MAVEN-SWEA ( Solar Wind Electron Analyser) Changes between SWEA/STEREO and SWEA/MAVEN

1. MAVEN-SWEA (Solar Wind Electron Analyser)Changes between SWEA/STEREO and SWEA/MAVEN Contents Swea new projectdevelopmentorganization Modelsphilosophy Interfaces SWEA reviewhistory Changes fromStereo to Mavenreasons Identified hardware changes SWEA detector cutoff Changes in detailswithcomments Conclusion MAVEN-SWEA instrument peer review / CESR

2. SWEA project development organization MAVEN-SWEA instrument peer review / CESR

3. Models philosophy Stereo: Two engineering test units (one delivered to SSL) Two flight models Spare parts (not assembled) Maven: One engineering unit Stereo upgraded (not delivered) One flight model Spare parts (not assembled) MAVEN-SWEA instrument peer review / CESR

4. Interfaces Mechanical interface SSL part thatcontains digital electronics (same as Stereo) Purging tube goingthroughholes to the MCPs via the PCBs center (same as Stereo) Electricalconnectionwith the interface board (SSL) with a pigtailconnector Glenair Micro-D 51 pins (see ICD for details) Pinlist to bemodified to implementredundant pin-puller command circuit (TBD -> CESR / SSL) MAVEN-SWEA instrument peer review / CESR

5. SWEA REVIEW HISTORY STEREO/ SWEA PDR September 11-12 2001 Presentation done by Francis COTIN STEREO / SWEA DOOR MECHANISM PEER REVIEW September 25 2002 in Toulouse STEREO SWEA CDR November 21-22 2002 Presentation done by Claude AOUSTIN MAVEN-SWEA instrument peer review / CESR

6. SWEA HARDWARE CHANGES FROM STEREO TO MAVEN Hardware changes have to be as much as possible limited due to limited man power and funding Severalnecessary hardware changes on SWEA detector have been identified by SSL and CESR Different mission context Differentaccomodation and thermal context. Anomalies reported on Stereo/SWEA -> Corrective actions Differentspecificationmeasurements (science) ICD requirements Parts obsolescence MAVEN-SWEA instrument peer review / CESR

7. Identified HW changes in SWEA detector MAVEN-SWEA instrument peer review / CESR

8. Maven-SWEA detector cutoff MAVEN-SWEA instrument peer review / CESR

9. HW change #5 CESR Redundant actuator circuit to be added Reason: ICD requirement Actuator control wires are routed along grid ribs, through the center of electronic boards down to the interface connector: there is no problem to route 4 additionnal wires . SSL and CESR have to discuss to fix details and update ICD. MAVEN-SWEA instrument peer review / CESR

10. HW change #9 CESR Scallopinner and outerhemisphere and top cap Reason: reducescatteredelectrons, avoidMCPs to count Uvs Top cap willbescalloped the sameway as outerhemisphere Innerhemispheredoesn’tneedscalopping See A. Fedorov report (spheresscalopping and coating) MAVEN-SWEA instrument peer review / CESR

11. HW change #10 CESR Change surface coating on top cap for a more conductive one On Stereo-SWEA , top cap was coated with Nuflon, this coating has been suspected to become more resistive at very low temperature and bring parasit offsets on top cap that could disturb low energy electrons measurements. Comments: Copper black or Ebanol-C coating candidate for top cap - TBD MAVEN-SWEA instrument peer review / CESR

12. HW change #11 CESR Change gain on deflectors to provide some head room to the max deflexion voltage (~+10-20%) Provide the ability to optimize the max deflection Comments: on Stereo, HV between 0 and 1500 v was applied on deflectors We should be able to apply 0-2Kv on Maven-SWEA deflectors Most of modifications that take place on HV board look feasible Components derating are still ok. MAVEN-SWEA instrument peer review / CESR

