Early trends on the Clouds and the Earth's Radiant Energy System (CERES) Flight Model 6 (FM6) instrument's performance

The Clouds and the Earth’s Radiant Energy System (CERES) scanning radiometer is designed to measure the solar radiation reflected by the Earth and thermal radiation emitted by the Earth. Five CERES instruments are already in service; two aboard the Terra spacecraft, launched in 1999; two aboard the Aqua spacecraft, launched in 2002, and one aboard the S-NPP spacecraft launched in 2011. A sixth instrument, flight model 6 (FM6), launched in November 2017 aboard the JPSS-1 satellite, began taking radiance measurements on January 6th, 2018. The CERES FM6 instrument uses three scanning thermistor bolometers to make broadband radiance measurements in the shortwave, total, and longwave regions. An internal calibration module (ICM) used for in-flight calibration is built into the CERES instrument package consisting of an anodized aluminum blackbody source for calibrating the total and longwave sensors, and a shortwave internal calibration source (SWICS) for the shortwave sensor. The calibration sources are used to define shifts or drifts in the sensor response over the life of the mission. Additional validation tests including solar calibrations and coastline detections are used to validate the pointing accuracy of the instrument and supplement the ICM data. This paper presents the results of FM6 on-orbit internal calibrations, discusses any ground to flight changes, describes trends in the calibration data, summarizes the results of the solar calibration and coastline detection analysis, and discusses strategies for comparing FM6 to other CERES instruments.