Stellar Calibration of the WIC and SI Imagers and the GEO Photometers on IMAGE/FUV
 
G. Gladstone, S. Mende, H. Frey, S. Geller, T. Immel, M. Lampton, J. Spann, J. Gerard, 
S. Habraken, E. Renotte, C. Jamar, P. Rochus, H. Lauche

The FUV instrument on the IMAGE spacecraft comprises three wide-field imagers, the
Wide-Band Imaging Camera (WIC) for observing N2 LBH (140--190 nm) emissions,
and the Spectrographic Imager (SI), which has a 121.8 nm channel for observing
red-shifted HI Lya photons and a 135.6 nm channel for observing OI 135.6 nm
emissions. In addition, three HI Lya photometers (GEO) are used to monitor the
geocorona. The fields of view are 17 degrees x 17 degrees for the WIC imager,
$15 degrees x 15 degrees for the two SI imagers, and 1 degree diameter for the
three GEO photometers. As the IMAGE spacecraft spins every 120 s, the GEO photometers
sweep out circles on the sky (at 0 degrees and +/- 30 degrees with respect to the
spacecraft spin plane), and the WIC and SI imagers use the Time Delay Integration (TDI)
method to construct images centered on the Earth. Many FUV-bright stars are seen in the
WIC, SI, and even the GEO data. We have used archived International Ultraviolet Explorer
(IUE) far-ultraviolet flux spectra for 22 of the brightest of these stars to help refine 
the FUV instrumental sensitivities. The stars chosen range in spectral type from B0V to 
A1IV, with magnitudes ranging from V=1.3 (a Cru) to V=4.7 (G Cen) (although many more 
fainter stars are also seen). The initial results of this stellar calibration will be
presented and compared with the pre-flight and dayglow modeling results. 

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Presented at the Fall American Geophysical Union Meeting, 
San Francisco, CA., December 15-19, 2000