Measurements of the Gegenschein brightness from the Solar Mass Ejection Imager (SMEI)

Icarus 203, 124−133, 2009

Measurements of the Gegenschein brightness from the Solar Mass Ejection Imager (SMEI)

A. Buffington, M.M. Bisi, J.M. Clover, P.P. Hick and B.V. Jackson
Center for Astrophysics and Space Sciences, Univ. of California, San Diego, CA

T.A. Kuchar
Institute for Scientific Research, Boston College, Chestnut Hill, MA

S.D. Price
Air Force Research Laboratory/Space Vehicles Directorate (AFRL/RVB), Hanscom AFB, MA

Abstract

The Gegenschein is viewed by the Solar Mass Ejection Imager (SMEI), which has provided near-full-sky broadband visible-light photometric maps for over 5 years. These have an angular resolution of about 0.5° and differential photometric stability of about 1% throughout this time. When individual bright stars are removed from the maps and an empirical sidereal background subtracted, the residue is dominated by the zodiacal light. The unprecedented sky coverage and duration of these measurements enables a definitive characterization of the Gegenschein. This article describes the analysis method for these data, presents a movie with time of the Gegenschein brightness distribution, determines empirical formulae describing its average shape, and discusses its variation with time. These measurements unambiguously confirm previous reports that the Gegenschein surface-brightness distribution has a decided peak in the antisolar point, which rises above a broader background.