Mr. Scott Powell Profile

Scott Powell

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Publications (10)

Proceedings Article | 9 August 2016 Paper

On-sky Doppler performance of TOU optical very high-resolution spectrograph for detecting low-mass planets

Jian Ge, Bo Ma, Sirinrat Sithajan, Michael Singer, Scott Powell, Frank Varosi, Bo Zhao, Sidney Schofield, Jian Liu, Nolan Grieves, Anthony Cassette, Louis Avner, Hali Jakeman, Matthew Muterspaugh, Michael Williamson, Rory Barnes

Proceedings Volume 9908, 99086I (2016) https://doi.org/10.1117/12.2232217

KEYWORDS: Planets, Doppler effect, Spectrographs, Robotics, Telescopes, Stars, Calibration, Double positive medium, Neptune, Space telescopes

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Proceedings Article | 2 August 2014 Paper

An infrared high resolution silicon immersion grating spectrometer for airborne and space missions

Jian Ge, Bo Zhao, Scott Powell, Peng Jiang, Berik Uzakbaiuly, David Tanner

Proceedings Volume 9143, 91434T (2014) https://doi.org/10.1117/12.2057235

KEYWORDS: Silicon, Infrared spectroscopy, Antireflective coatings, Spectroscopy, Spectrographs, Spectral resolution, Telescopes, Space operations, Space telescopes, Far infrared

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Proceedings Article | 28 July 2014 Paper

A robotic, compact, and extremely high resolution optical spectrograph for a close-in super-Earth survey

Jian Ge, Scott Powell, Bo Zhao, Frank Varosi, Bo Ma, Sirinrat Sithajan, Jian Liu, Rui Li, Nolan Grieves, Sidney Schofield, Louis Avner, Hali Jakeman, William Yoder, Jakob Gittelmacher, Michael Singer, Matthew Muterspaugh, Michael Williamson, J. Maxwell

Proceedings Volume 9147, 914786 (2014) https://doi.org/10.1117/12.2056970

KEYWORDS: Planets, Stars, Spectrographs, Calibration, Optical fibers, Doppler effect, Spectral resolution, Telescopes, Robotics, Optical resolution

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Proceedings Article | 24 July 2014 Paper

On-sky calibration performance of a monolithic Michelson interferometer filtered source

Jian Ge, Bo Ma, Scott Powell, Frank Varosi, Sidney Schofield, Nolan Grieves, Jian Liu

Proceedings Volume 9146, 914608 (2014) https://doi.org/10.1117/12.2057095

KEYWORDS: Calibration, Spectrographs, Doppler effect, Interferometers, Iodine, Precision calibration, Lamps, Planets, Absorption, Near infrared

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In the new era of searching for Earth-like planets, new generation radial velocity (RV) high resolution spectrographs requires ~0.1 m/s Doppler calibration accuracy in the visible band and a similar calibration precision in the near infrared. The patented stable monolithic Michelson interferometer filtered source called the Sine source emerges as a very promising calibration device. This Sine source has the potential of covering the practical working wavelengths (~0.38- 2.5 μm) for Doppler measurements with high resolution optical and near infrared high resolution spectrographs at the ground-based telescopes. The single frame calibration precision can reach < 0.1 m/s for the state of the art spectrographs, and it can be easily designed to match the intrinsic sensitivities of future Doppler instruments. The Sine source also has the great practical advantages in compact (portable) size and low cost. Here we report early results from on-sky calibration of a Sine source measured with two state-of-the-art TOU optical high resolution spectrograph (R=100,000, 0.38-0.9 microns) and FIRST near infrared spectrograph (R=50,000, 0.8-1.8 microns) at a 2 meter robotic telescope at Fairborn Observatory in Arizona. The results with the TOU spectrograph monitoring over seven days show that the Sine source has produced ~3 times better calibration precision than the ThAr calibration (RMS = 2.7m/s vs. 7.4m/s) at 0.49-0.62 microns where calibration data have been processed by our preliminary data pipeline and ~1.4 times better than the iodine absorption spectra (RMS=3.6 m/s) at the same wavelength region. As both ThAr and Iodine have reached sub m/s calibration accuracy with existing Doppler instruments (such as HARPS and HIRES), it is likely that the sine source would provide similar improvement once a better data pipeline and an upgraded version of a Sine source are developed. It is totally possible to reach ~0.1 m/s in the optical wavelength region. In addition, this Sine source offers potential very accurate calibration at 0.7-0.9 μm where ThAr lines are totally dominated by strong and saturated Argon lines and the ThAr calibration data are nearly useless. The early measurements with the FIRST near infrared spectrograph show that this Sine source produces very homogenous fringe modulations over 0.8-1.8 μm which can potentially provide better precision than the UrNe lamp for instrument drift measurements.

