Johns Hopkins University/Applied Physics Laboratory
Affiliation: Johns Hopkins University/Applied Physics LaboratoryEvent Date: Wednesday, November 6, 2019
Location: Building 33, Room H114Time: 1:30 PM
Measuring Earth's Energy Budget from a CubeSat
Measuring Earth’s energy budget from space is an essential ingredient for understanding and predicting climate. Observational requirements to achieve climate accuracy and continuity with existing datasets drive cost and define measurement approaches. The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) 3U CubeSat mission is a NASA Earth Science Technology Office–funded pathfinder that demonstrates technologies for the measurement of Earth’s radiation budget. RAVAN launched November 11, 2016, into a nearly 600-km, sun-synchronous orbit and collected data for over 20 months. RAVAN successfully demonstrated two key technologies. The first is the use of vertically aligned carbon nanotubes (VACNTs) as absorbers in broadband radiometers for measuring Earth’s outgoing radiation and the total solar irradiance. VACNT forests are arguably the blackest material known and have an extremely flat spectral response over a wide wavelength range, from the ultraviolet to the far infrared. The second technology demonstrated is a pair of gallium phase-change black body cells used as a stable reference to monitor the degradation of RAVAN’s radiometer sensors on orbit. Four radiometers (two VACNT; two cavity), the pair of gallium black bodies, and associated electronics were flown in a 3U CubeSat bus that allows for routine solar and deep-space attitude maneuvers. The radiometers showed excellent long-term stability over the course of the mission and a high correlation between the VACNT and cavity radiometer technologies. Although one of the black bodies failed after several months, the other provided a repeatable standard throughout the mission. Our philosophy was to combine a new, high-technology payload with an off-the-shelf CubeSat bus. The RAVAN bus is Blue Canyon Technologies’ first launched. This talk includes details of the technology development, payload development and accommodation on a commercial 3U CubeSat bus, and in-space validation, as well as efforts to evaluate the applicability of the RAVAN CubeSat as a whole to measurement of Earth’s energy budget. We also enumerate several lessons learned from all phases of the project.
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