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

Cindy L Young,William H Swartz,Christine Buleri,Trevor Jackson,William S Kirk,Patrick C Taylor,Rand Swanson,Constantine Lukashin,Joseph A Shaw,Thomas Stone,David R Doelling,Michael Cooney,Arnold Goldberg

doi:10.3390/rs12203281

Abstract

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.

Highlights

Climate change has the capacity to alter many aspects of the Earth system, as well as reduce economic stability, impact national infrastructure and security, and affect daily life
The Clouds and Earth’s Radiant Energy System (CERES) instrumentation was developed in the 1990s based on Earth Radiation Budget Experiment (ERBE)-scanner instrument heritage [1,2]
The Trutinor vision is to enable a 50-year-long, continuous Earth’s radiation budget (ERB) climate data record capable of resolving the key outstanding challenges in climate science

Summary

Introduction

Climate change has the capacity to alter many aspects of the Earth system, as well as reduce economic stability, impact national infrastructure and security, and affect daily life. The CERES approach for observations, using a single field-of-view radiometer, requires continuous scanning across the field of regard, increasing instrument mass and power use requirements to obtain Earth-view sampling. It must be hosted on a larger satellite with an imager, which determines if the CERES instrument is observing clouds, aerosols, or clear skies. A compact sensor integrated into a small satellite bus, relying on satellite pointing ability and flying in constellation with an existing imager, can result in an instrument concept with a smaller size and lower mass and power requirements Another issue with the current system is the insufficient measurement accuracy to tolerate a gap in the data record, which can be mitigated by improving the accuracy of the instrument’s on-orbit calibration. The concept is based on a push-broom radiometer approach with a microbolometer detector array

Science Motivation

State of ERB Technology

Findings

Conclusions