T. Travouillon

California Institute of Technology, Pasadena, California, United States

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Publications (85)121.12 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The TMT first light Adaptive Optics (AO) facility consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). NFIRAOS is a 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, and three low-order, infrared, natural guide star wavefront sensors within each client instrument. The first light LGSF system includes six sodium lasers required to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, modeling and validating the TMT first light AO systems and their components over the last two years. This will include pre-final design and prototyping activities for NFIRAOS, preliminary design and prototyping activities for the LGSF, design and prototyping for the deformable mirrors, fabrication and tests for the visible detectors, benchmarking and comparison of different algorithms and processing architecture for the Real Time Controller (RTC) and development and tests of prototype candidate lasers. Comprehensive and detailed AO modeling is continuing to support the design and development of the first light AO facility. Main modeling topics studied during the last two years include further studies in the area of wavefront error budget, sky coverage, high precision astrometry for the galactic center and other observations, high contrast imaging with NFIRAOS and its first light instruments, Point Spread Function (PSF) reconstruction for LGS MCAO, LGS photon return and sophisticated low order mode temporal filtering.
    SPIE Astronomical Telescopes + Instrumentation; 07/2014
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    ABSTRACT: At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical Observatories. The Gattini DomeA project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fish-eye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R), however, the absence of tracking systems, together with the ultra large field of view 85 degrees) and strong distortion have driven us to seek a unique way to build our data reduction pipeline. We present here the first measurements of sky brightness in the photometric B, V, and R band, cloud cover statistics measured during the 2009 winter season and an estimate of the transparency. In addition, we present example light curves for bright targets to emphasize the unprecedented observational window function available from this ground-based location. A ~0.2 magnitude agreement of our simultaneous test at Palomar Observatory with NSBM(National Sky Brightness Monitor), as well as an 0.04 magnitude photometric accuracy for typical 6th magnitude stars limited by the instrument design, indicating we obtained reasonable results based on our ~7mm effective aperture fish-eye lens.
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    ABSTRACT: SCAR, the Scientific Committee on Antarctic Research, is, like the IAU, a committee of ICSU, the International Council for Science. For over 30 years, SCAR has provided scientific advice to the Antarctic Treaty System and made numerous recommendations on a variety of matters. In 2010, Astronomy and Astrophysics from Antarctica was recognized as one of SCAR's five Scientific Research Programs. Broadly stated, the objectives of Astronomy & Astrophysics from Antarctica are to coordinate astronomical activities in Antarctica in a way that ensures the best possible outcomes from international investment in Antarctic astronomy, and maximizes the opportunities for productive interaction with other disciplines. There are four Working Groups, dealing with site testing, Arctic astronomy, science goals, and major new facilities. Membership of the Working Groups is open to any professional working in astronomy or a related field.
    Proceedings of the International Astronomical Union 08/2013; 8(S288):275-295. DOI:10.1017/S1743921312017000
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    ABSTRACT: At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction.
    Proceedings of the International Astronomical Union 08/2013; 8(S288):34-37. DOI:10.1017/S174392131201664X
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    ABSTRACT: During the site testing campaign for the Thirty Meter Telescope (TMT) in addition to the optical conditions of the atmosphere, measurements of the soil surface properties were obtained also. The dust concentration in the air was measured by means of dust sensors which were mounted underneath the mount of the site monitoring telescopes. The ground head fluxes and soil temperatures were measured several centimeters into the ground. On Cerro Armazones it was also possible to conduct an experiment to measure heat conduction of the soil. In this paper, all of these measurements are described, the results and their potential use is summarized.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2012; DOI:10.1117/12.926863 · 0.20 Impact Factor
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    ABSTRACT: Dome and mirror seeing are critical effects influencing the optical performance of ground-based telescopes. Computational Fluid Dynamics (CFD) can be used to obtain the refractive index field along a given optical path and calculate the corresponding image quality utilizing optical modeling tools. This procedure is validated using measurements from the Keck II and CFHT telescopes. CFD models of Keck II and CFHT observatories on the Mauna Kea summit have been developed. The detailed models resolve all components that can influence the flow pattern through turbulence generation or heat release. Unsteady simulations generate time records of velocity and temperature fields from which the refractive index field at a given wavelength and turbulence parameters are obtained. At Keck II the Cn2 and l0 (inner scale of turbulence) were monitored along a 63m path sensitive primarily to turbulence around the top ring of the telescope tube. For validation, these parameters were derived from temperature and velocity fluctuations obtained from CFD simulations. At CFHT dome seeing has been inferred from their database that includes telescope delivered Image Quality (IQ). For this case CFD simulations were run for specific orientations of the telescope respect to incoming wind, wind speeds and outside air temperature. For validation, temperature fluctuations along the optical beam from the CFD are turned to refractive index variations and corresponding Optical Path Differences (OPD) then to Point Spread Functions (PSF) that are ultimately compared to the record of IQ.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2012; DOI:10.1117/12.927182 · 0.20 Impact Factor
