The CubeSat Infrared Atmospheric Sounder (CIRAS) will measure upwelling infrared radiation of the Earth in the MWIR region of the spectrum from space on a CubeSat. The observed radiances have information of potential value to weather forecasting agencies and can be used to retrieve lower tropospheric temperature and water vapor globally for weather and climate science investigations. Multiple units can be flown to improve temporal coverage or in formation to provide new data products including 3D atmospheric motion vector winds. CIRAS incorporates key new instrument technologies including a 2D array of High Operating Temperature Barrier Infrared Detector (HOT-BIRD) material, selected for its high uniformity, low cost, low noise and higher operating temperatures than traditional materials. The detectors are hybridized to a commercial ROIC and commercial camera electronics. The second key technology is an MWIR Grating Spectrometer (MGS) designed to provide imaging spectroscopy for atmospheric sounding in a CubeSat volume. The MGS has no moving parts and includes an immersion grating to reduce the volume and reduce distortion. The third key technology is an infrared blackbody fabricated with black silicon to have very high emissivity in a flat plate construction. JPL will also develop the mechanical, electronic and thermal subsystems for CIRAS, while the spacecraft will be a commercially available CubeSat. The integrated system will be a complete 6U CubeSat capable of measuring temperature and water vapor profiles with good lower tropospheric sensitivity. CIRAS is scheduled for launch in the 2019 timeframe. The CIRAS is the first step towards the development of an Earth Observation Nanosatellite Infrared (EON-IR) capable of operational readiness to mitigate a potential loss of CrIS on JPSS or complement the current observing system with different orbit crossing times.
Background: IR Sounders Today
Numerical Weather Prediction (NWP) centers worldwide have demonstrated the value of hyperspectral infrared sounders to improving weather forecasts. The Atmospheric Infrared Sounder (AIRS) on the NASA Earth Observing System Aqua Spacecraft was the first hyperspectral infrared sounder to be used for operational forecast improvement. IR sounder radiances are assimilated into Global Circulation Models and NWP centers worldwide including the National Center for Environmental Prediction (NCEP), the European Center for Medium-Range Weather Forecast (ECMWF) and the UK Met Office. Six hours of forecast model improvement on the 5 day forecast has been achieved by assimilating AIRS data at NCEP and ECMWF by assimilating only 1 in 18 footprints1. An additional 5 hours of improvement on the 5 day forecast or more has been shown to be possible using cloud cleared radiances2. The AIRS and the Infrared Atmospheric Sounding Interferometer (IASI) impacts to operational 24-hour forecasts at ECMWF are roughly comparable and are second only to the collective impact of four AMSU units3. Finally, the Cross-track Infrared Sounder (CrIS) on the Joint Polar Satellite System (JPSS) has demonstrated comparable performance to the AIRS and IASI. The sounders have a wide field of view enabling coverage of the full context of severe weather events.
While the data from AIRS is assimilated into the operational forecasts at NCEP today, AIRS is expected to
complete its mission when the Aqua spacecraft runs out of fuel in the 2022 timeframe. We can expect CrIS and IASI instruments and their nearly identical replacements to be operational into the late 2030’s. Maintaining continuity of these important weather forecasting and climate data sets is critical to NASA and NOAA. NOAA has identified the need for an Earth Observing Nanosatellite - IR (EON-IR) as a low cost-to-orbit way to mitigate a potential gap4 in data of the CrIS on JPSS. A key objective of CIRAS is to demonstrate the technologies needed for an operational IR sounder, like EON-IR. In that respect, CIRAS is a pathfinder for EON-IR.
1. McNally, A.P., Watts, P.D., Smith, J.A., Engelen, R., Kelly, G.A., Thepaut, J.N., and Matricardi, M., 2006, The assimilation of AIRS radiance data at ECMWF, QJR Meteorol. Soc., 132, 935-957. doi: 10.1256/qj.04.171
2. J. Le Marshall, J. Jung, M. Goldberg, C. Barnet, W. Wolf, J. Derber, R. Treadon and S. Lord, “Using cloudy AIRS fields of view in numerical weather prediction”. Aust. Meteorological Magazine, 2008, vol. 57, pp. 249-254
3. Cardinali, C, Monitoring the observation impact on the short-range forecast, Q. J. R. Meteorol. Soc. 135: 239–250 (2009)
4. U.S. Government Accountability Office (GAO), “Report to the Committee on Science, Space, and Technology, House of Representatives, Polar Weather Satellites, NOAA Needs to Prepare for Near-term Data Gaps”, GAO-15-47, December 2014.
