The Johns Hopkins Gazette: June 19, 2000
June 19, 2000
VOL. 29, NO. 39


FUSE Ends First Year In Great Shape

By Michael Purdy
Johns Hopkins Gazette Online Edition

One year after they placed thousands of hours of dreaming, planning and hard work atop a rocket and blasted it into low-earth orbit, scientists and staff at the Far Ultraviolet Spectroscopic Explorer project, a NASA satellite observatory managed by Johns Hopkins, are sporting proud, relaxed grins.

The FUSE team is all smiles because they've survived an unexpectedly prolonged effort to get their observatory operational in space. After months of daunting challenges and many long days of hard work, they are finally just about where they want to be, and the observational data pouring down to Earth from FUSE has gone from trickle to stream to torrent.

"We're not 100 percent satisfied yet, but 80 to 90 percent feels pretty good," Warren Moos, FUSE project director and principal investigator, says. "Running a machine in space is never easy, but it's much, much better than it was six to eight months ago."

Bill Oegerle, chief of science operations for FUSE, agrees, noting, "It's been a hard life for the last year for a lot of people--deferred vacations, research and family time." Emphasizing that the staff didn't lose a single team member to burnout, he adds, "The teamwork has been pretty phenomenal. We're coming quickly to a point where we'll have the instrument optimized."

Scientists designed FUSE to analyze the chemical components of stars, planets and interstellar gases by dissecting the ultraviolet light they radiate. FUSE can analyze very short wavelengths of ultraviolet light with higher sensitivity and resolution than previously possible, and it does so from an ideal vantage point above the obscuring effects of Earth's atmosphere. All these characteristics make FUSE an ideal platform for probing various aspects of the origins of galaxies and the universe.

In a first for an orbital NASA observatory, to help cut back on project costs Hopkins agreed to build and oversee the day-to-day operation of FUSE with the aid of public collaborators and a private contractor, Honeywell Aerospace Services.

After last year's launch on June 24, FUSE's most serious problem was unexpected thermal effects as controllers moved it to view targets, and as it orbited around the Earth and crossed from night to day and back again. Scientists believe differences in the level of sunlight hitting the satellite during targeting operations or in the night-and-day transitions may be causing temperature differences in the satellite that can produce small shifts in certain key components. Though smaller than the width of a human hair, these shifts can disrupt the alignment of the satellite's four observation channels, shifting the intended target for observation out of the field of view of FUSE's spectrometer.

Oegerle reports that the movement problem is now nearly solved.

"We've been working to correlate the unexpected movements with what we're aiming the satellite at, and to develop automated solutions that allow us to realign the channels quickly, without investing hours or even days of human work," Oegerle says. "We've got that down pretty well for the widest of the apertures we use on the observation channels." He says a solution for the narrowest apertures, which allow observers to filter out some of the extraneous ultraviolet radiation from Earth's atmosphere, is in the works and should be available soon.

Additional problems were encountered with FUSE's guidance system. A set of gyros in FUSE had been calibrated in a manner that made it difficult for controllers to turn FUSE across wide swaths of sky without losing their guide stars, stars FUSE's onboard guidance systems use to make sure it is still pointing where it is supposed to point. This limited FUSE's abilities somewhat until March, when scientists were able to recalibrate the gyros and improve their performance dramatically.

Dealing with technical challenges such as these has caused the FUSE team many headaches during the first year. "The whole rug was pulled out from under mission planning," says FUSE mission planning chief Bill Blair. His team worked long hours to redesign most of the scheduling program to ensure that users can get the most useful results possible from FUSE in its expected life-span.

That life-span may take its first steps toward an extension when the FUSE team presents its results to a NASA "science productivity" review commission later this month.

"We're going to propose extending the FUSE mission two years beyond current plans," Moos says. Science productivity reviews take place every two years for programs that draw from a portion of the NASA budget known as Mission Operations and Data Analysis. The review assesses the quantity and quality of a project's scientific results to help NASA set its budget priorities.

The proposed extension is just one sign that things are coming together for FUSE.

According to FUSE research scientist Ken Sembach, a special issue of FUSE science papers, based on papers presented at a meeting early this year, is due this summer from Astrophysical Journal Letters. A second wave of FUSE papers will arrive over the next two months.

"We're definitely producing an enormous flood of data now," Sembach says. "We're about six months into normal operations, and have logged about 450 observations." Sembach says the FUSE project hit a watermark common to NASA projects several months ago as the rate of data coming in became too great for scientists to scrutinize immediately in detail. After brief checks for quality control, data from FUSE are sent to an archive across the street at the Hubble Space Telescope Science Institute.

"We're not feeling our way anymore," Blair concludes. "It's been a difficult time, but we've received a lot out of it. I'm very proud personally to have a fine mission rolling now."

Moos agrees. "We've definitely learned a lot of things by doing it this way, as the manager of day-to-day operations with a private contractor," he explains. "And that advice will be incorporated into other observatories that follow this pattern."

The fundamental lesson, according to Moos, is that adequate commercial infrastructure and resources are available to allow universities to manage moderate-sized missions such as FUSE.

"Universities can do this, with the help of contractors like Honeywell and the support of senior management," he says. "The university has to want to do it. Senior management here at Hopkins has been very active in terms of advice and oversight, and that's been very helpful. We couldn't have run a project of this size and visibility without their support."

To see FUSE's latest findings, log onto http://