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    ABSTRACT: Scintillation noise is a major limitation of ground base photometric precision. An extensive dataset of stellar scintillation collected at 11 astronomical sites world-wide with MASS instruments was used to estimate the scintillation noise of large telescopes in the case of fast photometry and traditional long-exposure regime. Statistical distributions of the corresponding parameters are given. The scintillation noise is mostly determined by turbulence and wind in the upper atmosphere and comparable at all sites, with slightly smaller values at Mauna Kea and largest noise at Tolonchar in Chile. We show that the classical Young's formula under-estimates the scintillation noise.The temporal variations of the scintillation noise are also similar at all sites, showing short-term variability at time scales of 1 -- 2 hours and slower variations, including marked seasonal trends (stronger scintillation and less clear sky during local winter). Some correlation was found between nearby observatories.
    Astronomy and Astrophysics 08/2012; 546. DOI:10.1051/0004-6361/201219954 · 4.48 Impact Factor
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    ABSTRACT: TMT collected a large multi-dimensional data set of site characteristics at its five candidate sites. In order to make an informed site decision, this data set was reduced to a one dimensional metric, the site merit function. This paper describes examples of some of the coefficients of this merit function, with an emphasis on the interpretation of the results of such an approach and its limitations.
  • T. Travouillon, M. Schöck, S. Els, R. Riddle, W. Skidmore
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    ABSTRACT: In the second part of this study, we compare both the wind speed and turbulence given by the Sodars with independent sets of measurements. In the case of the wind speed we compare the lowest Sodar data bin with a sonic anemometer located on a 7-m tower. The agreement between the two instruments was convincing with a regression slope near unity. The integrated turbulence measurements of the Sodars are compared with those obtained with a combined multi-aperture scintillation sensor and differential image motion monitor (MASS/DIMM) unit. It was found that the Sodars are indeed capable of quantitatively measuring optical turbulence, and agree with the MASS/DIMM measurements with a correlation coefficient of approximately 80% and a regression slope within 10% of unity. Additional acoustic noise in the Sodar data was identified using this comparison and removed from the data. KeywordsAstronomy–Atmospheric boundary layer–Sodar–Turbulence–Wind speed
    Boundary-Layer Meteorology 11/2011; 141(2):289-300. DOI:10.1007/s10546-011-9644-y · 2.53 Impact Factor
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    ABSTRACT: All Sky Cameras were deployed at all Thirty Meter Telescope (TMT) candidate sites to gather images for assessing the cloud statistics and light pollution. We developed two methods to assess clouds, a manual method based on inspection of blue and red movies, and an automated method based on photometric analysis of the images. We developed a light pollution analysis procedure and find that light pollution at the candidate sites is currently unimportant for TMT site selection.
  • T. Travouillon, M. Schöck, S. Els, R. Riddle, W. Skidmore
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    ABSTRACT: In this two-part study, we investigate the usefulness of Sodars as part of a large instrument suite for the study of high mountains in the site selection process of the Thirty Meter Telescope (TMT). In this first part, we describe the reproducibility of the measurements and the comparability of results from different sites for data taken with two complementary Sodar models: the XFAS and SFAS models manufactured by Scintec Inc. To this end, a cross-calibration campaign was conducted on two of the sites comparing both the wind speeds and the optical turbulence measurements of the different units. The specific set-up conditions and the low atmospheric pressure require us to make a compromise between the amount of data available for statistics and the quality of the data. For the comparison of the wind speed, results from the same models show a systematic difference of 12 and 9% for the XFAS and SFAS, respectively. The scatter between individual measurements, which includes instrumental, set-up and statistical fluctuation contributions, was found to be 21 and 23%. For optical turbulence, the respective values are 6 and 3% for the systematic difference and 46 and 67% for the scatter. These results show that Sodars can be useful tools for astronomical site testing for projects such as the TMT. KeywordsAstronomy–Atmospheric boundary layer–Sodar–Turbulence–Wind speed
    Boundary-Layer Meteorology 11/2011; 141(2):273-288. DOI:10.1007/s10546-011-9642-0 · 2.53 Impact Factor
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    ABSTRACT: After a site testing campaign spanning 5 sites over a period of 5 years, the site selection for the Thirty Meter Telescope (TMT) culminated with the choice of Mauna Kea 13N in Hawaii. During the campaign, a lot practical lessons were learned by our team and these lessons can be shared with current and future site testing campaign done for other observatories. These lessons apply to the preselection of the site, the ground work and operations of the campaign as well as the analysis of the data. We present of selection of such lessons in this paper preceded by a short summary of the TMT site testing activities.
