There are four basic operating modes of SXRP:
1. Memory Mode - When the SXRP instrument is turned on, it comes up in the memory mode. In this mode, only the mass memory processor is operating; this processor is responsible for accepting and responding to commands on the BIUS interface and for maintaining data in mass memory (either from SXRP or from another scientific instrument on SRG). In this mode all detectors and high-volta- ge power supplies are turned off as are the stepper motors that operate the rotating platform. Power in this mode has been measured to be approximately 4 Watts for the engineering model (EM) SXRP. In the flight model (FM), total power should be 8 Watts.
2. Observation Mode - This is the normal operating mode of the instrument. In this mode, all normal subsystems are turned on including all detectors, all high-voltage power supplies, all processing electronics, and the motor that rotates the rotating platform. The Observation Mode is established by executing a series of BIUS commands from the Memory Mode. In the Observation Mode, detectors are operating in their normal configuration and scientific is being generated and accumulated in mass memory. Power in this mode was measured to be 20.4 Watts for EM, which contains approximately half of the electronics of the FM. The power dissipation of the FM, with one rotation drive motor operating in 0.5 rpm, is estimated to be 38 Watts.
3. Motor Transfer Mode - If one motor fails, it is possible to disengage that motor and engage a backup motor. This process involves powering a mechanical actuator based on the expansion of paraffin wax. This process is accomplished in the Motor Transfer Mode. Note that this mode is only used in case of emergency and is not a normal operating mode. In this mode, motors are operating and energy is supplied to the paraffin actuators for approximately 3 minutes. High-voltage power supplies are turned off.
4. Graphite Transfer Mode - Normally, the graphite crystal is oriented so that incoming X-rays are reflected to one detector. If that detector fails, a motor can be commanded to rotate the crystal to reflect to an adjacent detector. This process is accomplished in the Graphite Transfer Mode. Note that this mode is only used in the case of emergency and is not a normal operating mode. Power during this mode has been measured to be about 25.5 Watts for the EM. This number should be roughly the same for the FM.