ECOSTRESS End-to-End Radiometric Validation

Abstract

The ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) will measure the brightness temperature (BT) of plants from the space station. This information will be used to generate products such as evapotranspiration (ET) over an effective diurnal cycle to better understand how much water plants need and how they respond to stresses (i.e. lack of water, sun, nutrients). The imaging radiometer on board the ECOSTRESS payload provides five thermal infrared (TIR) spectral bands with approximately 70m pixels and a nearly 400km swath. It incorporates many new technologies such as a high-speed Mercury Cadmium Telluride (MCT) focal plane array (FPA), black silicon calibration targets, and a thermal suppression filter allowing shortwave infrared (SWIR) bandpass. This radiometer has two on-board black-bodies to maintain calibration every sweep of the scan mirror (1.29s). The system has undergone an end-to-end test in a thermal-vacuum (TVAC) chamber showing excellent pre-flight radiometric results. This performance is in part enabled by newly developed, high-speed, low noise, readout electronics. The readout electronics converts all 32-analog channels to digital for downstream on board processing and downlink. Noise equivalent delta temperature (NEΔT) measurements and BT retrievals are well within requirements. The optical modulation transfer function (OMTF) is also within specification. The instrument was launched on SpaceX CRS-15 along with the Latching End Effector for Canadaarm2 as well as three Biarri-Squad cubesats. ECOSTRESS passed In-Orbit Checkout (IOC). This is where all systems as well as science/calibration data are checked and verified to be operational. The payload is currently in Phase E operations. ECOSTRESS uses a local WiFi that sends data from the payload to the ISS. Data packets are then downlinked to the Huntsville Operations Support Center (HOSC) and subsequently archived in the science data system (SDS) servers. A series of calibration targets (Lake Tahoe and the Salton Sea) have been utilized to verify the top of atmosphere radiometric integrity of the science data. Other geometrical targets such as the crop fields of California and a few large bridges around CONUS have been used to verify the geolocation accuracy when compared with previous data from (Visible Infrared Imaging Radiometer Suite) VIIRS and ASTER.