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    ABSTRACT: As part of a program to measure and evaluate atmospheric turbulence on mountains at the most northerly tip of North America, we have deployed two SODARs and a lunar scintillometer at the Polar Environment Atmospheric Research Lab (PEARL) located on a 600m-high ridge near Eureka on Ellesmere Island, at 80° latitude. This paper discusses the program and presents a summary of ground-layer turbulence and seeing measurements from the 2009-10 observing season.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.857409 · 0.20 Impact Factor
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    ABSTRACT: With the development of increasingly larger and more complex telescopes and instrumentation, site testing and characterization efforts also increase in both magnitude and complexity. This happens because the investment into larger observatories is higher and because new technologies, such as adaptive optics, require knowledge about parameters that did not matter previously, such as the vertical distribution of turbulence. We present examples of remaining questions which, to date, are not generally addressed by "standard" site characterization efforts, either because they are technically not (yet) feasible or because they are impractical. We center our observations around the experience gained during the Thirty Meter Telescope (TMT) site testing effort with an emphasis on turbulence measurements, but our findings are applicable in general to other current and future projects as well.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.857412 · 0.20 Impact Factor
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    ABSTRACT: Between February and April 2009 a number of ultrasonic anemometers, temperature probes and dust sensors were operated inside the CTIO Blanco telescope dome. These sensors were distributed in a way that temperature and dimensional wind speeds were monitored along the line of sight of the telescope. During telescope operations, occasional seeing measurements were obtained using the Mosaic CCD imager and the CTIO site monitoring MASS-DIMM system. In addition, also a Lunar Scintillometer (LuSci) was operated over the course of a few nights inside the dome. We describe the instrumental setup and first preliminary results on the linkage of the atmospheric conditions inside the dome to the overall image quality.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.856297 · 0.20 Impact Factor
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    ABSTRACT: In order to validate various assumptions about the operating environment of the Thirty Meter Telescope (TMT), to validate the modeling packages being used to guide the design work for the TMT and to directly investigate the expected operation of several subsystems we have embarked on an extensive campaign of environmental measurements at the Keck telescopes. We have measured and characterized the vibration environment around the observatory floor and at certain locations on the telescope over a range of operating conditions. Similarly the acoustic environment around the telescope and primary mirror has been characterized for frequencies above 2 Hz. The internal and external wind and temperature fields are being measured using combined sonic anemometer and PRT sensors. We are measuring the telescope position error and drive torque signals in order to investigate the wind induced telescope motions. A scintillometer mounted on the telescope is measuring the optical turbulence inside the telescope tube. This experimental work is supplemented by an extensive analysis of telescope and engineering sensor log files and measurements, primarily those of accelerometers located on the main telescope optics, primary mirror segment edge sensor error signals (residuals), telescope structure temperature measurements and the telescope status information.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.857960 · 0.20 Impact Factor
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    ABSTRACT: The high altitude Antarctic sites of Dome A and the South Pole offer intriguing locations for future large scale optical astronomical Observatories. The Gattini project was created to measure the optical sky brightness, large area cloud cover and aurora of the winter-time sky above such high altitude Antarctic sites. The Gattini-DomeA camera was installed on the PLATO instrument module as part of the Chinese-led traverse to the highest point on the Antarctic plateau in January 2008. This single automated wide field camera contains a suite of Bessel photometric filters (B, V, R) and a long-pass red filter for the detection and monitoring of OH emission. We have in hand one complete winter-time dataset (2009) from the camera that was recently returned in April 2010. The Gattini-South Pole UV camera is a wide-field optical camera that in 2011 will measure for the first time the UV properties of the winter-time sky above the South Pole dark sector. This unique dataset will consist of frequent images taken in both broadband U and B filters in addition to high resolution (R similar to 5000) long slit spectroscopy over a narrow bandwidth of the central field. The camera is a proof of concept for the 2m-class Antarctic Cosmic Web Imager telescope, a dedicated experiment to directly detect and map the redshifted lyman alpha fluorescence or Cosmic Web emission we believe possible due to the unique geographical qualities of the site. We present the current status of both projects.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.858187 · 0.20 Impact Factor
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    ABSTRACT: Atmospheric optical turbulence is the main driver of wavefront distortions which affect optical telescope performance. Therefore, many techniques have been developed to measure the optical turbulence strength along the line of sight. Based on data collected with the MASS (Multi Aperture Scintillation Sensor), we show that a large sample of such measurements can be used to assess the average three dimensional turbulence distribution above ground. The use of, and a more sophisticated instrumental setup for, such turbulence tomography will be discussed.
