Terra MODIS PWA Failure

October 22, 2020
By: LP DAAC

On October 5, 2020 at 15:21:12, Terra MODIS experienced a Printed Wire Assembly (PWA) failure that caused partial to full science data loss where the data could not be played back because of recording on the faulty PWA. The image below shows the data gaps for the global browse image of the night time orbits for October 6, 2020.

Terra MODIS data gaps for night time acquisitions for 2020-10-06

MOD02SSH, BAND 29, night time orbits
Data gaps for night time acquisitions for 2020-10-06

In order to minimize the overflow of onboard buffers and reduce the chance of buffers being filled and data overwritten, the day/night coverage ratio was shifted from 50/50 to 43.8/56.2 on October 7, 2020. This will minimize the chance of unscheduled and unrecoverable data loss. Due to this change there is an observed reduction in the overall Terra daytime coverage over Greenland and portions of Northern Russia as well as North America and Alaska. Global browse images prior to the ratio change and the reduced daytime coverage after the ratio change can be viewed below.

Terra MODIS daytime coverage with a day/night coverage ratio of 50/50 for 2020-10-06

MOD02SSH, TOP-OF-THE-ATMOSPHERE REFLECTANCE BANDS 1,4,3
Daytime coverage with a day/night coverage ratio of 50/50 for 2020-10-06

Terra MODIS day/night coverage ratio of 43.8/56.2 with reduced daytime coverage in the northern latitudes for 2020-10-08

MOD02SSH, TOP-OF-THE-ATMOSPHERE REFLECTANCE BANDS 1,4,3
Day/night coverage ratio of 43.8/56.2 with reduced daytime coverage in the northern latitudes for 2020-10-08

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