Title: RAVAN: Technology Demonstration and Applicability to Earth Radiation Budget Measurements
Presenting Author: William H. Swartz
Organization: JHU/Applied Physics Laboratory
Co-Author(s): Steven R. Lorentz, Philip M. Huang, Donald E. Anderson, Dong Wu

Abstract:
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) 3U CubeSat mission is a NASA Earth Science Technology Office-funded pathfinder to demonstrate technologies for the measurement the Earth's radiation budget, the quantification of which is critical for predicting the course of climate change over the next century. RAVAN launched November 11, 2016 into a nearly 600-km sun-synchronous orbit and is still operating and collecting data. RAVAN has successfully demonstrated two key technologies. First, we show measurements of Earth's outgoing energy with radiometers that use vertically aligned carbon nanotube (VACNT) absorbers. VACNT forests are some of the blackest materials known and have an extremely flat spectral response over a wide wavelength range. The measurements are made at both shortwave, solar-reflected wavelengths and in the thermal infrared. Second, we show the performance of two gallium phase-change cells that are used to monitor the degradation of RAVAN's radiometer sensors. A 3-axis controlled CubeSat bus allows for routine solar and deep-space attitude maneuvers, which are essential for calibrating Earth irradiance measurements. We also evaluate the applicability of the RAVAN CubeSat as a whole to measurement of Earth's radiation budget. Long-term and short-term stability are requirements, along with absolute accuracy. We discuss how RAVAN fares in meeting the stringent calibration requirements needed to advance the state of the art.