    Proceedings of SPIE - The International Society for Optical Engineering 07/2010; DOI:10.1117/12.856304 · 0.20 Impact Factor
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    ABSTRACT: The results of the characterization of precipitable water vapor in the atmospheric column carried out in the context of identifying potential sites for the deployment of the Thirty Meter Telescope (TMT) are presented. Prior to starting the dedicated field campaign to look for a suitable site for the TMT, candidate sites were selected based on a climatology report utilizing satellite data that considered water vapor as one of the study variables. These candidate sites are all of tropical or subtropical location at geographic areas dominated by high-pressure systems. The results of the detailed on-site study, spanning a period of 4 yr, from early 2004 until the end of 2007, confirmed the global mean statistics provided in the previous reports based on satellite data, and also confirmed that all the candidate sites are exceptionally good for astronomy research. At the locations of these sites, the atmospheric conditions are such that the higher the elevation of the site, the drier it gets. However, the data analysis shows that during winter, San Pedro Mártir, a site about 230 m lower in elevation than Armazones, is drier than the Armazones site. This finding is attributed to the fact that Earth's atmosphere is largely unsaturated, leaving room for regional variability; it is useful in illustrating the relevance of in situ atmospheric studies for understanding the global and seasonal variability of potential sites for astronomy research. The results also show that winter and spring are the driest seasons at all of the tested sites, with Mauna Kea (in the northern hemisphere) and Tolonchar (in the southern hemisphere) being the tested sites with the lowest precipitable water vapor in the atmospheric column and the highest atmospheric transmission in the near and mid-infrared bands. This is the tenth article in a series discussing the TMT site-testing project.
    Publications of the Astronomical Society of the Pacific 04/2010; 122(890):470-484. DOI:10.1086/651582 · 3.23 Impact Factor
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    ABSTRACT: The i-band observing conditions at Dome A on the Antarctic plateau have been investigated using data acquired during 2008 with the Chinese Small Telescope ARray. The sky brightness, variations in atmospheric transparency, cloud cover, and the presence of aurorae are obtained from these images. The median sky brightness of moonless clear nights is 20.5 mag arcsec^{-2} in the SDSS $i$ band at the South Celestial Pole (which includes a contribution of about 0.06 mag from diffuse Galactic light). The median over all Moon phases in the Antarctic winter is about 19.8 mag arcsec^{-2}. There were no thick clouds in 2008. We model contributions of the Sun and the Moon to the sky background to obtain the relationship between the sky brightness and transparency. Aurorae are identified by comparing the observed sky brightness to the sky brightness expected from this model. About 2% of the images are affected by relatively strong aurorae.
    The Astronomical Journal 01/2010; 140(2). DOI:10.1088/0004-6256/140/2/602 · 4.97 Impact Factor

Publication Stats

735 Citations
121.12 Total Impact Points

Institutions

  • 2006–2013
    • California Institute of Technology
      • Department of Astronomy
      Pasadena, California, United States
  • 2007–2012
    • Thirty Meter Telescope
      Pasadena, California, United States
  • 2010
    • Lawrence Berkeley National Laboratory
      Berkeley, California, United States
  • 2004
    • Carnegie Mellon University
      • Department of Physics
      Pittsburgh, Pennsylvania, United States
  • 2002–2004
    • University of New South Wales
      • School of Physics
      Kensington, New South Wales, Australia