Andrew Yee
February 24th 06, 05:01 AM
Office of News and Information
Johns Hopkins University
901 South Bond Street, Suite 540
Baltimore, Maryland 21231
Phone: 443-287-9960 Fax: 443-287-9920
CONTACT:
Lisa De Nike, (443) 287-9960
FOR IMMEDIATE RELEASE: February 23, 2006
Venerable Ultraviolet Satellite Returns to Operations
NASA's Far Ultraviolet Spectroscopic Explorer astronomy satellite is back
in full operation, its aging onboard software control system rejuvenated
and its mission extended by enterprising scientists and engineers after a
near-death experience in December 2004.
Observations with the orbiting telescope resumed Nov. 1, 2005, about ten
months after the third of four onboard reaction wheels, used to precisely
point the spacecraft and hold it steady, stopped spinning. After two
months of experience tweaking the new control system in November and
December, FUSE operations returned in January to a level of efficiency
comparable to earlier in the mission, mission managers said.
"It's really a level of performance that we never thought we would see
again," said William Blair, a research professor in physics and astronomy
at Johns Hopkins and FUSE's chief of observatory operations. "The old
satellite still has some spunk."
FUSE was launched in June 1999. Late in 2001, two of the reaction wheels
failed in quick succession, leaving the satellite temporarily unusable.
That time, science operations were successfully resumed within about two
months through a modification of flight control software and development
of a creative new technique to establish fine pointing control.
"The project aggressively pursued a similar track this time, but it was
even harder with just one operational reaction wheel," said George
Sonneborn, FUSE project scientist at NASA's Goddard Space Flight Center in
Greenbelt, Md. "Some people would say what we're doing is nearly
impossible."
Initially, at least three reaction wheels were required for the spacecraft
to conduct its scientific mission. The revised control mode developed in
2001 utilized the two remaining reaction wheels and drafted the
satellite's magnetic torquer bars into the effort to provide control in
all three axes. The MTBs (essentially, controllable electromagnets) apply
forces on the satellite by interacting with Earth's magnetic field. Now,
the FUSE control system has been modified again to use magnetic control on
two axes, which provides a tenuous but acceptable level of control in
place of the missing reaction wheels.
"It's like we had three strong muscles originally, and could point FUSE
wherever we wanted to," Blair said. "Now we have to control the pointing
with one strong muscle and two weak muscles. The revised control software
is like a good physical therapist, teaching the satellite to compensate."
Since its launch, FUSE has obtained more than 52 million seconds of
science data on everything from planets and comets in our solar system to
distant quasars and active galaxies, and every major class of object in
between. This information, compiled in the form of spectrographs rather
than visual images, provides astronomers with details about the physical
properties and characteristics of objects, from temperatures and densities
to chemical makeup.
Observations from the satellite have been used to discover an extended,
tenuous halo of very hot gas surrounding our Milky Way galaxy, and have
found evidence of similar hot gas haloes around other galaxies. FUSE has
also detected molecular hydrogen in the atmosphere of the planet Mars for
the first time. This has implications for the water history of our frozen
neighbor. In addition, FUSE observations first detected molecular nitrogen
in dense interstellar gas and dust clouds, but at levels well below what
astronomers had expected, requiring a return to the drawing board for
theories of interstellar chemistry.
NASA has twice extended what originally was planned as FUSE's three-year
mission to carry out a broad range of science programs for hundreds of
astronomers from around the world. To date, more than 350 publications
based on FUSE observations have been published in the professional
astronomy literature and many more are on the way. A new set of planned
observations for the coming year was accepted in December 2005 by NASA,
and the first of these has already been obtained.
"The recovery of FUSE operations is a tremendous testament to the
dedication and ingenuity of the scientists and engineers at Johns Hopkins
and at the Orbital Sciences Corp.," said Warren Moos, professor of physics
and astronomy and principal investigator for FUSE. "There are a large
number of astronomers in line waiting for FUSE observations that are now
being undertaken once again."
The Johns Hopkins University has primary responsibility for all aspects of
FUSE, including both the development and operational phases of the
mission. The FUSE science and satellite control center is on the Johns
Hopkins Homewood campus in Baltimore. FUSE partners include Honeywell
Technical Services Inc., the Johns Hopkins Applied Physics Laboratory, the
Canadian Space Agency, the French Space Agency, the University of Colorado
at Boulder, and the University of California, Berkeley, in addition to
Orbital Sciences Corporation.
FUSE is a NASA Explorer mission. Goddard Space Flight Center manages the
Explorers Program for NASA Headquarters in Washington, D.C.
