Early morning September 13, 2017, the Landsat 7 Solid State Recorder (SSR) experienced an anomaly. The Flight Operations Team (FOT) initial analysis of telemetry indicated what is referred to as an "SSR choke anomaly" where the SSR locks up. This condition has occurred multiple times over the past several years.
The FOT has a Standard Operating Procedure (SOP) to deal with choke anomalies, which involves commanding the SSR to low power mode, commanding the SSR to full power, and then performing an SSR dump. This "resets" the recorder.
Unfortunately, this reset procedure did not restore the SSR to normal operations.
Although Landsat 7 imaging operations have ceased for now, the ETM+ is fully powered to ensure the instrument's thermal balance is maintained. Telemetry from the spacecraft is reduced due to the inability to record the data and limited to real-time ground station downlinks which slows down the anomaly investigation.
Engineers are continuing detailed analysis of the problem to look at options for returning to full operation as quickly as possible.