Req. 5.3.6.1: "Deadtime during Normal Operations"

The SIU FSW shall contribute less than 0.5% to the deadtime at trigger rates less than 1 kHz and less than 5% at trigger rates greater than 1 kHz and less than 10 kHz. (During normal operations, the trigger rate is dominated by background events, with the gamma ray component being less than 10 Hz).

Basis (help)

[3] (5.2.13), [4] (5.4.10)

3: "LAT Performance Spec. - Level II(b) Spec." (LAT-SS-00010)

5.2.13: "Dead Time {SRD Table 2}"

The dead time shall be less than 100 usec per event.

The goal is to achieve dead time of less than 10 usec per event.

4: "LAT T&DF Subsystem Spec. - Level III Spec." (LAT-SS-00019)

5.4.10: "Event Dataflow Dead-Time for Average Orbital Conditions"

The dataflow system shall contribute less than 5% (tbr) to the instrument dead time at a L1TACK rate of 10 kHz (tbr), due primarily to background events, for average size events. Above 10 KHz dead-time shall increase to keep the throughput at 10 KHz.

Context (help)

Test(s)

013b: Operational Modes - Science Modes

This test shall verify correct transitions between the various science observation modes and proper operation of the LAT in those modes. The test shall involve all observation modes: Sky Survey Mode (non-rocking as well as various rocking profiles), Pointed Observation Mode, and Repointed Observation Mode.