Topic: Status of GOES-17 ABI L1b and CMI Data

Date/Time Issued: December 7, 2018 1935 UTC

Product(s) or Data Impacted: GOES-17 ABI L1b and CMI data

Date/Time of Initial Impact: November 28, 2018 at 2200 UTC

Date/Time of Expected End: M-BN/A

Length of Event: M-BN/A

Details/Specifics of Change: The GOES-R Peer Stakeholder - Product Validation Review for ABI L1b and CMI Provisional Maturity was held on November 28, 2018. As a result of this review, NOAA has confirmed that the ABI L1b and CMI data are at Provisional Validation Maturity as of November 28, 2018.

NOAA's GOES-17 satellite has not been declared operational and its data are preliminary and undergoing testing. Users receiving these data through any dissemination means M-B(including, but not limited to, PDA and GRB) assume all risk related to their use of GOES-17 data and NOAA disclaims any and all warranties, whether express or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose.

GOES-17 ABI L1b and CMI data will be considered operational once the GOES-17 satellite is declared operational in January 2019. The ABI L1b data products are calibrated and geo-located radiances of the 16 ABI bands over the Full Disk (FD) of the Earth, the Continental United States (CONUS) region, the Mesoscale (MESO) regions, and certain instrument calibration and engineering data. The CMI data products are reflectances for bands 1-6 and brightness temperatures for bands 7-16.

Provisional maturity means:

During the period when these data are Provisional but the GOES-17 satellite is non-Operational, there will be occasional interruptions to the flow while various post-launch tests occur which will be communicated through the GRB forum distribution list.

Users of the GOES-17 ABI L1b data bear responsibility for inspecting the data and understanding the known caveats prior to use. Below is the list of caveats that have been identified and are under analysis. Solutions are in development and testing.

Known issues being investigated include the following:

1. An anomaly with the GOES-17 ABI Loop Heat Pipe (LHP) prevents the instrument cooling system from maintaining the desired operating temperature at all times of the year. Also, the thermal stability is not maintained for some parts of the instrument during certain periods of the day and year.

a. For 13-14 hours a day, the Focal Plane Module (FPM) is maintained at a stable but elevated temperature (compared to GOES-16). During this period of time, it seems that the reduced functionality of LHP:

i. Does not affect the Imager Navigation and Registration (INR) performance for all channels.

ii. Does not affect the accuracy of radiometric calibration performance for channels 1-15.

iii. May have caused a warm bias of up to 0.4 K for Channel 16.

iii. Led to higher noise in channels 7-16 when compared to GOES-16. Four of these channels still meet the Mission Requirements; four nearly meeting the requirement; and Channels 12 and 16 are substantially noisier than GOES-16.

b. For the other 10-11 hours a day, the FPM temperature rises each night. During the roughly 100 days centered on the vernal and autumnal equinoxes:

i. INR performance may remain nominal.

ii. Radiometric calibration performance is less well known, but is further degraded and sometimes unusable, for Channels 8-16.

iii. The peak of the FPM temperatures occurs about 20 days before and after the equinox.

2. Stray light exists for Visible and Near IR (VNIR) bands approximately one hour before and after satellite local midnight during the eclipse season before the vernal (spring) equinox and after the autumnal (fall) equinox, and may exist in other days of the year. Effects include:

  1. Significant stray light for Channels 1-6 (VNIR) approximately one hour before and after satellite local midnight for approximately forty days before and after the vernal (spring) and autumnal (fall) equinox, and may exist in other days of the year.

  2. Stray light for Channel 7 approximately one hour before and after satellite local midnight for approximately forty days before and after the vernal (spring) and autumnal (fall) equinox within the Zone of Reduced Data Quality (ZRDQ).

3. Two channels are brighter than commonly-accepted values by more than 5% (the accuracy requirement):

  1. Channel 2 (0.64 M-BM-5m) radiances are approximately 8.9% brighter.

  2. Channel 5 (1.61 M-BM-5m) radiances are approximately 5.5% brighter.

4. Channel 3 (0.86 M-BM-5m) radiance may vary slowly by up to 5%. For example, an object with reflectance of 80% may appear as 78% at one time and 82% some months later. This may also happen to Channels 2 & 1 (0.64 M-BM-5m & 0.47 M-BM-5m) but to a much lesser degree (~1%).

5. Striping can be seen in ABI Channels 5 (1.61 M-BM-5m) and 8, 9, 10 (water vapor), 12 (9.61 M-BM-5m) and 16 (13.3 M-BM-5m).

6. Bias for many VNIR channels seems negatively correlated with scene radiance, i.e., the darker the scene, the more likely that the ABI radiances have positive bias, and vice versa.

7. Channel 1 (0.47 M-BM-5m) radiances may be higher on the west end than on the east end by up to 1%. For example, an object with reflectance of 80% may appear as 80.4% on an extreme west location and 79.6% on an extreme east position.

8. When the ABI is operating in Mode 3 (flex mode), remnants of periodic infrared calibration anomalies (PICA) may exist for several channels, especially for Channel 12 (9.6 M-BM-5m) and Channel 10 (7.4 M-BM-5m). This is seen through radiance or brightness temperature for every 3rd CONUS image being slightly lower than the other two. It is thought a similar error exists in FD and MESO images but is more difficult to visualize.

9. ABI Channels 8, 9, 10 (water vapor), 11 (8.5 M-BM-5m), and 12 (9.65 M-BM-5m) radiance may vary among the swaths.M-B This may cause banding.

10. There may be artificially cold pixels surrounding hot spots in Channel 7 (3.9 M-BM-5m).

For CMI, all the issues noted above for the radiances are valid, in addition to the following:

  1. Currently there are no data quality flags based on focal plane temperatures.

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