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Winter 1998

Space shuttle flies NCAR's white light coronagraph

by Zhenya Gallon

The Spartan satellite, containing HAO's coronagraph. The satellite itself is the package atop the framework. (Photo courtesy of NASA.)

Besides carrying Senator John Glenn, the space shuttle Discovery took a white light coronagraph on its mission of 29 October-7 November. The instrument was developed and built at NCAR's High Altitude Observatory (HAO) in collaboration with scientists at NASA (including former NCAR staff member Richard Fisher, now at Goddard Space Flight Center).

The WLC and its companion instrument, an ultraviolet coronal spectrometer (UVCS) developed at the Harvard-Smithsonian Center for Astrophysics, were on the Spartan 201-05, a small satellite laboratory launched from Discovery on 1 November and retrieved by its robot arm two days later. Data from the solar instruments collected on 26 observational orbits will be used to investigate the solar corona and the solar wind. In particular, the coronagraph provides a tool for determining electron densities of the corona. By launching the WLC from the space shuttle, researchers avoided the scattering of light caused by dust in the earth's atmosphere, which interferes with ground-based coronagraphs.

Project engineer Gregory Card has been HAO's liaison with NASA. He spent several years commuting between Boulder, Goddard Space Flight Center, and Kennedy Space Center to prepare the coronagraph and integrate it with the Spartan spacecraft. During the mission, Card managed a new WLC telemetry system from Johnson Space Center. The Technology Experiment Augmenting Spartan (TEXAS) system allowed transmission of images in near-real time, while an onboard recording system stored additional data. Traditional analog tapes were complemented by the Mini Gigabyte Backup (MGB) hard-disk recorder, designed and newly upgraded by HAO and Electricon with housing and internal components fabricated by the NCAR machine shop.

Card had high praise for the shuttle crew operating the Spartan, which included flight engineer and computer operator Scott Parazynski, mission specialist Steve Robinson on the Remote Manipulator System (the robot arm), and shuttle pilot Steve Lindsey. "They had rehearsed it so well [they] made it look effortless," says Greg. Within a few hours, "we were getting spectacular coronal images."

The new telemetry system functioned beyond Greg's best hopes. With the faster data rate of the TEXAS system, the WLC captured a new image every ten seconds, sending back about 700 images in near-real time. That's a lot more data than would have been possible with the onboard storage system alone--"one-third more than we'd normally get," Card says.

On past missions, the team had no way of knowing until Spartan was back on the ground whether systems were functioning and data was being gathered. "This time, we could interact with the instruments and see the data," says Fisher. Because TEXAS transmitted data about ten times faster than the onboard recorder, the mission has opened up a new area of investigation. "It lets us explore a temporal regime we haven't been able to see before. So we're going to look to see if things are happening more rapidly than we've seen [in the past]." Summing up the performance of the new telemetry, Fisher adds, "It worked out great. When it was at the very worst, it was at the wonderful level."

According to NASA's Craig Tooley, the MGB recorder collected a full-mission-length science and engineering data set. HAO's Andy Stanger will do the preprocessing, extracting images out of the raw data. The processed data will go to Fisher at Goddard and to HAO researchers Thomas Holzer, David Elmore, Alice Lecinski, and Joan Burkepile. In addition to matchups with the data from the UVCS, over the next year the team will examine the WLC results in relationship to coronal data from the Mauna Loa Solar Observatory's MK3 and MK4 coronameters, as well as the Large Angle and Spectrometric Coronagraph aboard NASA's Solar and Heliospheric Observatory (SOHO) satellite.

According to Card, this is the last flight for the Spartan solar research craft. NASA is turning its attention to constructing the space station, and "the shuttle [payload schedule] is tight, so it's hard to squeak in another Spartan mission." He adds, "It was a good thing to have Spartan fly at this time in the solar cycle. With SOHO and the new TRACE [Transition Region and Coronal Explorer] satellite launched this year, plus Mauna Loa up and running, we had [multiple] observations running simultaneously."

On the Web:
WLC images are available

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Edited by Carol Rasmussen, carolr@ucar.edu
Prepared for the Web by Jacque Marshall
Last revised: Tue Apr 4 14:56:02 MDT 2000