Prelaunch and On-orbit Electronic Calibration for Earth Observing Instruments

The Electronic Calibration (Ecal) tests are performed during various stages of instrument development to examine the linearity of the instrument electronics. During this process, charges with stepwise increments are injected in the analog electronics circuitry to generate a ramp signal that can be used to characterize any nonlinearities in the electronics. The prelaunch characterization of MODIS (on the Terra and Aqua platforms) and VIIRS (on SNPP, JPSS-1 and JPSS-2) involved a regular evaluation of the electronics linearity using the Ecal tests. On orbit, the Ecal tests have been regularly performed over the mission for both the MODIS instruments to derive the electronics gain and linearity. Unlike MODIS, the Ecal tests on the VIIRS instruments are performed on an as-needed basis. To date, no Ecal tests were performed for S-NPP VIIRS on orbit. The VIIRS instrument on JPSS-1 (now NOAA 20) was launched on November 18, 2017. An Ecal test was performed to support the instruments initial post-launch performance assessment. Shortly after the first on-orbit emissive band calibration, degradation in the instrument gain was observed for the LWIR bands (M15, M16 and I5). As a part of the investigation related to this anomaly, a second Ecal test was performed and results were compared with the prelaunch results. In this paper, we discuss the prelaunch Ecal tests and representative results from MODIS and VIIRS prelaunch characterization. Also, discussed are the on-orbit results from the two MODIS instruments as well as from the recently launched VIIRS instrument.