====== Telecon 20171010 ======

Attending:  Jamie, Brian, Julian, Kris, Shaul, Karl, Qi, Roger, Jeff F.

__Agenda:__ 

  * {{:large_and_small_apertures_20171010.pdf|Large and small aperture presentation}}
    * optical systems: large aperture and small aperture options (Qi)
    * noise model and focal plane options (for large and small apertures) (Young)
  * Scan pattern (Gorski, Delabrouille)


__Notes:__


Status of optics (Shaul)
  * Matrix of larg v. small and open v. crossed.
    * large, open is baseline.  Noise, weights, etc calculated and posted on Imager wiki page
      * current version is un-optimized optics.  **A/I** UMN to use coma corrected and optimized open dragone. Recalculate noise.
    * small open and crossed designs work. Noise is calculated.
      * What alpha, beta angles are allowed?  **A/I** UMN to investigate.
      * Motivation is to have a cost savings option
        * Question from group: Does cost truly scales with aperture? Or is complexity the bigger issue.
          * focal plane size, detector count, readout and power demands, etc. likely bigger driver.
          * Suggested: Are there other rocket options? If the payload is smaller this could be a savings location.
            * Likely that Falcon 9 is only choice.
    * large, crossed dragone still has sidelobe problems.  1.2m version is promising.  A work in progress.
  * Note: Al says PIXIE can observe with same scan strategy as imager.  Kris would like to see the details of how this works.

50 cm systems (Karl/Qi)
  * 3x hit in resolution
  * 4 K and 30 K systems.
  * 4 K gives better performance than baseline at high frequencies, ~> 300 GHz.
  * 30 K is worse at all frequencies.
  * Is > 300 GHz sensitivity very useful?
    * May not increase dust removal accuracy much.
    * High frequencies are largely for extra-galactic science and galactic dust science.
      * The 3x lower resolution may make these unappealing anyway.
        * General opinion that the resolution loss is a high price to pay.  
        * Makes the science less appealing.  This makes it less likely to appeal to Decadal Panel
  * open dragones (30 K and 4 K) are smaller and fewer pixels than baseline.
    * likely a cost savings.
    * 4 K assumes cooling an additional ~1m mirror, which adds cost.

Scan (Kris)
  * Higher spin rates a concern. Data rate may become an issue.
    * Past work by Amy said telemetry not an issue.  May need to be revisited.
  * possible spin rates in the 1-3 RPM range.  Being studied at JPL, Amy organizing.
    * needed for 1/f, data rate, ect.
  * **Kris** to present concerns with scan next week.