1. SESAME: Status and On-Comet Science
K. Seidensticker1, H.-H. Fischer2, K. Thiel2, I. Apathy3, W. Schmidt4
and the SESAME team
1DLR (Köln) , 2University of Köln, 3KFKI (Budapest), 4FMI (Helsinki)

2. Outline of Talk Flight operation Software Operation planning for 2008
Payload checkout #6
Software
Flight SW, EGSE-SW
Operation planning for 2008
SESAME On-Comet operation aspects
Funding and personnel
Conclusions
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

3. SESAME PC #6 Activities
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

4. PC #6: New Temperature Measuring Method
Left: Old method; no temperature values accessible < °C
Below: New method with two voltage references; temperatures (voltages) are given in columns 4 and 6; a calibration during Steins Fly-By is planned.
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

5. PC #6: SD2 Drill Rotation Test
CASSE time series data from three feet; three axes each; example: foot -Y, x
(a) Before drilling starts: predominantly vibration caused by Orbiter reaction wheels
FFT
(b) After start of SD2 drill motor
FFT
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

6. PC #6: CASSE Trigger Event (IDP ?)
During the 2. CASSE Triggered Mode sequence of the new ExtAFT (29. September 2007) an event eceeded the trigger level of +20 (ADC values) on the +X foot, ACC y-axis
Complete time series with 5980 samples;
Most of the “noise” is caused by vibrations excited by the orbiter reaction wheels;
Red lines indicate full y-scale.
Enlarged view (around t = 100 ms) of complete time series above;
x and z axes also show tiny signals;
thermal “cracking” or IDP?
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

7. PC #6: PP Active Mode (1)
SESAME software version FM-2 introduced wavelet-based data reduction.
First use of transmitter electrodes in the +X foot and at the MUPUS PEN.
A 1 kHz signal was injected with 20 Vp-p; the response was monitored via +Y and –Y feet sensors. The red lines mark the start of an injected sine wave in order to estimate the phase shift between current and response voltage.
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

8. PC #6: PP Active Mode (2)
The FFT spectrum (TX) shows the injected 1 kHz current and higher harmonics. The receiver (RX) registered additionally a component at about 60 Hz. PP-AM injects 20 frequencies with different amplitudes (5, 10 and 20 V) each and analyzes the responses.
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

9. PC #6: PP Passive Mode
First use of PP Passive Mode foreseen for plasma waves detection during descent
The potential difference between the +Y and –Y sensors is sampled with 40 kHz for 0.2 s.
The lowest frequency bin contains also offset components, the highest contains digital noise.
The left panel shows the command parameters;
Langmuir Probe flag ”65535” means ”no plasma wave detected”.
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

10. PC #6: New Flight Software FM-2
Major upgrades implemented / planned for SW FM-2
CASSE: Implementation of Triggered Mode: detection of external signals like cometary quakes and MUPUS-PEN insertion
CASSE: Fixing of wrong channel assignment (due to FPGA program flaw: missing reset) (postponed to FM-3)
CASSE: New temperature measuring mode; calibration U vs. T pending
DIM: Autonomous measuring depending on dust flux and sensor status (implemented, but further ground tests needed)
PP: Improved data sampling strategy; on-board data evaluation for active and passive modes; wavelet filtering of time series
General: HK data content improved; time-stamp included; science data processing revised
FM-2 successfully uploaded during PC #6 (September 2007)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

11. SESAME EGSE Software EGSE software “AliBaba” for SESAME
Goals
Parsing of rolbin-files and formatting of SESAME science and HK records
Quick-look data check (science data and HK) and export
Applicable for all hardware versions in use (FM, GRM, EGSE)
Browsing on telemetry level
Version released
Fully qualified for all PC #6 SESAME procedures and flight software version FM-2
Recently implemented AliBaba upgrades
Improved presentation and analysis of PP and DIM data
Display of CASSE Triggered Mode
Presentation of revised health-check and housekeeping data
Improved service for lab operation: handle increasing file size during measurements
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

12. SESAME Planning for PC #8
Participation in Flywheel test (SES_7)
Flywheel operation not representative for descent (CVP repetition?)
But should help to prepare SESAME instruments for descent test (PC #12?)
CASSE Measurement during SD2 Drill Test (SES_8 and SES_14)
Repetition of PC #6 tests planned by SD2 team
Additional inter-foot sounding by CASSE in order to characterize landing gear and sole actuators and receivers
Vibration measurements during Orbiter Wheel Offloading (SES_9)
Test of CASSE Triggered Mode
Improved frequency resolution compared to PC #4
Thermal test of Philae soles (SES_10)
Part 1: Preparation of thermal calibration during Steins fly-by (PC # 8: without solar illumination of soles, solar distance ca. 2 AU)
Measure temperatures of all CASSE sole sensors being heated by CASSE accelerometers with new method.
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

13. SESAME Planning for Steins Fly-By
Vibration measurements during Orbiter Wheel Offloading (SES_9)
24 h before Close Approach
Can be cancelled if PC #8 operation is possible and successful
Thermal test of Philae soles (SES_10)
Part 2: Measure temperatures of all CASSE sensors with old and new method
Get temperature data from soles illuminated by sun and being in shadow
Obtain new calibration curve (voltages vs. temperature)
Later on: Try to model dynamic thermal behavior of soles for on-comet application
Operate CASSE and DIM in a “dusty environment” (SES_11)
Search with CASSE (Triggered Mode) and DIM (Burst Continuous Mode) for dust particles when Philae attitude is favorable (around Close Approach)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

