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Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”)

Design Review Spartan IR Camera E Loh, Physics-Astronomy Department, Michigan State University East Lansing, 22 May 2001. Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”) Optical alignment (ref: “Alignment” & “SOBER”) System Design & Electronics (ref. “Electronics”)

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Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”)

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  1. Design Review Spartan IR CameraE Loh, Physics-Astronomy Department, Michigan State University East Lansing, 22 May 2001 Science Goals (ref: NSF proposal) Optical Design (ref. “Optical Design”) Optical alignment (ref: “Alignment” & “SOBER”) System Design & Electronics (ref. “Electronics”) Mechanical Design (ref. “Mechanical Design”) Budget & Schedule (ref. “Budget & Schedule”)

  2. The Team • Jason Biel, technician • Measurements for vacuum design • Electronics designer & technician • Mike Davis, graduate student • Optics • Owen Loh, Okemos High, volunteer • Finite-element analysis • Drafting • Tom Palazzolo, head, Phys-Ast shop • Mechanical shop, design advice, contact for mechanical designers & job shops • Jack Baldwin, Brooke Gregory, Ron Probst, Dan Edmunds, Phys-Ast EE, advisors • E Loh DR SOAR Spartan IR Camera

  3. 1. Science Goals Tip-tilt corrected imaging in the J, H, & K bands • To cover the wide, corrected field (5’) • To resolve FWHM of median seeing (0.15–-0.23”) • To resolve high-contrast features at the diffraction limit (0.08” @H & 0.11” @K) DR SOAR Spartan IR Camera

  4. Point-spread Function with Tip-Tilt Correction • Point spread function is not a gaussian • Diffraction spike Top quartile Median seeing DR SOAR Spartan IR Camera

  5. Image Width • Sub 0.5” images w/o tip-tilt • 0.15-0.23” images w tip-tilt • Telescope optics preserves images Telescope degradation. Goodyear CDR DR SOAR Spartan IR Camera

  6. 2. Optical Design • Concept • Image Quality • Tolerances DR SOAR Spartan IR Camera

  7. Optical Concept • Requirements • Large number of pixels [ 2 x 5’ / 0.08” = 7500 pixels ] • Large telescope image [ 5’ x 4.2m x 16 = 100mm square] • Rockwell 2048x2048 HgCdTe detector • 4 detectors & 7500 pixels  two plate scales • Reflective optics  large telescope image • Off-axis collimator & camera mirror • Parent design: two paraboloids • Perfect image for 1:1 & small field • Real design for change in plate scale • Adjust conic constants, distances • Field flattening lens DR SOAR Spartan IR Camera

  8. Design • Four 20482 detectors • Two plate scales: 0.08 & 0.04”/pixel • 20 filters near pupil • Focal plane mask • coronagraphy • spectroscopy DR SOAR Spartan IR Camera

  9. Image Quality: Spot Diagram • 9 Field points in a grid. Corners are corners of 4 detectors. • H band Airy disk f/11 f/21 DR SOAR Spartan IR Camera

  10. Image Quality: Strehl Ratio • 9 Field points in a grid. Corners are corners of 4 detectors. • Strehl is very high for diffraction sampled cases, f/21 in H and K bands Sampled for diffraction limit DR SOAR Spartan IR Camera

  11. Tolerances • Error budget • Loss of Strehl of ~0.07mag • Alignment • Manufacturing DR SOAR Spartan IR Camera

  12. Alignment Tolerances 6mil 1mil over 6in DR SOAR Spartan IR Camera

  13. Focal lengths are absorbed in focus SORL can manufacture conic constants Surface irregularity Peak-to-valley is l/16 to l/4. l = 633nm Manufacturing Tolerances DR SOAR Spartan IR Camera

  14. Align at room temperature with point source, SOBER, & CCD SOBER f/16 beam Move SOBER & shift stop to mimic pupil at 10m z stage mimics curved focal surface of telescope Tolerances 1mm & 1º Image in IR? TBD Alignment with SOBER LED & pinhole Lenses z stage Sliding stop R- stage ISB surface Soar Beam Simulator DR SOAR Spartan IR Camera

  15. Intensity of 9 field points indicates error Alignment Indicator Y-decenter of collimator 0.34mm X-tilt of fold #1 of 0.2mrad DR SOAR Spartan IR Camera

  16. Test of Alignment Defect: I7<I9 x-position of collimator; wrong y-tilt of lens; right Defect: I5<I8 x-tilt of fold #1 DR SOAR Spartan IR Camera

  17. 3. System Design & Electronics • System • Electronics • Software • Motors • Vacuum DR SOAR Spartan IR Camera

  18. System Design Legend Camera Controller Detector Fiber optic In control rack Camera Controller Camera Controller Detector PC Camera Controller Detector Umbilical NI 6533 Camera Controller Detector RS232 RS232 Stages Motor Controller DeviceNet RS232 Pressure Sensor In vacuum On camera Ethernet Custom Observer Data Archive Telescope Control Elsewhere Commercial DR SOAR Spartan IR Camera