Proceedings Article | 8 July 2014 Paper

On-sky performance of a high resolution silicon immersion grating spectrometer

Jian Ge, Scott Powell, Bo Zhao, Sidney Schofield, Frank Varosi, Craig Warner, Jian Liu, Sirinrat Sithajan, Louis Avner, Hali Jakeman, Jakob Gittelmacher, William Yoder, Matthew Muterspaugh, Michael Williamson, J. Maxwell

Proceedings Volume 9147, 91471A (2014) https://doi.org/10.1117/12.2057023

KEYWORDS: Planets, Stars, Near infrared, Infrared spectroscopy, Spectroscopy, Spectrographs, Telescopes, Sensors, Optical fibers, Silicon

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Proceedings Article | 24 September 2012 Paper

Design and performance of a new generation, compact, low cost, very high Doppler precision and resolution optical spectrograph

Jian Ge, Bo Zhao, Scott Powell, Ji Wang, Adam Fletcher, Liang Chang, John Groot, Xiaoke Wan, Hali Jakeman, Derek Myers, Elliot Grafer, Jian Liu, Frank Varosi, Sidney Schofield, Alexandria Moore, Maria-Ines van Olphen, Jordan Katz, Rory Barnes

Proceedings Volume 8446, 84468R (2012) https://doi.org/10.1117/12.925795

KEYWORDS: Planets, Stars, Doppler effect, Telescopes, Calibration, Spectrographs, Sensors, Exoplanets, Spectral resolution, Photons

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Proceedings Article | 24 September 2012 Paper

High resolution Florida IR silicon immersion grating spectrometer and an M dwarf planet survey

Jian Ge, Scott Powell, Bo Zhao, Ji Wang, Adam Fletcher, Sidney Schofield, Jian Liu, Matthew Muterspaugh, Cullen Blake, Rory Barnes

Proceedings Volume 8446, 84463O (2012) https://doi.org/10.1117/12.925788

KEYWORDS: Planets, Stars, Near infrared, Calibration, Infrared spectroscopy, Spectrographs, Silicon, Sensors, Telescopes, Exoplanets

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We report the system design and predicted performance of the Florida IR Silicon immersion grating spectromeTer (FIRST). This new generation cryogenic IR spectrograph offers broad-band high resolution IR spectroscopy with R=72,000 at 1.4-1.8 μm and R=60,000 at 0.8-1.35 μm in a single exposure with a 2kx2k H2RG IR array. It is enabled by a compact design using an extremely high dispersion silicon immersion grating (SIG) and an R4 echelle with a 50 mm diameter pupil in combination with an Image Slicer. This instrument is operated in vacuum with temperature precisely controlled to reach long term stability for high precision radial velocity (RV) measurements of nearby stars, especially M dwarfs and young stars. The primary technical goal is to reach better than 4 m/s long term RV precision with J<9 M dwarfs within 30 min exposures. This instrument is scheduled to be commissioned at the Tennessee State University (TSU) 2-m Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in spring 2013. FIRST can also be used for observing transiting planets, young stellar objects (YSOs), magnetic fields, binaries, brown dwarfs (BDs), ISM and stars. We plan to launch the FIRST NIR M dwarf planet survey in 2014 after FIRST is commissioned at the AST. This NIR M dwarf survey is the first large-scale NIR high precision Doppler survey dedicated to detecting and characterizing planets around 215 nearby M dwarfs with J< 10. Our primary science goal is to look for habitable Super-Earths around the late M dwarfs and also to identify transiting systems for follow-up observations with JWST to measure the planetary atmospheric compositions and study their habitability. Our secondary science goal is to detect and characterize a large number of planets around M dwarfs to understand the statistics of planet populations around these low mass stars and constrain planet formation and evolution models. Our survey baseline is expected to detect ~30 exoplanets, including 10 Super Earths, within 100 day periods. About half of the Super-Earths are in their habitable zones and one of them may be a transiting planet. The AST, with its robotic control and ease of switching between instruments (in seconds), enables great flexibility and efficiency, and enables an optimal strategy, in terms of schedule and cadence, for this NIR M dwarf planet survey.

