GOES-17 imagery and a cooler Set Point temperature

April 19th, 2022 |
GOES-17 Band 10 Infrared (Upper Level water vapor imagery, 7.34) imagery, 1531 UT on 19 April 2022 (Click to enlarge)

At 1500 UTC today, the Set Point temperature on the cryocooler was re-set to a cooler temperature (the effect of the warmer Set Point temperature is discussed here: Bands 10 and 12 had more lines of missing data related to the warming of the satellite by the Sun). The cryocooler works to reduce the thermal load on the satellite, but during seasonal peak heating (see the figure on Page 5 in this document), it is unable to counteract fully the effects of the malfunctioning Loop Heat Pipe on GOES-17.

The figure below compares Focal Plane Temperatures on 16 April (with the warmer Set Point temperature) and 19 April (during which day the cooler Set Point Temperature was re-implemented). (More comparison imagery is at this website; imagery for Band 10 on 16 April is here; from 19 April is here) Note how the brightness temperature difference between GOES-16 and GOES-17 is very different (one might say noisy) on 16 April, and on 19 April until about 1530 UTC, after which point it stabilizes at less than about 0.25K warmer for GOES-17. The change in the Focal Plane Module (FPM) Temperature is also apparent: The FPM is about 3K cooler than on 16 April starting around 1500 UTC on 19 April. This is because of the change in the Set Point on the cryocooler that occurred at that time.

GOES-17/GOES-16 brightness temperature differences within a small region (Blue stars/line) and Focal Plane Temperature (Black Line/magenta stars) from 0000-1730 UTC on 16 and 19 April 2022 (Click to enlarge)

GOES-17 Image Degradation due to a warmer Set Point temperature

April 15th, 2022 |
GOES-17 Band 10 (7.34 µm), Band 12 (9.61 µm) and Airmass RGB imagery over the PACUS sector, 0001 UTC on 15 April 2022 (Click to enlarge)

During the current warm period for GOES-17, when the sun’s position leads to excessive heat build-up on GOES-17 because of the poorly-functioning Loop Heat Pipe, the Set Point temperature has been increased from 92.8 K. This change occurred on 11 April 2022 and it is scheduled to last for one week — the daytime ‘stripiness’ should relax on 19 April when the Set Point temperature changes back to a cooler temperature (90 K). The figure below (from this NESDIS/STAR link) shows Focal Plane Temperatures at different time scales. The Set Point change is apparent in the figure showing the last 10 days; a second Set Point temperature occurred on 9 April, but that one did have such a big effect on imagery. Note how the warmest Focal Plane Temperature has been increasing in the past 10 days.

GOES-17 Focal Plane Temperature at different timescales (Click to enlarge)

You might ask: What is the Set Point temperature and why is it affecting these two bands? The cryocooler is a secondary cooling mechanism on GOES-R satellites (the Loop Heat Pipe is another cooling mechanism). Heat from the cryocooler’s operation actually warms up the satellite. So, warming the cryocooler set point decreases that thermal load. That warmer setpoint, however, means the focal plane of the ABI is warmer (as evidenced in the image above), and that warmer focal plane degrades select bands for all 24 hours. The benefit of a warmer cryocooler is that the number of nightly images completely missing related to the Loop Heat Pipe is not quite so long. In other words, for Band 10, all of the daytime images have some degradation, but the number of completely missing night-time images is decreased (compared to what would happen if the Set Point were cooler!). This pdf shows predictions for how warm the Focal Plane Temperature might get over the course of this year; note (on page 5) that the April heating period is the warmest, and that (page 6) Bands 10, 12 and 16 are the most affected bands.

Because Band 10 (and Band 12) data are used in some RGBs — such as the airmass RGB shown above — those RGBs will also be affected for this week.

GOES-17 Scanning designed to reduce heating-caused data outages

April 24th, 2020 |

GOES-17 Upper Level Water Vapor (Band 8, 6.19 µm) Infrared Imagery, 0400-1620 (Click to animate)

NOAA/NESDIS has modified the GOES-17 Mode 6 scanning schedule during times of increased data-outages related to the faulty Loop Heat Pipe (LHP) mechanism (Blog Post 1, 2, 3 on that subject;  see also here) on GOES-17.  (The OSPO Notification is here).  Between 0600 and 1200 UTC, Full Disk scans are imaged every 15 minutes, rather than every 10;  the two flexible mesoscale sectors (including the one with a default location over Alaska) are scanned every 2 minutes, rather than every minute;  the GOES-17 ‘CONUS’ domain, also known as the PACUS domain, typically scanned every 5 minutes, is not scanned at all.  These modifications will be in place in 2020 from 9 April through 1 May, from 12 August through 1 September and from 14 October through 31 October.  Dates for 2021 (and beyond) have not yet been determined.  The ‘time-time’ chart for this modified scanning is shown below (figure source).

