MAVENSWEA Solar Wind Electron Analyser Changes between SWEASTEREO
MAVEN-SWEA (Solar Wind Electron Analyser) Changes between SWEA/STEREO and SWEA/MAVEN Contents • Swea new project development organization • Models philosophy • Interfaces • SWEA review history • Changes from Stereo to Maven reasons • Identified hardware changes • SWEA detector cutoff • Changes in details with comments • Conclusion 30 September 2020 MAVEN-SWEA instrument peer review / CESR 1
SWEA project development organization SWEA (Stereo) SWEA (Maven) Co-Is J. A. Sauvaud C. Mazelle (lead Co-I) J. A. Sauvaud, D. Toublanc Technical responsible (PM) C. Aoustin (F. Cotin) JJ Thocaven Quality Assurance C. Aoustin (F. Cotin) D. Moirin Project Admin & Doc H. Perrier Q. M. Lee Mechanics J. Rouzaud Electronics J. L. Medale JJ Thocaven, P. Rouger Thermal M. Cassignol M. Bouye Integration P. Souleille, E. Lecomte Calibrations A. Fedorov, Th. Moreau A. Fedorov, P. Rouger 30 September 2020 MAVEN-SWEA instrument peer review / CESR 2
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) 30 September 2020 MAVEN-SWEA instrument peer review / CESR 3
Interfaces Ø Mechanical interface SSL part that contains digital electronics (same as Stereo) Ø Purging tube going through holes to the MCPs via the PCBs center (same as Stereo) Ø Electrical connection with the interface board (SSL) with a pigtail connector Glenair Micro-D 51 pins (see ICD for details) Pinlist to be modified to implement redundant pin-puller command circuit (TBD -> CESR / SSL) 30 September 2020 MAVEN-SWEA instrument peer review / CESR 4
SWEA REVIEW HISTORY • STEREO/ SWEA PDR o o • STEREO / SWEA DOOR MECHANISM PEER REVIEW o • September 25 2002 in Toulouse STEREO SWEA CDR o o 30 September 2020 September 11 -12 2001 Presentation done by Francis COTIN November 21 -22 2002 Presentation done by Claude AOUSTIN MAVEN-SWEA instrument peer review / CESR 5
SWEA HARDWARE CHANGES FROM STEREO TO MAVEN Hardware changes have to be as much as possible limited due to limited man power and funding Several necessary hardware changes on SWEA detector have been identified by SSL and CESR q Different mission context q Different accomodation and thermal context. q Anomalies reported on Stereo/SWEA -> Corrective actions q Different specification measurements (science) q ICD requirements q Parts obsolescence 30 September 2020 MAVEN-SWEA instrument peer review / CESR 6
Identified HW changes in SWEA detector Item Description Reason 5 Redundant actuator circuit to be added ICD requirement 9 Scallop inner and outer hemispheres & top cap Reduce scattered electrons & UVs 10 Change surface coating on top cap for a more conductive one To avoid charging issue as on Stereo 11 Change gain on deflectors to provide some head room to the max deflection voltage (+10% to +20%) Ability to optimize the max deflection 12 Reduce exposed area of insulators (grid washers) Avoid charging effects 13 Parts obsolescence issue (e. g. LTC 1024 AMD/883) Obsolete parts 14 Potential Amptek A 111 issues Some failures on Stereo 16 Change A 111 to A 121 Improve count rate & dead time correction 18 Change geometry factor, inner hemisphere diameter ? (TBD) Etreem events, alternative to A 121 19 Metallize back of deflectors Less exposed insulators 20 Silver epoxy Eurofarad HV capacitors Soldering caused them to crack 21 Add thermal strain relief for connection to HV capacitors Avoid thermal stresses 22 Change surface properties of delectors (& top cap): need a black coating that will survive atomic oxygen Avoid overheating from thrusters & aeroheatng (~0. 1 W/cm² all absorbed) 30 September 2020 MAVEN-SWEA instrument peer review / CESR 7
Maven-SWEA detector cutoff 30 September 2020 MAVEN-SWEA instrument peer review / CESR 8
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. 30 September 2020 MAVEN-SWEA instrument peer review / CESR 9
HW change #9 CESR Scallop inner and outer hemisphere and top cap Reason: reduce scattered electrons, avoid MCPs to count Uvs Top cap will be scalloped the same way as outer hemisphere Inner hemisphere doesn’t need scalopping See A. Fedorov report (spheres scalopping and coating) 30 September 2020 MAVEN-SWEA instrument peer review / CESR 10
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 30 September 2020 MAVEN-SWEA instrument peer review / CESR 11
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: 30 September 2020 on Stereo, HV between 0 and 1500 v was applied on deflectors We should be able to apply 0 -2 Kv 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 12
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 30 September 2020 MAVEN-SWEA instrument peer review / CESR 13
HW change #13 CESR Potential parts obsolescence issues (e. g. LTC 1024 AMD/883) Reason: Obsolete parts Comments: Op Amp LTC 1024 used on Stereo - SWEA is now obsolete Cesr have enough parts from Stereo in stock and will re-screen The use of the same parts avoids to re-route HV board PCB A quotation for new screeninghas been asked to Hirex Technology (same group as Tecnologica) They have proposed to re-qualify existing lot (doc PRO_2911_01 -1. pdf) - External visual inspection - Hermeticity test - Electrical measurements at room temperature -DPA on sample 30 September 2020 MAVEN-SWEA instrument peer review / CESR 14
HW change #14 CESR Potential Amptek A 111 F QA issues Reason: Failures has been reported on Stereo-SWEA FM amplifier board. Comments: 30 September 2020 On Stereo, A 111 F had been purchased with Amptek « Option 1 » screening On SWEA-Maven, same devices have been ordered with Option 2 screening (NASA Goddard Space Flight Center Preferred Parts List (PPL-20), GSFC S-311 -P 698) -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 -Optional extended Burn-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 15
HW change #16 CESR Change A 111 to A 121 Reason: Improve count rate , brings dead time correstion capability Comments: A 121 case is much bigger and heavier than A 111, 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 - A 111 F 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 30 September 2020 MAVEN-SWEA instrument peer review / CESR 16
HW change #18 CESR Change geometric factor - may be hemisphere diameter Extreem events, alternative to A 111 to A 121 change Comments: V 0 is already an alternative to geometric factor change TBD 30 September 2020 MAVEN-SWEA instrument peer review / CESR 17
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). 30 September 2020 MAVEN-SWEA instrument peer review / CESR 18
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 30 September 2020 MAVEN-SWEA instrument peer review / CESR 19
CONCLUSION q SWEA – MAVEN is mostly very similar to SWEA – STEREO in terms of design, development plan, etc q The instrument has been selected and funded by CNES (French space agency) with very limited funding (same instrument as for Stereo, very limited changes) q Several necessary changes have been identified by SSL and CESR due to: Ø New scientific requirements Ø New mission profile Ø Anomalies reported on STEREO Ø Instrument improvement q Most of changes have been evaluated and can be implemented q SSL and CESR have to discuss and meet agreement as soon as possible on a few remaining changes and open points. 30 September 2020 MAVEN-SWEA instrument peer review / CESR 20
- Slides: 20