1. 19 May 2010, ESOC Eberhard Grün and Harald Krüger
WG3 Meeting
19 May 2010, ESOC
Eberhard Grün and Harald Krüger

2. Agenda
Introduction
Gas and dust flux tubes; orbit and pointing requirements of in-situ and remote sensing instruments - E. Grün
Routine observations (Monitoring, Dust collection & analysis) – all
Presentation and discussion of individual mission scenarios, objectives and key instruments - all
Completeness of mission scenarios with respect to objectives – all
State and usage of mission scenarios in the Rosetta Operations Concept - all
Deep Impact: Icy patches and jets at Tempel 1 – Mike A’Hearn
Gas and Dust production of 67P/CG - Marco Fulle
Status of Engineering Environment Model – Michael Müller

3. 1. Introduction Activities since last SWG:
Jorge Diaz del Rio (Mission Independent Group) presented the Rosetta Science Ground Segment (SGS) Operations Concept
WG chairs together with RSOC developed relation between Mission Scenarios and Science Objectives of STT with the aim to (1) relate mission scenarios to mission phases and (2) to support the SGS Operations Concept:
(1) requires input from comet modeling
(2) interface between SGS Operations Concept and Mission Scenarios is unclear

4. 2. Gas and Dust Flux Tubes - Orbit and Pointing Requirements
Gas emitted from an active area can be found in a wide cone (~60 deg. from surface normal). Typical gas speeds are a few 100 m/s, therefore, the time-of-flight of a molecule to Rosetta is a few minutes.
Dust emitted from an active area can be found in a narrow cone (jet, ~10 deg. from surface normal). Dust speeds are size dependent and range from a few m/s for mm-sized grains to ~100 m/s for micron-sized grains. Therefore, the time-of-flight of a dust grain to Rosetta is several minutes to a few hours. Hence the source region of big particles is not at the nadir but can be several 10 deg. rotated away.

5. 9P/Tempel 1
Deep Impact, Farnham et al., 2007

6. Orbit Requirements
Form the analysis of the team responses to the WG3 Test Case we distinguish the following orbit categories:
Bound orbits (circular or elliptic):
Equatorial orbit
Polar orbit
Fixed local time orbit
Terminator orbit
Partially synchronous orbit (i.e. highly elliptic orbit)
Unbound Orbit:
Hyperbolic fly-by
J. Fertig reminded us (cf. his presentation at 26th Rosetta SWT June 11, 2009) that inside 2 to 3 AU (depending on gas pressure and nucleus density) no bound orbits will be available because of the gas pressure onto the spacecraft. Drift orbits outside the sphere of influence (50 to 100 km) and up to ~15 close (few nuclear radii) fly-bys will be possible.

7. Orbit and Pointing Requirements
Remote sensing instruments ALICE, MIRO, OSIRIS, VIRTIS
In-situ instruments GIADA, ROSINA, RPC
Dust collection instruments COSIMA, MIDAS
CONCERT
Coordinated measurements between orbiter and PHILAE

8. 3. Routine observations (Monitoring, Dust collection & analysis)
RO-SGS-TN-0025 (11 May 2010) states:
Monitoring instruments should provide their entries in the Science Themes Table to capture specific requirements associated to their observations. However it is understood that their monitoring role implies that they shall operate continuously during the comet phase, as agreed and stated in their specific EID-B.
Monitoring Instruments: GIADA, ROSINA, RPC (?)
Dust Collection and Analysis Instruments: COSIMA, MIDAS (?)
Does this apply to all instrument modes?

9. 4. Science Mission Scenarios9
Sample

10. 5. Completeness of mission scenarios with respect to objectives
Sample

11. Request to look at the Science during the Pre-Landing Phase
Science Subtheme 1A “NUCLEUS DYNAMICS” objectives not covered by Mission Scenarios: Inertia tensor, Orbit, and Rotation state*
Obtain from WG1 the list of observations require for safe landing
Identify and prioritize other observations desired and possible during this phase
*Remark from Flight Dynamics: Much of the above will be dealt with as part of Mission Operations

12. 6. Some Questions to SGS Operations Concept
How the information contained in the mission scenarios is eventually being used to generate an operations profile?
What is the relation between mission scenario and observation requests?
How a selection is made when several instruments (e.g. all remote sensing instruments) contribute to specific science objective?
How are regularly repeated monitoring observations (SMS-31) interleaved with dedicated observations?
Several mission scenarios need to be executed several times during the mission, therefore, they have no specific completion criterion.
Some mission scenarios require observations by in-situ and remote sensing instruments. But they have very different orbit and pointing requirements and, hence, can not be executed consecutively. How is this being handled.
How will secondary vs. prime instruments be handled for a specific mission scenario.
In the new concept of defining Mission Scenarios by WGs in parallel to SGS the WGs will determine how to best deal with these questions.

