discussed at an international symposium to be held at the University of Victoria in August 2004,” he added.
For the past two years, engineers and scientists at the Johns Hopkins University in Baltimore, Maryland, at Orbital Sciences Corporation in Dulles, Virginia, at NASA Goddard Space Flight Center in Greenbelt, Maryland, and at the Canadian Space Agency in Saint-Hubert, Québec, have worked together to change the flight software used for science observations. The three spacecraft computers – the Attitude Control System, the Instrument Data System, and the processor on the Fine Error Sensor (FES) guide camera, provided by the Canadian Space Agency – all received new software directly in space via up-links established in mid-April 2003.
“We have uploaded new flight software, and can operate FUSE with any number of gyroscopes, including none, if the time comes that all six gyroscopes fail,” said Dr. George Sonneborn, FUSE project scientist from the NASA Goddard Space Flight Center in Greenbelt, Md. “This is a significant conceptual and technical development that brings a new tool to the designers of new and existing satellites, and bodes well for continued FUSE operations” Sonneborn added.
The new FES software was developed by ComDev, from Cambridge, Ontario, who built the guiding cameras for FUSE, together with specialists from the University of Toronto. Testing of the new flight software was carried out on the ‘engineering model’ camera in NRC’s Herzberg Institute of Astrophysics in Victoria, British Columbia. The software was then shipped to Johns Hopkins University, where it was coupled with the spacecraft computers, while normal science observations were continuing with the gyros.
FUSE can now operate without gyroscopes with no degradation in science data quality and only a slight loss of observation scheduling efficiency. The gyroscopes aboard FUSE do not move the satellite, but they provide information on how the spacecraft is moving or drifting over time. One gyroscope failed in May 2001 and the five remaining gyroscopes all show signs of age.
“We were lucky that the existing gyros kept working while we developed and tested the new system on the ground, “said Dr. Jeff Kruk of the Johns Hopkins University, the FUSE systems scientist and one of the primary designers of the ingenious new system. “Now that the new software is in place and tested, we can all breathe easier.”
FUSE has also survived the loss of two of its four reaction wheels in late-2001. The reaction or momentum wheels are devices that normally allow the satellite to be held steady and/or moved from one pointing direction to another. Through quick thinking, engineers and scientists modified control software to use devices called Magnetic Torquer Bars to provide stability in place of the missing reaction wheels. These devices interact with the earth’s magnetic field to move the telescope from one target to the next.
Looking ahead, NASA has just released the call for proposals for new observations with the satellite by astronomers from around the world during its fifth year of operations. Canadian astronomers are guaranteed a minimum of 280 orbits of observing time per year with FUSE.
FUSE is managed by the Johns Hopkins University for NASA Goddard Space Flight Center and the Office of Space Science at NASA Headquarters in Washington. Two Canadian scientists are employed at Johns Hopkins University by the Canadian Space Agency to help operate FUSE. Partners include the JHU Applied Physics Laboratory, the Canadian Space Agency, the European Space Agency (ESA), and primary spacecraft contractor Orbital Sciences Corporation. Launched in June 1999, FUSE is a space telescope that performs high-resolution far-ultraviolet spectroscopy of a broad range of astronomical objects. FUSE observes light at shorter wavelengths than the Hubble Space Telescope, thus providing a complementary capability.