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Particles and Fields Package Pre-Ship Review 3 SWEA March 1, 2013 Section 2: SWEA

Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission. Particles and Fields Package Pre-Ship Review 3 SWEA March 1, 2013 Section 2: SWEA David L. Mitchell. SWEA Team - SSL. SWEA (Solar Wind Electron Analyzer) Instrument Lead: David L. Mitchell Electrical:

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Particles and Fields Package Pre-Ship Review 3 SWEA March 1, 2013 Section 2: SWEA

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  1. Mars Atmosphere and Volatile EvolutioN (MAVEN) Mission Particles and Fields Package Pre-Ship Review 3 SWEA March 1, 2013 Section 2: SWEA David L. Mitchell

  2. SWEA Team - SSL SWEA (Solar Wind Electron Analyzer) Instrument Lead: David L. Mitchell Electrical: Ellen Taylor, Dorothy Gordon (Digital) SeldaHeavner (LVPS) Miles Robinson, Peter Berg (HVPS) Chris Scholz (Technician) Mechanical: Paul Turin Thermal: Millan Diaz-Aguado

  3. Christian Mazelle (Lead CoI) Jean-Jacques Thocaven (PM, Electronics) Jean-André Sauvaud, Dominique Toublanc (CoIs) Andrei Fedorov (Detector simulations, Calibrations) Jean Rouzaud (Mechanics, Environmental tests) Claude Aoustin (CESR Technical Manager) Philippe Rouger (Electronics) Eric Lecomte (Integration, Coating) Qiu Mei Lee (Documentation) David Moirin BTS Industrie (Quality Assurance) Marc Bouyé OMP (Thermal) CNES can bring expertise on request (components, EMC…) SWEA Team – IRAP

  4. SWEA Science Goals • Magnetic Topology & Plasma Regime • Crustal Magnetospheres/Cusps • Draped Field Lines o o o

  5. SWEA Science Goals MGS MAG/ER • Electron Impact Ionization • Magnetic Pileup Region • Ionosphere

  6. SWEA Science Goals Mars Express Shadow 2.35 RM Photo-ionization of CO2by solar h @ 304 Å ESCAPE PEB h-electrons MPB 5 4 3 R (MSO) 2 1 0 Escape associated with heavy ions (M> 16) -3 -2 -1 0 1 2 X (MSO)

  7. SWEA will complete calibrations March 6 SWEA has four open PFRs, all on Monitor status SWEA schedule: Final (4th) Assembly: Feb 6 Functional Tests: Feb 8-11 Vibration: Feb 12 Post-Vibe Functional Tests: Feb 14-16 Thermal Vacuum: Feb 16-21 Magnetics: Feb 22 Calibrations Feb 23 to Mar 6 Delivery Mar 7 SWEA Status

  8. SWEA PFR Status

  9. SWEA PFR Status

  10. Contamination (PFR 122)(Same chart shown in IPSR part 2; 11/19/12) • Redesigned top cap closing mechanism so it does not close all the way • 0.5 mm gap when cover is “closed” • No contact with outer hemisphere during vibe/launch • No gasket • Outer hemisphere was inspected with SEM • Rubbed area composed of Cu and S, with a trace of Se. • Consistent with burnished Cu2S blacking  NO exposed Al. • We can proceed with existing parts • Increased purge flow (26 SLH) to compensate for gap • Instrument fully disassembled and cleaned to remove particulates • Analyzer carefully inspected during reassembly • MCP’s and MCP mounting hardware inspected under microscope • Instrument passed electrical resistance/continuity tests during assembly and bench functional after assembly

  11. Discharges (PFR’s 59, 122, 131) • SWEA was disassembled following TVAC #2 (PFR 131) • Two-pronged mitigation approach: • Reduce probability of discharges: • Measure MCP resistance over temperature in TVAC, then tune HVPS for stable operation over measured range of loads • Apply conformal coating to high voltage traces • Replace HVPS harness with new routing to avoid sensitive components (transformers and opamps) • Increase the operating temperature from -25 C to +10 C • Modify MCP HV ramp procedure to include >10-min pauses at 1200, 1600, and 2000 V • Provide better protection for preamps: • Add fast Schottky diodes to unused pads on Preamp board • Keep existing protection diodes on Anode board

  12. SWEA PFR 136 • Noise at the end of Cycle 8 TVAC • No droop in MCP HV • No droop in NR HV • Counts not correlated with sweep pattern

