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Title: Astrometric calibration and performance of the Dark Energy Camera

Abstract

In this study, we characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500 Mpix, 3-deg2 science field of view and across four years of operation. This is done using internal comparisons of ~4 × 107 measurements of high signal-to-noise ratio stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to ≈10 μm when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Errors in this astrometric model are dominated by stochastic variations with typical amplitudes of 10–30 mas (in a 30 s exposure) and 5'–10' coherence length, plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of these atmospheric distortions is not closely related to the seeing. Given an astrometric reference catalog at density $$\approx 0.7\,{\mathrm{arcmin}}^{-2},$$ e.g., from Gaia, the typical atmospheric distortions can be interpolated to ≈7 mas rms accuracy (for 30 s exposures) with $$1^{\prime} $$ coherence length in residual errors. Remaining detectable error contributors are 2–4 mas rms from unmodelled stray electric fields in the devices, and another 2–4 mas rms from focal plane shifts between camera thermal cycles. Thus the astrometric solution for a single DECam exposure is accurate to 3–6 mas (≈0.02 pixels, or ≈300 nm) on the focal plane, plus the stochastic atmospheric distortion.

Authors:
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Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States); Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Org.:
DES Collaboration
OSTI Identifier:
1361381
Alternate Identifier(s):
OSTI ID: 1346375; OSTI ID: 1369280; OSTI ID: 1423239
Report Number(s):
arXiv:1703.01679; FERMILAB-PUB-17-057-AE; arXiv:1710.10943; FERMILAB-PUB-17-459-AE
Journal ID: ISSN 0004-6280; KJ0402000; KJ0503000; ERKJ311; ERKJEPM
Grant/Contract Number:  
AC05-00OR22725; AC02-07CH11359; AC02-76SF00515; AST-1615555; SC0007901
Resource Type:
Accepted Manuscript
Journal Name:
Publications of the Astronomical Society of the Pacific
Additional Journal Information:
Journal Volume: 129; Journal Issue: 977; Journal ID: ISSN 0004-6280
Publisher:
Astronomical Society of the Pacific
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY

