The story of Glory: Earth and solar science on one unique satellite

The Glory satellite program is underway at the orbital sciences campus in northern Virginia. This program is under contract with NASA Goddard Space Flight Center (GSFC). The Glory satellite bus was previously used for the vegetation canopy LIDAR (VCL) program, a mission designed to measure the Earth's vegetation coverage, depth, and topography by using short laser pulses from a LIDAR (light detection and ranging) system. The Glory program is refurbishing the VCL bus that was in the middle of integration and test when the VCL program was shut down. Many changes are being made to the VCL bus to configure it to serve the Glory science mission objectives. The Glory science mission includes polar atmospheric aerosol measurements with cloud observation and total solar irradiance monitoring. The low Earth orbit satellite (LEO) is scheduled for launch in late 2007 with the intention of broadening the search for the causes of global warming. The mission is intended to measure the composition of greenhouse gases, which little is known about currently, as well as solar effects on the environment using the following instruments: an aerosol polarimetry sensor (APS), cloud cameras and a total irradiance monitor (TIM). The APS instrument is a multispectral polarimetric sensor designed for collection of visible, near-infrared, and shortwave infrared polarized radiometric data scattered from aerosols and clouds. The APS is a continuous scanning, nadir-viewing sensor that makes along-track, multiangle observations of Earth and atmospheric spectral radiance. The cloud cameras are dual-band, imagers that employ a nonscanning, staring detector array that is akin to a star tracker, but Earth-viewing. The cloud cameras provide continuous cross-track coverage over a narrow swath centered on the APS along-track footprint using an optical imaging system. The TIM is an active cavity solar irradiance radiometer that consists of four identical radiometer cavities to provide redundancy and help detect changes in instrument response caused by exposure to solar radiation and other orbital effects. It takes data continuously throughout the orbit and does periodic calibrations on the disc of the sun and of the redundant cavities to monitor the effects of aging. Using a combination of heritage data and knowledge from the Orb View 3 and 4 programs as well as VCL, the Glory program is dedicated to a successful mission. This paper describes the design differences at system and subsystem levels between VCL and Glory focusing on the science missions, as well as the heritage program influences that are employed.