Proceedings Article | 13 September 2012 Paper

Wide-field tracking of moving objects with a compact multi-object dispersed fixed-delay interferometer

Jian Ge, Xiaoke Wan, Derek Myers, Scott Powell

Proceedings Volume 8450, 84501C (2012) https://doi.org/10.1117/12.926689

KEYWORDS: Doppler effect, Interferometers, Remote sensing, Spectrographs, Germanium, Imaging systems, Cameras, Velocity measurements, Data processing, Head

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Proceedings Article | 13 September 2012 Paper

Silicon immersion gratings and their spectroscopic applications

Jian Ge, Bo Zhao, Scott Powell, Adam Fletcher, Xiaoke Wan, Liang Chang, Hali Jakeman, Dimitrios Koukis, David Tanner, Dennis Ebbets, Jonathan Weinberg, Sarah Lipscy, Rich Nyquist, John Bally

Proceedings Volume 8450, 84502U (2012) https://doi.org/10.1117/12.925803

KEYWORDS: Infrared spectroscopy, Silicon, Spectroscopy, Spectrographs, Stars, Near infrared, Diffraction gratings, Infrared telescopes, Coating, Spectral resolution

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Silicon immersion gratings (SIGs) offer several advantages over the commercial echelle gratings for high resolution infrared (IR) spectroscopy: 3.4 times the gain in dispersion or ~10 times the reduction in the instrument volume, a multiplex gain for a large continuous wavelength coverage and low cost. We present results from lab characterization of a large format SIG of astronomical observation quality. This SIG, with a 54.74 degree blaze angle (R1.4), 16.1 l/mm groove density, and 50x86 mm² grating area, was developed for high resolution IR spectroscopy (R~70,000) in the near IR (1.1-2.5 μm). Its entrance surface was coated with a single layer of silicon nitride antireflection (AR) coating and its grating surface was coated with a thin layer of gold to increase its throughput at 1.1-2.5 m. The lab measurements have shown that the SIG delivered a spectral resolution of R=114,000 at 1.55 m with a lab testing spectrograph with a 20 mm diameter pupil. The measured peak grating efficiency is 72% at 1.55 m, which is consistent with the measurements in the optical wavelengths from the grating surface at the air side. This SIG is being implemented in a new generation cryogenic IR spectrograph, called the Florida IR Silicon immersion grating spectrometer (FIRST), to offer broad-band high resolution IR spectroscopy with R=72,000 at 1.4-1.8 um under a typical seeing condition in a single exposure with a 2kx2k H2RG IR array at the robotically controlled Tennessee State University 2-meter Automatic Spectroscopic Telescope (AST) at Fairborn Observatory in Arizona. FIRST is designed to provide high precision Doppler measurements (~4 m/s) for the identification and characterization of extrasolar planets, especially rocky planets in habitable zones, orbiting low mass M dwarf stars. It will also be used for other high resolution IR spectroscopic observations of such as young stars, brown dwarfs, magnetic fields, star formation and interstellar mediums. An optimally designed SIG of the similar size can be used in the Silicon Immersion Grating Spectrometer (SIGS) to fill the need for high resolution spectroscopy at mid IR to far IR (~25-300 μm) for the NASA SOFIA airborne mission in the future.

Proceedings Article | 15 July 2010 Paper

Design, performance, and early results from extremely high Doppler precision instruments in a global network

Jian Ge, Bo Zhao, John Groot, Liang Chang, Frank Varosi, Xiaoke Wan, Scott Powell, Peng Jiang, Kevin Hanna, Ji Wang, Rohan Pais, Jian Liu, Liming Dou, Sidney Schofield, Shaun McDowell, Erin Costello, Adriana Delgado-Navarro, Scott Fleming, Brian Lee, Sandeep Bollampally, Troy Bosman, Hali Jakeman, Adam Fletcher, Gabriel Marquez

Proceedings Volume 7735, 77350H (2010) https://doi.org/10.1117/12.857366

KEYWORDS: Planets, Telescopes, Doppler effect, Stars, Calibration, Spectrographs, Sensors, Spectral resolution, Interferometers, Iodine

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