For more on the FUSE mission and future status updates, visit the FUSE
website at
http://fuse.pha.jhu.edu
Johns Hopkins University
901 South Bond Street, Suite 540
Baltimore, Maryland 21231
Phone: 443-287-9960 Fax: 443-287-9920
CONTACT:
Lisa De Nike, (443) 287-9960
FOR IMMEDIATE RELEASE: February 23, 2006
Venerable Ultraviolet Satellite Returns to Operations
NASA's Far Ultraviolet Spectroscopic Explorer astronomy satellite is back
in full operation, its aging onboard software control system rejuvenated
and its mission extended by enterprising scientists and engineers after a
near-death experience in December 2004.
Observations with the orbiting telescope resumed Nov. 1, 2005, about ten
months after the third of four onboard reaction wheels, used to precisely
point the spacecraft and hold it steady, stopped spinning. After two
months of experience tweaking the new control system in November and
December, FUSE operations returned in January to a level of efficiency
comparable to earlier in the mission, mission managers said.
"It's really a level of performance that we never thought we would see
again," said William Blair, a research professor in physics and astronomy
at Johns Hopkins and FUSE's chief of observatory operations. "The old
satellite still has some spunk."
FUSE was launched in June 1999. Late in 2001, two of the reaction wheels
failed in quick succession, leaving the satellite temporarily unusable.
That time, science operations were successfully resumed within about two
months through a modification of flight control software and development
of a creative new technique to establish fine pointing control.
"The project aggressively pursued a similar track this time, but it was
even harder with just one operational reaction wheel," said George
Sonneborn, FUSE project scientist at NASA's Goddard Space Flight Center in
Greenbelt, Md. "Some people would say what we're doing is nearly
impossible."
Initially, at least three reaction wheels were required for the spacecraft
to conduct its scientific mission. The revised control mode developed in
2001 utilized the two remaining reaction wheels and drafted the
satellite's magnetic torquer bars into the effort to provide control in
all three axes. The MTBs (essentially, controllable electromagnets) apply
forces on the satellite by interacting with Earth's magnetic field. Now,
the FUSE control system has been modified again to use magnetic control on
two axes, which provides a tenuous but acceptable level of control in
place of the missing reaction wheels.
"It's like we had three strong muscles originally, and could point FUSE
wherever we wanted to," Blair said. "Now we have to control the pointing
with one strong muscle and two weak muscles. The revised control software
is like a good physical therapist, teaching the satellite to compensate."
Since its launch, FUSE has obtained more than 52 million seconds of
science data on everything from planets and comets in our solar system to
distant quasars and active galaxies, and every major class of object in
between. This information, compiled in the form of spectrographs rather
than visual images, provides astronomers with details about the physical
properties and characteristics of objects, from temperatures and densities
to chemical makeup.
Observations from the satellite have been used to discover an extended,
tenuous halo of very hot gas surrounding our Milky Way galaxy, and have
found evidence of similar hot gas haloes around other galaxies. FUSE has
also detected molecular hydrogen in the atmosphere of the planet Mars for
the first time. This has implications for the water history of our frozen
neighbor. In addition, FUSE observations first detected molecular nitrogen
in dense interstellar gas and dust clouds, but at levels well below what
astronomers had expected, requiring a return to the drawing board for
theories of interstellar chemistry.
NASA has twice extended what originally was planned as FUSE's three-year
mission to carry out a broad range of science programs for hundreds of
astronomers from around the world. To date, more than 350 publications
based on FUSE observations have been published in the professional
astronomy literature and many more are on the way. A new set of planned
observations for the coming year was accepted in December 2005 by NASA,
and the first of these has already been obtained.
"The recovery of FUSE operations is a tremendous testament to the
dedication and ingenuity of the scientists and engineers at Johns Hopkins
and at the Orbital Sciences Corp.," said Warren Moos, professor of physics
and astronomy and principal investigator for FUSE. "There are a large
number of astronomers in line waiting for FUSE observations that are now
being undertaken once again."
The Johns Hopkins University has primary responsibility for all aspects of
FUSE, including both the development and operational phases of the
mission. The FUSE science and satellite control center is on the Johns
Hopkins Homewood campus in Baltimore. FUSE partners include Honeywell
Technical Services Inc., the Johns Hopkins Applied Physics Laboratory, the
Canadian Space Agency, the French Space Agency, the University of Colorado
at Boulder, and the University of California, Berkeley, in addition to
Orbital Sciences Corporation.
FUSE is a NASA Explorer mission. Goddard Space Flight Center manages the
Explorers Program for NASA Headquarters in Washington, D.C.
For more on the FUSE mission and future status updates, visit the FUSE
website at
http://fuse.pha.jhu.edu