the ravan cubesat mission: on-orbit...

The RAVAN CubeSat mission: On-orbit results William H. Swartz,1 Steven R. Lorentz,2 Philip M. Huang,1 Donald E. Anderson1

Collaborators: Allan W. Smith,2 Yinan Yu,2 John Carvo,3 and Dong Wu4

1Johns Hopkins University Applied Physics Laboratory, Laurel, MD USA2L-1 Standards and Technology, Manassas, VA USA3Blue Canyon Technologies, Boulder, CO USA4NASA/Goddard Space Flight Center, Greenbelt, MD USA

Flashback: Savannah, November 2015

March 21, 2018RAVAN CubeSat Mission • Sun–Climate Symposium • Lake Arrowhead, California • [email protected] 2

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. Papadakis1 1JHU/Applied Physics Laboratory, 2OmniEarth, 3L-1 Standards and Technology, 4NASA/Goddard Space Flight Center

also Philip M. Huang,1 Edward L. Reynolds,1 Allan Smith,4 and David M. Deglau1

Funding: NASA Earth Science Technology Office

RAVAN payload

Reminder: This is a CubeSat


JPSS (pre-launch configuration)

RAVAN

• 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

Context and some conclusions


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)


Cavityradiometers

VACNTradiometers

Galliumsource

Galliumsource

Doors

VACNT absorber

Payload

RAVAN

Carbon nanotubes are at the heart of RAVAN


VACNT SEM image

RAVAN radiometerhead

Compact payload

RAVAN CubeSat Mission • Sun–Climate Symposium • Lake Arrowhead, California • [email protected] 7

100

μm

Radiometer head assembly

Technology 1: Carbon nanotube radiometer absorber

Technology 2: Gallium phase-change black body cells

Tem

pera

ture

(a

rbitr

ary

units

)

Payload door assembly

Cavityradiometers

VACNTradiometers

Galliumsource

Galliumsource

Doors

March 21, 2018

Carbon nanotube “forest”

Ga solid–liquid phase transition

Launched Nov 2016, still flying


Credit: United Launch Alliance, Lockheed Martin

RAVAN (~575 km)

130° FoV

Launch 11/11/16

RAVAN 3U CubeSatBlue Canyon Technologies bus

March 21, 2018

(dark space)

Instrument long-term stability, but short-term fluctuations

RAVAN CubeSat Mission • Sun–Climate Symposium • Lake Arrowhead, California • [email protected] 9March 21, 2018

VACNT Total VACNT SW


Dark offsets

Gains

~5 W/m2

Solar (eclipse) observations


SunMoon

March 21, 2018

Solar observations



Radiometer Earth (nadir) observations


Total

SW

Data downlink (volume) hampered by ground-level UHF interference.

VACNT/cavity relative stability (Earth-viewing)


ERBS Total

ERBS SW

[Wong et al., TGRS, in press, 2018]

Leveraging ERBE non-scanner to get to RAVAN’s “TOA” flux, and comparison with CERES


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 satellite-altitude flux, altitude/lat/lon/time

RAVAN time–space averaged TOA flux

RAVAN instantaneous TOA flux

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

• Future for RAVAN project- Continued on-orbit operations- Intercomparison of Earth nadir data, with LaRC

• Funding: NASA Earth Science Technology Office


Cavityradiometers

VACNTradiometers

Galliumsource

Galliumsource

Doors

VACNT absorber

Payload

RAVAN

 

 

   

   

   

   

   

   

       

   

 

   

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March 21, 2018

the ravan cubesat mission: on-orbit...

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