Preparing the next Teamx-I – By learning from previous one.
response from TeamX, 90 slides on sub-systems.
Section summaries in presentation. No cost discussion today. 15 pages in each sub-system.
Need to do homework on some items before next TeamX
Systems:
I&T will be analyzed in next teamX, was not analyzed here. Still marked as weakness due to complexity.
telescope systems at various temperatures (40 K, 4 K, 100 mK) make testing the end to end alignment challenging.
Will continue discussion with Bill J. and Tomo next week.
Definition: OGSE, optical ground support equipment. Testing equipment that doesn't fly.
Future threats: add “cost of cooler” Comments: this is a cost threat more than a technology threat
FP and detectors
Str: TES have ground based heritage. detector 1/f shown to be acceptable. future options for MKIDS.
Roger will lead 1/f story for final report. Tomasso is running gain variation and per rotation calibration options (assuming 10 mHz 1/f knee)
General comment: detector 1/f isn't the only important 1/f term. Other issues (temperature stability) may dominate.
Only modulation is sky rotation and scan speed.
Weak + future threat: Impact of cosmic rays.
Jeff Fillipini has looked into this. As has Roger. Roger will lead report summary.
Work to reduce impact is also being done at Berkeley.
Hannes: What about optical coupling?
This hasn't been finalized. Roger: coupling via lenslets hasn't been shown at high frequencies.
Electronics
Weak: Temperature limits.
TeamX assumed what is currently used. but would used space qualified electronics, so this won't be an issue
Amy: TeamX usually gives reports to science teams, not reviewers. Amy is talking with TeamX/NASA to point out that reports need to be crafted so a general review audience understands the issues. Easily address comments like this risk getting blown out of porportion.
Optics:
Weakness: maturity of mechanical and thermal design of focal plane.
this work is in progress for next TeamX
Thermal:
3HE, testing for MIRI was expensive. even if those tests done for PICO, < $1M so ignore it.
Cost is large. $900M for cooling, 50% of instrument cost. This is largest thermal risk point.
Mechanical:
Strength: scalable, simple, nothing radical
Weakness: optics alignment complex.
Address by pointing out WMAP and Planck have done this successfully, should not be weakness, will address in next TeamX
Configuration
Threat: No volume margin for primary mirror inside the shade
Shaul: this is being worked on, should have some margin by next TeamX
Focal Plane V4 (Karl)
simpler focal plane, 2 wafer sizes.
roughly 1000 more detectors at high frequency. Sensitivity same. (0.61 uK vs 0.62)
FP could go further out in X,
Current reflectors need to be larger if we increase focal plane; but we can increase focal plane with current strehl limits.
Central wafer issues:
multi- and mono band pixels coexist
insufficient bond pads for number of bolos on this wafer.
4000 bolos on 4“ wafer. Hannes: fit ~2000 bolos on 6” wafer in past.
We are assuming 100 um per bond pad. 4 inch wafer.
2 mm between tiles, may be too small. For EBEX, ~5 mm. Karl to check
Roger to get spacing number from recent BICEP arrays
Kris: We need to think about how pixels are aligned to scan direction and how this impacts map making.
are we making single detector maps? multi detector maps? do pixels need to follow the same path on the sky as a neighbor?
This may require slight rotations of the focal plain.