EOS Calibration Program

An important goal of the Earth Observing System (EOS) program is to make comparative measurement over many years from Earth-orbiting spacecraft to detect changes in terrestrial parameters, particularly climatic changes. To accomplish this goal, the calibration of the various remote-sensing flight instruments must be known over this entire time period to within a few percent, from the visible through the infrared. To this end, several investigators have instruments carrying their own on-board calibration devices, while others plan to view known sites or to view active field campaign sites after launch. Still others plan to depend on the intrinsic stability of their instruments, combined with consistency checks between channels and detectors. None of these techniques appear to have the potential for completely satisfying the requirement of knowing the characteristics of the instruments to better than a few percent over several years, especially when measurement continuity, combined with expected satellite lifetimes, requires that the instruments be on different platforms.

A possible solution to this problem has been discussed for some time within the EOS Terra and Aqua platform communities, namely, performing spacecraft calibration attitude maneuvers (CAMs) to allow the instruments to view the Moon and/or cold space. The Moon provides an on-orbit radiance target whose properties are essentially invariant over time, while cold space provides an on-orbit zero level reference for detectors and electronics, particularly in the thermal infrared.

Calibration Attitude Maneuvers for the EOS Terra Platform: Engineering and Thermal Feasibility and Limitations and Science Benefits PDF File (currently unavailable).

Animation of Proposed Lunar/Deep Space Maneuver for EOS Terra 7.4 MB QuickTime Movie

Animation of Proposed Lunar/Deep Space Maneuver for EOS Aqua 11.5 MB QuickTime Movie