Long Term Science working group status LSWT Venice, 30/03-01/04/2009

2 LSWT meeting, Venice, 30/03-01/04/2009 OBJECTIVES  The objective of this working group (2 workshops held on 10-11/02 and 04/03) is to set up the lander functioning when the primary battery is fully discharged, that is when available energy is minimal  For that we have to:  Study the external conditions on the comet between 3 and 2 AU  Check the individual sub-system constraints in these conditions of T° and power (CDMS, PSS and secondary battery, TCS and absorbers, TxRx, …)  Set up Philae and CDMS modes to cope with all kind of conditions  Check if all test means are available to test this phase  Make that all is feasible before end of 2009

3 LSWT meeting, Venice, 30/03-01/04/2009 COMET ENVIRONMENT IMPLICATIONS  Comet at 3 AU means a limited power received by 2 ways inside the thermal controlled compartment:  Solar panels redistributed in thermal and electrical energy  Absorbers redistributed in thermal energy only  The different conditions of illumination are depending on 2 parameters only (co-obliquity , latitude  ), from which 28 cases are simulated and 14 cases can be extracted (choosing the right hemisphere) R 

4 LSWT meeting, Venice, 30/03-01/04/2009 COMET ENVIRONMENT IMPLICATIONS  Thermal environment gives constraints to:  the lander total dissipation  the external wall temperatures : T° cells and cell efficiency  Cold temperatures are favourable (first calculations made by CNES with the SABER tool show from +25°C to -100°C the cell efficiency is increased of about 25%)  Radiation dose effects are not favourable (first PoliMi results)  Other effects as dust or ice covering, shadows  AI on CNES for gas refreezing  AI on PoliMi for cell tests  Total dissipation and particularly by the absorbers during nights has to be precisely determined  AI on DLR

5 LSWT meeting, Venice, 30/03-01/04/2009 COMET ENVIRONMENT IMPLICATIONS  First thermal map at 3 AU (LAM/ O. Groussin) -40°C sub-solar point, -140°C night side

6 LSWT meeting, Venice, 30/03-01/04/2009 COMET ENVIRONMENT IMPLICATIONS  Optimisation of Philae orientation: X Y X 200 °330 ° Sun illumination W3 W1 W2 W4 W5  Confirmation of best attitude: to turn Wall3 (W3) to Sun highest elevation (generally South direction in northern hemisphere, North in southern)  When to do this pointing ?

7 LSWT meeting, Venice, 30/03-01/04/2009 COMET ENVIRONMENT IMPLICATIONS  Optimisation of Philae landing site (values after orientation) 3 AU

8 LSWT meeting, Venice, 30/03-01/04/2009 SUB-SYSTEMS CONSTRAINTS  Primary and secondary working ranges  SB maximum charge (around 95%) and maximum discharge (double protection)  SB best working temperatures in charge / discharge (AI on CNES)  Charge level measurement (CDMS measures worst case)  Solar arrays performances (AI on PoliMi)  At cell level, T° tests  At array level, shadowing and radiation effect  Shunts and MPPTs performances (AI on MPS)  Consolidation of power required by each sub-system (LUM values verified by each responsible)

9 LSWT meeting, Venice, 30/03-01/04/2009 CDMS – PHILAE BASIC MODES PROPOSAL  Philae Wake-Up mode: this mode is required when Philae shutdown is mandatory During nights, shutdown. During day, when SA are illuminated enough, this mode is automatically switched on and compartment heating starts  CDMS Super-Low power mode: DPUs are alternately ON and OFF with regularly the 2 DPUs OFF, TCS heating and SB charging possible with power in excess, Minimal power: 2,4 W  CDMS Low power mode: DPUs are alternately ON and OFF, TCS heating and SB charging possible with power in excess, Minimal power: 3,6 W  CDMS Nominal mode: 2 DPUs ON, TCS heating and SB charging possible with power in excess, Minimal power: 4,8 W

10 LSWT meeting, Venice, 30/03-01/04/2009 CDMS – PHILAE BASIC MODES PROPOSAL  Philae quiet mode: CDMS in nominal mode + 1 Rx ON every 30 mn for 2 mn, TCS heating and SB charging possible with power in excess Power: 7,3 W (peak value)  Philae nominal mode: CDMS in nominal mode + TxRx working during visibilities, TCS heating and SB charging possible with power in excess Power: 10,8 W (for visibility periods) -> SC TM retrieval only possible in this mode -> if the landing site is correctly chosen, if landing is nominal (operational LG / orientation possible, nominal attitude, no shadowing), possibility to achieve PQM at 3 AU (TBC)

11 LSWT meeting, Venice, 30/03-01/04/2009 OPEN POINTS ON PHILAE WORKING DURING LTS  23 open actions  Decisions to be taken at the next workshop on 27/04  Confirmation of CDMS and Philae working modes (rationale: to remain as simple as possible)  Check if all contingency cases have been taken into account  Check what has to be monitored / commanded by Ground Segment according to modes (list of HK and TC parameters, strategy of MM EEPROM use, strategy of TxRx use)  Assess the possibility to do science in CDMS modes below the nominal modes (on solar panels immediate power, on SB during comet nights)  Determine the nominal operational loop when Philae nominal power mode is achieved for day and night (science every day)

12 LSWT meeting, Venice, 30/03-01/04/2009 LTS SPECIFIC TESTS  The current Solar Array Simulator is not usable at GRM because of too small currents  Specification of a new SAS on-going between PoliMi and LCC  Delivery of new SAS planned in autumn  In parallel to SDL tests, LTS tests will be done after CDMS V8.0 delivery end of September and before delivery to ESA in January 2010  only 3 months  Priority to SDL phase testing in case too much work