Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry
Author(s)Simcoe, Robert A.; Croll, Bryce J.; Sullivan, Peter W.
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We have designed, constructed, and tested an InGaAs near-infrared camera to explore whether low-cost detectors can make small (≤1 m) telescopes capable of precise (<1 mmag) infrared photometry of relatively bright targets. The camera is constructed around the 640 × 512 pixel APS640C sensor built by FLIR Electro-Optical Components. We designed custom analog-to-digital electronics for maximum stability and minimum noise. The InGaAs dark current halves with every 7°C of cooling, and we reduce it to 840 e[superscript -]s[superscript -1]pixel[superscript -1] (with a pixel-to-pixel variation of ±200 e[superscript -]s[superscript -1]pixel[superscript -1]) by cooling the array to 20°C. Beyond this point, glow from the readout dominates. The single-sample read noise of 149 [superscript -]e is reduced to 54 [superscript -]e through up-the-ramp sampling. Laboratory testing with a star field generated by a lenslet array shows that two-star differential photometry is possible to a precision of 631 ± 205 ppm (0.68 mmag) hr[superscript -1/2] at a flux of 2.4 × 10[superscript 4] e[superscript -]s[superscript -1]. Employing three comparison stars and decorrelating reference signals further improves the precision to 483 ± 161 ppm (0.52 mmag) hr[superscript -1/2]. Photometric observations of HD80606 and HD80607 (J - 7.7 and 7.8) in the Y band shows that differential photometry to a precision of 415 ppm (0.45 mmag) hr[superscript -1/2] is achieved with an effective telescope aperture of 0.25 m. Next-generation InGaAs detectors should indeed enable Poisson-limited photometry of brighter dwarfs with particular advantage for late-M and L types. In addition, one might acquire near-infrared photometry simultaneously with optical photometry or radial velocity measurements to maximize the return of exoplanet searches with small telescopes.
DepartmentMassachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space Research
Publications of the Astronomical Society of the Pacific
University of Chicago Press, The
Sullivan, Peter W., Bryce Croll, and Robert A. Simcoe. “Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry.” Publications of the Astronomical Society of the Pacific 125, no. 931 (September 2013): 1021–1030. © 2013 The Astronomical Society of the Pacific
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