1 / 46

REXIS Detector Packaging and Assembly

REXIS Detector Packaging and Assembly. Harrison Bralower REXIS Engineering Peer Review 9/18/12. Review Team. Rick Foster (MKI) Steve Graham (GSFC IRT) Don Jennings (GSFC) Steve Kissel (MKI) Bob Reich (LL) Joe Schepis (GSFC) Joel Villaseñor (MKI) Keith Warner (LL). Review Goals.

duante
Télécharger la présentation

REXIS Detector Packaging and Assembly

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. REXIS Detector Packaging and Assembly Harrison Bralower REXIS Engineering Peer Review 9/18/12

  2. Review Team • Rick Foster (MKI) • Steve Graham (GSFC IRT) • Don Jennings (GSFC) • Steve Kissel(MKI) • Bob Reich (LL) • Joe Schepis (GSFC) • Joel Villaseñor (MKI) • Keith Warner (LL)

  3. Review Goals • To determine if an appropriate CCD packaging geometry has been designed • To determine if appropriate materials for the CCD package have been chosen for REXIS • To determine if an appropriate detector assembly geometry has been designed that meets instrument alignment and telemetry requirements • To determine if a suitable flexprint cable has been designed that meets the electrical and mechanical needs of the instrument

  4. Review Process • Feel free to ask questions at any time • Please fill out RFA forms for any actions you’d like me or the REXIS team to take • All RFAs will be closed by PDR at the end of January • Paper RFAs should be given to me or Becky • Electronic RFAs should be emailed to me (bralower@mit.edu) and Becky (becki@mit.edu) • We are hoping for a team report of this review (and all other peer reviews) to be issued at some point

  5. Agenda • Project and Instrument Overview • CCD Thermal Environment • CCD Packaging Geometry • Detector Assembly Geometry • Material Selection for Packaging and Detector Assembly • Fe-55 Check Source Design • Radiation Damage Mitigation • Flexprint Cable Design • Scheduling and Cost

  6. Project and Instrument Overview

  7. What is OSIRIS-REx? • The Origins, Spectral Interpretation, Resource Identification, (and) Security REgolith eXplorer is a NASA New Frontiers mission to asteroid 1999 RQ36 • Asteroid has a heliocentric orbit that intersects Earth’s orbit; it can usually be found between here and Mars • 1-in-1000 chance asteroid hits Earth in 2169 • OSIRIS-REx Mission objectives • Return at least 60g of asteroid regolith to Earth and characterize the sample in situ • Globally map the asteroid topology and mineralogy • Measure orbital perturbations due to Yarkovsky effect • Compare data to ground measurements of other nearby asteroids • REXIS is a Class-D student payload whose primary operations occur in Phase 5B of the OSIRIS-REx mission Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  8. What is REXIS? Detector Assembly Support Structure (DASS) Coded Mask • REgolith • We study asteroid dust • X-ray • We monitor X-rays fluoresced out of the asteroid by incident solar X-rays (which we also monitor) • Imaging • We use CCDs and coded-mask imaging algorithms to globally and spatially map the asteroid • Spectrometer • We identify spectral lines in the collected X-rays to determine the chemical composition of the asteroid Radiation Cover Detector Array Radiator Electronics Box Thermal Isolation Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  9. REXIS Science Mission Sun • We want to identify the distribution of elements on the surface of RQ36 with a spatial resolution of 50m or better • O, Mg, Fe, Al, Si, S with SNR > 10 • These all emit X-rays between 0.5-10keV, which the REXIS CCDs can detect with high quantum efficiency and spectral resolution • REXIS supports OSIRIS-REx by finding possible TAGSAM sites of interest • REXIS characterizes candidate sample sites and provides context for the sample return • Monitoring solar X-rays provides context for X-rays measured off the asteroid RQ36 Solar X-rays X-ray Fluorescence (XRF) Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  10. Coded-Mask Imaging • Consider a mask pattern in front of the detectors • Photons from any direction cast a shifted shadow of the mask pattern onto the detectors • Intensity of shifted pattern corresponds to how bright that direction is in the field of view • Simple ray-tracing algorithms can determine what all possible shifted patterns look like • Spatial cross-correlation of data and mask pattern reveals the most statistically likely direction of incident X-rays Detector Plane Image Coded Aperture Mask Reconstructed Image

