We have developed an optical design for a high resolution spectrograph in response to NASA’s call for an extreme precision Doppler spectrometer (EPDS) for the WIYN telescope. Our instrument covers a wavelength range of 380 to 930 nm using a single detector and with a resolution of 100,000. To deliver the most stable spectrum, we avoid the use of an image slicer, in favor of a large (195 mm diameter) beam footprint on a 1x2 mosaic R4 Echelle grating. The optical design is based on a classic white pupil layout, with a single parabolic mirror that is used as the main and transfer collimator. Cross dispersion is provided by a single large PBM2Y glass prism. The refractive camera consists of only four rotationally symmetric lenses made from i-Line glasses, yet delivers very high image quality over the full spectral bandpass. We present the optical design of the main spectrograph bench and discuss the design trade-offs and expected performance.
We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance error budget. While natively focused on the performance of the NEID instrument, this modular performance budget is immediately adaptable to a number of current and future instruments. Such an approach is an important step in charting a path towards improving Doppler measurement precisions to the levels necessary for discovering Earth-like planets.
The Miniature Exoplanet Radial Velocity Array (MINERVA) is a U.S.-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7-m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high-precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. We describe the design of MINERVA, including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, California, and their on-sky performance is validated. The design and simulated performance of the spectrograph is briefly discussed as we await its completion. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b—a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence in 2015.
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.
We present a new and innovative near-infrared multi-band ultraprecise spectroimager (NIMBUS) for SOFIA. This design is capable of characterizing a large sample of extrasolar planet atmospheres by measuring elemental and molecular abundances during primary transit and occultation. This wide-field spectroimager would also provide new insights into Trans-Neptunian Objects (TNO), Solar System occultations, brown dwarf atmospheres, carbon chemistry in globular clusters, chemical gradients in nearby galaxies, and galaxy photometric redshifts. NIMBUS would be the premier ultraprecise spectroimager by taking advantage of the SOFIA observatory and state of the art infrared technologies.
This optical design splits the beam into eight separate spectral bandpasses, centered around key molecular bands from 1 to 4μm. Each spectral channel has a wide field of view for simultaneous observations of a reference star that can decorrelate time-variable atmospheric and optical assembly effects, allowing the instrument to achieve ultraprecise calibration for imaging and photometry for a wide variety of astrophysical sources. NIMBUS produces the same data products as a low-resolution integral field spectrograph over a large spectral bandpass, but this design obviates many of the problems that preclude high-precision measurements with traditional slit and integral field spectrographs. This instrument concept is currently not funded for development.