GOES-14 Sounder Operations

January 31st, 2016

GOES-14 Sounder DPI of Total Precipitable Water (TPW) at 1800 UTC on 31 January 2016 [Click to enlarge]

GOES-14 Sounder DPI of Total Precipitable Water (TPW) at 1800 UTC on 31 January 2016 [click to enlarge]

GOES-14, over the Equator at ~105º W Longitude, has been activated in support of SRSO-R Operations in February 2016. One-minute imagery will commence on Monday 1 February. The GOES-14 Sounder has also been activated to fill in, temporarily, for the GOES-13 Sounder that has been inactive since November 2015. An animation of all 19 Sounder channels is available at this link; animations of Derived Product Images (DPI) of Total Precipitable Water from GOES-14, as shown above, are available here, with GOES-14 DPI of Lifted Index available here.

GOES-13 Sounder Anomalies

November 23rd, 2015

GOES-15 Visible (0.63 µm) images [click to play animation]

GOES-13 Sounder Band 5 Infrared (13.4 µm) images, 0847 and 0947 UTC on 20 November [click to enlarge]

On 20 November, at 0922 UTC, the GOES-13 Sounder experienced an anomaly (the GOES-13 Sounder had Filter Wheel anomalies in 2012 as well: Link; Link). GOES Engineers determined that the Filter Wheel had stopped moving (the filter wheel aligns the infrared detectors with the incoming data) so data were not scanned. The image above shows the 13.4 µm (a CO2 channel) image before and after the anomaly. All 18 infrared channels are affected; the visible channel (band 19) continues sending usable data. GOES Engineers continue to investigate the problem. GOES Sounder derived products (such as Total Precipitable Water) are affected, and are no longer being produced or disseminated (Link). From an email from SSD: (Link)

*Update #2: * **Effective immediately; all the GOES-13 (GOES-East)
sounding products are ceased to produce and stop distribution as we are
experiencing an anomaly with the sounder instrument. Engineers are
investigating the problem. We will inform you when we resume our normal
operations.

*Update #1: * GOES-13 (GOES-East) Sounder IR Data Outage

*Topic:* GOES-13 (GOES-East) Sounder IR Data Products Outage

*Date/Time**Issued:*November 20, 2015 1955Z*
*

*Product(s) or Data Impacted:*

GOES-13 (GOES-East) Sounder data
Blended Hydrometorological Products – Blended TPW
Microwave AWIPS Products – Blended TPW
Microwave McIDAS Products – Blended TPW
GOES Gridded Cloud Product
GOES VARiable data
AFEP/Ingestor – GOES
N-AWIPS Ingest
Single Field of View BUFR
Single Field of View SDPI for AWIPS
Single Field of View TPW
Sounding ASOS SCSP
Web Pages

*Date/Time of Initial Impact:*November 20, 2015 0922Z **

*Date/Time of Expected End:* TBD

*Length of Outage:* TBD

*Details/Specifics of Change:*GOES-13 (GOES-East) Sounder instrumentis experiencing an anomaly. Engineers are investigating the problem. GOES-13 Sounder IR data is not available. **Effective immediately all the GOES-13 (GOES-East) sounding products are ceased to produce and stop distribution as we are experiencing an anomaly with the sounder instrument. Engineers are investigating the problem. We will inform you when we will resume our normal operations.


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Update 19 January 2016
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GOES-14 is scheduled to broadcast 1-minute SRSO-R data starting 1 February. GOES-14 will be activated on 25 January, with a maneuver shortly thereafter. It is likely that GOES-14 Sounder data will be broadcast from 1-25 February (GOES-14 Sounder Timing will be adjusted to match GOES-13 Sounder Timing) when the GOES-14 Imager is broadcasting SRSO-R data.

GOES-15 Navigation Anomalies

May 4th, 2015
GOES-15 0.62 µm visible imagery, times as indicated on 3 May 2015 (click to enlarge)

GOES-15 0.62 µm visible imagery, times as indicated on 3 May 2015 (click to enlarge)

A GOES-15 (GOES-West) Star Tracker failed on 23 April 2015 at 2032 UTC. This leaves just one working Star Tracker; consequently image navigation has degraded. The image above shows three successive visible images centered near Crater Lake, OR, on 3 May 2015. The navigation shifts over time. An animation of 3.9 µm imagery, below, also from May 3rd (available here as an mp4), shows image navigation shifts throughout the day. A two-day animation of visible imagery centered on the Washington coast near Hoquiam (bottom, available here as an mp4) also shows the navigation anomalies that can be as much as 8 km in the infrared. Users who require precise animation in their GOES-15 imagery should be alert to this issue. NOAA/NESDIS, NASA and factory engineers are investigating possible fixes; GOES-15 status updates will appear here.

GOES-15 3.9 µm infrared imagery, 1400-2200 UTC on 3 May 2015 (Click to enlarge)

GOES-15 3.9 µm infrared imagery, 1400-2200 UTC on 3 May 2015 (click to enlarge)

GOES-15 0.62 µm infrared imagery, 1400-2200 UTC on 1 and 2 May 2015 (Click to enlarge)

GOES-15 0.62 µm infrared imagery, 1400-2200 UTC on 1 and 2 May 2015 (click to enlarge)

More on the GOES-13 Imager Co-Registration Error

February 10th, 2015

The longwave infrared (10.7 µm) and shortwave infrared (3.9 µm) channels on GOES-13 have been shown in the past to have poor co-registration, meaning that the sensors are not viewing the same pixel at the same time. This error can lead to false signals in (for example) the IR Brightness Temperature Difference product that has historically been used to detect fog and low stratus. The error can propagate to other products as well, such as GOES-R IFR Probabilities (a data fusion product used to detect fog). The error is most obvious along north-south shorelines.

