15 research outputs found
End-to-end Simulation of the SCALES Integral Field Spectrograph
We present end-to-end simulations of SCALES, the third generation
thermal-infrared diffraction limited imager and low/med-resolution integral
field spectrograph (IFS) being designed for Keck. The 2-5 micron sensitivity of
SCALES enables detection and characterization of a wide variety of exoplanets,
including exoplanets detected through long-baseline astrometry, radial-velocity
planets on wide orbits, accreting protoplanets in nearby star-forming regions,
and reflected-light planets around the nearest stars. The simulation goal is to
generate high-fidelity mock data to assess the scientific capabilities of the
SCALES instrument at current and future design stages. The simulation processes
arbitrary-resolution input intensity fields with a proposed observation pattern
into an entire mock dataset of raw detector read-out lenslet-based IFS frames
with calibrations and metadata, which are then reduced by the IFS data
reduction pipeline to be analyzed by the user.Comment: 13 pages, 8 figures, Society of Photo-Optical Instrumentation
Engineer
Forecasting cosmic acceleration measurements using the Lyman- forest
We present results from end-to-end simulations of observations designed to
constrain the rate of change in the expansion history of the Universe using the
redshift drift of the Lyman- forest absorption lines along the
lines-of-sight toward bright quasars. For our simulations we take
Lyman- forest lines extracted from Keck/HIRES spectra of bright quasars
at , and compare the results from these real quasar spectra with mock
spectra generated via Monte Carlo realizations. We use the results of these
simulations to assess the potential for a dedicated observatory to detect
redshift drift, and quantify the telescope and spectrograph requirements for
these observations. Relative to Liske et al. (2008), two main refinements in
the current work are inclusion of quasars from more recent catalogs and
consideration of a realistic observing strategy for a dedicated redshift drift
experiment that maximizes . We find that using a
dedicated facility and our designed observing plan, the redshift drift can be
detected at significance in 15 years with a 25m telescope, given a
spectrograph with long term stability with and 25% total system
efficiency. To achieve this significance, the optimal number of targets is four
quasars, with observing time weighted based upon and
object visibility. This optimized strategy leads to a 9% decrease in the
telescope diameter or a 6% decrease in the required time to achieve the same
S/N as for the idealized case of uniformly distributing time to the same
quasars.Comment: 13 pages, 12 figures, accepted for publication in MNRA
Characterization of diamond-turned optics for SCALES
High-contrast imaging has been used to discover and characterize dozens of
exoplanets to date. The primary limiting performance factor for these
instruments is contrast, the ratio of exoplanet to host star brightness that an
instrument can successfully resolve. Contrast is largely determined by
wavefront error, consisting of uncorrected atmospheric turbulence and optical
aberrations downstream of AO correction. Single-point diamond turning allows
for high-precision optics to be manufactured for use in astronomical
instrumentation, presenting a cheaper and more versatile alternative to
conventional glass polishing. This work presents measurements of wavefront
error for diamond-turned aluminum optics in the Slicer Combined with an Array
of Lenslets for Exoplanet Spectroscopy (SCALES) instrument, a 2-5 micron
coronagraphic integral field spectrograph under construction for Keck
Observatory. Wavefront error measurements for these optics are used to simulate
SCALES' point spread function using physical optics propagation software poppy,
showing that SCALES' contrast performance is not limited by wavefront error
from internal instrument optics.Comment: Techniques and Instrumentation for Detection of Exoplanets X
The Planetary Systems Imager: 2-5 Micron Channel
We summarize the red channel (2-5 micron) of the Planetary Systems Imager
(PSI), a proposed second-generation instrument for the TMT. Cold exoplanets
emit the majority of their light in the thermal infrared, which means these
exoplanets can be detected at a more modest contrast than at other wavelengths.
PSI-Red will be able to detect and characterize a wide variety of exoplanets,
including radial-velocity planets on wide orbits, accreting protoplanets in
nearby star-forming regions, and reflected-light planets around the nearest
stars. PSI-Red will feature an imager, a low-resolution lenslet integral field
spectrograph, a medium-resolution lenslet+slicer integral field spectrograph,
and a fiber-fed high-resolution spectrograph.Comment: 7 pages, 5 figure
Update on the Preliminary Design of SCALES: the Santa Cruz Array of Lenslets for Exoplanet Spectroscopy
SCALES (Santa Cruz Array of Lenslets for Exoplanet Spectroscopy) is a 2-5
micron high-contrast lenslet integral-field spectrograph (IFS) driven by
exoplanet characterization science requirements and will operate at W. M. Keck
Observatory. Its fully cryogenic optical train uses a custom silicon lenslet
array, selectable coronagraphs, and dispersive prisms to carry out integral
field spectroscopy over a 2.2 arcsec field of view at Keck with low ()
spectral resolution. A small, dedicated section of the lenslet array feeds an
image slicer module that allows for medium spectral resolution (),
which has not been available at the diffraction limit with a coronagraphic
instrument before. Unlike previous IFS exoplanet instruments, SCALES is capable
of characterizing cold exoplanet and brown dwarf atmospheres ( K) at
bandpasses where these bodies emit most of their radiation while capturing
relevant molecular spectral features.Comment: 24 pages, 13 figures, SPIE Astronomical Instruments and Telescopes
2020 conferenc
Detecting Earth-like Biosignatures on Rocky Exoplanets around Nearby Stars with Ground-based Extremely Large Telescopes
As we begin to discover rocky planets in the habitable zone of nearby stars with missions like TESS and CHEOPS, we will need quick advancements on instrumentation and observational techniques that will enable us to answer key science questions, such as What are the atmospheric characteristics of habitable zone rocky planets? How common are Earth-like biosignatures in rocky
planets?} How similar or dissimilar are those planets to Earth? Over the next decade we expect to have discovered several Earth-analog candidates, but we will not have the tools to study the atmospheres of all of them in detail. Ground-based ELTs can identify biosignatures in the spectra of these candidate exo-Earths and understand how the planets' atmospheres compare to the Earth at different epochs. Transit spectroscopy, high-resolution spectroscopy, and reflected-light direct imaging on ELTs can identify multiple biosignatures for habitable zone, rocky planets around M stars at optical to near-infrared wavelengths. Thermal infrared direct imaging can detect habitable zone, rocky planets around AFGK stars, identifying ozone and motivating reflected-light
follow-up observations with NASA missions like HabEx/LUVOIR. Therefore, we recommend that the Astro2020 Decadal Survey Committee support: (1) the search for Earth-like biosignatures on rocky planets around nearby stars as a key science case; (2) the construction over the next decade of ground-based Extremely Large Telecopes (ELTs), which will provide the large aperture and
spatial resolution necessary to start revealing the atmospheres of
Earth-analogues around nearby stars; (3) the development of instrumentation that optimizes the detection of biosignatures; and (4) the generation of accurate line lists for potential biosignature gases, which are needed as model templates to detect those molecules