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XMM-Newton EPIC TTD Meeting Preparation for next eclipse season
7th Feb 2001 Mauro Casale

ESA H/Q: 7th February 2001

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Facts / lessons learned from previous eclipses
1) the eclipses will occur before perigee in the period 19-03-2001 /

24-04-2001

2) the shortest time between "end of eclipse" and Perigee time is about 22 minutes; in most of the other cases it is around 30-31 min except at the beginning where it is longer (up to 1 h for the first eclipse). 3) the manual procedures used during the last eclipse season for the activation of the EPIC instruments worked very well; conversion of these manual procedures into automated procedures implies a major effort and a considerable risk and it is dependent on System changes (e.g. implementation of RCR-461 at the SOC, relaxation of the constraint on max number of parameters in an ED at the MOC). The EPIC activation will therefore be left unchanged (i.e. manual operations)
ESA 4) the OM and RGS's activation can be "easily" H/Q : 7th Februaryinto an converted 2001 automated procedure; during the next eclipse season OM & RGS's will therefore be activated via automatic timeline.

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Targets
1)

Minimize the thermal excursions on the instruments by optimizing the OFF/ON sequence/st rategy (see below)

2) Increase further the overall efficiency: start instrument operations (Observation window) at perigee + 4.5 h Advantages will be: - execute EPIC calibration exposures as well at the beginning of REV - save science time for RGS

3) Minimize the preparation activity (DB/IFOP); basically almost all DB items already exist and are fully debugged (only a few to be defined)
ESA H/Q : 7th February 2001

4) Relax criticality of RCR-461 at the SOC

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Principles
1) The post perigee window arrangement in the timeline will be as follows: Perigee + 40 min: AOS TC Perth, start of AOS_CHK window (duration = 30 min) Perigee + 1 h 10 min: start of SOPS window for RWL biasing (duration = 50 min) Perigee + 2 h: start of SOPS window for preparation of next eclipse (TT command load etc.); duration = 70 min Perigee + 3 h 10 min: start of Instrument ACTIVATION window 2) The EPIC can be switched on still before perigee; this will be always possible under VILSPA coverage. takes 5 minutes. This activity takes 5 minutes and it will be manually executed (one single ED) 3) The EPIC instruments will be manually activated in the period Perigee + 40 min and Perigee + 3h in parallel with other activities; tentatively this will be done in the following periods: - activation of MOS-1 & MOS-2 still under VILSPA coverage (one ED per instrument of a duration of 35 min; the two instruments can be activated in parallel via two MSTACK) - activation of EPIC-PN during the SOPS window for preparation for next eclipse (under Perth); one single ED of a duration of 40 min 4) It will be no problem to execute the first slew in parallel (all or partially) with the automated activation activities of ESA H/Q : 7th February 2001 OM and RGS;

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Base-line for instrument re-activation
· · · · · · · · · T0 - 30 min: End of Eclipse T0 - 20 min: Manual switch of EPIC's & thermal control activation (ED EE0011); will be executed under VILSPA coverage T0 - 15 min: Start activation of EPIC-MOS1/2 (ED's EE0110, KE0110); dura tion
= 35 min

T0: Perigee pass T0 + 30 min: LOS VILSPA T0 + 40 min: AOS TC Perth T0 + 2 h: activation of EPIC-PN (ED FE0110) in pa rallel with MOC activities (SOPS
window)

T0 + 3 h 10 min: Start of ACTIVATION window in the timeline: automatic activation of RGS-1/2 and OM T0 + 4h 35 min: End of Activation / Start of Observation window in the ESA H/Q : 7th February 2001 Timeline

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Strategy to minimise thermal excursions (1)
· · · · · · · · · · T0 - 4h: end of observation window T0 - 3.5h: 3 TTC's for safe-standby of EPIC, p-n TTC deleted if everything is nominal, so that EPCHEPEA stay on. T0 - 2h: one TTC for EPIC p-n to safe standby (EPEA-EPCH OFF, no htr); this TTC will be let to execute. T0 - 1.6/1h: Eclipse start. ECLIPSE signal switch EPICs off, all eltr htr OFF and turn on CCD substitution heater (branch A only) T0 - 1.6/1h: Eclipse start + 5 min: OM heater reconfig: Nom OFF / Red ON; 2 TTC's T0 - 1.0/0.5h: Eclipse End T0 - 20 min: Switch on EPIC's + thermal control (EPEA-EPCH OFF, no htr) + RGS electronic Htr on T0 - 15 min: Start of EPIC-MOS reconfiguration (EPEA-EPCH on within 10 minutes) T0 + 1h: Two TTC for EPIC CCD htr A+B on, TTCs deleted before if EPIC Switch-on successful T0 + 2h: Start of EPIC-PN Quad-CCD's ON
ESA H/Q : 7th February 2001

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Strategy to minimise thermal excursions (2)
Advantages of above strategy a re:
1) RAE-RFC are OFF without htr for max 1h in eclipse + 1.25h during activation. This is less than the usua l 8h of RGS in SETUP during normal perigee.

2) The EPEA-EPCH are off without eltr htr for ~ 2.5h with more than 3h to stabilize before the start of the cl osed cal. 3) The p-n CCD's are left without thermal con trol with a single substitution heat er for max 2.5h. This should limit the CCD temperature excursion to only a few degrees as ther e will be no earth shine whil e we are in eclipse. Even if we miss the EPIC switch-on before perigee, the second substitut ion htr will go on after max 2.8h from the beginning of the eclipse; by that time (or soon after depending of the S/C attitude) we will also get the earth shine and albedo on the radiators. ESA H/Q : 7th February 2001

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