Stability of Satellite Observations

Abstract:

Satellites offer unparalleled capabilities for monitoring the Earth System, often supplying consistent global observations where limited information is available. A constant concern with satellite observations is their stability over time. Orbital paths, instrument components, temperature, power levels, radiation and even internal calibration mechanisms are all sources of potential degradation in data quality. Satellite overlap periods are critical to creating long-term, stable datasets from multiple satellites; these overlap periods are considerably more important when in situ observations are not available. The Solar Radiation and Climate Experiment (SORCE) and Total and Spectral Irradiance Sensor (TSIS) overlap from early 2018 through early 2020 allow an intercomparison of Spectral extra-terrestrial solar spectral irradiance from these two satellite missions. This long overlap period allows testing of basic assumptions about the value of overlap in creating long-term records. Results will be shown for quantification of offsets and drifts across the full solar spectrum of wavelengths observed. Results indicate that previously used estimates of “one year of overlap” are not fully supported by the collected data. The need for overlap is determined by the observed agreement between the data from the two satellites, with the exact dependence governed by a few basic factors including variability, autocorrelation and drift.