13. HW change #12 CESR Reduce exposed areas of insulators (grid washers) Avoid parasit charged areas in field of view Comments: Special care will be taken to visible insulated parts in FOV during fabrication, assembly and tests. SWEA detector mechanical parts are currently in fabrication MAVEN-SWEA instrument peer review / CESR

14. HW change #13 CESR Potential parts obsolescence issues (e.g. LTC1024AMD/883) Reason: Obsolete parts Comments: Op Amp LTC1024 used on Stereo - SWEA isnowobsolete Cesr have enough parts fromStereo in stock and willre-screen The use of the same parts avoids to re-route HV board PCB A quotation for new screeninghas been asked to HirexTechnology (same group as Tecnologica) They have proposed to re-qualifyexisting lot (doc PRO_2911_01-1.pdf) - Externalvisual inspection - Hermeticity test - Electricalmeasurementsat room temperature -DPA on sample MAVEN-SWEA instrument peer review / CESR

15. HW change #14 CESR PotentialAmptek A111F QA issues Reason: Failures has been reported on Stereo-SWEA FM amplifier board. Comments: On Stereo, A111F had been purchasedwithAmptek « Option 1 » screening On SWEA-Maven, samedevices have been orderedwith Option2 screening (NASA Goddard Space Flight Center Preferred Parts List (PPL-20), GSFC S-311-P698) -Pre-assembly Parts Qualification (Element Evaluation) -Package Evaluation -Customer Precap Visual Inspection -Destructive Bond Pull Test on sample devices -Die Shear Test on sample devices -Moisture Test -OptionalextendedBurn-In -Pre and Post Burn-In Deltas -Additional Quality Control Inspections (QCI) -Lot Qualification (1000 hours Steady State Life Test at 125°C on sample devices) MAVEN-SWEA instrument peer review / CESR

16. HW change #16 CESR Change A111 to A121 Reason: Improve count rate , brings dead time correstion capability Comments: A121 case is much bigger and heavier than A111, it is not possible to fit 16 devices on the amplifier board, except if they are installed in stand up position and so the mechanical housing has to be re-designed and the three PCBs have to be re-routed This change leads to many hardware modifications . There has been a discussion between CESR and SSL and it has been decided not to change amplifiers: - To avoid many expensive hardware modifications - A111F is a good solution in more than 90% of the cases - The detector transmission has to be taken in account to determine the maximum counts supported by the charge amplifiers MAVEN-SWEA instrument peer review / CESR

17. HW change #18 CESR Change geometric factor - may be hemisphere diameter Extreem events, alternative to A111 to A121 change Comments: V0 is already an alternative to geometric factor change TBD MAVEN-SWEA instrument peer review / CESR

18. HW change #19 CESR Metalize back of deflectors Reason: Less exposed insulators Comments: The deflectors are made of Ultem, insulating material with a gold coating The golden layer did not cover the back of deflectors on Stereo, leaving insulated areas able to be charged and potential parasit electic fields. Another possibility is to change deflectors material to aluminium. This option has been considered for Maven and would oblige to fix deflectors with insulated washers (deflectors should be polarized between zéro and 2 Kv). MAVEN-SWEA instrument peer review / CESR

19. HW change #20 & 21 CESR Change silver epoxy HV capacitors soldering process Reason: HV caps cracked on Stereo – SWEA Comments: - define different soldering process - Analyse the anomaly with Cnes expert (T Battault) - Define different HV caps fixation * Lower temperature soldering * Stick the caps with epoxy glue charged with glass balls MAVEN-SWEA instrument peer review / CESR

20. CONCLUSION SWEA – MAVEN is mostly very similar to SWEA – STEREO in terms of design, development plan, etc The instrument has been selected and funded by CNES (French space agency) with verylimited funding (same instrument as for Stereo, very limited changes) Several necessary changes have been identified by SSL and CESR due to: New scientific requirements New mission profile Anomalies reported on STEREO Instrument improvement Most of changes have been evaluated and can be implemented SSL and CESR have to discuss and meet agreement as soon as possible on a few remaining changes and open points. MAVEN-SWEA instrument peer review / CESR