Terahertz Radiometer Design for Thermospheric Wind Sounding

ABSTRACT: The ionosphere and upper atmosphere play a major role in Air Force and DoD missions, including communications, navigation, surveillance, and satellite drag. Understanding how the ionosphere affects these DoD missions is tied in part to understanding its motion and variability. Thermospheric winds contribute significantly to the morphology and variability of the ionosphere. Despite the high priority placed upon thermospheric neutral winds by the Air Force, its ability to make persistent and accurate wind measurements with high resolution, global coverage, and frequent sampling is extremely limited. In response to the SBIR Topic AF-121-066 we propose to develop a conceptual design for a 2.0 THz Oxygen-line Radiometer (THOR2.0) for thermospheric wind sounding. The proposed instrument design will be consistent with the established CubeSat mass, fit/form, and power resources. The THOR2.0 instrument proposed here will use a design based on the highly successful NASA MLS and ESA Herschel/HIFI instruments. THOR2.0 will provide full diurnal coverage of thermospheric winds in the 90-150 km region as well as temperature and atomic oxygen density profiles in the 90-250 km region, thereby addressing the needs of the Air Force to satisfy Ionospheric Key Performance Parameters identified in the Air Force Integrated Operational Requirements Document (IORD) II. BENEFIT: The THOR2.0 (2.0 THz Oxygen-line Radiometer) instrument is a significant step toward miniaturizing submillimeter wave radiometer for CubeSat missions. The proposed instrument will be capable of providing day and night thermospheric wind profiles in the 90-150 km region, not afforded by instruments operating in the visible or near-infrared wavelengths (e.g. Fabry-Perot Spectrometers or Interferometers). In addition, the spatial coverage in the vertical offered by the proposed instrument will be far better than can be achieved by any in-situ measurements. Thermospheric winds measured from the THOR2.0 instrument are expected to provide important inputs to ionospheric assimilative models being developed by the Air Force. It is expected that the unique capability of THOR2.0 to make day/night measurements and its robust yet small SWaP design will make it the instrument of choice for CubeSat missions dedicated to observing the thermospheric neutral winds.