The figure below (Courtesy Tony Schreiner, SSEC/CIMSS) shows differences averaged over 6 pixels near the eastern shore of northern Lake Superior.  The orange line (labeled ‘Original’) represents differences arising from the operational algorithm used before November 2014.  Note that at 0700 UTC for this date and (clear) location (0600 UTC Surface Map) the brightness temperature difference nevertheless showed a negative value because the 10.7 µm pixel was over the cold lake and the 3.9 µm pixel was over warmer land. Shoreline on the western side of the lake would have a positive value: there, the 10.7 µm pixel would be over warm land and the 3.9 µm pixel (co-registered too far to the east) would be over cold water. This positive signal is consistent with fog detection.


Slide3
In November 2014, NESDIS implemented a fix to mitigate the co-registration issue (Link). One-pixel shifts were applied to the shortwave infrared (3.9 µm) data to force a better alignment. The red line in the figure above (labeled ‘Current Ops’) shows brightness temperature differences that occurred when that fix was used; a one-pixel shift occurred, usually around 0700 and 1700 UTC, and that shift reduced the average error. However, it also introduced a phenomena of fog signals appearing (or disappearing) quickly as the shift occurred. The animation below shows high clouds clearing in a small region over the Lake Michigan shoreline east of Green Bay; a fog signal appears suddenly at 0700 UTC. Similarly, in this toggle over Baja California, fog is indicated on the western coastline of Baja at 0630 UTC (before the pixel shift) and on the eastern/southern coastline of Baja at 0700 UTC (after the pixel shift). Imagery over the St. Lawrence shows fog/low clouds along the south shore of Anticosti Island in the mouth of the St. Lawrence at 0630 UTC; at 0700 UTC, that indication of fog is gone, but it has appeared along the western shore of the St. Lawrence River.

Reg_11-3.9_Sat_20150204_0545_0800

GOES-13 Brightness Temperature Difference (10.7 -3.9), 4 February 2015, 0545 – 0800 UTC (Click to enlarge)

The red line in the figure above also shows a shift at 1700 UTC, and that shift is apparent in data as well, as shown in the brightness temperature difference product, below, north of Lake Superior. The apparent shift occurs in the 1700 UTC image.

Reg_11-3.9_Sat_20150208_1630_1700

GOES-13 Brightness Temperature Difference, 1630, 1645 and 1700 UTC on 8 February 2015 (Click to enlarge)

Between the 1515 and 1545 UTC imagery on 9 February 2015, a software change was implemented by NESDIS (link), and that now operational software is represented by the green line (labeled ‘Resample’) in the figure above. Rather than a step function change, a smoothly varying change is applied to the co-registration over the course of the day. This has reduced the obvious changes in brightness temperature difference fields that occurred between 0645 and 0700 and between 1645 and 1700 UTC. Consider the two animations below (Courtesy Jim Nelson, SSEC/CIMSS). In both, the former operational technique (the red line in the figure above) is on the left and the current operational technique (the green line in the figure above) is on the right. The operational change has certainly eliminated the jump that was occurring at 0700 and 1700 UTC.

GOES13_BTD_0645_0700_08_09Feb2015

GOES-13 Brightness Temperature Difference fields, 0645 and 0700 UTC on 9 February (Left) and 10 February (Right)

GOES13_BTD_1645_1700_08_09Feb2015

GOES-13 Brightness Temperature Difference fields, 1645 and 1700 UTC on 8 February (Left) and 9 February (Right)

Note that even the green line in the figure up top shows errors approaching 1 C at times during the day (and that may change over the course of the year). It is therefore still possible to find cases in which the brightness temperature difference field from GOES erroneously indicates fog or low stratus. The toggle below shows data from 10 February, after the operational change. A fog/stratus signal is indicated by the GOES Brightness Temperature Difference product along the eastern shore of Lake Michigan; however, there is no signature of fog/stratus on the VIIRS Day Night Band and brightness temperature difference (11.35µm – 3.74µm) imagery from Suomi NPP. As always, a positive indication of a phenomena in data should always be verified with other data types.

GOES-13 Brightness Temperature Difference (10.7 µm - 3.9 µm), Suomi NPP Day Night Band (0.70 µm) and Suomi NPP Brightness Temperature Difference (11.35 µm - 3.74 µm), 10 February 2015, 0715 UTC (Click to animate)

GOES-13 Brightness Temperature Difference (10.7 µm – 3.9 µm), Suomi NPP Day Night Band (0.70 µm) and Suomi NPP Brightness Temperature Difference (11.35 µm – 3.74 µm), 10 February 2015, 0715 UTC (Click to animate)

[Added, Friday the 13th]: The co-registration error between the longwave and shortwave infrared bands on the GOES-13 Imager is larger than on any of the other Imagers from GOES-8 through GOES-15. For more information, see here and here.

Comparison of co-registration errors between various GOES satellites

Comparison of co-registration errors between various GOES satellites