Calculation Method of Earth-Atmosphere Stray Light Illuminance on Low-orbit Space Cameras

Abstract

The earth-atmosphere stray light can lower contrast ratio and SNR of spatial optical remote sensors, or even fail the system at certain conditions. Errors in the calculation of the stray light illuminance based on point source are very large, for the satellite's altitude is only several hundred kilometers and far less than the radius of the earth. This paper proposed a stray light illuminance calculating method which viewed the earth as a plane stray source and introduced the method in detail. Using the calculating method, earth-atmosphere stray light illuminance on the camera image plane for a low-orbit space camera at a typical position is calculated, and the results were compared with those calculated by viewing the earth as a point source, which evidently show that, when considering the earth-atmosphere stray light's effects on low-orbit space cameras, it's necessary to treat the earth as a plane extended light source.

Development of the Arcsecond Pico Star Tracker (APST)

“…The maximum stray light angle is due to the Earth, incident on the APST is known as È max . 20) The average radius of the Earth R earth is 6,370 km, H is the altitude of the orbit (500 km) and the È max is 68°. The maximum radius of the effective stray light region R max , È max ¼ arcsin ðR earth =ðR earth þ HÞÞ ð11Þ…”

Star Selection algorithm for Arcsecond Pico Star Tracker

“…It also shows the effective stray light region of the Earth. The maximum stray light angle is due to the Earth incident on the APST is known as Фmax[31].The average radius of the Earth, Rearth, is 6370 km, H is the altitude of the orbit (500 km) and the Фmax is 68°. The maximum radius of the effective stray light region is Rmax.…”