GOES-12 « CIMSS Satellite Blog

Update on GOES-12 Cycle Slips

June 7th, 2012

GOES-12 10.7 µm IR image using Side 1 electronics (left) and Side 2 electronics (right)

At 1645 UTC on 6 June, an Electronics Side Swap occurred for GOES-12 to mitigate the effects of Cycle Slips that were occurring around 0800-1300 UTC each day (See this link for an explanation). No Cycle Slips occurred in the GOES-12 imager data on 7 June; as a result, the images are much cleaner. The image above shows an enhanced 10.7 µm image from June 4 2012 using the Side 1 electronics, which side was plagued by cycle slips, and from June 7 2012 using the Side 2 electronics, which show no cycle slips.

GOES-12 Imager (all channels) for 0945 UTC on June 4th and on June 7th (click image to play animation)

The Cycle Slips affected all bands. Click the image above to see the improvement across all bands between 0945 UTC on 4 June and 0945 UTC on 7 June. Note that there will be slight differences for a given input radiance in the computed brightness temperature for each band for the Side 2 Planck conversion coefficients versus the Side 1 Planck conversion coefficients. Those differences are, for Band 2, 0.0001K for both detectors; for Band 3, -0.0001 K for detector ‘a’, 0.0631 K for detector ‘b’; for Band 4, -0.0001 K for both detectors and for Band 6, 0.0119 K. These differences are much smaller than the instrument noise.

Real-time imagery of GOES-South America imager and sounder data are available here.

Posted in Calibration/Anomalies, GOES-12 | No Comments »

GOES-12 Imager Cycle Slips

May 9th, 2012

GOES-12 Imager from 1045 UTC 9 May 2012 (click image to play animation of all bands)

GOES-M was launched in 2001 and as GOES-12 served as the operational GOES-East satellite from April 1, 2003 until April 14th, 2010, and has been serving recently as GOES-South America, providing Weather Services on that Continent with routine Imager and Sounder data.

Recently, the GOES-12 Imager has been experiencing ‘cycle slips‘, which manifest themselves in imagery as lines that are shifted, as shown in the loop above of the 5 Imager channels (Individual channels are here: 0.65 µm, 3.9 µm, 6.5 µm, 10.7 µm, 13.3 µm). Cycle slips occur as the satellite on-board software loses track of where the image mirror used to view the Earth is in its scan cycle. After the scan system initializes at the start of a scan cycle, the system expects consistent behavior, and no resources are allocated to track which cycle the mirror is in. Only increments are tracked. If the mirror is moving and a hiccup occurs, that anomaly (which is manifest as a shift in the center of the line) continues until the next system initialization.

The reason for the uptick in the number of Cycle Slips is unknown.

The images in this blog entry were generated using McIDAS-V.

(Update, 4 June 2012: An Imager Electronics Side Swap is scheduled for June 6, 2012, for GOES-12 (GOES-South America) based on the Manufacturer’s Recommendation as a potential remedy to mitigate the ongoing Cycle Slips. The side switch will be performed at 1615 UTC on 6 June 2012. The duplicate sensors that will now be used have not yet been used during GOES-12′s life. Because new sensors are being used, new look-up tables and calibration coefficients have been computed and are available here. Also, see page 29 in this pdf for more information on the two detector sets. Here is the notification of coming changes.)

Posted in Calibration/Anomalies, General interpretation, GOES-12, McIDAS-V | No Comments »

Volcanic ash plume from Popocatépetl in central Mexico

April 18th, 2012

GOES-15 (left), GOES-12 (center), and GOES-13 (right) visible channel images (click image to play animation)

A small volcanic ash plume from Popocatépetl in central Mexico was seen streaming east-southeastward on GOES-15 (GOES-West), GOES-12, and GOES-13 (GOES-East) visible channel images (above; click image to play animation) during the early morning hours on 18 April 2012. Satellite imagery over this particular region is available every 15 minutes on a routine basis from GOES-13, but only every 30 minutes from GOES-15 and every 3 hours from GOES-12.

According to the advisory issued by the Washington VAAC (below), the volcanic ash was extending upward to an altitude of around 23,000 feet.

Washington VAAC advisory

Posted in GOES-12, GOES-13, GOES-15, Volcanic activity | No Comments »

Large mesoscale convective system over Argentina

February 7th, 2012

GOES-12 10.7 µm IR channel images (click image to play animation)

McIDAS images of 4-km resolution GOES-12 10.7 µm IR channel data (above; click image to play animation) showed the development of a very large mesoscale convective system (MCS) over Argentina on 07 February 2012. A number of smaller, discrete thunderstorms initially began to develop around 14:45 UTC, which then eventually merged into a large MCS having large areas which exhibited cloud top IR brightness temperatures of -80 C and colder (purple color enhancement). Multiple “enhanced-v” storm top signatures could be seen at various times, which is a satellite signature of thunderstorms that are capable of producing either tornadoes, large hail, or damaging winds.

Much more detail in the cloud top IR brightness temperature structure can be seen in a 375-meter resolution Suomi NPP VIIRS 11.45 µm image at 18:21 UTC (below). The coldest VIIRS IR brightness temperatures sensed was -96 C (darker violet color enhancement) — much colder than the -77 C seen on the corresponding 18:15 UTC GOES-12 IR image. The black striping seen along the right side of the image is an artifact of the side-to-side scan strategy of the VIIRS instrument; software to remove these artifacts and create a smoother-looking image is under development.