====== Telecon 20171003 ======

Attending:  Al, Roger, Jacques, Jeff F., Shaul, Karl, Qi, Ranajoy, Brian \\

__Agenda:__ 

   * Imager + Spectrometer (Karl) {{:pico_and_pixie_20171003.pdf|Spectrometer Slides}}
   * Focal plane + noise model (Karl) {{:pico_fdm_noise_model_status_20171003.pdf|Noise model slides}}
   * optical system (Qi) {{::crossdragone_d100cm_f4.5_fov10deg_10032017.pdf|}}
   * Scan parameters (Shaul (for Kris))

__Notes:__

Imager + Spectrometer (Karl)
  * mini-PIXIE, 20 cm mirrors, 10x38x48 FTS
    * Same boresight angle
    * Share same cooling system
  * mass of mini-PIXIE, ~20 kg in total, barrel contributes most of it.
    * detector assembly is  < 1kg
  * Imager focal plane mass: not known yet.  **A/I** Brian to ping Roger.
  * with Open Dragone
    * same boresight as Imager, although not necessary
    * quite small, fits easily
  * with Cross Dragone
    * boresights don't match, but scan pattern does (beta is same in both cases)
    * Al: it’s okay. There will be some time delay between imager and spectrometer scans, but it does not matter much.
  * Boresight and spin axis
    * It’s not required to have boresight along the spin axis. PIXIE did plan to align with spin axis,allows fitting of Q/U of each pixel before moving to next pixel.
      * It’s okay to not do this. The current main driver is the sky coverage.
  * FTS box is not required to be with optical tubes, it can be anywhere as long as an optical path exists.
    * The detectors can even be on the Imager focal plane.
  * Tradeoffs: 
    * question of cost, might limit imager size
      * Current primary costs: cooling,  telescope,  readout, and detectors
      *  marginal costs when increasing
  * Aside:
    * Check Open Dragone fit, to see if there is conflict between mirrors and cone.  **A/I** UMN to check.
    * structural issues with support for mirrors?
      * Brian: JPL is working on this question.

Noise Model (Karl)
  * Biggest change: safety factor → 2
  * Squid is the largest contribution
     * Using 3.5 pA/rt(Hz).  **A/I** Karl checking with Hannes at NIST about proper number to quote.
  * Roger: all these numbers are fine.
  * Cross check between Karl and Roger.  noise matches except for:
    * bunching noise, a factor of 2
    * bunching noise does not contribute too much, ~15%; all other are same
    * **A/I** Karl, track down 2 in bunching noise.  Possibly polarization related.
  * Richard’s correction on Coma
    * more detectors at high frequencies, for both Open and Cross Dragone
    * can weight CMB frequencies more heavily.
  * Can optimize edge taper
    * including correlated photon bunching noise from CMB (correctly) and mirrors (incorrectly, but with factor of 2)
      * Next step: Karl to implement full correct calculation for mirrors.
    * best mapping speed is near 2 F lambda.  Current Open Dragone pixels are at 2 F lambda.
 
Optics (Qi)
  * New cross-dragone with +/- 10 deg FOV
    * f/4.5, 1m aperture, requires deployable shields.
    * deployable shields should be V-grooves as well. leave design to thermal engineers. Just put place-holder in current model
  * both cross dragones' focal planes view sky after 1 reflection off tertiary
  * total sensitivity is better than Open dragone (baseline)
    * assumes full telescope is 4 K
    * also number of detectors is larger.  3k for Open, 7k and 11k for new crossed designs.
  * How does larger f-number give better sensitivity?  Opposite what is normally said.  From CORE, increasing f-number gave no benefit since pixels grew at same rate focal plane grew.
    * **A/I** Karl/Qi to sort out scaling of focal plane with f-number.

Scan delayed to next week.