Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC

1. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion 1. PDD Activities - Status of PDD inputs - Discussion of each instrument PDD in turn (what is needed, what is outstanding and who can supply details?) 2. Feasibility/Technical Actions and Studies - Summary of status of actions (Harrison) - Open discussion on recommendations to ESA based on actions - What next? Completion of remaining actions? Report? How do we relay recommendations to ESA? - Solar Orbiter Scientific Goals

2. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion Feasibility/Technical Studies & Actions Aim: To demonstrate feasibility of paylaod, especially given the thermal & particle environment, & the mission limitations (e.g. telemetry, autonomy). Make recommendations to ESA. Last Meeting: Technical challenges identified and listed. Action list set up and assigned. Web site: Web site http://www.orbiter.rl.ac.uk/solarorb/rspwg/, lists actions, provides notes from initial meeting, action spread sheet, Action Completion reports. Other documents (e.g. PDDs) can be found at http://zeus.nascom.nasa.gov/~bfleck/Orbiter/PLWG/Documents/.

3. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 1. Pointing: It is recommended that a hard mounted, joint-pointing policy be adopted, which is in keeping with the science goals of the mission, but will save mass and power. We recommend a co-pointing accuracy of 2 arcminutes and an absolute pointing accuracy of 2 arcminutes. (~1/5 of minimum FOV). 2. Image Stabilisation: It is recommended that one central signal from one instrument, such as from VIM, be used for all instruments that use an image stabilisation system, to save mass and complexity. 3. Resources: All options should be considered by the Project to maximise the payload mass, telemetry, memory capacity and power; the scientific return is increased with increased payload resource. [* Ensure PDDs are consistent & recommendations are passed to ESA study]

4. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 4. Thermal Control: (i) Given the extreme thermal environment, it is recommended that there be a study of a spacecraft-wide approach to thermal control. e.g. What actions can be taken at a S/C level to dampen the thermal variations, to dissipate heat, to allow access to open space etc… even to reduce aphelion! (ii) Some instrument thermal studies have been completed. The rest should be completed over the next few months. We must demonstrate thermal feasibility; this is our biggest challenge. (iii) However, the thermal interfaces between the instruments and spacecraft are not defined at all and this does restrict instrument models (e.g. assume thermal isolation through mount, assume view of shield…). Is there any spacecraft input beyond that of the Pre-Assessment study report?

5. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 5. ESA Study of LCVRs: Liquid Crystal Variable Retarders (LCVRs) may be critical to the operation of VIM & UVC - (as polarization modulators). No LCVR has been in vacuum for a long period & put into extended operation after a long time, & the radiation impacts must be considered. We must ensure that this is included in the two PDDs as an area requiring test activities.

6. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 6. Contamination Control & Degradation Due to the Environment: (i) Instrument teams must adopt a stringent contamination policy in the laboratory, but also in operations (e.g. long out-gassing period). (ii) A test activity on the degradation of selected optical surfaces, including multilayers and filters, at high temperatures and with extreme particle flux levels is recommended as part of a Solar Orbiter development programme. The test activity is to be defined by Schuehle, Poletto and Korendyke. This will be consistent with the PDDs but will specify the tests required in detail.

7. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 7. Detector Development: Most instruments call for detector systems now under development, e.g. 4kx4k 5 micron back-thinned APS or solar-blind BOLD/diamond. This is a technology development critical to Orbiter and both the basic APS and solar-blind detector development programmes should be supported with Orbiter in mind.

8. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 8. Autonomous Target Selection/Pointing: There is some concern over the use of intelligent on-board target identification/selection to re-point Orbiter for scientific observations. In principle, autonomous target selection in this way is feasible and it should be studied further – perhaps by a Science Definition Team and the ESA Project. 9. Planning and Operations Cycle: A study of the possible planning and operations scenario has recommended a 150-day planning cycle approach, possibly with a dedicated science centre. The Science Definition Team and the ESA Project must examine the study report and decide on an approach prior to the AO.

9. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion RECOMMENDATIONS 10. Operations Scenario & Memory: After discussing the 30-day per 150-day orbit observation scenario, it is clear that the 30-day observation period per orbit is a sensible scientific approach and is beneficial from the thermal point of view. However, it is suggested that options for encounter rehearsals and basic synoptic observations – both requiring low telemetry – could be considered for the rest of the orbit. 11. Solar Orbiter Goals: The Solar Orbiter goals are NOT well/properly defined. This is beginning to ‘hurt’ – i.e. potential proposing groups are not really able to ‘tune’ their instruments to the priority goals. We have generated an action to recommend the best approach to this (Gabriel).

10. Solar Orbiter Payload Working Group Mid-term meeting - 25-26 November 2002, ESTEC Summary of Remote Sensing Discussion Remaining Activities Action Progress to date: 73 actions listed at last meeting. About 50% complete or satisfied at this time. The rest have been reassessed. Plan to complete by February. Final Report: Based on action studies – April/May 2003. Recommendations: Pass to ESA from SOPWG or via PDDs as they arise. Work with Thierry/Bernhard/Richard to ensure all recommendations covered. Studies/Tests Required: Some test activities to be defined – and passed on to ESA a.s.a.p. PDDs: Refine as much as possible. Goals: Refine goals and submit to ESA/S.O. Science Definition Team.