Satellite Operations Updates - Total Operational Weather Readiness - Satellites (TOWR-S)

Mode 6: GOES-E/W ABI Operational Flex Mode Transition to 10 Minute Cycle

March 29, 2019

5 minute read

On Tuesday, April 2 at 1600Z, Flex Mode for both GOES-E (GOES-16) and GOES-W (GOES-17) Advanced Baseline Imagers (ABIs) will transition to Mode 6, subject to Critical Weather Day (CWD) status.

Why Mode 6?

Mode 6 Flex Mode will consist of 10-minute full disk scans instead of the 15-minute scans of Mode 3. This will align the imagery cadence with the current Himawari and future European Meteosat Third Generation satellites, the latter of which are planned for launch starting in 2021. Mode 6 will also generate 10-minute Puerto Rico, Hawaii, and Alaska sectors for SBN users.  This mode will generate the same 5-minute CONUS and 1-minute mesoscale imagery products produced previously under Mode 3 operation. This change will go into effect for both GOES-E and GOES-W at the same time.

Additionally, Mode 4 continuous full disk scan mode will continue to be available and requestable through the ​​​​​​current MDS process.

What changes should I expect in Mode 6 operations?

Mode 3 will be retired and will no longer be available as an operational mode. Mode 6 operations have been extensively tested, including five official tests since December 2018, the most recent being on March 19 - 22, 2019. This change will be transparent to all AWIPS systems, as AWIPS menus and configurations will remain the same.

AWIPS Mesoscale Sector Display Issue​​​​​​​

During Mode 6 testing, an AWIPS mesoscale display issue was identified when multiple mesoscale images are displayed concurrently. This is due to changes in the timing relationship between Mesoscale Sector 1 (MESO-1) and Mesoscale Sector 2 (MESO-2) as the satellite scans the earth. The Mesoscale Sector a forecaster time-matches to in AWIPS will always display every frame (e.g. has an asterisk to the left of the legend display in the bottom right-hand-corner).  However, the companion Mesoscale Sector image will experience repeats and frame skips to varying degrees (e.g. GOES-W concurrent mesos, with time-matching on MESO-2, versus the same displays but time-matched to MESO-1). Several solutions to address this AWIPS display artifact are under development and more details on them will be forthcoming.

AWIPS selects images to display at the same time-based on the shortest amount of time between the two products selected for ‘time-matching’.  Table 1 below can be used to predict when an image will be repeated or skipped.

​​​Table 1. GOES-E and GOES-W: Mesoscale Sector Scene Start Times relative to Mode 6 FD Scan Cycle​​​​​​​​​​​​​​

Example:  If GOES-W MESO-1 and MESO-2 are displayed, with MESO-1 selected for time-matching, then the MESO-2 image from 01:01 will be repeated, matching the MESO-1 00:27 and 01:27 images.  In this case, the MESO-2 01:57 image will be skipped.

ABI Thermal Calibration Improvements

The GOES-R Program has implemented two improvements to the ABI thermal calibration as part of the introduction of Mode 6.

1. The first is an acceleration of the calibration cycle. The 10-minute cycle incorporates a thermal calibration sequence every five minutes. In the immediate term, this will improve the quality of CONUS and Mesoscale scene performance immediately leading up to and immediately following Loop Heat Pipe (LHP) related outages. Future NESDIS updates will extend those enhancements to the full disk scenes as well.  



2. Second, the Periodic Infrared Calibration Anomaly (PICA) present in GOES-E and GOES-W imagery is being mitigated through enhancements to the calibration sequence. PICA is essentially the result of radiative cooling and heating of the detector array through the telescope, for which the thermal control system is unable to compensate. Evidence of the detector array temperature variation can be observed as a periodic “pulsating” effect in IR channel imagery.  Calibration activities involve deep space looks by the instrument, including alternating looks at stars for navigation. These cool the detector array. However, upon resumption of scanning the Earth, the detectors initially register colder temperatures, which is followed by a gradual warm-up, as scanning continues. GOES-R Program Calibration engineers have come up with a novel mitigation to the problem through implementation of a “nadir stare” at the Earth directly below the satellite after the cold calibration, equalizing the temperature before image scanning. These actions are being performed for both GOES-E and GOES-W. Further details on GOES-W ABI performance can be read here.