1. TELESCOPE ANALOG CONTROL Martin Frericks, Frans Zwart

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

3. 3 TAC performance requirements Nominal telescope temperature ~+20°C) Nominal telescope temperature ~+20°C) Temperature stability of telescope ±3°C Temperature stability of telescope ±3°C Temperature gradient over telescope <5°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 Needed heating power for telescope: 0-30W (TBC, possibly lower, MPE 10W?) No SPF No SPF

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

5. 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: 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 thermal coupling between control loops influence from and stability of external thermal sources 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: No SPF: warm redundancy? Must be compliant with: heater(s) and temperature sensor(s) in telescope heater(s) and temperature sensor(s) in telescope S/C power (single power bus?), TAC power switching S/C power (single power bus?), TAC power switching IDC IDC

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

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