  13. SWEA PFR 136 • Noise stops when MCP HV powered off • Noise returns at beginning of next MCP ramp (~50 V)

  14. SWEA PFR 136 • Noise features: • Can appear after several days of operation under vacuum • Spontaneously appears and disappears • No evidence for droop in the MCP or sweep voltages • Not correlated with sweep enable/disable or with sweep pattern • Noise stops when MCP HV is set to zero. • Tendency to occur at the leading edges of MCP HV ramp steps, even at low voltage (but also occur at steady MCP voltage) • Tendency to be worse at cold temperatures (but only three episodes to go on) • Possible causes: • Noise features implicate components on the HVPS, possibly the transformer or stack, which work hard during MCP ramps • Onset of noise after days in vacuum suggests slow outgassing from a trapped volume • Many changes were made to the HVPS to improve stability. These were thoroughly tested on the EM and flight spare, but is it still possible to enter an unstable state? • Path Forward: • Continuous 24/7 operation in the calibration chamber until Wed (3/6) • Upgrade EM to be as flight-like as possible, continue testing EM • Design plan of action in case noise recurs in flight

  15. SWEA PF L3 Requirements Reference: MAVEN_SWEA_PLAN_0165

  16. SWEA Calibration • Beam profile varies by ~25% • Calibrations performed at LIN = 0.5 cm (as shown) • YAW axis slightly offset from aperture plane

  17. SWEA Calibration Recalibrating analyzer constant and concentricity after multiple reassemblies • Ka is 1% higher than IRAP calibration • Concentricity is slightly improved • Ka variation (1.4%) < energy resolution (18%)

  18. SWEA Calibration (PF 70, 71) • 360o FOV (16 sectors, 22.5° per sector) • no evidence for cross talk, except Anode 15 (peak cross talk is ~1%)

  19. SWEA Calibration (PF 71) • Deflector Calibration • deflection range verified from -50° (limited by harness) to +60° • simulations (IRAP and SSL) give ±60° deflector range • deflector calibration agrees with simulation to better than 1 deg symbols: measured linear fit simulation

  20. SWEA Calibration (PF 67, 68, 70) dQ = 7.1° (measured) = 6.4° (simulation) Sensor Energy-Angle response at 4 keV dE/E = 17% (measured SSL) = 18% (measured IRAP) = 16% (simulation)

  21. SWEA Calibration (PF 67, 68, 70) • Low Energy Electron Measurements: • Helmholtz coils null the field at the location of the sensor head. • Static residual fields (caused by magnetized items in the room) are ~2000 nT from the chamber wall (electron gun) to the center line. • Variable residual fields are ~few 100 nT 3-axis Helmholtz coils Electron Gun Ion Gun

  22. SWEA Calibration (PF 67, 68, 70) dQ = 11° (measured) = 6.4° (simulation) 4° deflection in residual field dE/E = 16% (measured) = 16% (simulation) Sensor Energy-Angle response at 10 eV Evidence that beam is deflected and defocussed

  23. SWEA Calibration (PF 69) Sweep pattern repeats every 2 sec (requirement is < 20 sec)

  24. SWEA Calibration (PF 66) • Requirement: G > 0.005 cm2 ster eV/eV • IRAP Calibration: G = 0.009 cm2 ster eV/eV • BUT … SWEA has been disassembled and reassembled 4 times • Channel plates replaced on the fourth assembly • Geometric Factor is combination of electrostatic optics, grid transmissions, and MCP efficiency • Calibrations during the past week show that present optics are very close to the optics as originally calibrated at IRAP. • Grid transmissions should be identical (same parts used). • MCP efficiency is the largest source of uncertainty (~20%)

  25. SWEA Calibration (PF 65) A111F Saturation 25% dead time correction Highest electron fluxes observed during ~10-year MGS mission, scaled to MAVEN SWEA count rate per sector. With a geometric factor per sector of 2.5 x 10-4 cm2 ster, peak electron fluxes during extreme conditions are still well below the saturation level of A111F preamps • SWEA test pulser generates peak count rate of 7 x 105 counts/sec/sector • Corresponds to energy flux of 109 eV/cm2-sec-ster-eV (with G = 0.009) • Requirement: energy fluxes from 104 to 108 eV/cm2-sec-ster-eV

  26. SWEA Vibration • Test was run to completion. • No failures. • UUT passed post-vibration functional test. • UUT Analyzer maintained optical alignment, verified during pre-shipment calibration in calibration chamber on Feb 14-16, 2013 • First natural frequency was >270Hz. • Sine surveys passed • Excitation spectrum met • Overall RMS levels were met • Force limiting was performed adequately I J K Instrument Coordinate System

