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imagerteleconnotes20180124

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imagerteleconnotes20180124 [2018/01/24 15:06] – kyoungimagerteleconnotes20180124 [2018/02/01 11:29] (current) – bcrill
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 Attitude control Attitude control
-  * Bill?: points out having 2 or more scan modes would have been very helpful for Planck. Break time constant and beam shape degeneracies.+  * Shaul: Pointing Control is how well spacecraft points at a direction; Pointing Knowledge is how well we know where it points at; Pointing stability is how stable pointing is in terms of changing rate. 
 +  * Ben: thinking about map to understand definitions of pointing knowledge, control and stability; that's how engineers talk about them. 
 +  * PICO rquires 6 arcsec pointing knowledge, which about 1/10 of the smallest beam. 
 +  * Shaul thinks we do not need more than 1 degree of pointing control. 
 +  * Bill: pointing stability is associated with spin; we may also think about how stable spin axis is aligned with star camera. 
 +  * Bill: points out having 2 or more scan modes would have been very helpful for Planck. Break time constant and beam shape degeneracies. Shaul: right now we fix on having only 1 scan strategy, but it can be discussed.
   * Jacques: 3 star sensors garuntees 1'' pointing knowledge. This is the easiest and likely to be reasonable in cost.  Worth just using 3.   * Jacques: 3 star sensors garuntees 1'' pointing knowledge. This is the easiest and likely to be reasonable in cost.  Worth just using 3.
   * Jacques: Thoughts from CORE,   * Jacques: Thoughts from CORE,
-    * Pointing control is to eliminate gaps in map. 24'' ensures no gaps in single detector maps. +  * Pointing control is to eliminate gaps in map. 24'' ensures no gaps in single detector maps. 
-    * 24'' was technically doable for Core with reaction wheels.  Should check if that is true for PICO, if the engineers don't scream, then stop worrying about it. +  * 24'' was technically doable for Core with reaction wheels.  Should check if that is true for PICO, if the engineers don't scream, then stop worrying about it. 
-      * Shaul: reaction wheels are current assumption for PICO+  * Shaul: reaction wheels are current assumption for PICO
   * **A/I** Shaul to check with Amy about 24'' control with wheels.   * **A/I** Shaul to check with Amy about 24'' control with wheels.
 +
 +  * Additional note from Brendan: Planck achieved 2 arcsecond rms pointing reconstruction [[https://wiki.cosmos.esa.int/planckpla2015/index.php/Detector_pointing|(see Planck Explanatory Supplement)]]
 +
  
 I + T, lessons from Planck, options for PICO. (Tomo) I + T, lessons from Planck, options for PICO. (Tomo)
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     * page 19, calibrations done for Planck shown.      * page 19, calibrations done for Planck shown. 
       * spectral response not fully measured on ground, can't be sense        * spectral response not fully measured on ground, can't be sense 
-    * Shaul: has Planck over tested any optics?+    * Shaul: has Planck over tested or under tested any optics?
       * Bill: most valuable was cold photogrammetry of flight optics. Other tests were of interest, but not as critical.       * Bill: most valuable was cold photogrammetry of flight optics. Other tests were of interest, but not as critical.
-      * Mirror material?  Bill: Silicon carbide. Jacques: Core proposal used silicon carbide, but now in doubt. carbide is expensive, machining challenge, large thermal contraction.  Aluminum is cheaper, easier. +      * Mirror material?  Bill: Silicon carbide, lower mass solution than aluminum. Jacques: Core proposal used silicon carbide, but now in doubt. carbide is expensive, machining challenge, large thermal contraction.  Aluminum is cheaper, easier. 
-        * Shaul: TeamX assumed aluminum mirrors. Silicon carbide may over run cost.  Aluminum cost around $10.+        * Shaul: TeamX assumed aluminum mirrors. Silicon carbide may over run cost.  Aluminum below $10M.
   * Discussion on hold until next week due to time.   * Discussion on hold until next week due to time.
  
imagerteleconnotes20180124.1516827984.txt.gz · Last modified: 2018/01/24 15:06 by kyoung

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