Important voltage, temperature, and current levels on the payload are monitored and supplied to the telemetry to permit diagnosis of the instrument condition. A total of 100 analog housekeeping signals are monitored by CUBIC . 93 of these are multiplexed onto 64 primary MUX channels, with several channels submultiplexed further to accommodate all 100 signals. The primary MUX channels A1 -- A64 are conditioned and multiplexed on the housekeeping board and digitized with 12 bit precision by the ADC on the signal chain board. Two of these channels (A4 and A29) are submultiplexed on the power supply board. In addition, the 32 DAC channels are used to control signals to both CCDs. While they are not actually multiplexed, the voltage levels can be different for the two CCDs and many of these channels are therefore monitored separately for the two CCDs by the housekeeping software (MUX channels A25 -- A28, A33, A34, A37 -- A41, A43 -- A46, and A48 -- A57). These analog housekeeping signals are listed in Tables 12--14. Note that the data conversion formulae given here are for 12 bit HK values (as stored in our Science Data). Some of these HK channels are provided to the SAC-B central HK memory as 8 bit values. Those must be multiplied by 16 before they can be converted to engineering units using these conversions.
Table 12: Analog Housekeeping Signals and MUX Channel Assignments
Table 13: Analog Housekeeping Signals and MUX Channel Assignments (continued)
Table 14: Analog Housekeeping Signals and MUX Channel Assignments (continued)
Seven additional signals are digitized on the Power Supply Board and are presented directly to the ICP. These signals originate on the primary side of the power supply. In order to retain isolation between the primary and secondary power, these data are digitized on the primary side and the digitized signals are passed to the secondary side through an opto-isolator. These isolated analog housekeeping signal channels, I1 -- I7, are listed in Table 15.
Table 15: Isolated Analog Housekeeping Signal Assignments
All housekeeping data are included in the CUBIC science data telemetry stream, where they are formatted into the CUBIC science and frame headers in a hierarchical fashion (see §4.6). The most critical housekeeping functions are also provided to the Telemetry Processor for inclusion in the SAC-B housekeeping data in order to facilitate quick-look analysis of the CUBIC status by the ground station. These include the most significant 8 bits of 23 of the analog signals listed above plus two 8 bit binary status words. These signals are described further in §4.4.11.