14. CASSE: Science Objectives and Measurements
LSE-CAS-O1: Determine elastic properties of cometary surface layer
LSE-CAS-O2: Determine macro-structure of surface layer (layering, inhomogeneities)
LSE-CAS-O3: Locate and analyze micro-seismic events
Measurements
LSE-CAS-M1: Determine longitudinal and shear wave velocities by active sounding from foot to foot
LSE-CAS-M2: Generate reflection and refraction seismograms by active sounding (CASSE and MUPUS-Pen)
LSE-CAS-M3: Register external signals with several sensors (Passive triggered listening)
Relation to other Instruments
MUPUS: Use MUPUS-PEN hammering as external vibration source
SD2: Use SD2 drilling as external vibration source (TBD)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

15. Experiment with MUPUS-PEN Simulator
Simulator hammering on an ice-block (W*D*L = 50*30*70 cm3) in the DLR Cold Lab (Chr. Krause)
Accelerometer signal of z-axis (pointing to PEN) in 35 cm distance from insertion point
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

16. DIM: Science Objectives and Measurements
LSE-DIM-O1: Study the fluxes and dynamics of near-surface cometary particle flow
LSE-DIM-O2: Determine physical properties of cometary grains
LSE-DIM-O3: Contribute to the understanding of cometary activity and the formation of cometary mantles
Measurements
LSE-DIM-M1: Measure parameters of the electrical signal caused by particle impact on piezo-electric plate
LSE-DIM-M2: Determine average signal height in case single impacts can not be discriminated
LSE-DIM-M3: Determine flow rate and direction as well as temporal variations
Relation to other Instruments
GIADA: Correlate DIM data with GIADA observations (TBD)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

17. PP: Science Objectives and Measurements
LSE-PP-O1: Determine electrical properties of the cometary surface matter and its evolution
LSE-PP-O2: Monitor electron density variation and the comet’s outgassing activity
Measurements
LSE-PP-M1: Inject alternating currents of different frequencies into the cometary surface and monitor variations of induced electrical potential (active mode)
LSE-PP-M2: Monitor potential difference variations (passive mode)
Relation to other Instruments
ROMAP: Compare permeability measurements
MUPUS: PP electrode deployment; temperature of surface matter
APXS: PP electrode deployment; surface composition
CIVA: Observation of MUPUS-Pen and Philae soles
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

18. Open issues during the cruise phase
Until hibernation: development and test of additional measurement and operation methods => further upgrades of flight and EGSE software
Development of software planning tool for command generation and resource calculation
Ongoing calibration (in space and on Earth) of SESAME instruments and development of analysis programs
Detailed planning and testing of 67P/C-G operation phases (S-D-L, FSS and long-term science)
Archiving (PDS), documentation, knowledge management
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

19. Long-term SESAME Planning
PC #6: FM-2 Upload
PC #8: Flywheel test; therm. calibration
Steins Fly-By: Thermal Calibration
PC #10: FM-3 Upload
PC #12: Flywheel Test, IF-Test, FM-3.5 Upload?
Lutetia Fly-By: Search for IDPs?
2014: FM-4 Upload?
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

20. Readiness for FSS and long-term science
SESAME is not fully ready
CASSE
Basic operation modes are operational
Increase on-board autonomy (e.g. trigger level setting, averaging)
Correction or compensation of hardware problems, e.g. missing H/W reset or varying offsets
DIM
Autonomous Mode is implemented, but ground validation is pending PP
Final functionality is operational
Determine stray capacitances after separation from orbiter (PP-AM)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

21. Long-term science: goals and operation
Goals: Evolution of surface properties and cometary activity with rotational and orbital phase
Basic operation modes and sequence have been defined for RSOC commissioning test (2004)
Operation sequence has to be upgraded using capabilities of new flight software version FM-2 (and planned features of FM-3 software)
Operation (duration about 1 h) should be conducted twice to once per comet week at special local times (sunrise, noon, sunset and midnight).
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

22. Funding and Personnel CASSE / SESAME DIM PP
Large changes at DLR possible; people and test units relocation?
Personnel (DLR): K. Seidensticker (PI), K. Gusbeth (student, Ground S/W), Univ. Köln: K. Thiel, H.-H. Fischer (until !) (both Co-Is, Flight S/W, operation)
DIM
Personnel (KFKI AEKI): I. Apáthy (PI), A. Péter (engineering) (both retired!)
A. Juhász (Co-I, KFKI RMKI); diploma student PP
In-house funding for Rosetta support, external funding for special activities on application?
Personnel: FMI: W. Schmidt (PI), M. Genzer (operations), J. Ryno (S/W support); Co-Is: ESTEC: H. Laakso, R. Trautner; CETP: M. Hamelin
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007

23. A difficult way to 67P/C-G: Conclusions
Slow progress due to limited resources
Software (flight and ground) upgrades are needed for efficient use of hardware and telemetry limitations
Improving analysis methods, e.g.:
CASSE: Identification of wave types; analysis of seismograms
DIM: More precise impact model
PP: More calibration work
Complex permittivity vs. ice concentration, composition, temperature
Preserve the knowledge!
Upgraded definition of SESAME comet science operations (SDL, FSS and long-term)
3rd Post-Launch Philae Experimenters Workshop Budapest, December 2007