The solar disk sextant (SDS) is a spaceborne instrument for precise measurement of the apparent solar diameter. These measurements, with simultaneous measurements of the solar irradiance, will calibrate the historical record of solar diameter measurements to determine whether changes in the total solar radiation at the top of the atmosphere have contributed to climate change. A critical component of the SDS instrument is the beam-splitting wedge (BSW) that provides the reference angle for measurement of the solar diameter. This project will develop and evaluate several BSW designs to determine which can be used in a long-duration space environment. Specifically, this project will evaluate molecular bonding of the BSW optical components to provide a stable wedge angle; a double-wedge design to correct for chromatic aberration; fabrication processes for the wedge filter; interferometric methods for pre-flight calibration of the wedge angle; and on-orbit wedge calibration procedures using the orbital variations in the Sun-to-SDS distance. The SDS has been selected as a joint NASA/Italian Space Agency experiment to complement other NASA climate programs such as the precipitation and radiation measurements to be provided by the Tropical Rainfall Measurement Mission.
Potential Commercial Applications:The effort will expand the firm's capabilities for providing specialized space hardware subsystems. The potential for penetrating the European market is particularly important in terms of U.S. participation in this rapidly expanding area.
