ROM SAF - NRT Notification Detail

NRT Notification Detail

Expected degradation of GRAS l1b data, today

DATE: 2011-01-19 09:01
TYPE: NRT-GTS

Description

Dear GRAS SAF GTS user Issued 2011-01-19 09:00 UTC Due to the yearly Metop-A clock reset upstream GRAS level 1b data is expected to be degraded from tonight at 21:19:49 UTC in instrument sensing time and some hours onwards. GRAS SAF products will be flagged accordingly. Please see detailed message from EUMETSAT below: Kind regards The GRAS SAF Team Forwarded message: Subject:Expected GRAS data quality degradation starting tomorrow, 19. Jan 2011, 21:19:49 UTC From: Christian Marquardt Date: 2011-01-18 16:35 UTC Dear all, every half year, Metop's onboard clock counter (not the one inside GRAS, but the satellite-wide one) goes through a rollover and starts from 0 again. The GRAS processing is affected because some telemetry data is timestamped with this satellite clock rather than GRAS' internal clock. In the past, the inconsistenty of time stamps of some measurement data caused by the rollover of one clock counter has led to a reset of the GRAS Precise Orbit Determination. We expect that the same will happen tomorrow evening (our time), because the next rollover will take place shortly after 19 January 2011, 21:19:49 UTC (measurement time) We expect that GRAS level 1 data will be degraded and flagged accordingly for up to 5 hours after the event, i.e. approximately until 03:00 UTC on 20 January 2011. During this period, we will monitor the GRAS performance to ensure that the Precise Orbit Determination converges appropriately. In case there should be an extended period of data degradation, we will inform you in a seperate email. We apologize for the inconvenience. With kind regards, Christian. -- Dr. Christian Marquardt, Polar System Product Expert EUMETSAT, Am Kavalleriesand 31, D-64295 Darmstadt, Germany

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