Telescope Guiding with a HyViSI H2RG Used in Guide Mode Lance Simms Detectors for Astronomy /2/09

Overview of Talk Brief overview of Hybrid SiPIN CMOS and the HyViSI Specs of our H2RG in context of guiding Persistence: the X-factor Results from Kitt Peak 2.1m unguided Results from guiding the Kitt Peak 2.1m telescope with a HyViSI H2RG 8/2/092

10/6/09 HyViSi SiPIN Arrays H4RG MUX H4RG detector Teledyne’s Hybrid Visible Silicon (HyViSi) PIN (P-Intrinsic-N) Diodes p + implant n-n- V SUB

H2RG /2/09 Specs and Fe 55 Spectra for H2RG Most of these specs can be folded into centroid accuracy calculations….so what’s the point of testing guide mode for an empirical result?

H2RG Telescope Data Picture taken of Saturn after Exposure + Dither shows Persistence Very interesting that contrast is still detectable in persistent image even though all pixels in previous exposure were saturated Raw Read; No subtraction Where Saturn is in this exposure Where Saturn was in last exposure

6 Persistence from Stars Persistence Effect seen in all HyViSIs “Core” Pixels rapidly gain counts “Halo” pixels see a decrease in counts, but eventually integrate positively “Sky” pixels are unaffected, providing measure of what photocurrent should be Effect lasts for ~ seconds depending on offending star flux and fluence Core Halo Sky *Image snippets have first read subtracted; Plot shows raw ADU Where star is in this exposure Where star was in last exposure time

Effect on Centroid Measurement 8/2/09 7 1st ramp 2nd ramp *Image snippets have first read subtracted “Wedges” in atmospheric turbulence can cause large displacements of image for hundreds of milliseconds What happens if bright star light is displaced? Does image persistence create large error in calculated centroid? 7

Persistence Model 8/2/098

Attempt to Simulate 8/2/099

Observing at Kitt Peak We brought the RIDL Dewar to the Kitt Peak 2.1m Tested 3 HyViSi detectors on 3 separate runs –4/24/07-5/1/07H4RG-007 –11/13/07-11/20/07H1RG-022 –12/11/07-12/19/07H2RG Lovely snow storm in December! 8/2/0910

Kitt Peak 2.1m Details Up Right: LSST Baseline Filters Above: Dewar attached to 2.1m Telescope Right: Oscillations in Right Ascension and Declination caused by periodic error of worm gear in motors

Application of Guide Windows In a CCD, frame rate depends on size of CCD even when using a “window” In CMOS, window frame rate is independent of imager size 8/2/09 LSST Focal Plane Wouldn’t it be nice if all LSST detectors could be used for guiding?

Guide Mode HxRG multiplexers have a “Guide Mode” - Full frame integration while subwindow is readout - Readout is interleaved …. Pixels integrating charge Full frame drop or read Window reset or read We used guide mode to guide 2.1m telescope with sequence on right

Short Exposures without Guiding 8/2/09 NGC26813 Combining multiple short exposures yields good point spread function Image of NGC2681 from stack of 40 second exposures

Long Exposure Without Guiding 1800 second exposure of M=6.55 in V-band star SAO54817 taken with H1RG-022 Tracking error smears stars and makes them look like jelly beans

Long Exposure With Guiding 8/2/ second exposure of M=7 in V-band star IRAS taken with H2RG PSF is reduced greatly. Guide window affects pixels in shared rows and columns Guide Window sampled at 25 hz for 8 seconds before moving telescope

Guide Mode Comparison

Summary Guide Mode of HyViSI offers unique feature to guide telescope while simultaneously taking deep field exposures Centroid accuracy for guide star can be predicted with standard signal to noise calculations that fold in read noise, dark current, etc. Effect of Persistence is less trivial since analytical fits to latent images have large errors Empirical results from using H2RG at Kitt Peak 2.1m show that persistence of guide star does not negatively impact centroid measurements 8/2/0918

Additional Slides 8/2/0919

Dark Current H4RG shows higher dark current than other SiPIN devices Teledyne indicates source of problem was found in unit cell and fixed New H4RG has order of magnitude less dark current 8/2/0920

Read Noise Total CDS Noise on H4RG ~ 15 e - CDS Noise on H1RG and H2RG ~8 e - Plot on left shows noise with multiple non-destructive samples 8/2/0921

Detective Quantum Efficiency Integrating sphere with monochromator and calibrated photodiode used to obtain QE vs. wavelength 8/2/0922