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Register a new userThe Deep Neural Network based Photometry Framework for Wide Field Small Aperture Telescopes
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Wide field small aperture telescopes (WFSATs) are mainly used to obtain scientific information of point--like and streak--like celestial objects. However, qualities of images obtained by WFSATs are seriously affected by the background noise and variable point spread functions. Developing high speed and high efficiency data processing method is of great importance for further scientific research. In recent years, deep neural networks have been proposed for detection and classification of celestial objects and have shown better performance than classical methods. In this paper, we further extend abilities of the deep neural network based astronomical target detection framework to make it suitable for photometry and astrometry. We add new branches into the deep neural network to obtain types, magnitudes and positions of different celestial objects at the same time. Tested with simulated data, we find that our neural network has better performance in photometry than classical methods. Because photometry and astrometry are regression algorithms, which would obtain high accuracy measurements instead of rough classification results, the accuracy of photometry and astrometry results would be affected by different observation conditions. To solve this problem, we further propose to use reference stars to train our deep neural network with transfer learning strategy when observation conditions change. The photometry framework proposed in this paper could be used as an end--to--end quick data processing framework for WFSATs, which can further increase response speed and scientific outputs of WFSATs.
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The Simons Observatory (SO) is an upcoming cosmic microwave background (CMB) experiment located on Cerro Toco, Chile, that will map the microwave sky in temperature and polarization in six frequency bands spanning 27 to 285 GHz. SO will consist of one 6-meter Large Aperture Telescope (LAT) fielding $sim$30,000 detectors and an array of three 0.42-meter Small Aperture Telescopes (SATs) fielding an additional 30,000 detectors. This synergy will allow for the extremely sensitive characterization of the CMB over angular scales ranging from an arcmin to tens of degrees, enabling a wide range of scientific output. Here we focus on the SATs targeting degree angular scales with successive dichroic instruments observing at Mid-Frequency (MF: 93/145 GHz), Ultra-High-Frequency (UHF: 225/285 GHz), and Low-Frequency (LF: 27/39 GHz). The three SATs will be able to map $sim$10% of the sky to a noise level of 2 $mu$K-arcmin when combining 93 and 145 GHz. The multiple frequency bands will allow the CMB to be separated from galactic foregrounds (primarily synchrotron and dust), with the primary science goal of characterizing the primordial tensor-to-scalar ratio, $r$, at a target level of $sigma left(rright) approx 0.003$.
Small aperture telescopes provide the opportunity to conduct high frequency, targeted observations of near-Earth Asteroids that are not feasible with larger facilities due to highly competitive time allocation requirements. Observations of asteroids with these types of facilities often focus on rotational brightness variations rather than longer-term phase angle dependent variations (phase curves) due to the difficulty of achieving high precision photometric calibration. We have developed an automated asteroid light curve extraction and calibration pipeline for images of moving objects from the 0.43 m Physics Innovations Robotic Telescope Explorer (PIRATE). This allows for the frequency and quality of observations required to construct asteroid phase curves. Optimisations in standard data reduction procedures are identified that may allow for similar small aperture facilities, constructed from commercially available/off-the-shelf components, to improve image and subsequent data quality. A demonstration of the hardware and software capabilities is expressed through observation statistics from a 10 month observing campaign, and through the photometric characterisation of near-Earth Asteroids 8014 (1990 MF) and 19764 (2000 NF5).
In this white paper (WP), we highlight several examples of small and moderate aperture telescopes that are being used for education and/or research. We further discuss potential costs for establishing new, small observatories, as well as joining existing international consortia. The WP includes a brief overview of select observing sites, with a discussion on how small telescopes at exceptional observing locations can be competitive, under certain circumstances, with larger and more expensive facilities located at poorer sites. In addition to research, these facilities enable many different types of educational experiences for wide range of people, from high school students to undergraduates to graduate students to postdocs. Canada should remain committed to partnering with large, international observatories such as CFHT, Gemini, and TMT, but it should also negotiate international agreements and commit funding to expand the use of small and moderate research observatories at domestic and international sites through coordination with the NRC, the Tri-Council, and the Canadian Foundation for Innovation. Both capital and operational costs (with site rental costs allowed) need to be included in support possibilities. CASCA should establish and maintain a small to moderate telescope expression of interest database that would help to facilitate Canadian institutions in organizing consortia, particularly for smaller institutions. The astronomical community should work with the NRC to make existing facilities more accessible to the astronomical community for research. This could involve, for example, automating the Plaskett and/or providing travel funds for supporting classical observing modes. Finally, a small to moderate aperture facility in the Arctic would be a world-class observatory and should be advanced over the next decade.
HATSouth is the worlds first network of automated and homogeneous telescopes that is capable of year-round 24-hour monitoring of positions over an entire hemisphere of the sky. The primary scientific goal of the network is to discover and characterize a large number of transiting extrasolar planets, reaching out to long periods and down to small planetary radii. HATSouth achieves this by monitoring extended areas on the sky, deriving high precision light curves for a large number of stars, searching for the signature of planetary transits, and confirming planetary candidates with larger telescopes. HATSouth employs 6 telescope units spread over 3 locations with large longitude separation in the southern hemisphere (Las Campanas Observatory, Chile; HESS site, Namibia; Siding Spring Observatory, Australia). Each of the HATSouth units holds four 0.18m diameter f/2.8 focal ratio telescope tubes on a common mount producing an 8.2x8.2 arcdeg field, imaged using four 4Kx4K CCD cameras and Sloan r filters, to give a pixel scale of 3.7 arcsec/pixel. The HATSouth network is capable of continuously monitoring 128 square arc-degrees. We present the technical details of the network, summarize operations, and present weather statistics for the 3 sites. On average each of the 6 HATSouth units has conducted observations on ~500 nights over a 2-year time period, yielding a total of more than 1million science frames at 4 minute integration time, and observing ~10.65 hours per day on average. We describe the scheme of our data transfer and reduction from raw pixel images to trend-filtered light curves and transiting planet candidates. Photometric precision reaches ~6 mmag at 4-minute cadence for the brightest non-saturated stars at r~10.5. We present detailed transit recovery simulations to determine the expected yield of transiting planets from HATSouth. (abridged)
High-precision astrometry requires accurate point-spread function modeling and accurate geometric-distortion corrections. This paper demonstrates that it is possible to achieve both requirements with data collected at the high acuity wide-field K-band imager (HAWK-I), a wide-field imager installed at the Nasmyth focus of UT4/VLT ESO 8m telescope. Our final astrometric precision reaches ~3 mas per coordinate for a well-exposed star in a single image with a systematic error less than 0.1 mas. We constructed calibrated astro-photometric catalogs and atlases of seven fields: the Baades Window, NGC 6656, NGC 6121, NGC 6822, NGC 6388, NGC 104, and the James Webb Space Telescope calibration field in the Large Magellanic Cloud. We make these catalogs and images electronically available to the community. Furthermore, as a demonstration of the efficacy of our approach, we combined archival material taken with the optical wide-field imager at the MPI/ESO 2.2m with HAWK-I observations. We showed that we are able to achieve an excellent separation between cluster members and field objects for NGC 6656 and NGC 6121 with a time base-line of about 8 years. Using both HST and HAWK-I data, we also study the radial distribution of the SGB populations in NGC 6656 and conclude that the radial trend is flat within our uncertainty. We also provide membership probabilities for most of the stars in NGC 6656 and NGC 6121 catalogs and estimate membership for the published variable stars in these two fields.
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