GOES-R Satellite Series Mode 6 Testing and GOES-17 Imagery Anomalies

February 7, 2019

 2:30 minute read

In the coming weeks, NESDIS will perform two tests of the GOES Advanced Baseline Imager (ABI) operating in Mode 6. Mode 6 is an enhancement to the current ABI Flex Mode (Mode 3), in which a full disk image is taken every ten minutes instead of every fifteen minutes.

On Feb. 8, the first ABI Mode 6 test will occur for GOES-16 from 15z to 17z. On Feb. 19, the second ABI Mode 6 test will occur for both GOES-16 and GOES-17, beginning at 15z and concluding on Feb. 22 at 15z.  This will be a 72 hour test.

These tests are important to NWS because ABI Mode 6 will likely become the primary operational mode for both GOES-16 and GOES-17 on or after March 13, 2019. Additionally, GOES-R engineers determine operating ABI in the new Mode 6 timeline will help alleviate the impact of a newly identified anomaly called the Periodic Infrared Calibration Anomaly (PICA). PICA is currently impacting the 7.4 um Low-Level Water Vapor Channel and the 9.6 um Ozone Channel on the GOES-17 ABI.

For more details on ABI Mode 6 Testing, refer to the previous TOWR-S announcement, GOES-17 ABI Mode 6 Testing [Jan. 25, 2019] here.

PICA is caused by the existing Loop Heat Pipe (LHP) issue. When PICA occurs, a loop of CONUS imagery shows small fluctuations in the brightness temperatures of the image.  Specifically, three consecutive images will show a “hot” “hot” “cold” pattern. PICA can make it challenging for forecasters trying to detect changes in brightness temperature. 

According to GOES-R product quality engineer Dave Pogorzala, the LHP issue makes it more difficult for the ABI to maintain a consistent temperature, causing the PICA anomaly to occur. As the ABI operates, it takes time between scans of the Earth to calibrate itself. This can be done by looking out into space, looking at a star, or by looking at a blackbody. To mitigate PICA, GOES-R satellite engineers have created a new calibration scan strategy for the GOES-17 ABI, and that strategy has been programmed into the GOES-17 Mode 6.

Below are AWIPS screenshots of three consecutive CONUS images from the GOES-17 7.4 um Low-Level Water Vapor channel, taken on Feb. 6, 2019, at 17:22, 17:27 and 17:32 over the western United States. Note the brightness temperatures for the first two images are slightly warmer than the third image.

 

AWIPS screenshots of three consecutive CONUS images from the GOES-17 7.4 um channel, taken on Feb. 6, 2019, at 17:22, 17:27 and 17:32.

 

​PICA will be significantly mitigated once GOES-17 switches over to Mode 6 permanently on or after March 13, 2019.

For questions or concerns, contact the TOWR-S team by joining the ‘towr-s’ group via the NWS Chat.