Subject: Administrative::S-NPP Spacecraft Control Computer (SCC) This is a multi-part message in MIME format. --------------080208010004050806080900 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit *Topic:* S-NPP Spacecraft Control Computer (SCC) Clock Slope Update: GPS SCC Drift Issue *Date/Time Issued:* August 19, 2015 2041 UTC *Product(s) or Data Impacted:* All S-NPP data *Date/Time of Initial Impact:* August 19, 2015 1423 UTC *Date/Time of Expected End:* August 19, 2015 2125 UTC *Length of Outage:* 07:00 *Details/Specifics of Change:* An update to the SCC Clock slope was performed on August 19, 2015 at 14:23 UTC at Svalbard Contact 19738. This updated slope is calculated on the ground and sent to the spacecraft with an updated basetime and slope via an uploaded SCC Table 2. During the 19738 contact, this updated Table 2 was uploaded and it was observed that the SCC Clock was demonstrating a +999.989 ms drift relative to the GPS time, which is greater than nominal operational range; a drift of 0 is the targeted value. A problem was identified in the reporting of SCC Clock slope from the ground reference image when onboard basetime is updated via a command rather than a table load, as was recently done as part of the 2015 June 30 leap second. This problem introduced an error into the reported current basetime which caused errors to propagate into the generated SCC Table 2 load and resulted in this larger then expected drift. A corrected SCC Table 2 has been generated and will be loaded at SVL 19742, at 21:12z. Further notices will follow once GPS SCC clock drift has been reduced to nominal range. Contact Information for Further Information: ESPC Operations at ESPCOperations@noaa.gov at 301-817-3880 Web Site(s) for applicable information: N/A You have been sent this and other notifications because you have opted in to receive it. If for any reason, you wish to unsubscribe, please contact ESPC Help Desk at ESPCOperations@noaa.gov or (301) 817-3880. Please note: it may take up to two business days to process your unsubscribe request. --------------080208010004050806080900 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit

Topic: S-NPP Spacecraft Control Computer (SCC) Clock Slope Update: GPS SCC Drift Issue

Date/Time Issued: August 19, 2015 2041 UTC

Product(s) or Data Impacted: All S-NPP data

Date/Time of Initial Impact: August 19, 2015 1423 UTC

Date/Time of Expected End: August 19, 2015 2125 UTC

Length of Outage: 07:00

Details/Specifics of Change: An update to the SCC Clock slope was performed on August 19, 2015 at 14:23 UTC at Svalbard Contact 19738. This updated slope is calculated on the ground and sent to the spacecraft with an updated basetime and slope via an uploaded SCC Table 2.

During the 19738 contact, this updated Table 2 was uploaded and it was observed that the SCC Clock was demonstrating a +999.989 ms drift relative to the GPS time, which is greater than nominal operational range; a drift of 0 is the targeted value.

A problem was identified in the reporting of SCC Clock slope from the ground reference image when onboard basetime is updated via a command rather than a table load, as was recently done as part of the 2015 June 30 leap second. This problem introduced an error into the reported current basetime which caused errors to propagate into the generated SCC Table 2 load and resulted in this larger then expected drift.

A corrected SCC Table 2 has been generated and will be loaded at SVL 19742, at 21:12z. Further notices will follow once GPS SCC clock drift has been reduced to nominal range.

Contact Information for Further Information: ESPC Operations at ESPCOperations@noaa.gov at 301-817-3880

Web Site(s) for applicable information: N/A

You have been sent this and other notifications because you have opted in to receive it. If for any reason, you wish to unsubscribe, please contact ESPC Help Desk at ESPCOperations@noaa.gov or (301) 817-3880. Please note: it may take up to two business days to process your unsubscribe request.

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