GP-B Post-Flight Analysis—Final Report - Gravity Probe B - Stanford ...

4.3.1.1 Automated Telemetry Data ProcessingIn addition to decommutation of the L0 data, an important function of the Gravity Probe B data processingalgorithms was to clean up incoming data. Data had to be thoroughly vetted to remove redundant points andfiller packets, along with noisy data caused by interference or antenna problems. While data integrity wasparamount, high priority was also given to efficiency in this cleanup process. The data processing group isproud of its capability to process ten hours of spacecraft data is less than an hour—well within the specification.A tremendous effort was made to automate data processing—to the extent possible—so that data was madeavailable as quickly as possible. After data from the GP-B satellite was telemetered to the ground station, the fileswere sent to SAFS at Goddard Space Flight Center in Maryland. Data files were transferred via the NASA IOnetinto the MOC, and detected by the automated data processing less than five minutes after arrival. TDPautomatically checked for errors, filler packets and redundant data points, placing the cleaned data into the L0database, and the decommutated data into the L1 database. L1 data could then be called by the various IDL andMatlab analysis tools used by the GP-B science and engineering team. All daily web plots, SAFS confirmationemails, user notification emails and data processing logbook entries were automated. More importantly, thesystem was designed with error handling in mind. For example, if data was expected at Stanford but had notarrived in a specified time, automated software alerted personnel on the data processing team. Furthermore,data with problems were rejected automatically before entering the Telemetry Database and staff was alerted viaemail.Figure 4-4. Data flow through the GP-B’s automated data processing.4.3.1.2 Data CaptureData capture was excellent. The data processing group was able to process 100% of all the data received by theground stations, keeping verifiable good data and not allowing corrupted or suspect frames. Since day 111,2004, ~85 hours of data in total were not present. However, this was non-recoverable data—places where therecorder was not on or commanding wasn’t possible. All data gaps over 10 seconds have been accounted for aseither spacecraft antenna switch activity, or they have been correlated to a specific vehicle or commandanomaly. Approximately 1,680 vehicle data files were processed between launch in April 2004 and the end of thepost-science calibration phase in September 2005. Over 300 gigabytes of raw data was stored, in addition todatabase storage. Table 4-9 lists events and sources of lost data.Gravity Probe B — Post Flight Analysis • Final Report March 2007 109