  11. CCD Thermal Environment

  12. CCD Thermal Environment Asteroid QIR & QAlbedo QSolar QRadiation Sun Radiator Sun Shield Heat Strap (DASS to Radiator) QPower QParasitic EB CCDs OSIRIS-REx S/C Deck Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  13. Thermal Design Considerations • Each CCD must dissipate ~61mW of heat (TBR) • Asteroid IR and albedo, intra-instrument radiative exchange, power to operate the CCDs, and parasitic conduction from electronics • Science requirements demand CCDs remain at -50°C (TBR) or colder • Actual requirement determined by imaging simulation • Baseline CCD design temperature is -60°C • CCDs are passively cooled via conduction through DASS and thermal strap to radiator, which radiates to deep space • Based on simulation the radiator may reach -70°C, leaving 10°C forconduction losses, unmodeled contact resistances, and margin • Lowest achievable radiator temperature in phase 5B is TBR

  14. CCD Packaging Geometry

  15. Lincoln Labs CCID-41 • Heritage dating to ACIS (CCID-17) and Astro-E2 (CCID-41) • Designed for X-ray applications • 1024 x 1026 pixels • 24µm x 24µm pixel size • Consistent with L3 specs • Split frame-store • Back-illuminated • Covered with 220nm aluminum for optical blocking • Supports charge injection • REXIS uses a 2 x 2 array of these CCDs Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  16. CCD Packaging Options • Lincoln can provide different packaging options depending on the application • Invar pedestal • Used for tight-tolerance applications • Invar can be heat-treated to match the CTE of silicon • Kovar/alumina ZIF socket • Used primarily for development applications in a lab setting • Ceramic package • Used for looser-tolerance applications • Cheapest and easiest to produce • Custom packaging(e.g. integrating mechanical and electrical interfaces in one structure for PanSTARRS) Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  17. REXIS Packaging Design • What does REXIS need in a detector package? • Low mass • Good CTE match to silicon • Easy alignment • Replaceable CCDs • Low thermal resistance • Launch survivability • ACIS heritage package meets most of these requirements Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  18. REXIS Packaging Trade • Invar package is not ideal for this application • Coded-mask imaging is very robust against misalignment and other error sources • Invar is heavy and has poor thermal conductivity • Kovar/alumina ZIF package isn’t really intended for flight • Kovar is heavy • Would require custom ZIF socket or other connector • Thermal management would be difficult • CCDs not replaceable • Package not rated below -40°C; REXIS operates at -60°C • CCDs already ship in alignment • Ceramic package is (relatively) simple • Low mass (4 packaged ACIS CCDs have a total mass of ~200g) • Easy to connect to electronics since we pick the connectors • CCDs are individually replaceable • Thermal management much simpler • Rated to -80°C (according to LL); has flown at -120°C (ACIS) • Harder to align—each CCD must be in alignment individually

  19. REXIS Packaging Design CCD (underlying adhesive not shown) • Design is almost the same as ACIS package • Some design elements subjected to trades or redesign • Ceramic substrate material • Metal parts material • Flexprint design Ceramic Substrate Metal Tee Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  20. Detector Assembly Geometry

  21. Detector Assembly Requirements • What do we need in a detector assembly? • Low mass • Low thermal resistance • Keep CCDs aligned with respect to each other and the mask • Protect CCDs from radiation damage • Shield frame-store from incident photons • Minimize stray light from striking CCDs • Provide means of checking CCD degradation in flight • Fit within existing REXIS footprint (if possible) • Provide breakout of CCD electrical connections to electronics • Must not fluoresce in detectable range • All aluminum parts in field of view will be gold-coated

  22. Detector Assembly Requirements • Distance between active imaging areas of CCDs 768 ± TBR µm • REXIS bins single 24µm x 24µm pixels into 16 x 16 (384µm x 384µm) superpixels • Gaps in data should be an integer multiple of superpixel size • Actual gap between packages is less due to inactive silicon on die edges • Tolerance on requirement is TBR by HCO • Maximum misalignment requirements • ΔX/ΔY translational shift (in detector plane): ±0.0384cm • ΔZ translational shift (normal to detector plane): +6.67/-4.00cm • Rotational shift about X and Y: ±1.54° • Rotational shift about Z: ±0.40° • All mechanical parts must have first natural frequency >90Hz (TBR) • All mechanical parts must survive launch • Will perform preliminary launch load and vibration analysis before PDR

  23. REXIS Detector Assembly Mount (DAM) Flexprint Attachment Points Fe-55 Source RTV Pocket Package Carrier Tee (bondedto package) Delivery Box Mount Point Active Imaging Area Assembly Tension Screw Flexprint Slot Radiation Shield Alignment Pin Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  24. REXIS Detector Assembly Mount (DAM) Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  25. REXIS Detector Assembly Mount (DAM) • DAM Mass and Size • 329.83g • 11.39cm(L) x 8.16cm(W) x 2.87cm(H) • Does not include flexprint or radiation cover Flexprint Route Flexprint Bonded to Package Here Connector Oriented Normal to End Shield Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  26. Material Selection for Packaging and Detector Assembly

