The mission planning software uses an earth limb angle of 3 degrees as the boundary between occulted and non-occulted data. This condition (evaluated on 1 minute intervals) controls whether the guest observer selected Event Analyzers are processing data or suspended. The Standard data modes both collect data through (non SAA) occulted periods. Observations of Cen X3 on October 2 provide illustration as the occults were grazing. The short term timeline shows occulted periods from mission time 86985301- 86986201 and 86991061-86991061.
Figure 10 shows the standard 2 counting rate (sum of all layers and all detectors with 16 second intervals) during this observation, while figure 11 shows the elevation angle plotted on the same horizontal scale. All of this data was captured by the SOF real time system, processed by XFF with the realtime option. The lightcurve was produced with SAEXTRACT 3.6 and the filter file was produced with XTEFILT 1.3.
The GOF recommenation for selecting non-occulted data is usually to select data with elevation greater than 10 degrees. This requires additional selection beyond taking all of the data in the on surce files...
Figure 10: Cen X3 data showing 2 grazing occults. Data from 10144-03-01-04, PI Prince
Figure 11: Cen X3 elevation data. Data from 10144-03-01-04, PI Prince