Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

FUSE "brain transplant" secures future of orbiting observatory

22.07.2003


Scientists and engineers who work with the Far Ultraviolet Spectroscopic Explorer have pulled off a second daring and unprecedented rescue of the satellite observatory from serious guidance problems. This time, though, they didn´t actually wait for the guidance problems to happen.



In response to hints of the potential for future new difficulties with FUSE´s gyroscopes, which are used to check the satellite´s pointing accuracy, researchers redesigned software for three computers aboard FUSE and recently uploaded the new software to the computers.

The staff of FUSE, operated for NASA by Johns Hopkins University, compared the feat to a "brain transplant." They currently maintain detailed control of FUSE´s precise orientation through the gyros´ ability to sense even very small shifts in the satellite´s position. If too many of the gyros stop working, however, the new software will allow controllers to switch over to using the fine error sensor, a camera aboard FUSE, in their place. In the new guidance mode, detailed information on where FUSE is pointing will be determined via the positions of key stars imaged in the fine error sensor.


Jeff Kruk, principal research scientist in physics and astronomy in the Kreiger School of Arts and Sciences at Johns Hopkins and deputy chief of observatory operations for FUSE, said the new "zero gyro" mode has already been tested and proved to be even more effective at keeping the satellite precisely pointed.

"We´ve had several periods of a week or so where we´ve taken the gyros out of the loop and flown on the new software, and the pointing stability is actually a little better with the fine error sensor than it is with the gyros," Kruk said.

But Kruk and Warren Moos, professor of astronomy at Johns Hopkins and principal investigator for FUSE, cautioned that there´s still work to be done in fine-tuning and error-proofing the new system.

"Things are going extremely well so far," Moos said. "We haven´t found any major problems, but we´re not out of the woods yet."

FUSE, launched in 1999, has gathered important data about the universe by analyzing light in the far ultraviolet portion of the electromagnetic spectrum. The "brain transplant" in April was the second improvised but extraordinary effort to rescue the orbiting probe from approximately 500 miles below on Earth. In December 2001, the failure of the second of four guidance system components known as reaction wheels sent FUSE into a pre-programmed "safe mode" configuration. In less than two months of intense work, engineers and scientists were able to bring the satellite back online using parts known as magnetic torquer bars in place of the reaction wheel.

This year´s pre-emptive rescue and the testing of the associated software have had little if any impact on FUSE´s scheduled scientific observations, said Bill Blair, chief of observatory operations for FUSE and a research professor of physics and astronomy at Johns Hopkins.

"Since the upload, which took about a week, we´ve been back to normal science operations," he explained. "But there´s also been a long, low-level tail of activity to just kind of optimize things and track down small problems with the new software."

The upgrades are a product of nearly two years of work by engineers and scientists at Johns Hopkins, Orbital Sciences Corp., Honeywell Technical Solutions Inc., NASA Goddard Space Flight Center and the Canadian Space Agency. Researchers began to work on a new method for guiding FUSE when one of FUSE´s six gyros, always anticipated to have a finite lifespan, went dead unexpectedly early on May 31, 2001. Two gyros were built into FUSE for each of the three axes of motion. If any axis were to lose both gyros, controllers would no longer be able to point FUSE precisely.

"We were highly motivated when the first gyro went dead on May 31," Moos recalled with a wry laugh. "There have been very, very few attempts to fly precision-pointed spacecraft without gyros, and learning how was a major step forward."

Among the obstacles faced by controllers was developing ways to make sure information could be sent back and forth quickly enough between FUSE´s three main computers. Moos compared the process to trying to stop a fall from a tree–not only is there very little time to sense when an appropriate branch might be within reach, but the time send a mental command to reach out and grab that branch is also very short.

Controllers also had to develop a way to deal with the periods when the guide stars used by the fine error sensor to fix FUSE´s position were eclipsed by the Earth as FUSE orbited around it. Moos said their solution depends in part on detailed models of how torque from the Earth´s gravitational field will twist the satellite, and in part on readings they could obtain from an instrument aboard FUSE known as a magnetometer.

Kruk added that the new software uploaded to FUSE in April contained improvements to several housekeeping functions in the satellite, in part to prepare it for reduced round-the-clock human monitoring as FUSE enters an extension of its originally planned mission.

"We were able to build in more smarts to make FUSE capable of gracefully handling almost anything that might come up," Kruk explained.

Blair concluded, "With these repairs in place, and astronomers from around the world lining up to use FUSE, the mission is on track for at least several more years of operations."

Michael Purdy | EurekAlert!
Further information:
http://www.jhu.edu/news_info/news/home02/mar02/fuse.html

More articles from Physics and Astronomy:

nachricht Exploring the mysteries of supercooled water
01.03.2017 | American Institute of Physics

nachricht Optical generation of ultrasound via photoacoustic effect
01.03.2017 | American Institute of Physics

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

Im Focus: Safe glide at total engine failure with ELA-inside

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded after a glide flight with an Airbus A320 in ditching on the Hudson River. All 155 people on board were saved.

On January 15, 2009, Chesley B. Sullenberger was celebrated world-wide: after the two engines had failed due to bird strike, he and his flight crew succeeded...

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

A better way to measure the stiffness of cancer cells

01.03.2017 | Health and Medicine

Exploring the mysteries of supercooled water

01.03.2017 | Physics and Astronomy

Research team of the HAW Hamburg reanimated ancestral microbe from the depth of the earth

01.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>