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private:teleconsnotes20171108 [2017/11/08 14:45] – hananyprivate:teleconsnotes20171108 [2017/11/08 16:09] (current) – kyoung
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 ====== Telecon Notes 20171108 ====== ====== Telecon Notes 20171108 ======
  
-Attendance:  \\+Attendance: Al, Shaul, Julian, Lloyd, Raphael \\
  
-Notes by:  Karl \\+Notes by: Karl  \\
  
 === Agenda === === Agenda ===
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   * Status of spectrometer decision; Please be prepared to opine on whether we should keep a spectrometer on the spacecraft at the possible expense of a reduction in the Imager aperture and sensitivity   * Status of spectrometer decision; Please be prepared to opine on whether we should keep a spectrometer on the spacecraft at the possible expense of a reduction in the Imager aperture and sensitivity
   * Emphasis of efforts in the near future   * Emphasis of efforts in the near future
 +    * Update Science Predictions, work on STM
 +    * Imager - prepare for TeamX (December)
 +    * Set up demonstration of component separation and systematics mitigation
 +    * Second workshop 
  
 === Notes === === Notes ===
 +
 +__Spectrometer conversation with Al__
  
 Hi Al, Hi Al,
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 scales as sqrt(time) and sqrt(etendu). scales as sqrt(time) and sqrt(etendu).
  
-  * If there were no foregrounds, reaching 5 sigma requires 13x PIXIE sensitivity. +  * If there were no foregrounds, reaching 5 sigma requires 13x PIXIE sensitivity. This could be PIXIE with 153 months of observations, or a larger Super-PIXIE spectrometer with (say) 4 sets of mirrors and 54 months observation. 
-  This could be PIXIE with 153 months of observations, or a larger Super-PIXIE + 
-  spectrometer with (say) 4 sets of mirrors and 54 months observation.+  * Foregrounds seriously degrade the prospects of detection.  A rough scaling is that the synchrotron amplitude and spectral index need to be measured to 0.1%.   Achieving this with PIXIE's baseline 15 GHz spectral bin width requires 390x PIXIE sensitivity for a worst-case scenario (no help from spatial information) and ~80x PIXIE sensitivity for a more realistic scenario with foreground cleaning such as SMICA that includes spatial information.  This could be achieved using some combination of longer integration time (10 year mission like WMAP), fatter beams (7 deg tophat like FIRAS) and multiple cloned FTS assemblies (12 copies). 
 + 
 +  * Foreground subtraction is substantially improved by adding channels below 30 GHz.  Fourier transform spectroscopy is not ideal for such low-frequency observations, so this would better be addressed by adding an absolute photometer of some sort, sharing the same calibrator as the FTS.  Adding a low-frequency photometer could reduce the sensitivity requirement of the FTS from the 390x PIXIE sensitivity above to perhaps 30x PIXIE. One such scenario would have 4 years integration, 5 deg beams, and 3 copies of the FTS assembly. 
 + 
 +Much of this analysis is captured in https://arxiv.org/pdf/1705.01534.pdf. It seems that a Super-PIXIE that includes a low-frequency photometer could indeed get a reliable detection of the Silk damping signal. 
 + 
 +Cheers, Al 
 + 
 + 
 +__General notes__ 
  
-  * Foregrounds seriously degrade the prospects of detection.  A rough scaling +Foreground Workshop -- skipped everyone online knows already.
-  is that the synchrotron amplitude and spectral index need to be measured +
-  to 0.1%.   Achieving this with PIXIE's baseline 15 GHz spectral bin width +
-  requires 390x PIXIE sensitivity for a worst-case scenario (no help +
-  from spatial information) and ~80x PIXIE sensitivity for a more realistic +
-  scenario with foreground cleaning such as SMICA that includes spatial +
-  information.  This could be achieved using some combination of longer +
-  integration time (10 year mission like WMAP), fatter beams (7 deg tophat +
-  like FIRAS) and multiple cloned FTS assemblies (12 copies).+
  