  19. Umbilical Card Camera card One of 4 channels shown • Provenance • CCD system Fiber-optic tranceiver Master clock Logic Analyzer Serializer deserializer Test pod For debugging Existing CCD Software on Alpha FIFO NI 6533 interface DRV11 interface In FPGA NI 6533 Laptop-type power supply DR SOAR Spartan IR Camera

  20. Camera Card • Provenance: CCD camera • 4 analog channels for 4 quadrants Timer & clock generator Buffer Logic Analyzer Amplifier &16-bit ADC (2 12-bit ADC) Instruction Test pod Detector Laptop-type power supply Fixed voltages (digital pot) Serializer deserializer In FPGA Diodes Temperature Fiber-optic tranceiver Phase-locked loop Umbilical card DR SOAR Spartan IR Camera

  21. Umbilical Card • 3U 100160 mm • Tested w/ CCD software To existing computer Fiber optic to 4 detectors NI 6533 FPGA 7V in 160mm To logic analyzer DR SOAR Spartan IR Camera

  22. Camera Card • 3U 100160 mm • Low crosstalk • 5-mil between signal & ground layers • Delivery expected in 2 weeks • 2.5ms/pixel • 4 channels • Power: 1.4W 7V in Signal chains Fiber optic Flex cables to detector Neck between analog & digital circuits FPGA DR SOAR Spartan IR Camera

  23. Noise • Detector noise is about 10e–; noise on amplifier glow is 5e–. • Electronics noise is 6e–. • Coupling from a saturated channel is about 2e–. • Coupling from clocks on cable is large. • Sampling signal must wait 100ns after clock transition. DR SOAR Spartan IR Camera

  24. Detector Card • Card butts on 2 sides • Connects to camera card with 5 flex cables, which are thermal resistors. • 3 layers with 5-mil G10. Flex cables Electrically isolated straps to nitrogen dewar ZIF socket Detector DR SOAR Spartan IR Camera

  25. Software • Functions [copied from Optical Imager] • Control detector • Scripting • Communicate with motors • Communicate with telescope control system • Communicate with user • ArcView • Used for all SOAR instruments • CTIO will debug ArcView with Optical Imager, the commissioning instrument • LabView, “visual programming” • Independent of hardware  obsolescence is obsolete • Self documenting • Easy to do. ArcView costs < 1 man-year DR SOAR Spartan IR Camera

  26. Software Tasks • Design • Use commercial parts with LabView drivers • Modify ArcView • Computer send commands and receives data from camera controller through NI 6533 card. • Replace Leach controller & driver with NI 6533 card. • Our card has a 4k sample FIFO • 0.6ms margin for 4 detectors reading simultaneously • Write software for summing pictures • Change software for formatting picture • Change motor controls • Add temperature & vacuum sensing DR SOAR Spartan IR Camera

  27. Motion • Phytron stages DT-90 & MT-85 • Vacuum compatible • Stepper motor • Indexing switch • Limit switches • Open loop; controller stores position • Controller • RS232 to computer • LabView • Heat • Shutoff power? Cooler? DR SOAR Spartan IR Camera

  28. Vacuum Measurement • Granville-Phillips ion gauge • Computer readout via DeviceNet • LabView • 12W; need to shut off DR SOAR Spartan IR Camera

  29. 4 Mechanical Design • Cryogenic optical box • A-frame attachment to vacuum enclosure • Analysis of flexure • Vacuum enclosure • Analysis of stress • Transfer of forces from A-frame to instrument mounting box (ISB) • Mechanisms using warm stages • Layout • Proof of concept • Flexure • Heat load • Operating temperature of stage & optics DR SOAR Spartan IR Camera

  30. Cryogenic Optical Box • Symmetric box having two plates equidistant from optics. • Gravity vector is in plane. • Optics supported by both plates. • Torque perpendicular to plates • Box is attached near focal surface of telescope • Rotation of optical box causes no boresight error. DR SOAR Spartan IR Camera

  31. A-frame Attachment • Connect cold optical box to warm vacuum enclosure • Complies with shrinkage of optical box • Web weak in z • Hold box w/o sag • Web strong in x & y • Heat load is 0.7 W for 4 A-frames. Weak for thermal compliance Strongest; max sag: 14m or 0.04” Al leg G10 web G10 ring Section removed for clarity Bolt to optical box Bolt to warm vacuum enclosure Safety stop DR SOAR Spartan IR Camera

  32. Rotation of Optical Box • Gravity parallel to mounting plate. (Causes boresight error) • First approximation • Optical box rotates 40mrad as a unit • Sag is 14m at telescope focus. • More precisely • Error is greater for gravity perpendicular to mounting plate. • Rotation within box is 2.3mrad peak-to-peak • Boresight shifts 0.007”. 0–155mrad 34–46mrad DR SOAR Spartan IR Camera

  33. Vacuum Enclosure • Aluminum plate, mostly 1/2” • Max stress is here • Max is tensile strength / 2.2. • Code for pressure vessels is 3.5. • Is this OK? DR SOAR Spartan IR Camera