The CIRAS payload includes a scan mirror capable of rotating 360º to view Earth, cold space and an internal blackbody for calibration. The Scan Mirror Assembly consists of a single planar gold coated aluminum mirror mounted at 45º to the axis of a stepper motor. The blackbody is a simple flat plate composed of black silicon, heat sunk and instrumented with a temperature sensor, and provides high emissivity and durability in a compact design. Energy from the scan mirror is collected using a 3-element all-refractive telescope. Energy from the telescope is focused onto the entrance slit of an all refractive MWIR Grating Spectrometer (MGS). The telescope and spectrometer are to be developed by Ball Aerospace. The spectrometer disperses the energy across the spectral range and produces a 2-dimensional image at the focal plane with one direction spatial (504 pixels) and the other spectral (625 channels).
The detector array uses the JPL HOT-BIRD photosensitive material mounted on a Lockheed Martin Santa Barbara Focalplane (SBF) 193 Readout Integrated Circuit (ROIC). The ROIC is mounted in a custom Integrated Cooler Dewar Assembly (ICDA) to be developed by IR Cameras. The dewar contains a cold filter mounted close to the focal plane, and a window at the interface between the dewar and the optics.
The CIRAS subsystem electronics are primarily commercial. A payload electronics board will be developed to interface the various subsystems. Clocks, biases and A/D conversion are performed using military-grade electronics also provided by IR Cameras. JPL will develop the payload electronics to interface with the scanner, camera, cryocoolers, blackbody and spacecraft electronics.
Cooling of the spectrometer to 190K and the narrow spectral range of the filters minimize background loading on the detector. Use of a Ricor cryocooler for the optics is included in the current design but alternate coolers will be investigated. The detector is cooled to 120K also using a Ricor cryocooler, heat sunk to the warm radiator. Electronics, cryocooler and spacecraft waste heat is dissipated in warm temperature radiators on all remaining surfaces except nadir and anti-nadir.
CIRAS will be developed as a stand-alone payload with mechanical, thermal, and electrical interfaces to the spacecraft. Radiators will be detachable to allow easy integration of the payload and reattachment after integration with the spacecraft.
The CIRAS spacecraft will be a commercial 6U system (industry procurement) with deployable solar panels and additional batteries. The spacecraft will provide communications, navigation, power and on-board processing and formatting of the raw data stream from the payload. The spacecraft structure will have custom features to allow a clear scan field of view and for mounting the payload components.
The payload development and test will take 20 months followed by spacecraft integration and test of 2 months. In-flight operations will take a minimum of 3 months after launch consisting of system activation, calibration and data acquisitions. CIRAS is TRL 5 upon entry and TRL 7 after flight demonstration.
News and Events
February 18, 2016: CIRAS selected for NASA’s CubeSat Launch Initiative (CSLI). CSLI provides the integration of the CIRAS instrument onto the launch vehicle and covers the cost of launching CIRAS into space. The actual launch vehicle is not known at this time.
September 25, 2015: CIRAS awarded to NASA JPL as part of the NASA Earth Science Technology Office (ESTO) In-space Validation of Earth Science and Technologies (InVEST) program.
Thomas S. Pagano: Thomas S. Pagano is the Principal Investigator for CIRAS and the Project Manager for the AIRS/AMSU/HSB Suite of instruments on the EOS Aqua Spacecraft. He was the lead engineer responsible for the calibration of the AIRS instrument in orbit. Prior to joining JPL in 1997, he was the Chief Systems Engineer on the MODIS instrument development program at Raytheon SBRS since 1985. He has a BS in Physics from UC Santa Barbara, and an MS in Physics from Montana State University. He holds 2 US patents and is author of numerous papers on space remote sensing systems.
For more information, please contact:
Thomas S. Pagano, NASA/JPL, 4800 Oak Grove Dr., M/S 264-300, Pasadena, Ca 91109, (818) 393-3917