-  * Foreground subtraction is substantially improved by adding channels below +Spectrometer status 
-  30 GHz.  Fourier transform spectroscopy is not ideal for such low-frequency +  * time for final tally of opions. Shaul will poll those not on call. 
-  observations, so this would better be addressed by adding an absolute +  * decision of inclusion of spectrometer at possible expense of imager aperture and/or sensitivity. 
-  photometer of some sort, sharing the same calibrator as the FTS.  Adding +  * measurement of silk dampening at 5 sigma?  needs Super-PIXIE or larger. details above. 
-  a low-frequency photometer could reduce the sensitivity requirement +  * Al: mini-PIXIE valuable insurance.  garuntees high S/N dust foregrounds. Also different systematics especially on large scales.  Gives 2 methods to measure reionization bump which is more compelling.  Reionization bump is major science goal. 
-  of the FTS from the 390x PIXIE sensitivity above to perhaps 30x PIXIE. +  * Raphael: Agree we need Reionization bump. But worry about loss of resolution in small case --> can't delense with PICO alone.  What about just probe spectrometer? 
-  One such scenario would have 4 years integration, 5 deg beams, and +    * Al: should get reionization bump cleanly. But can't delense. So need ground synergy to get recombination bump down to r ~ 10^-4.  Risk because don't know what ground will be able to do. 
-  3 copies of the FTS assembly.+       * Spectral distortions?  Recombination lines at 2-3 sigma. Not a blind detection.  Silk dampening out of reach for FTS.  Possible with additional photometer, see above. 
 +         * spectral lines are easier than silk dampening do to different foregrounds. silk damping more limited by foreground removal. 
 +     * Shaul: How well does probe-PIXIE do low frequency foregrounds? Al: depends on your bandwidth choices to get lowest frequencies. Then FTS does poorly in lowest bands.  Need a low frequency photometer. 
 +  * Shaul: Early on look at Super-PIXIE concluded that benefit was only recombination lines. Not a large gain over $250M PIXIE. We can reconsider this. 
 +  * Raphael: Goal seems like B-modes + X. What is X in spectrometer case?  What are differences in r measurement for various instrument cases? 
 +    * Al: comes down to what scales matter most for inflation science.  Large imager overlaps in l with S4, l > 50 will be down from ground.  Prime reason for space is lowest l's. Spectrometer focuses almost exclusively on lowest l's, and get spectral distortions which can't be done from ground.  Goal is see reionization bump and overlap only somewhat with ground l range.  Review panel of PIXIE thought there was no strong driver for space observation as r would be seen from ground. 
 +      * Julian/Raphael: best imager can do 10x better than ground.  This could be arguement.  Then have legacy full-sky maps for community.   
 +  * Raphael: Current STM largely mirrors S4. Reionization lines would be interesting. 
 +  * Lloyd: High frequency accessible from space is valuable. Resolution loss limits galaxy formation science, which is largest benefit at high frequency.   
 +  * Raphael: Combination seems weakest. They take away from each other.  
 +    * Lloyd: Agree, hybrid loses too much from both. 
 +    * Julian: Limits range of both. See concerns that you're doubling risk. 
 +    * Raphael: 1 benefit is hybrid could garauntee reionizaiton bump.  Don't know if imager alone can get this yet. 
 +  * Lloyd: looks like spectrometer doesn't add a lot. Imager has sufficient frequency bands to control dust. 
 +  * Shaul: hybrid is concerning. We don't know if spectrometer is critical so its insurance may not be needed. Science loss is large.  For now, keep large imager as this gives most science deliverables.  Hybrid does worse in science deliverables than either single case. 
 +  * Shaul: For now, move to TEAM-X with large imager.  If engineering resources allow can broach idea of combination. See how the costs look.  Will contact others, can still entertain other options in future. 
 +    * R: Does r forecast exist for a Super-PIXIE? **Al** will provide estimates. 
 +      * R: such a mission is complete complement to ground observations.
  
-Much of this analysis is captured in https://arxiv.org/pdf/1705.01534.pdf +Efforts in near future 
-It seems that a Super-PIXIE that includes a low-frequency photometer +  * new focal plane designed with 2x sensitivity over V2.4 
-could indeed get a reliable detection of the Silk damping signal.+    * update new science predictions 
 +    * sensitivities are posted on imager wiki, but not fully released.  Format needs to be cleaned up.  total map noise 0.66 uK*arcmin.  R: like S4 on full sky. 
 +  * demonstrate component separation and systematics mitigation 
 +    * need some type of pipeline to show imager can get to predicted r levels.  Given foregrounds. Even a crude method is needed.  Only ~6 months remaining. 
 +      * Shaul: Focus on 3 most concerning systematics (from WG) since we're time limited.  So won't do full systematics review. 
 +      * Foregrounds component separation? What people do we have? 
 +        * Julian: 3 parts: 1-Define inputs, sky model and mission model. 2-run simulations. 3-analyze those simulations for parameter estimation. 
 +          * Foregrounds workshop should give inputs. 
 +          * Andreas will have time to generate maps.  
 +          * Not clear who would analyze maps for science numbers. 
 +             * if just r people exist who have done this (Raphael: code may not be ready for full sky.  Will test in short term.  May need to update estimator.) 
 +             * if want foreground maps need more people.  Not clear who would do this. 
 +               * R: if reconstructing foregrounds you pay a penalty on r. can do 2 analyses seperately.  Have codes to do foregrounds reconstruction and can run some. 
 +        * Shaul: We can pay someone to dedicate to foregrounds. Or use data challenge via community. 
 +          * R: Seems like workshop is beginning of this effort. The establishment of sky model at workshop is important. 
 +          * Shaul: concerned focus after workshop may drift away. Might need a person dedicated to this task.  Anyone know of a person who wants to work on this for ~6 months on this? Funding exists. 
 +          * Julian:  If money exists can get more of Andreas Zonca time. 
 +            * Andreas Zonca worked on Planck LFI. Generating, analyzing simulations.  He's at San Diego supercomputing center. Half of his time (~$80k) is dedicated to running TOAST simulation relating to S4.  Julian could buy more of his time and focus him on probe. Expertise is on preparing sky models, less (but some) expertise on analyzing for parameters. 
 +            * Shaul: Check in with Charles and JPL on funding. 
 +        * Shaul: Also need to do a small study on probe timescale, not get dragged into the complete study for a final satellite mission.
  
-    Cheers, 
-     
-        -- Al 
  
private/teleconsnotes20171108.1510173923.txt.gz · Last modified: 2017/11/08 14:45 by hanany

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