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Thermal Control System Requirements for Telescope: Heating, Stability, and Interfaces

This document outlines the functional and performance requirements for the telescope's thermal control system. Key features include active heating with a target temperature around +20°C, a temperature stability of ±3°C, and a gradient of less than 5°C. The system will utilize a single control loop with a power range of 0-30W, emphasizing low power dissipation. Additional requirements highlight the need for SpaceWire interface compatibility, proper EMC considerations, and the management of varying loads on the power bus, ensuring reliability and independence of thermal control loops.

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Thermal Control System Requirements for Telescope: Heating, Stability, and Interfaces

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  1. TELESCOPE ANALOG CONTROL Martin Frericks, Frans Zwart

  2. TAC functional requirements • Provide active heating for telescope • temperature sensor readout • heater driver, incl. thermal control loop (PID) • no cooling • No additional temperature sensors at mirror assembly to be read out by TAC • Internal analog housekeeping • SpaceWire interface with IDC • DC/DC converter, regulators, current limiters

  3. TAC performance requirements • Nominal telescope temperature ~+20°C) • Temperature stability of telescope ±3°C • Temperature gradient over telescope <5°C  1 control loop sufficient (16 heaters in series/parallel & 1 temp. sensor?) • Needed heating power for telescope: 0-30W (TBC, possibly lower, MPE 10W?) • No SPF

  4. TAC design issues (1/3) • ON/OFF temperature control with varying duty cycle (versus continuous control) Pro: • low power dissipation in TAC components Con’s • EMC • varying load to S/C power bus • Special harness requirements • type of shielding (ON/OFF control) • heat conductance: no issue

  5. TAC design issues (2/3) • In case several thermal control loops for the telescope are desired, their stability, reliability and thus design complexity depend on their independence: • thermal coupling between control loops • influence from and stability of external thermal sources In case of complexity a test on sub-system level may be desired to verify proper working of TAC. • No SPF: warm redundancy? Must be compliant with: • heater(s) and temperature sensor(s) in telescope • S/C power (single power bus?), TAC power switching • IDC

  6. TAC design issues (3/3) • SpaceWire interface with IDC: • chip set and/or IP block for SpaceWire from ISAS/JAXA available? • DC/DC converter • Is there a possibility that ISAS delivers secondary voltages for the TAC (e.g. via the IDC)? • Heating power directly from S/C power bus? (Requirements from S/C power bus w.r.t. reliabililty, no SPF etc.?)

  7. Input from consortium partners • Design and requirements equivalent to eROSITA (e.g. temperature sensors)? • Design analysis, concept and schematics available from MPE? • IDC simulator from ISAS available as UCE for TAC testing? • EEE parts available via ISAS or GSFC?

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