  27. SWEA Magnetics • Overview • The SWEA magnetic moment was measured on 2/22/2013 using the DC magnetics screening procedure (MAVEN_PF_TP_040, Rev A) • SWEA was first rotated twice with the sensor head pointing up (run 1) and then twice with the enable plug pointing at the magnetometer at the start of the run (run 2). • SWEA was then subjected to a perming field of 16 Gauss for 30 seconds in each axis. • The magnetic moment was measured (as above, runs 3 and 4) after the perm to verify no susceptibility. Reference: MAVEN_PF_TR_058_SWEA_Magnetics

  28. SWEA Magnetics before perming after perming Reference: MAVEN_PF_TR_058_SWEA_Magnetics

  29. SWEA Magnetics 3. Conclusion The requirement for the unit is to have a magnetic dipole less than 25 mA-m2. This corresponds to a maximum field at a distance of 30 cm from the unit of 185 nT. The magnetometer was placed 30 cm from the unit. As the field variations due to the instrument in the plots show a difference approximately 10 times less than this requirement, the unit passes the test. Note: SWEA was tested with its red tag cover in place. The cover was pre-screened and found to be slightly magnetic, but not enough to be measurable at 30 cm. Some of the slight perming after DC exposure may come from the cover and not the instrument. Reference: MAVEN_PF_TR_058_SWEA_Magnetics

  30. SWEA Thermal Overview • ERD Verifications • Thermal testing temperatures • Thermal vacuum test • Survival soaks • Operational cycles • Thermal balance • Heater tests • Changes to model • Changes to SWEA thermal design • New SWEA temperatures and heater power budget

  31. SWEA ERD Verification

  32. SWEA Testing Temperatures *Survival and operational heater set-point now at 10°C

  33. SWEA Thermal Vacuum Test (Thermal Balance) • Performed 4 cycles, 1st cycle was thermal survival. Heaters were tested. Thermal balance was performed in the 1st cycle. At least 4 hour dwell durations. No HV tested. Isolators and MLI Removed, Enable plug Operational LPT, TB LPT LPT LPT Chamber Break LPT, TB LPT LPT LPT Old Cold Operational Cold Survival Heater Test Cycle: 1 2 3 4

  34. SWEA Thermal Vacuum Test (3rd Test) Bakeout (TQCM) Bakeout (TQCM) Cycle: 1 2 3 4 5 6 7 8 LPT LPT LPT LPT LPT CPT CPT CPT CPT LPT LPT LPT LPT CPT CPT CPT CPT HV on

  35. SWEA TVAC (Thermal Balance Test) MLI Germanium Black Kapton Radiator MLI

  36. SWEA Cold Plate Balance

  37. SWEA Hot Plate Balance

  38. SWEA Heater Thermal Balance

  39. SWEA TC Locations TC-9 Top Housing TC-8 Flange TC-7 Housing-Base TC-6 Radiator-Chamfer TC-5 Electronics-Base TC-4 Mounting Plate

  40. SWEA Balance Data (all in deg. C) Hot Thermal Balance (0.78 W electr.) Heater Thermal Balance (3.1 W Heater) Cold Thermal Balance (0.73 W electr.)

  41. Heater Test • Current Heater setpoint at 10ºC, verified through analysis from verified model (through balance)

  42. SWEA Temperatures = Achieved Margin = Within 5 °C of AFT Limit = > AFT Limit

  43. SWEA Heater

  44. SWEA Changes to Model • For Thermal Balance purposes • Changed contact between analyzers grid and top of the housing with the electronics box • Added radiation contact • For heater power budget • Reduced radiator, increased MLI blanket (also performed during thermal balance – small MLI blanket added) • Flight MLI blanket modified to reflect this change, LM already building it

  45. SWEA Thermal Conclusions • SWEA performed well at all testing temperatures • HV done from cycles 5-8 • Small modifications done to thermal design of SWEA • MLI blanket changed • Heater set-point changed to 10ºC

  46. Power (28 V) No HV Cold: 25 mA Hot: 25 mA HV on, non-sweeping Cold: 35 mA Hot: 42 mA HV on, sweeping Cold Peak: ~52 mA Hot peak: ~59 mA Mass 1.780 kg as measured mass NTE is X kg SWEA Resources

  47. SWEA Outstanding Items Need to continue monitoring for discharges (PFR’s 59, 122, 131). Need to continue monitoring for excessive noise (PFR 136). Duplicate calibration tests to be performed in August. SWEA is currently in the calibration chamber under high vacuum since Feb 23. Calibration to continue until March 3. 11 of 15 PFRs are closed; 2 are on monitor status; 2 are in process Documentation status … see SMA section

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