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| imagerteleconnotes20171114 [2017/11/14 12:52] – hanany | imagerteleconnotes20171114 [2017/11/21 10:03] (current) – hanany | ||
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| ====== Telecon 20171114 ====== | ====== Telecon 20171114 ====== | ||
| - | Attending: | + | Attending: |
| __Agenda: | __Agenda: | ||
| - | * Readout - drivers and open questions (Shaul) | + | |
| - | * Cooling - drivers and open questions (Shaul) | + | |
| * Cosmic Rays (Jeff) | * Cosmic Rays (Jeff) | ||
| - | * Grasp (Brad) | + | |
| - | * larger diffraction limited field of view (Hills) | + | |
| - | * Noise model (Young) | + | |
| - | * Deployable trade-off (Qi) | + | __Delayed to next week:__ |
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| * Scan angles (Gorski) | * Scan angles (Gorski) | ||
| + | |||
| + | __Notes:__ | ||
| + | |||
| + | New items to consider: | ||
| + | Readout - drivers and open questions (Shaul) | ||
| + | * Largely information from S4 | ||
| + | * Options: FDM, TDM, | ||
| + | * Two issues: wire count requiring cooling power, power consumed by warm electronics. | ||
| + | * Power use -- back of envelope 500 W for 10k detectors (FDM) | ||
| + | * TDM - more wires at 100 mK. lower power use ~ 100 W for 10k detectors | ||
| + | * None of this has been optimized for power use. ASICs have not been included. | ||
| + | * FDM has thought about this somewhat, **Shaul** to pull out numbers from LiteBIRD assumptions | ||
| + | * TDM, **Roger** will work on TDM estimates. | ||
| + | * 3rd option: microwave mux, in demo stage on MUSTANG. | ||
| + | |||
| + | Cooling - drivers and open questions (Shaul) | ||
| + | * Initial discussions with Chris Paine (JPL) | ||
| + | * primary 30 K (passive), may need to be tweaked to 40 K | ||
| + | * secondary 4-6.5 K (MIRI 3-stage PT, MIRI from JWST high TRL, as precooler for JT) | ||
| + | * currently at 6.5, could change to 4K. | ||
| + | * **UMN** calculate stop at 6.5 K. | ||
| + | * focal plane, 100 mK. | ||
| + | * **UMN** calculate sensitivity change if 50-150 mK? | ||
| + | * options: Continuous ADR (Goddard), single shot ADR from Duband | ||
| + | * Jacques: dilution option at TRL 4, present at space cryo workshop in April. engineering model in 2 years. | ||
| + | * To still consider: | ||
| + | * thermal loads from supports, wiring, coolers, optical loads from IR filters. | ||
| + | * How to implement IR filters -- stop is 1.2 m. Needs tech development. | ||
| + | * questions on how to get diameters, how large areas effect optics, etc. | ||
| + | * Needs a leader to interface with tech group: **UMN** to find point person. | ||
| + | * Chris Paine is in charge of loads based on structure being developed at JPL. Roger will provider wiring counts. | ||
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| + | Cosmic Rays (Jeff) | ||
| + | * mitigation in light of Planck. | ||
| + | * Jeff knows TDM. does anyone have FMD experience? | ||
| + | * cosmic rays are large signal. can have larger effect. | ||
| + | * **Qi** to work with Jeff to provide EBEX numbers. | ||
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| + | Grasp (Brad) | ||
| + | * get better primary illumination and sidelobe information. | ||
| + | * will calculate sidelobe response to moon, earth, etc. | ||
| + | * our 140cm Open dragone is in GRASP. | ||
| + | * ready for physical optics calculations. | ||
| + | * Richard: start with gaussian, but need to quickly consider actual beams from detectors. | ||
| + | * Kris: Planck was limited in what GRASP could do. Time intensive. Are there any time savers, efficiencies implemented? | ||
| + | * Shaul: Doing rough case for now. Just get location of significant sidelobes, polarization response for few detectors, other major features. | ||
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| + | larger diffraction limited field of view (Hills) | ||
| + | * More detailed notes here: {{:: | ||
| + | * adjusting mirrors to correct for coma. Done via Zemax optimization. | ||
| + | * plots of FOV at pixel frequencies. | ||
| + | * 10x area improvement at low frequencies. | ||
| + | * also can include curved focal plane. ~ 3m radius of curvature. ~ 1 cm shift at edge of FOV | ||
| + | * also astigmatism in X direction is cancelled. | ||
| + | * fov ~ 50% larger in area, some of this is at very wide X angles, would require larger mirrors. | ||
| + | * curved focal plane also slightly improves telecentricity. | ||
| + | * **UMN** to check if larger mirrors fit in sun shade cone | ||
| + | * Open optics have large distortion in Y as you move in X across the FP. | ||
| + | * square grid of points on sky end up in curved pattern on focal plane. | ||
| + | * you're calibrating to locate beams anyway, so not issue. | ||
| + | * need to check polarization effects. | ||
| + | * Crossed design doesn' | ||
| + | * lack of telecentricity affects stop illumination. | ||
| + | * curved FP improves this slightly over flat case. | ||
| + | * also needs to be checked in GRASP. | ||
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