Citation Formats

Bernstein, G. M., Armstrong, R., Plazas, A. A., Walker, A. R., Abbott, T. M. C., Allam, S., Bechtol, K., Benoit-Lévy, A., Brooks, D., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Cunha, C. E., Costa, L. N. da, DePoy, D. L., Desai, S., Diehl, H. T., Eifler, T. F., Fernandez, E., Fosalba, P., Frieman, J., García-Bellido, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D. J., Kent, S., Krause, E., Kuehn, K., Kuropatkin, N., Li, T. S., Maia, M. A. G., March, M., Marshall, J. L., Menanteau, F., Miquel, R., Ogando, R. L. C., Reil, K., Roodman, A., Rykoff, E. S., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., and Tarle, G. Astrometric calibration and performance of the Dark Energy Camera. United States: N. p., 2017. Web. doi:10.1088/1538-3873/aa6c55.
Bernstein, G. M., Armstrong, R., Plazas, A. A., Walker, A. R., Abbott, T. M. C., Allam, S., Bechtol, K., Benoit-Lévy, A., Brooks, D., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Cunha, C. E., Costa, L. N. da, DePoy, D. L., Desai, S., Diehl, H. T., Eifler, T. F., Fernandez, E., Fosalba, P., Frieman, J., García-Bellido, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D. J., Kent, S., Krause, E., Kuehn, K., Kuropatkin, N., Li, T. S., Maia, M. A. G., March, M., Marshall, J. L., Menanteau, F., Miquel, R., Ogando, R. L. C., Reil, K., Roodman, A., Rykoff, E. S., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., & Tarle, G. Astrometric calibration and performance of the Dark Energy Camera. United States. doi:10.1088/1538-3873/aa6c55.
Bernstein, G. M., Armstrong, R., Plazas, A. A., Walker, A. R., Abbott, T. M. C., Allam, S., Bechtol, K., Benoit-Lévy, A., Brooks, D., Burke, D. L., Rosell, A. Carnero, Kind, M. Carrasco, Carretero, J., Cunha, C. E., Costa, L. N. da, DePoy, D. L., Desai, S., Diehl, H. T., Eifler, T. F., Fernandez, E., Fosalba, P., Frieman, J., García-Bellido, J., Gerdes, D. W., Gruen, D., Gruendl, R. A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D. J., Kent, S., Krause, E., Kuehn, K., Kuropatkin, N., Li, T. S., Maia, M. A. G., March, M., Marshall, J. L., Menanteau, F., Miquel, R., Ogando, R. L. C., Reil, K., Roodman, A., Rykoff, E. S., Sanchez, E., Scarpine, V., Schindler, R., Schubnell, M., Sevilla-Noarbe, I., Smith, M., Smith, R. C., Soares-Santos, M., Sobreira, F., Suchyta, E., Swanson, M. E. C., and Tarle, G. Tue . "Astrometric calibration and performance of the Dark Energy Camera". United States. doi:10.1088/1538-3873/aa6c55. https://www.osti.gov/servlets/purl/1361381.
@article{osti_1361381,
title = {Astrometric calibration and performance of the Dark Energy Camera},
author = {Bernstein, G. M. and Armstrong, R. and Plazas, A. A. and Walker, A. R. and Abbott, T. M. C. and Allam, S. and Bechtol, K. and Benoit-Lévy, A. and Brooks, D. and Burke, D. L. and Rosell, A. Carnero and Kind, M. Carrasco and Carretero, J. and Cunha, C. E. and Costa, L. N. da and DePoy, D. L. and Desai, S. and Diehl, H. T. and Eifler, T. F. and Fernandez, E. and Fosalba, P. and Frieman, J. and García-Bellido, J. and Gerdes, D. W. and Gruen, D. and Gruendl, R. A. and Gschwend, J. and Gutierrez, G. and Honscheid, K. and James, D. J. and Kent, S. and Krause, E. and Kuehn, K. and Kuropatkin, N. and Li, T. S. and Maia, M. A. G. and March, M. and Marshall, J. L. and Menanteau, F. and Miquel, R. and Ogando, R. L. C. and Reil, K. and Roodman, A. and Rykoff, E. S. and Sanchez, E. and Scarpine, V. and Schindler, R. and Schubnell, M. and Sevilla-Noarbe, I. and Smith, M. and Smith, R. C. and Soares-Santos, M. and Sobreira, F. and Suchyta, E. and Swanson, M. E. C. and Tarle, G.},
abstractNote = {In this study, we characterize the ability of the Dark Energy Camera (DECam) to perform relative astrometry across its 500 Mpix, 3-deg2 science field of view and across four years of operation. This is done using internal comparisons of ~4 × 107 measurements of high signal-to-noise ratio stellar images obtained in repeat visits to fields of moderate stellar density, with the telescope dithered to move the sources around the array. An empirical astrometric model includes terms for optical distortions; stray electric fields in the CCD detectors; chromatic terms in the instrumental and atmospheric optics; shifts in CCD relative positions of up to ≈10 μm when the DECam temperature cycles; and low-order distortions to each exposure from changes in atmospheric refraction and telescope alignment. Errors in this astrometric model are dominated by stochastic variations with typical amplitudes of 10–30 mas (in a 30 s exposure) and 5'–10' coherence length, plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of these atmospheric distortions is not closely related to the seeing. Given an astrometric reference catalog at density $\approx 0.7\,{\mathrm{arcmin}}^{-2},$ e.g., from Gaia, the typical atmospheric distortions can be interpolated to ≈7 mas rms accuracy (for 30 s exposures) with $1^{\prime} $ coherence length in residual errors. Remaining detectable error contributors are 2–4 mas rms from unmodelled stray electric fields in the devices, and another 2–4 mas rms from focal plane shifts between camera thermal cycles. Thus the astrometric solution for a single DECam exposure is accurate to 3–6 mas (≈0.02 pixels, or ≈300 nm) on the focal plane, plus the stochastic atmospheric distortion.},
doi = {10.1088/1538-3873/aa6c55},
journal = {Publications of the Astronomical Society of the Pacific},
number = 977,
volume = 129,
place = {United States},
year = {2017},
month = {5}
}

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