This article describes the
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FIMS-SPEAR was the primary payload aboard the STSAT-1 microsatellite (Science and Technology Satellite-1, formerly known as KAISTSat-4), which in September 2003 was injected into a 700 km Sun-synchronous orbit at 98.2 deg inclination with an orbital period of 98.5 minutes and a ~34 minute eclipse. The SaTReC Mission Operations Center in Daejeon, Korea was used to control the mission and receive data. Observations for each orbit were scheduled to begin about 360 s after eclipse entry and end about 300 s before eclipse exit. The spacecraft orbited about 14–15 times per day around the earth. One to two orbits/day were devoted for the aurora and airglow observations of the northern nightside aurora, 4–5 orbits/day for communication with the ground station, and 7–10 orbits/day for astronomical observations.
The data taken during the observations were stored in the Mass Memory System (MMS) and downloaded to the ground station two to three times a week. Unstable receiver sensitivity caused errors in the downloaded MMS data packets. The data were received at least twice to minimize the errors.
The three-axis–controlled spacecraft platform used a star tracker to achieve ~5 arcmin pointing knowledge, pointed accuracy of ~6 arcmin, and a stability of ~12 arcmin.
Pointings avoided the Sun by 45 deg and the spacecraft velocity vector by 60 deg, and were limited to zenith angles of less than 100 deg.
Various pointing modes were used for survey, target, and calibration observations.
Note: pointed observations (including both the fixed inertial pointing and calibration pointing modes above) were conducted on the Vela supernova remnant, the Antlia Supernova Remnant, the Lupus Loop, the Cygnus Loop, the Monogem Ring, RCW 114, G65.3+5.7, the Orion-Eridanus Superbubble, the Loop I/North Polar Spur, GSH 006-15+7, the Spica nebula, the ζ-Ophiuchi H II region, the Taurus region, the Ophiuchus region, the Draco Cloud, the Aquila Rift, the Taurus-Perseus-Auriga Complex, and the Rho Ophiuchi cloud complex. A list of science papers from the mission teams is available here.
FIMS observations were performed in 1%, 10%, or 100% shutter aperture modes by adjusting the shutter steps depending on the expected flux level of the target objects. The aurora or dayglow was observed using the 1% shutter mode or 10% mode. The shutter was open 100% for the most astronomical observations. A few astronomical observations were made intentionally in the 10% mode (and sometimes unintentionally due to errors in the electronics). In early operations, the AS (AstroPhysics) observation mode was adopted; in the AS mode, the sky observations were performed for ~25 secs by opening the shutter, and then the shutter was closed for 5 secs to measure the detector background. However, the team soon recognized that the AS mode was not as useful as originally expected because of the uncertainties in attitude information, exposure time, and errors in the FIMS data packets. The AS mode was not used after March 2004 except for a few orbits.
While at least 40% of FIMS-SPEAR data suffered from some form of these problems, the teams created successful schemes to recover high-quality data, as described in Data Processing.
Starting in November 2004, a problem occurred in the battery of the satellite system. Observations were intermittently attempted, but after May 2005, observations were no longer possible and science operations ceased.
In approximate order of priority for the general user:
A full-text re-print of Korpela et al. 2003 is made available here with the permission of the publisher (SPIE) and first author (E. Korpela). Eric J. Korpela, Jerry Edelstein, Peter Berg, Mark Shane Bowen, Raymond Chung, Michael Feuerstein, Wonyong Han, Jeffrey S. Hull, Ho Jin, Dae-hee Lee, Kyung-wook Min, Uk-won Nam, Kaori Nishikida, Jin-geun Rhee, Kwangsun Ryu, Kwangil Seon, Barry Y. Welsh, Insoo Yuk, "The SPEAR science payload," Proc. SPIE 4854, Future EUV/UV and Visible Space Astrophysics Missions and Instrumentation, (24 February 2003); https://doi.org/10.1117/12.459970. |
*Written before launch, while manufacturing and testing were still taking place.
†Currently available only in Korean, with English abstract/tables/figures.