Changes to the routine GOES-13 Scanning Schedule

March 4th, 2014 |
GOES-13 10.7 µm images (click to play animation)

GOES-13 10.7 µm images (click to play animation)

Tests are underway this week to determine the impact of augmented GOES-13 (GOES-East) imager coverage. The animation above shows the coverage for routine scanning on 3 March 2014 between 1645 UTC and 1945 UTC. CONUS, Extended Northern Hemisphere and Full Disk images are included. The Optimized GOES-East schedule is available at this link. Note the presence of local solar RFI (radio frequency interference) in the 1645 UTC image; solar contamination resulted in no 1702 UTC image at all, as expected (link). Data at SSEC that are contaminated by solar RFI are typically replaced by data from CLASS, as times of local solar RFI in Madison, WI typically do not overlap with times of local solar RFI at Wallops Island, VA.

The difference in CONUS coverage is shown below in the toggle of the 1732 UTC image from 3 March and the 1730 UTC image from 4 March. The Optimized Image scan allows for more routine scanning of the Caribbean Sea, for example.

GOES-13 10.7 µm images at ~1730 UTC on 3 and 4 March (click to enlarge)

GOES-13 10.7 µm images at ~1730 UTC on 3 and 4 March (click to enlarge)

Side-by-side views of GOES-13 10.7 µm images.  CONUS from 3 March, 1732 UTC (left) and Optimized CONUS from 4 March, 1730 UTC (right) (click to enlarge)

Side-by-side views of GOES-13 10.7 µm images. CONUS from 3 March, 1732 UTC (left) and Optimized CONUS from 4 March, 1730 UTC (right) (click to enlarge)

A side-by-side image of the regular and optimized CONUS scans is shown above. Note that the optimized scan has a slightly different time (Nominal times for each image are in the panel labels). Thus, batch jobs that access imagery by time must be altered. Side-by-side imagery for the entire test period is below. The 1645 UTC imagery should cover the same domain, but RFI interference is different on the two days. The test period ends before the 1902 UTC image. In the animation below, the CONUS images at half-past the hour show the increase in domain size.

Side-by-side views of GOES-13 10.7 µm images, 1645 UTC through 1902 UTC on March 3 2014 (Left, default schedule) and March 4, 2014 (right, optimized schedule). (click to animate)

Side-by-side views of GOES-13 10.7 µm images, 1645 UTC through 1902 UTC on March 3 2014 (Left, default schedule) and March 4, 2014 (right, optimized schedule). (click to animate)

Four-hour animation of Puerto Rico Regional Sector, 17-20 UTC on 4 March 2014 (click to enlarge)

Four-hour animation of Puerto Rico Regional Sector, 17-20 UTC on 4 March 2014 (click to enlarge)

As noted above, the optimized scan strategy significantly improves coverage in the Caribbean. In fact, the Puerto Rico Regional Sector is now almost completely covered. The animation above shows that sector for 2 hours with the expanded coverage during the test, and the subsequent two hours. Compare, for example, the 1830 UTC image, during the test, to the 1931 UTC image after the test (image toggle comparison).

GOES-13 Navigation anomalies due to a maneuver

February 19th, 2014 |
GOES-13 0.63 µm visible channel images (click to play animation)

GOES-13 0.63 µm visible channel images (click to play animation)

A GOES-13 (GOES-East) North/South Station Keeping maneuver was performed on Wednesday, February 19, 2014, beginning 1145 UTC, and ending at 1945 UTC (Link). During this time, the navigation of the satellite degraded mostly in the north-south direction. At 1945 UTC, after the maneuver ended, the navigation snapped back to normal. (Compare the 1932 and 1945 UTC images).

Navigation error tracking is available online for some geostationary satellites. For example, this link, off this page, shows landmark errors from MTSAT. NOAA’s OSPO maintains a site for GOES satellites; however, results are posted weekly. (Link).

GOES-13 Sounder Anomalies continue

November 4th, 2013 |
Composite of GOES-15/GOES-13 3.9 µm shortwave IR images (click image to play animation)

Composite of GOES-15/GOES-13 3.9 µm shortwave IR images (click image to play animation)

The GOES-13 Sounder has been experiencing anomalies that manifest themselves as missing pixels since mid-Summer. The missing pixels apparently arise because of slight fluctuations in the speed of the sounder instrument filter wheel. The number of missing pixels per Sounder image peaked in late September, just after the Equinox, with up to 700 missing pixels (out of 63000) per Sounder image over CONUS. At present, missing pixels vary between 100 and 250, with a maximum typically around 2200 UTC and a minimum between 0600 and 1000 UTC. In the animation above, the missing pixels show as black; the GOES-15 Sounder data have no missing pixels.

Realtime GOES Sounder imagery is available at this link. The Sounder anomalies are present in all 19 of the GOES-13 spectral bands, as evident in the toggle below between an image in late September (when error counts were highest) and early November (when error counts were lower). GOES Engineers continue to monitor this situation and investigate possible solutions.

GOES-13 Sounder 19-band display, 1800 UTC 27 September and 1600 UTC 4 Nov 2013 (click image to enlarge)

GOES-13 Sounder 19-band display, 1800 UTC 27 September and 1600 UTC 4 Nov 2013 (click image to enlarge)

GOES-13 Sounder Anomalies

September 16th, 2013 |
GOES-13 10.7 µm IR channel images (click unage to play animation)

GOES Sounder DPI Lifted Index from 1300 UTC 15 September

The GOES-13 Sounder has been experiencing an increased number of unexpected scan line lengths. This was originally detected on 1 July 2013 and it has become more common since 12 September 2013. The anomaly is manifest in the data by occasional pixel gaps in all channels of the Sounder images. Some images show only a single gap (and therefore just one missing pixel); other images have several gaps. In the image above, the missing values are the black pixels just off the North Carolina coast (for example), or near the Mississippi River in southwestern Mississippi. Note that missing data only is present in the GOES-13 part of the domain. The GOES-15 signal is clean. The root cause of this error is under investigation. From NESDIS: “No telemetry violations have occurred, and all Sounder filter wheel telemetry data, including Filter wheel currents and period monitors, are within expected values.”

The missing pixels are also present in the real-time Sounder data available at CIMSS at this link. An example from September 15th is shown below. Or, click here for a composite (GOES-13/GOES-15) single-band image.

GOES-13 10.7 µm IR channel images (click unage to play animation)

GOES Sounder DPI Lifted Index from 1300 UTC 15 September

A quick analysis at two times (0246 and 1446 UTC) suggests that prior to 28 August, errors per image were limited to 20 or so pixels. Between 28 August and 9 September, fewer than 100 pixels were affected each hour. Since 10 September, the number of pixels affected in each image has increased one some days to more than 200. There are nearly 64000 pixels in each sounder image, so the number of bad points remains a small percentage of the total.