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 March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
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 (50%) Quality Assurance C. Aoustin (F. Cotin) D. Moirin Project Admin & Doc H. Perrier Q. M. Lee Mechanics J. Rouzaud Electronics J. L. Medale P. Rouger Thermal M. Cassignol - Integration P. Souleille, E. Lecomte Calibrations A. Fedorov, Th. Moreau A. Fedorov, P. Rouger March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
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) March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
Interfaces Ø Sensor head Mechanical interface with SSL digital electronics part (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 has been modified to implement redundant pin-puller command circuit (see ICD CESR-IRAP / SSL) March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
SWEA REVIEW HISTORY • STEREO/ SWEA PDR o o • STEREO / SWEA DOOR MECHANISM PEER REVIEW o • November 21 -22, 2002 Presentation done by Claude AOUSTIN Maven/Swea peer review (pre-PDR) o o March 28, 2011 September 25, 2002 in Toulouse STEREO SWEA CDR o o • September 11 -12, 2001 Presentation done by Francis COTIN Feb 3 -4, 2010 in Toulouse Presentation done by Maven/Swea team MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
SWEA HARDWARE CHANGES FROM STEREO TO MAVEN Hardware changes have to be limited as much as possible 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 March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
Item UCB/CESR 5 CESR 9 CESR 10 CESR Description Reason redundant actuator circuits - need to bring down 4 wires from the actuator and out the connector [6 spares] ICD requirement OK Scalloping on inner and outter hermispheres & top cap Change gain on deflectors to provide some head room to the max deflection voltage (~+10 -20%) CESR 12 CESR 13 CESR 14 CESR 18 CESR 19 CESR 20 CESR 21 CESR Copper black provide the ability to optimize the max deflection Reduce exposed area of insulators (grid washers) avoid charging effects Potential parts obsolecence issues (e. g. LTC 1024) - TBR LTC 1024 is obsolete Potential Amptek A 111 QA issues some failures on STEREO may make qualifying this part more difficult - TBR CESR 16 OK Have stock, will re-screen Full NASA screening improve count rate & dead time correction capability Difficult Change geometric factor? [maybe inner hemisphere] [TBD] xx avoid charging issue seen on STEREO OK Change to A 121 - TBR 22 reduce scattered electrons OK Change surface coating on top cap to a more conductive one 11 CESR comments extreem events, alternative to A 121 (#16) metalize back of deflectors less exposed insulators OK Silver epoxy HV caps Soldering caused them to crack add thermal strain relief for connections to HV caps avoid thermal stresses change surface properties of deflectors Need a black coating which will survive atomic oxygen (This is a question for top cap too, see 10) to avoid overheating due to thrusters and aeroheating (~0. 1 W/cm 2, all absorbed). Change deflectors profile to allow more homogenous angle response Try to improve incident particle angle range CESR March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011 Simulation : SSL Deflectors modifications made on Stereo EM detector tested in vacuum at CESR 7
Maven-SWEA detector cutoff March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #5 IRAP 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. ICD updated. March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #9 IRAP 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 hemispheres Both inner & outer hemispheres need scalopping (was only on outer) Round scalopping has been chosen (easier to implement) See A. Fedorov report (Propagation of the secondary electrons along the analyser for different serration types) « Conclusion: the round scalopping on the both hemispheres improves the suppression of the secondary electrons by factor 3 » March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #10 IRAP 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. Conclusion: Copper black Cu 2 S has been chosen to coat top cap and hemispheres • Well known process and contractor • Same coating as for Stereo Cu 2 S Gold March 28, 2011 Top cap coating MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #10 IRAP – parts coating overview Green: black copper Cu 2 S Red: black nickel (non magnetic) External parts may have to withstand high temperature from thrusters during maneuvers External parts must not be affected by atomic oxygens (=> non magnetic black nickel) Most of the time, SWEA is in the SC shadow, so very cold March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011 12
HW change #11 IRAP 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 -2 Kv on Maven-SWEA deflectors Most of modifications that take place on HV board are feasible Components derating are still ok. HV transformers have been fabricated taking in account the max deflexion voltage (2 k. V) and the oscillation frequency (100 Khz) March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
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 have been fabricated with special care taken to minimize exposed insulated parts areas. March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #13 CESR Potential parts obsolescence issues (e. g. LTC 1024 AMD/883) Reason: Obsolete parts Comments: Some parts such as LTC 1024 (opamp) or 54 HC 4040 (counter) were either obsolete or with too old date code. Both remaining stocks from Stereo have been re-lifed by Hirex (hirex. fr) Reports available. - External visual inspection - Hermeticity test - Electrical measurements at room temperature - DPA on sample March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #14 CESR Potential Amptek A 111 F QA issues Reason: Failures has been reported on Stereo-SWEA FM amplifier board. Comments: On Stereo, A 111 F had been purchased with Amptek « Option 1 » screening On SWEA-Maven, same devices have been ordered with Option 1+ screening (NASA Goddard Space Flight Center Preferred Parts List (PPL-20), GSFC S-311 -P 698) - Amptek Option « 1 » screening (Stereo like) - Customer pre-cap visual inspection. - Extended Burn-In to total of 240 H. - Lot qualification (1000 hours Steady State Life Test at 125°C on sample lot) March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #16 IRAP 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 March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #18 IRAP Change geometric factor - may be hemisphere diameter Extrem events, alternative to A 111 to A 121 change Comments: V 0 is already an alternative to geometric factor change March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #19 IRAP 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. - Deflectors material (Ultem) have been changed to aluminium. This option has led to re-design parts near deflectors (fixed with insulated washers) - Gaps have been designed to take in account new deflection voltages (polarization between zero and 2 Kv). - Main reason to use aluminium instead of ultem is thermal: deflectors may have to support high temperature (600°C) coming from s/c thrusters during maneuvers: Ultem could not withstand so high temperature. - The golden coating both under bottom deflector and on outer sphere external part (see slide #12) reduces thermal coupling between the lower deflector and the analyser. March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change #20 & 21 IRAP Change silver epoxy HV capacitors soldering process Reason: HV caps cracked on Stereo – SWEA Comments: - Meeting has been held with Cnes boards assembly expert (T Battault) - Different HV caps welding and fixation have been defined: * Pre-heating of boards and parts at 70 -80°C * Place the board on heating table at 70°C * Weld the capacitors in four points with controled solder temperature * Stick the caps with minimum amount of epoxy glue charged with glass balls March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
HW change - Parts potentially exposed to radiation dose • LTC 1024 op amps shielded with 1 mm thick copper pads • Electronic boards aluminium housing made thicker : 2. 65 mm (weight +70 g) March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011 21
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/IRAP 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 have been or can be implemented q SSL and CESR/IRAP have discussed and met agreement on a few other changes. March 28, 2011 MAVEN SWEA instrument Pre-CDR Peer Review @ IRAP March 28 -29, 2011
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