‘Time-Time’ chart for GOES-17 Scanning during Mode 3 Cooling operations. Cyan regions denote no ABI scanning activity, green regions are Meoscale sector scans, pink denotes the full disk scan. Other colors show navigation and calibration times. Note the lack of a 5-minute PACUS scan (Click to enlarge)

This change in scanning strategy mitigates heating-caused imagery losses because it reduces the amount thermal energy absorbed by the ABI when it is pointed towards a warm source (that is, Earth) instead of cold outer space.  By reducing the scanning periods, OSPO reduced (but did not eliminate) the span of time during which time data from many of the infrared channels of the ABI are unusable because of saturated sensors.

Note in the animation above how the time-step changes at 0600 UTC to every 15 minutes, and then changes back to every 10 minutes at 1200 UTC.  A slower animation from 0530 – 0630 UTC (link) shows that increment change more clearly.  Because the so-called CONUS scan does not happen, GOES-17 CONUS scan imagery is not available during this time window;  of course, data are available in the CONUS region via the every-15-minute Full Disk scans.

The image below, courtesy Mat Gunshor, CIMSS, (derived from this website) shows how this Mode 3 Cooling Operations reduces the window when data are unavailable.  The time span when data are unusable (highlighted by the green double-headed arrows) is shorter in 2020 as a result of this new scanning strategy.  Also, the peak Focal Plane Module (FPM) Temperature is reduced, which may have implications for the long-term health of the satellite.

Comparisons between GOES-16 and GOES-17 Low-Level water vapor infrared imagery (Band 10, 7.34 µm).  Julian day 104 from 2019 (left) and 2020 (right).  GOES-16 and -17 Full-Disk imagery at the end of the time series as shown.  Time series plots (bottom) show the Focal Plane Module (FPM) temperature (black) and the GOES-17 – GOES-16 brightness temperature difference (blue) for a region centered on the Equator equidistant between the two satellite sub-points.

GOES-17 ABI Temperature Data Quality Flags (TDQF) thresholds updated

October 2nd, 2019 |

Top: Thumbnails of GOES-17 and GOES-16 ABI Band 12 (9.6 µm) on August 1, 2019. Bottom: Time series of GOES-17 minus GOES-16 brightness temperature for a region located between the two satellites. Also plotted is the GOES-17 Focal Plane Temperature. The reduced duration of the GOES-17 data to be flagged is highlighted. [click to enlarge]

As of 19:45 UTC on August 8, 2019, the new Look-Up-Table (LUT) went into operations for use in the GOES-17 ABI Temperature Data Quality Flags (TDQF). These hotter thresholds are possible due to the recent implementation of the Predictive Calibration algorithm.  Note that the image also includes the percent good (and conditionally usable) values (flagged 0 or 1) for both GOES-16 and GOES-17 ABI. Recall there are 5 Data Quality Flags for ABI data:

  • DQF:percent_good_pixel_qf = 1.f ;
  • DQF:percent_conditionally_usable_pixel_qf = 0.f ;
  • DQF:percent_out_of_range_pixel_qf = 0.f ;
  • DQF:percent_no_value_pixel_qf = 0.f ;
  • DQF:percent_focal_plane_temperature_threshold_exceeded_qf = 0.f

The last one, DQF:percent_focal_plane_temperature_threshold_exceeded_qf, reports what percentage of the images pixels are warmer than the threshold value. Note that the thresholds on both the increasing and decreasing temperatures are also reported in the meta-data.

Near realtime brightness temperature comparisons between GOES-16 and GOES-17, as well as historical comparisons for a region centered on the equator and half way between the two satellites.

From the NOAA Notification:

Product(s) or Data Impacted: GOES-17 ABI auxiliary field change

Date/Time of Initial Impact: August 8, 2019 1945 UTC

Details/Specifics of Change:

The GOES-17 ABI Temperature Data Quality Flags (TDQF) thresholds for the thermal bands have been updated to the values in the table below.  This update will make utilizing the TDQF more effective for flagging saturated data caused by the GOES-17 ABI cooling system anomaly. There will be no impacts to distribution caused by this update.

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]

Update (10/02/2019)

On October 2, 2019, at 17:04 UTC, updates for a number of the ABI GOES-17 DQF thresholds were implemented in the operational system. NOAA Notification: https://www.ospo.noaa.gov/data/messages/2019/MSG2751954.html

Table of updated Temperature Quality Data Flag thresholds

Table of updated Temperature Quality Data Flag thresholds [click to enlarge]. The bold numbers are those values that were updated on October 2nd.