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-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.)

Aurora Borealis seen on Suomi NPP VIIRS Day/Night Band imagery

May 9th, 2012
Suomi NPP VIIRS 0.7 µm Day/Night Band + 11.45 µm IR + "Fog/stratus product" images

Suomi NPP VIIRS 0.7 µm Day/Night Band + 11.45 µm IR + "Fog/stratus product" images

An AWIPS comparison of Suomi NPP VIIRS 0.7 µm Day/Night Band (DNB), 11.45 µm IR, and IR brightness temperature difference “Fog/stratus product” images at 06:51 UTC on 09 May 2012 (above) revealed several ribbons of the aurora borealis (which showed up as bright west-to-east oriented features on the DNB image over Ontario and Quebec, Canada). Note that there was no correlation between these bright DNB aurora features and any high cloud features on the 11.45 µm IR image, or  any low cloud or fog features on the legacy “fog/stratus product” image.

These aurora features would have been along the southern periphery of the auroral oval, which was expanding southward at that time  according to images from the Space Weather Prediction Center (below).

Space Weather Prediction Center auroral oval product images

Space Weather Prediction Center auroral oval product images

Photos of the aurora borealis were taken from Upsala, Ontario — located approximately halfway between Thunder Bay (station identifier CYQT) and Dryden (station identifier CYHD) — and posted on Spaceweather.com. These photos were taken about an hour prior to the VIIRS images shown above.