GOES-E fall eclipse period: Good and bad news (mostly good)

[AJC3]

OK, the bad news first: It starts next week - Sunday morning, August 15th to be exact.

http://www.ssd.noaa.gov/PS/SATS/eclipse.html

Now, for the good news: It will be largely transparent for the tropics - i.e. there will be MUCH LESS of a loss of imagery during the early morning hours. There is a shorter window - between midnight (0400 UTC) and (0615 UTC), and most of the time, only a few (not all) images are lost during the window.

[Frank2]

Like the turning leaves (up north) that is also one sure sign of Fall...

[KWT]

Ah thats superb, and that time will be when I'm sleeping as well here in the UK so I'm not going to miss anything when I'm awake...good times!

[JonathanBelles]

thanks for posting that! I was beginning to wonder about it, and I'm glad the eclipse period is much smaller.

[tgenius]

I thought the new sats going up would eliminate eclipse outages completely? Or did I understand incorrectly?

[tgenius]

anybody know if thats the case or not? I've been curious about it.

[supercane]

Actually the future is now. Per this SSD bulletin, "GOES-13 (East) is not affected by eclipse." You can refer to the Autum 2010 eclipse schedule to verify this. Hillger and Schmit explain in the article "Observing Systems: The GOES-13 Science Test: A Synopsis", Bulletin of the American Meteorological Society, vol. 90, issue 5, p. 592ff:

Eclipse periods occur when the satellite passes into the shadow of the Earth, a biannual event, lasting several hours a night for about 6 weeks during both spring and fall. During this time, the satellite’s solar panels do not receive the energy needed to power the satellite. The outage for a given day varies, from as little as 1 hour to as much as 2.5 hours. By using larger spacecraft batteries to supply data through eclipse periods, the GOES-N/O/P system addresses one of the major limitations of the current GOES series. Other outage periods include “Keep Out Zones” (KOZ), when there is a possibility that the Sun, when in view on either side of the Earth, can contaminate imagery by being within the field of view (FOV) of the instruments.
A sequence of 15-minute images from 12 September 2006 comparing GOES-13 to GOES-12 shows the effect of the eclipse (Fig. 2). Rather than one long gap while the Sun is either within view on each side of the Earth or behind the Earth, there are two shorter gaps only when the Sun is within view on each side of the Earth.
With the new capability of acquiring data during KOZ comes the risk of allowing images contaminated with energy from the Sun.

This CIMSS Satellite Blog entry states the same thing but is slightly less wordy:

One of the important changes made to the GOES-N/O/P series of satellites is the addition of increased onboard battery capacity to enable the satellites to continue to provide imager and sounder data during the Spring and Fall season “eclipse periods”. During these eclipse periods (which can last 1-3 hours), the GOES satellites are in the Earth’s shadow, so their solar panels cannot provide power to all of the satellite instrument payloads.

The summary version is the eclipse period is dead (at least for GOES-E), but images will still be missing due to KOZ, or in the more modern vernacular, Stray Light Exclusion Zone (SLZ). A slide from this presentation summarizes the changes in eclipse outages across the different satellites in the GOES series:

GOES-I/M Series
-No imaging during eclipse
-No imaging when solar intrusion angle less than 6 degrees
-0 - 3 hour daily outage based on both eclipse and keep out zone
GOES-NOP Series
-Imaging during eclipse Batteries sized to provide operation through maximum eclipse period (~72 minutes)
-No imaging when solar intrusion angle less than 6 degrees
-Solar intrusion similar to GOES-I/M (similar instruments)
-0 - 2 hour daily outage based only on keep out zones
GOES-R Series
-0 - 1 hour daily outage based only on Keep Out Zones
-Smaller solar intrusion angle than GOES-I/M imager

Hope this helps!

[tgenius]

thanks Supercane.. looks good that the eclipse window is gone but all we have is the KOZ now.