13. 7. Deep Impact: Icy patches and jets at Tempel 1 Mike A’Hearn

14. 8. Gas Loss Rates and Dust Fluxes – Marco Fulle
67P Gas loss rates (Dominique & Marco):

15. 9. Status of Engineering Environment Model - Michael Müller
Objective of Model is the prediction of operationally relevant parameters:
Forces on SC
Torques on SC
Radiation environment (relevant for SAS, STR, CAM, SA)
Surface coverage by dust
Prediction must be based on recent Rosetta measurements and is done by empirical calibration of parameters.

16. Next WG3 Activities
Identify and prioritize other observations desired and possible during pre-landing phase
Consider possible orbits (terminator, drift, and close fly-by orbits) for Mission Scenarios
Adjust role of monitoring (GIADA, ROSINA, RPC) and dust collection (COSIMA, MIDAS) instruments in Mission Scenarios, i.e. consider mostly remote sensing instruments (ALICE, MIRO, OSIRIS, VIRTIS) in Mission Scenarios
Streamline Mission Scenarios (remove redundancies) in order to provide a tool box to assemble a time line

18. 9P/Tempel 1
Deep Impact, Farnham et al., 2007

19. Remote sensing orbits for ALICE, MIRO, OSIRIS, VIRTIS
From an orbit close to the terminator (6h/18h local time) most of the sun lit and night sides can be observed. Especially limb observations of the sub-solar point are possible from a terminator orbit. Since illumination conditions are important for some specific observations orbits at other local times may be required.

20. Remote sensing pointing for ALICE, MIRO, OSIRIS, VIRTIS
Remote sensing observations of a specific target on the nucleus require accurate pointing of Rosetta.
Limb observations allow the determination of dust emission from the tangent point on the nucleus.
For only very specific observations off-nucleus pointing may be required.
Scans and maps may require special spacecraft orientations in order to facilitate these observations in an efficient way.
Spectrometers with slit may require special slit orientation with respect to target.

21. In-situ orbits for GIADA, ROSINA, RPC
Most of the gas and dust emission arrive from anywhere on the sun-lit hemisphere of the nucleus. Rosetta has to fly through the gas and dust flux tubes (jets) from a specific active area in order to relate the in-situ measurements to a specific position on the nucleus. Therefore, in-situ instruments will generally require various orbits ranging from terminator orbits to orbits over the sub- solar point.

22. Dust collection orbits for COSIMA, MIDAS
COSIMA and MIDAS have two modes for dust collection:
Priority dust collection and analysis.
Priority dust collection requires close fly-by orbits through dense parts of the coma with high enough dust density that the collection requirements of COSIMA and MIDAS are fulfilled. GIADA measurements are required to quantify the collected dust fluence.
Background dust collection and analysis.
The analysis of all collected particles occurs mostly in mode 2. Background dust collection and analysis is performed in parallel with any other measurement and has no orbit and pointing requirements.

23. In-situ pointing for GIADA, ROSINA, RPC and dust collection instruments COSIMA, MIDAS
Pointing for in-situ instruments is generally not very critical. Generally, close nadir pointing will be required. S/C slews may be required to scan through the velocity distribution of gas and dust.

24. Special orbits for CONCERT
CONCERT will require special orbits orientations in order to facilitate special configurations between orbiter, nucleus and lander.
Special Pointing for CONCERT
CONCERT will require special pointing for optimum transmission and reception of radio waves.
Only while Philae is alive

25. Only while Philae is alive
Special orbits for coordinated measurements between orbiter (remote sensing) and PHILAE
Coordinated measurements between remote sensing instruments on the orbiter and any lander instruments require in most cases visibility of the landing site in day light. A partially synchronous orbit (i.e. highly elliptic orbit in the rotational equator plane of the nucleus) provides the longest visibility period for the lander.
Only while Philae is alive

26. Only while Philae is alive
Special pointing for coordinated measurements between orbiter and PHILAE
The orbiter pointing should follow the landing site for sufficient time to perform the coordinated measurements. Since nucleus rotation is faster than the movement of the orbiter along the orbit lander visibility will be available only for a period ~6 h per nucleus revolution depending on landing position.
Only while Philae is alive

27. WG3 Activity (in brief)
Clean-up of Science Themes Table (STT) together with RSOC (latest version distributed by Claire on 14 May).
STT shall act as input for Information Repository for RSOC (relational database).
Instrument teams provided input to observational scenarios and to test cases.
Review and merging of Science Mission Scenarios (30 for WG2/3) during meeting of WG chairs in Paris February Began phasing of Science Mission Scenarios along the nominal mission duration.
AI to WG chairpersons: relate Science Mission Scenarios to Science Themes/Subthemes and Science Objectives (draft document sent to instrument teams by Eberhard on 30 April).
Feedback received from MIRO, COSIMA and ROSINA so far.