The RAVAN CubeSat mission: On-orbit results William H. Swartz, 1 Steven R. Lorentz, 2 Philip M. Huang, 1 Donald E. Anderson 1 Collaborators: Allan W. Smith, 2 Yinan Yu, 2 John Carvo, 3 and Dong Wu 4 1 Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA 2 L-1 Standards and Technology, Manassas, VA USA 3 Blue Canyon Technologies, Boulder, CO USA 4 NASA/Goddard Space Flight Center, Greenbelt, MD USA
Flashback: Savannah, November 2015 The RAVAN CubeSat Mission: Progress toward a new measurement of Earth outgoing radiation William H. Swartz (JHU/Applied Physics Lab) Lars P. Dyrud, 2 Steven R. Lorentz, 3 Dong L. Wu, 4 Warren J. Wiscombe, 4 and Stergios J. Papadakis 1 1 JHU/Applied Physics Laboratory, 2 OmniEarth, 3 L-1 Standards and Technology, 4 NASA/Goddard Space Flight Center also Philip M. Huang, 1 Edward L. Reynolds, 1 Allan Smith, 4 and David M. Deglau 1 Funding: NASA Earth Science Technology Office RAVAN payload RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 2
Reminder: This is a CubeSat RAVAN JPSS (pre-launch configuration) RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 3
Context and some conclusions Earth radiation budget is a hard problem (still is) - Solar irradiance solved (relatively speaking) - Earth outgoing radiation has not been measured from space with sufficient absolute accuracy We entered the fray with RAVAN - Primary goal: NASA ESTO technology demonstration - Science goal: Demonstrate ERB measurements for future constellation mission The good - Carbon nanotubes ( VACNTs ) work in space, specifically as radiometer absorbers - Gallium phase-change black bodies for calibration monitoring - Long-term stability with respect to solar irradiance and cavity technology - We open/close payload doors and precision-point at the Sun/Earth/space daily on a 3U CubeSat - Lessons learned at multiple scales The less good - Short-term fluctuations problematic, most likely due to inadequate thermal knowledge and control Status: What are we doing with RAVAN currently? - Still flying, targeting CERES coincidences - Working with NASA LaRC to assess absolute accuracy vs. CERES RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 4
RAVAN is an Earth energy budget constellation pathfinder RAVAN: Radiometer Assessment using Vertically Aligned Nanotubes CubeSat project funded through NASA ESTO s InVEST program Principally a technology demonstration CubeSat = High-risk Led by Johns Hopkins University Applied Physics Laboratory (APL), Laurel, Maryland Partners: - L-1 Standards and Technology (L-1): Steven Lorentz (also NISTAR) - Blue Canyon Technologies (BCT) Pathfinder for an Earth energy (radiation) budget constellation Combines - Vertically aligned carbon nanotube radiometer absorber and black body emitter (APL) - Gallium fixed-point black body calibration source (L-1) - Compact, low-cost radiometer payload (L-1/APL) - 3U CubeSat bus, I&T, operations (BCT) Gallium source Doors VACNT absorber Cavity radiometers VACNT radiometers Gallium source Payload RAVAN RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 5
Carbon nanotubes are at the heart of RAVAN VACNT SEM image RAVAN radiometer head RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 6
Compact payload Technology 1: Carbon nanotube radiometer absorber Gallium source Cavity radiometers VACNT radiometers 100 μm Carbon nanotube forest Radiometer head assembly Technology 2: Gallium phase-change black body cells Doors Temperature (arbitrary units) Gallium source Ga solid liquid phase transition Payload door assembly RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 7
Launched Nov 2016, still flying (dark space) RAVAN (~575 km) 130 FoV RAVAN 3U CubeSat Blue Canyon Technologies bus Credit: United Launch Alliance, Lockheed Martin Launch 11/11/16 RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 8
Instrument long-term stability, but short-term fluctuations VACNT Total VACNT SW Dark offsets ~5 W/m 2 Gains VACNT Total VACNT SW RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 9
Solar (eclipse) observations Sun Moon RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 10
Solar observations VACNT Total VACNT SW RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 11
Radiometer Earth (nadir) observations Data downlink (volume) hampered by ground-level UHF interference. Total SW RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 12
VACNT/cavity relative stability (Earth-viewing) ERBS Total ERBS SW [Wong et al., TGRS, in press, 2018] RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 13
Leveraging ERBE non-scanner to get to RAVAN s TOA flux, and comparison with CERES RAVAN satellite-altitude flux, altitude/lat/lon/time RAVAN instantaneous TOA flux RAVAN time space averaged TOA flux Fig. 3. ERBE nonscanner data processing system diagram. From On the Lessons Learned from the Operations of the ERBE Nonscanner Instrument in Space and the Production of the Nonscanner TOA Radiation Budget Dataset [Wong et al., TGRS, in press, 2018] RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 14
Conclusions RAVAN successfully operating on orbit, now >16 months ESTO technologies demonstrated on-orbit - Vertically aligned carbon nanotubes as radiometer absorbers - Gallium phase-change cells as calibration reference Long-term stability demonstrated - Stable solar measurements (<0.5% during mission) - Stable VACNT/cavity Earth measurement intercomparisons Total: 0.01% /year trend SW: 4% /year trend Short-term fluctuations (thermal?) problematic and reminiscent of ERBE non-scanner Gallium source Doors VACNT absorber Cavity radiometers VACNT radiometers Gallium source Payload Future for RAVAN project - Continued on-orbit operations - Intercomparison of Earth nadir data, with LaRC Funding: NASA Earth Science Technology Office RAVAN RAVAN CubeSat Mission Sun Climate Symposium Lake Arrowhead, California bill.swartz@jhuapl.edu March 21, 2018 15