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FourStar Image Motion Stephen Smee (410) 516-7097.

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Presentation on theme: "FourStar Image Motion Stephen Smee (410) 516-7097."— Presentation transcript:

1 FourStar Image Motion Stephen Smee (410)

2 FourStar CDR Optomechanical Design 18 October Instrument Flexure ●Goals Determine the image motion and defocue under a 1g load for a 15 deg. rotation of the rotator ●Modeling strategy Model vessel flexure, dewar sag, and camera module sag −Image motion due to camera module sag is 1.3:1 −Image motion due to vessel flexure and dewar sag is 1:1 −Defocus results from detector tilt and motion along the optical axis Superimpose results to calculate image shift and defocus

3 FourStar CDR Optomechanical Design 18 October Image Motion ●Image motion results from flexure in the camera module mount and motion of the detector Zero Gravity The red dot is a star, the crosshair is fixed to the detector array Apply gravity to CM 1g Apply gravity to vessel and dewar 1g  CM  Det Image motion =  CM -  Det

4 FourStar CDR Optomechanical Design 18 October Vessel Flexure Model ●Half-symmetric model ●Vessel divided into eight segments ●Density of each section adjusted to represent internal components CG of simplified model matches quite well to actual model ●1842 lb astatic vertical load applied to load ring ●1g load applied to entire vessel ●Fixed boundary condition at the conical adapter

5 FourStar CDR Optomechanical Design 18 October Vessel Flexure Results ●Dewar Support Ring motion Full Dewar −Decenter: 13.5  m −Tilt: 0.8  m top-to-bottom across the detector Empty Dewar −Decenter: 4  m −Tilt: 0.1  m top-to-bottom across the detector Dewar Support Ring

6 FourStar CDR Optomechanical Design 18 October Dewar Flexure Model g ●Gravity Loading Dewar: 55 lbs LN2: 25.8 lbs Detector: 7.6 lbs Filter wheel: 15.5 lbs Flattener wheel: 9.5 lbs Detent assembly: 2.3 lbs Total lbs ●Moment Loading Filter wheel: 62.2 in∙lbs Flattener wheel: in∙lbs Detector: 10.8 in∙lbs Detent assembly: 5.6 in∙lbs

7 FourStar CDR Optomechanical Design 18 October g Dewar Flexure Results ●Dewar Motion Full Dewar −Decenter: 16  m −Tilt: 0.3  m top-to-bottom across the detector Empty Dewar −Decenter: 13  m −Tilt: 0.4  m top-to-bottom across the detector

8 FourStar CDR Optomechanical Design 18 October Flexure Model (3X) Fixed Boundary Condition CM load applied to this face (86 lbs) Gravity loading applied to all elements Boundary Conditions Loading 200K * 300K * * Note: Temperature and the resulting radial contraction was included in the model Tied interface between the support pin and the titanium flexure

9 FourStar CDR Optomechanical Design 18 October Flexure Results 1g Loading Ring center sags ” Image motion due to motion of the CM support ring is 1.3:1. Therefore the image motion due to a 1g load is ” or 33 um. Tilt is negligible and image motion is insensitive to tilt U1

10 FourStar CDR Optomechanical Design 18 October Flexure Results Summary ●1g decenter of detector Full dewars:  Det = 29.5  m Empty dewars:  Det = 17  m ●1g image motion due to camera module sag  CM = 33  m ●1g image motion Full dewars: 3.5  m Empty dewars:16  m ●Image motion over a 15 deg rotation Full dewars: 0.9  m (< 1/3 pixel) Empty dewars: 4.2  m ( < 1/3 pixel) ●Defocus is well within the ± 30  m diffraction limited DOF


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