Hy Vi Si Focal Plane Guider M Lampton

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Hy. Vi. Si Focal Plane Guider M. Lampton U. C. Berkeley Space Sciences Lab

Hy. Vi. Si Focal Plane Guider M. Lampton U. C. Berkeley Space Sciences Lab originally 4 Feb 2002 augmented 5 March 2004 rewritten 6 June 2006

Motive • Collaboration June 2006 – Session on focal plane guiding – Adopted Rockwell

Motive • Collaboration June 2006 – Session on focal plane guiding – Adopted Rockwell Hy. Vi. Si • What problems will we encounter? – Run OK uncooled during prelaunch checks? – Is interpixel coupling a problem? – Full frame OK for locating test beam? – Commonality with NIR+Sidecar Slice? • guider-unique slice software uploadable? 2

“A high accuracy star guider with application to SNAP” Secroun et al, Experimental Astronomy

“A high accuracy star guider with application to SNAP” Secroun et al, Experimental Astronomy June 2002 • Plenty of stars V=12 to 16 to guide on: – – – GSC counts, NEP & SEP: 500/sqdeg down to V=14. 5 expect ~ 1000/sqdeg down to V=16 200 x 200 arcsec FOV, expect <N>=3 guide stars/field Prob(0)=exp(-3) ~ 5%, hence >95% fields better than this confirmed by numerical experiments • Plenty of photons per star, even at V=16: – – – – – typical video-rate frontside CCDs have QE*BW ~ 150 nm 13000 e/sec thanks to our two meter aperture! at 30 fps = 437 e/star in each frame binomial shot noise = 11 e rms; other noise = 30 e rms therefore centroid position error = 7% of one pixel, single frame if 1 pixel = 100 mas, 1 -D RMS error = 7 mas single frame Consequence of white power spectrum with 7 mas over 15 Hz BW? if no gyros, and ACS BW=1 Hz => 1. 9 mas RMS each axis. potential improvements: two guide stars; Kalman filter; gyros. . 3

http: //www. rsc. rockwell. com/imaging/hyvisi/ 4

http: //www. rsc. rockwell. com/imaging/hyvisi/ 4

http: //www. rsc. rockwell. com/imaging/hyvisi/ 5

http: //www. rsc. rockwell. com/imaging/hyvisi/ 5

Hy. Vi. Si at 300 K. . 6

Hy. Vi. Si at 300 K. . 6

Hy. Vi. Si at 250 K. . 7

Hy. Vi. Si at 250 K. . 7

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Overresolution: 18μm pixels vs 4μm rms blur 9

Overresolution: 18μm pixels vs 4μm rms blur 9

Overresolution: 18μm pixels vs 8 um rms blur 10

Overresolution: 18μm pixels vs 8 um rms blur 10

Conclusions • Room temperature dark current is not a problem for Hy. Vi. Si

Conclusions • Room temperature dark current is not a problem for Hy. Vi. Si • Overresolution is not a problem – Nominal system blur for SNAP is 7. 7 μm rms – defocussing is always available to enlarge this for guiders • Photon throughput is sufficient – < 0. 2 milli arcsecond s/c jitter contribution at 13 th magnitude – <0. 8 milli arcsecond s/c jitter contribution at 16 th magnitude • Commonality with NIR Sidecar & slice electronics is attractive 11