  34. Transfer of Forces to Bolts on ISB • Does the vacuum enclosure transfer forces between the A-frames and the bolts on the instrument mounting box (ISB) without sag? Yes. Sag is 2m. Optical box Bolts to A-frames Bolts to ISB Sides of vacuum enclosure DR SOAR Spartan IR Camera

  35. Mechanisms • Two filter wheels • Loose tolerances • Focal-plane mask • 300m along optic axis, 18m in transverse direction • Collimator insertion • Tilt 5mrad (1”) as instrument turns for boresight with tip-tilt sensor • Camera mirror insertion • Tilt 5mrad as instrument turns • Rotate lens-detector by 112.7±0.6mrad • Tilt 0.2mrad (30m over 150mm) • Move lens-detector assembly for focusing Difficult DR SOAR Spartan IR Camera

  36. Layout of Mask & Filter Wheel • Load is balanced  Easy to meet tolerances. • Phytron DT-90 rotational stages • Integrated stepper motor, indexing switch, limit switch • Spring constant 2mrad/(N-m). Wobble is ±15mrad (Clarification needed.) Optical box Rotation stage Vacuum enclosure Mask wheel Filter wheel DR SOAR Spartan IR Camera

  37. Layout of Mirror Insertion • Mirrors must be balanced to meet 5mrad tolerance. Vacuum enclosure Rotation stage Mirror Optical box Counterweight Background mirror f/21 collimator f/11 camera DR SOAR Spartan IR Camera

  38. Proof of Concept: Insert f/21 Mirror • Requirements. Cold mirror — warm stage — cold optical box • Support with tilt < 5mrad • Keep mirror cold • Keep stage warm • Minimize heat load • Comply with thermal expansion • Precepts • Balance load • Use G10 A-frames to control conduction & comply with thermal expansion • Shield stage from cold to control radiation • Allow stage to absorb radiation from warm vacuum enclosure DR SOAR Spartan IR Camera

  39. Mirror Insertion 4 A-frames f/21 collimator Center mass Counterweight DT90 rotational stage 4 A-frames between stage & bracket (hidden) Bracket attaches to optical box DR SOAR Spartan IR Camera

  40. Results for f/21 Insertion • A-frames have 1x1x5mm legs. • Balance within 1mm. • Wrap stage in 10 layers of aluminized mylar. • Results • Conduction is 170mW • Tilt is 2mrad; tolerance for boresight alignment is 5mrad. • Sag with mirror vertical is 8m; tolerance for internal alignment is 0.8mm. • Sag with mirror horizontal is 4m; tolerance for focus is 15m. • Temperature of mirror is 88K. • Temperature of stage is 2K below ambient. (Area of radiator is 10% that of the stage.) DR SOAR Spartan IR Camera

  41. 5 Budget & Schedule • Budget • Contingency • Descope • Risk to budget • Schedule DR SOAR Spartan IR Camera

  42. Budget • Not allocated or charged: Majority of electrical engineer, mechanical engineer, project management, drafting (done so far), and finite-element analysis. DR SOAR Spartan IR Camera

  43. Contingency vs Remaining Tasks • Tracking of tasks since budget of Aug 2000 • Electronics design is 17% over budget. ($5k of $29k) • Design of telescope simulator is 65% over budget. ($5k of $8k) • Optics design is 31% under budget. ($6k of $19k) • Overall budget dropped $100k because mechanical design firmed up, optics shortened, and mirror quotes dropped. • Contingency is 36% of remaining tasks. DR SOAR Spartan IR Camera

  44. Descope • Descope 2nd plate scale, J, H, K, Ks filters only, spectroscopy & coronagraphy. • Descope will be treated as contingency. • Descoped items will be added as contingency allows. • Possible formula: spend if Budgeted Contingency > 1.5 Actual Contingency DR SOAR Spartan IR Camera

  45. Risk to Project • Number of risks covered • A big item is $100k. • Labor for optical box, mechanisms, enclosure is $70k with $30k contingency • Drafting: 3 mo. • Internal shop: 7 mo. • External shop: 1 mo. • Technician: 6 mo. • Contingency, $193k, covers 2 big risks • Descope, $175k, covers 2 big risks. • Descope & contingency  remaining tasks of descoped instrument DR SOAR Spartan IR Camera

  46. Schedule Overview DR SOAR Spartan IR Camera

  47. Detector • Multiplexer & engineering-grade device delivered. • Long slack time before science-grade detector is needed. DR SOAR Spartan IR Camera

  48. Electronics • 7 mo. slack DR SOAR Spartan IR Camera

  49. Optical Box, Enclosure, & Mechanisms • Optical box & enclosure will soon be a critical task. • Plans for mechanisms have changed. • Swales Aerospace’s estimate is 3 times higher than that of 1998. • New plan is to purchase high quality, warm stages & design non-precision parts. • Short slack. DR SOAR Spartan IR Camera

  50. Optics • Optics & filters are behind schedule. • Estimated time is 2–3 times longer than vendors’ quotes of 26 weeks, because of word-of-mouth tales. • Schedule could be made up with immediate requisitions and on-time deliveries DR SOAR Spartan IR Camera

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