Preliminary Photometric Calibration of LASCO C3 Coronagraph Images using Pre-Flight Laboratory Images of Standard Sources and In-Flight Images of Standard Stars

Session 36 - Solar Activity.
Display session, Tuesday, June 11
Tripp Commons,

[36.21] Preliminary Photometric Calibration of LASCO C3 Coronagraph Images using Pre-Flight Laboratory Images of Standard Sources and In-Flight Images of Standard Stars

C. M. Korendyke, M. J. Koomen, M. D. Andrews, G. E. Brueckner, J. W. Cook, K. P. Dere, R. A. Howard, D. J. Michels, J. D. Moses, J. S. Morrill, N. E. Moulton, S. E. Paswaters, D. G. Socker, O. C. St. Cyr, D. Wang (NRL), P. L. Lamy, A. Llebaria, M. V. Bout (Laboratoire d"Astronomie Spatiale, France), R. Schwenn, B. Podlipnik (Max-Planck-Institut Germany), D. K. Bedford, D. A. Biesecker, C. J. Eyles, S. Plunkett, G. M. Simnett (Univ. of Birmingham, United Kingdom)

The C3 coronagraph is a wide field (\pm8.0 degrees), externally occulted, white light coronagraph. The instrument is one of three coronagraphs comprising the Large Angle Spectrometric COronagraph (LASCO) experiment mounted on the Solar Heliospheric Observatory satellite. The satellite was launched on Dec. 2, 1996; C3 observations began in early Jan. 1997. The coronagraph optical train includes a set of five broadband color filters mounted in a wheel. Prior to flight, an image was obtained through each color filter of a well characterized, rear-illuminated, opal glass diffusing screen. The C3 in-flight images, in addition to the coronal structures, also contain several hundred bright stars. We present a comparison of the photometric calibration derived from standard stars with the laboratory measurements. The resulting calibration is then used to examine color variations in the white light corona over the field of view. The LASCO experiment was developed by a scientific consortium of members from NRL (USA), MPAe (Germany), LAS (France) and U. Birmingham (United Kingdom).

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