Trutinor: A Conceptual Study for a Next-Generation Earth Radiant Energy Instrument

Uninterrupted and overlapping satellite instrument measurements of Earth’s radiation budget from space are required to sufficiently monitor the planet’s changing climate, detect trends in key climate variables, constrain climate models, and quantify climate feedbacks. The Clouds and Earth’s Radiant Energy System (CERES) instruments are currently making these vital measurements for the scientific community and society, but with modern technologies, there are more efficient and cost-effective alternatives to the CERES implementation. We present a compact radiometer concept, Trutinor (meaning “balance” in Latin), with two broadband channels, shortwave (0.2–3 μm) and longwave (5–50 μm), capable of continuing the CERES record by flying in formation with an existing imager on another satellite platform. The instrument uses a three-mirror off-axis anastigmat telescope as the front optics to image these broadband radiances onto a microbolometer array coated with gold black, providing the required performance across the full spectral range. Each pixel of the sensor has a field of view of 0.6°, which was chosen so the shortwave band can be efficiently calibrated using the Moon as an on-orbit light source with the same angular extent, thereby reducing mass and improving measurement accuracy, towards the goal of a gap-tolerant observing system. The longwave band will utilize compact blackbodies with phase-change cells for an absolute calibration reference, establishing a clear path for SI-traceability. Trutinor’s instrument breadboard has been designed and is currently being built and tested.

[1]  Kris J. Becker,et al.  Modeling the brightness of the Moon over 350 - 2500 nm for spacecraft calibration , 2001, SPIE Remote Sensing.

[2]  Joseph A. Shaw,et al.  Modeling infrared lunar radiance , 1999 .

[3]  Thomas C. Stone,et al.  Status of use of lunar irradiance for on-orbit calibration , 2002, Optics + Photonics.

[4]  Andrew E. Dessler,et al.  Observations of Climate Feedbacks over 2000–10 and Comparisons to Climate Models , 2013 .

[5]  Piers M. Forster,et al.  Inference of Climate Sensitivity from Analysis of Earth's Energy Budget , 2016 .

[6]  S. Klein,et al.  The relationship between interannual and long‐term cloud feedbacks , 2015 .

[7]  H. Kieffer,et al.  The Spectral Irradiance of the Moon , 2005 .

[8]  B. Barkstrom,et al.  Clouds and the Earth's Radiant Energy System (CERES): An Earth Observing System Experiment , 1996 .

[9]  K. Trenberth,et al.  Earth's annual global mean energy budget , 1997 .

[10]  R. W. Shorthill,et al.  The sunlit lunar surface , 1972 .

[11]  Paul E. Johnson,et al.  Modeling the non-grey-body thermal emission from the full moon , 1991 .

[12]  Lukas H. Meyer,et al.  Summary for Policymakers , 2022, The Ocean and Cryosphere in a Changing Climate.

[13]  S. Seneviratne,et al.  The energy balance over land and oceans: an assessment based on direct observations and CMIP5 climate models , 2015, Climate Dynamics.

[14]  Patrick C. Taylor,et al.  Evaluation of the Arctic surface radiation budget in CMIP5 models , 2015 .

[15]  Bruce R. Barkstrom,et al.  The Earth Radiation Budget Experiment (ERBE). , 1984 .

[16]  Jonathan M. Gregory,et al.  Accounting for Changing Temperature Patterns Increases Historical Estimates of Climate Sensitivity , 2018, Geophysical Research Letters.

[17]  Carsten Standfuss,et al.  Top-of-Atmosphere Radiance-to-Flux Conversion in the SW Domain for the ScaRaB-3 Instrument on Megha-Tropiques , 2009 .

[18]  Nipa Phojanamongkolkij,et al.  Achieving Climate Change Absolute Accuracy in Orbit , 2013 .

[19]  Bruce A. Wielicki,et al.  Numerical Terradynamic Simulation Group 2011 Challenges of a Sustained Climate Observing System , 2018 .

[20]  Patrick Minnis,et al.  Unfiltering Earth Radiation Budget Experiment (ERBE) Scanner Radiances Using the CERES Algorithm and Its Evaluation with Nonscanner Observations , 2014 .

[21]  Patrick Raberanto,et al.  Radiometric and Spectral Characteristics of the ScaRaB-3 Instrument on Megha-Tropiques: Comparisons with ERBE, CERES, and GERB , 2010 .

[22]  Donald J. Wuebbles,et al.  Ch. 11: Arctic Changes and their Effects on Alaska and the Rest of the United States. Climate Science Special Report: Fourth National Climate Assessment, Volume I , 2017 .

[23]  Lacy G. Cook.  The last three-mirror anastigmat? , 1992, LASE.

[24]  S. Klein,et al.  Analyzing the dependence of global cloud feedback on the spatial pattern of sea surface temperature change with a Green's function approach , 2017 .

[25]  Wenying Su,et al.  Next-generation angular distribution models for top-of-atmosphere radiative flux calculation from CERES instruments: validation , 2015 .

[26]  D. Randall,et al.  Mission to planet Earth: Role of clouds and radiation in climate , 1995 .

[27]  G. Holsclaw,et al.  Absolute Ultraviolet Irradiance of the Moon from the LASP Lunar Albedo Measurement and Analysis from SOLSTICE (LLAMAS) Project , 2013 .

[28]  Aaron Kennedy,et al.  Assessment of NASA GISS CMIP5 and Post-CMIP5 Simulated Clouds and TOA Radiation Budgets Using Satellite Observations. Part I: Cloud Fraction and Properties , 2014 .

[29]  Edwin F. Harrison,et al.  Earth Radiation Budget Experiment (ERBE) archival and April 1985 results , 1989 .

[30]  Constantine Lukashin,et al.  The Moon as a Climate-Quality Radiometric Calibration Reference , 2020, Remote. Sens..

[31]  Allan W. Smith,et al.  RAVAN: CubeSat Demonstration for Multi-Point Earth Radiation Budget Measurements , 2019, Remote. Sens..

[32]  Patrick Minnis,et al.  Quantifying the Dependence of Satellite Cloud Retrievals on Changes in Instrument Calibration. , 2017, Journal of climate.

[33]  Antonio J. Busalacchi,et al.  Designing the Climate Observing System of the Future , 2017 .