  27. Thermal Model of Assembly Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  28. Ceramic Substrate Trade • Two metrics: CTE match to silicon and thermal conductivity • Cost not a metric due to low price per part and low part volume • Substrate thickness still an open trade • Nominally 1/8” from ACIS heritage • Need to do shock/vibration analysis to find minimum substrate thickness Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  29. Ceramic Substrate Trade

  30. Metal Parts Trade • Detector assembly has three metal parts (not including radiation shielding) • Tee (bonded to package) • Array structure (holds CCDs and is screwed into the DASS) • Package carrier (screwed into array structure and bonded to CCD package with RTV epoxy) • Considered two materials: Beryllium and aluminum • Plot on previous slide includes only aluminum parts in model • ΔT across DAM lower than expected with aluminum parts • Beryllium provides lower mass, higher thermal conductivity, and better CTE match to other parts at significant risk to project • No justification for using beryllium in design

  31. Fe-55 Check Source Design

  32. Fe-55 Check Source • CCDs degrade with exposure to space environment • Spectral lines shift in mean energy and become broader with time • Installing a known radiation source in the assembly can be used for in-flight calibration and monitoring of CCD health • Fe-55 is a very common laboratory radiation source • Fe-55 has peaks at 5.9keV and 6.4keV, which can be used to check CCD performance against requirements set at 6keV • Requirements for check source • Must not radiate towards other instruments on OSIRIS-REx • Must provide enough counts • Must not contaminate asteroid data • Proposed source: Eckert & Ziegler IERB19058 • 81nCi ± 30% activity; 50mm(L) x 2mm(W) x 0.3mm(H)

  33. Fe-55 Source Placement • Source placement driven by data constraints • Not enough data allocation to illuminate whole array • Even at 100 counts per second (cps) source activity we only get 22 counts per hour per superpixel for illuminating the whole array • This is not enough telemetry data but would be half of the overall data budget • Since we are primarily interested in how each CCD varies along the readout direction we can illuminate a one superpixel-wide strip along the edge of each CCD • At 10cps activity we get ~200 counts per hour per superpixel, which is equivalent to ~5% of the overall data budget • This assumes the CCD does not spatially vary perpendicular to the readout direction

  34. Fe-55 Source Placement Radiation Shield Collimator Abutment Gap Fe-55 Source Pockets for Mass and Thermal Resistance Reduction Shim Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  35. Radiation Damage Mitigation

  36. Radiation Cover Hinge Frangibolt Aluminum Cover Weak Point Titanium Bolt Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  37. Radiation Damage • Electronics require shielding from ionizing and non-ionizing radiation • Most chips will latch up or fail • REXIS does not use latching chips • CCDs degrade instead • Non-ionizing radiation will displace silicon atoms from crystal lattice and create electron traps • Decreases charge transfer efficiency (CTE) in CCDs, which shows up as a gain decrease • To first order, CCDs will record sum of actual and gain-shifted peaks • As gain shift increases with damage, spectral lines get broader Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  38. Radiation Damage • Spectral lines widen until science requirements are violated • Charge injection will delay this • Data from Astro-E2 relates change in CTE to radiation dose for REXIS CCDs • By finding lowest tolerable CTE we can find the maximum acceptable dose and size the shield • Current depth: 5.5mm (TBR) Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  39. Flexprint Cable Design

  40. Flexprint Cable Requirements • Low mass • High thermal resistance • Circuit remains out of CCD FoV • Mounts to detector assembly • Must survive launch • Must provide strain relief on flexprint • No vias on CCD end • Kavli has shown via failure under thermal cycling • Shielded video output/frame-store lines • Glenair 890-011 37-pin Nanominiature connector is current baseline • .725”(L) x .125” (W) x .255”(D) • Looking into AirBorn connectors for compatibility with existing detector electronics Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  41. Flexprint Cable Design • This circuit delivers analog video through output JFETs to the detector electronics • Also contains reverse-protection diodes and filter capacitors, plus an RTD for monitoring CCD temperature • Four layers at rigid connector end, one layer in flexible middle and rigid CCD end • Smaller and more compact than Astro-E2 flexprint • Output connects to electronics box via jumper cable • Routed either through DASS or out truss side panels—trade still open 4-Wire RTD 2-56 Through Holes Output Protection Diodes Connector Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  42. Flexprint Cable Design Strain Relief Zones • Frame-store and output video lines are shielded at entry to the rigid connector end • Does not appear in Gerber files • Mechanical design of flexprint has 1.1mm bend radius for strain reliefs at CCD end and in the middle • Is this enough strain relief? Shielded Zone Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  43. Scheduling and Cost

  44. Engineering Model Scheduling Regolith X-ray Imaging Spectrometer – REXIS – Detector Packaging Peer Review September 18, 2012

  45. Engineering Model Cost

  46. Questions?

More Related