Terra MODIS PWA Failure

Dec. 21, 2020

On November 8, 2020, Terra Moderate Resolution Imaging Spectroradiometer (MODIS) acquisitions switched to a flexible schedule for alternating orbits to enable greater daytime coverage over polar regions. The alternating schedule is an improvement over the day/night coverage ratio of 44.2/55.8 that was initially used following the PWA failure.

Oc. 5, 2020

On Oct. 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.

Contact the Land Processes Distributed Active Archive Center (LP DAAC) User Services with any questions.

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 44.2/55.8 on October 7, 2020. This minimized the chance of unscheduled and unrecoverable data loss. The new day/night ratio resulted in an observed reduction in the overall Terra daytime coverage over Greenland and portions of Northern Russia as well as North America and Alaska.