Method for using the moon's thermal output to track calibration drifts in instruments on board satellites observing the earth

摘要

A method of calibrating a spectrometer, while orbiting the Earth, includes the steps of (a) determining a period of time in which the Moon is within a field of view (FOV) of the spectrometer and (b) stopping the FOV of the spectrometer during this period of time. During this period of time, multiple “free views” of the Moon are available, in which lunar IR intensities may be received by the spectrometer that are comparable to intensity levels obtained from an internal calibration test (ICT) on a satellite. The method measures the IR radiance from the Moon during this period of time. After filtering the lunar IR radiances by an integral function, the spectrometer is calibrated using the “free views” as a benchmark.

主权项

1. A method of calibrating a spectrometer orbiting the Earth, the method comprising the steps of:
imaging the Earth, using the spectrometer, for long-term observations of the Earth's albedo; imaging the Moon by raster scanning the Moon during multiple periods using a scan mirror of the spectrometer, wherein each period provides a short-term observation of the Moon; sampling energy returned from the Moon during each period from raster scan data obtained during each period of the multiple periods; integrating the sampled energy over the multiple periods; autocorrelating the sampled energy; and when the results of the autocorrelation of the sampled energy indicate that the integrated sampled energy has changed over the multiple periods by a delta amount, calibrating the spectrometer using the delta amount determined based on the autocorrelation.