ROM SAF - NRT Notification Detail

NRT Notification Detail

Degraded GRAS level 1 b data

DATE: 2011-03-15 09:10
TYPE: NRT-GTS

Description

Dear GRAS SAF GTS user Issued 2011-03-15 09:10 UTC Upstream GRAS level 1 b data was degraded between 2011-03-11 and 2011-03-14 at approx. 20:00 UTC. Please see detailed messages from EUMETSAT below. Kind regards The GRAS SAF Team Forwarded Message: Subject: Re: GRAS Orbit and Data Quality degradation since 11 Mar 2011 From:Christian Marquardt Date:2011-03-14 23:04 UTC Dear all, we've successfully brought a converged orbit state vector into the operational processing of GRAS data, and things appear to be working as usual again. All GRAS level 1b (and higher) data for observations taken after 20:00 UTC on 13 Mar 2011 should be of nominal quality. With kind regards, Christian. Forwarded Message: Subject: GRAS Orbit and Data Quality degradation since 11 Mar 2011 From: Christian Marquardt Date: 2011-03-14 20:24 UTC Dear all, unfortunately, I have to report on another case of data degradation going on in our operational processing. Starting on 11 March 2011 (Friday), mean bending angle values in the 60-80km altitude range started to become different for rising and setting GRAS occultations. Things seemed to recover to normal late on 12th, but developed a similar asymmetry (though with opposite sign) during yesterday (13th March). The time series (red for rising, blue for setting) is available at http://yfrog.com/gzd8rovj. According to an initial analysis of the data, the impact on data quality (i.e., biases) below 35km altitude is minor or negligible. Note that bending angle data quality has *not* been flagged as degraded. As in previous cases, the data degradation is most likely related to the occurance of another minor geomagnetic storm on the 11th. Our operational Precise Orbit Determination occasionally develops along-track errors in the order of a few meters under these circumstances, which result in the asymmetric behaviour of rising and setting occultations. We have reset the POD on our secondary ground segment a few hours ago, and will transfer the orbit parameters into the operational processing as soon as it has successfully converged. We do not expect an outage or another POD reset; the processing should just pick up the better orbit and produce nominal level 1b immediately. I'll let you know once this has happened. With our sincere apologies for the renewed data degradation, Christian. -- Dr. Christian Marquardt, Polar System Product Expert EUMETSAT, Eumetsat Allee 1, D-64295 Darmstadt, Germany

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