Differences

This shows you the differences between two versions of the page.

--- imagerteleconnotes20180124 [2018/01/24 15:06] – kyoung
+++ imagerteleconnotes20180124 [2018/02/01 11:29] (current) – bcrill
@@ Line 23: / Line 23: @@
 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: 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.
+  * 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)
@@ Line 48: / Line 56: @@
     * page 19, calibrations done for Planck shown.
       * 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.
-      * 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.

User Tools

Differences

Page Tools