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FSW Requirement 5.3.19.7 (prev, next)

Req. 5.3.19.7: "Thermal Constraints for Power-On"

The FSW shall ensure that thermal constraints, as defined in [26], stored onboard by telecommand, are met prior to enabling power-on of EPUs, TEMs, and TPSs.

Basis (help)

[26] (11.3)

    26: "LAT Environmental Spec." (LAT-SS-00778)

      11.3: "Temperature Limits"

      The LAT and its subsystems shall be designed and tested to operate/survive the temperature extremes shown in Table 27. For all subsystems but Electronics, the temperatures shown are for the hottest/coldest part of the subsystem, and indicate the extremes to which the subsystem must be tested. For the electronics boxes, the temperatures shown are for the box interface to the heat sink.

      The survival temperature limits shown are test temperatures for subsystems with units off.

      Qualification temperature (QT) limits indicate the range over which the unit will operate within specifications at beginning of life (BOL). Other qualification testing or analysis should demonstrate that the unit also functions within specification at end of life (EOL) at QT. See Section 14 for a definition and description of the test temperatures. Qualification limits shall be used for all prototype qualification units and protoflight qualification (PFQ) units. During LAT thermal-vacuum testing, sink temperatures will be adjusted until at least one subsystem temperature 10 degrees C beyond its operating limit, with the goal of most subsystems reaching this limit.

      Acceptance Test (AT) temperature limits specify the range over which the unit will operate within specifications at both BOL and EOL. Operating within specifications at EOL will be shown by having sufficient margin over BOL conditions. All flight hardware shall be tested to AT limits.

      Operating limits are the on-orbit operational temperature extremes for the component. This bounds the temperature predictions of the LAT thermal models, with a minimum margin of 5 degC.

      ... table ...

Context (help)

Test(s)

    015: LAT Thermal Control System (TCS)

    This test shall verify that the SIU FSW can properly execute the algorithms of the TCS implementation, and that the TCS implementation successfully maintains the LAT within thermal limits.