SCALES (Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy) is a 2 micron to 5 micron high-contrast lenslet-based Integral Field Spectrograph (IFS) designed to characterize exoplanets and their atmospheres. The SCALES medium-spectral-resolution mode uses a lenslet subarray with a 0.34 x 0.36 arcsecond field of view which allows for exoplanet characterization at increased spectral resolution. We explore the sensitivity limitations of this mode by simulating planet detections in the presence of realistic noise sources. We use the SCALES simulator scalessim to generate high-fidelity mock observations of planets that include speckle noise from their host stars, as well as other atmospheric and instrumental noise effects. We employ both angular and reference differential imaging as methods of disentangling speckle noise from the injected planet signals. These simulations allow us to assess the feasibility of speckle deconvolution for SCALES medium resolution data, and to test whether one approach outperforms another based on planet angular separations and contrasts.
The Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy (SCALES) is an under-construction thermal infrared high-contrast integral field spectrograph that will be located at the W. M. Keck Observatory. SCALES will detect and characterize planets that are currently inaccessible to detailed study by operating at thermal (2 μm to 5 μm) wavelengths and leveraging integral-field spectroscopy to readily distinguish exoplanet radiation from residual starlight. SCALES’ wavelength coverage and medium-spectral-resolution (R ∼ 4,000) modes will also enable investigations of planet accretion processes. We explore the scientific requirements of additional custom gratings and filters for incorporation into SCALES that will optimally probe tracers of accretion in forming planets. We use ray-traced hydrogen emission line profiles (i.e., Brγ, Brα) and the SCALES end-to-end simulator, scalessim, to generate grids of high-fidelity mock datasets of accreting planetary systems with varying characteristics (e.g., Teff, planet mass, planet radius, mass accretion rate). In this proceeding, we describe potential specialized modes that best differentiate accretion properties and geometries from the simulated observations.
The Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy (SCALES) is a 2 μm to 5 μm, high-contrast Integral Field Spectrograph (IFS) currently being built for Keck Observatory. With both low (R ≲ 250) and medium (R approximately 3500 to 7000) spectral resolution IFS modes, SCALES will detect and characterize significantly colder exoplanets than those accessible with near-infrared (approximately 1 μm to 2 μm) high-contrast spectrographs. This will lead to new progress in exoplanet atmospheric studies, including detailed characterization of benchmark systems that will advance the state of the art of atmospheric modeling. SCALES’ unique modes, while designed specifically for direct exoplanet characterization, will enable a broader range of novel (exo)planetary observations as well as galactic and extragalactic studies. Here we present the science cases that drive the design of SCALES. We describe an end-to-end instrument simulator that we use to track requirements and show simulations of expected science yields for each driving science case. We conclude with a discussion of preparations for early science when the instrument sees first light in approximately 2025.
The Slicer Combined with an Array of Lenslets for Exoplanet Spectroscopy (SCALES) instrument is a lenslet-based integral field spectrograph that will operate at 2 to 5 microns, imaging and characterizing colder (and thus older) planets than current high-contrast instruments. Its spatial resolution for distant science targets and/or close-in disks and companions could be improved via interferometric techniques such as sparse aperture masking. We introduce a nascent Python package, NRM-artist, that we use to design several SCALES masks to be non-redundant and to have uniform coverage in Fourier space. We generate high-fidelity mock SCALES data using the scalessim package for SCALES’ low spectral resolution modes across its 2 to 5 micron bandpass. We include realistic noise from astrophysical and instrument sources, including Keck adaptive optics and Poisson noise. We inject planet and disk signals into the mock datasets and subsequently recover them to test the performance of SCALES sparse aperture masking and to determine the sensitivity of various mask designs to different science signals.
We present the design of SCALES (Slicer Combined with Array of Lenslets for Exoplanet Spectroscopy) a new 2-5 micron coronagraphic integral field spectrograph under construction for Keck Observatory. SCALES enables low-resolution (R∼50) spectroscopy, as well as medium-resolution (R∼4,000) spectroscopy with the goal of discovering and characterizing cold exoplanets that are brightest in the thermal infrared. Additionally, SCALES has a 12x12” field-of-view imager that will be used for general adaptive optics science at Keck. We present SCALES’s specifications, its science case, its overall design, and simulations of its expected performance. Additionally, we present progress on procuring, fabricating and testing long lead-time components.
The direct characterization of exoplanetary systems with high contrast imaging is among the highest priorities for the broader exoplanet community. As large space missions will be necessary for detecting and characterizing exo-Earth twins, developing the techniques and technology for direct imaging of exoplanets is a driving focus for the community. For the first time, JWST will directly observe extrasolar planets at mid-infrared wavelengths beyond 5 μm, deliver detailed spectroscopy revealing much more precise chemical abundances and atmospheric conditions, and provide sensitivity to analogs of our solar system ice-giant planets at wide orbital separations, an entirely new class of exoplanet. However, in order to maximise the scientific output over the lifetime of the mission, an exquisite understanding of the instrumental performance of JWST is needed as early in the mission as possible. In this paper, we describe our 55-hour Early Release Science Program that will utilize all four JWST instruments to extend the characterisation of planetary mass companions to ∼15-20 μm as well as image a circumstellar disk in the mid-infrared with unprecedented sensitivity. Our program will also assess the performance of the observatory in the key modes expected to be commonly used for exoplanet direct imaging and spectroscopy, optimize data calibration and processing, and generate representative datasets that will enable a broad user base to effectively plan for general observing programs in future cycles.
HgCdTe detectors with longer wavelength cutoffs were created for extending the lifetime of space-based applications because of their higher operating temperatures compared to arsenic doped silicon (Si:As) detectors. In addition to lower dark currents, the HgCdTe detectors also have higher quantum efficiencies compared to Si:As detectors. We are testing a HgCdTe detector with a 12.8 micron cutoff presented in Cabrera et al 2019 using HAWAII electronics in fast read-out mode to understand this array’s viability in instruments behind future ELT s that will directly image Earth-like planets. An f/100 system is required to operate the detector on a thirty meter diameter telescope without saturating, therefore we are the same f# system on the modified cryostat used to test and characterize the detector. We will present initial results on the detector’s quantum efficiency from 2 to 12 microns, read noise, dark current, and ability to tolerate flux levels that would be seen on future ELTs.
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 (< 300) spectral resolution. A small, dedicated section of the lenslet array feeds an image slicer module that allows for medium spectral resolution (5000 10000), 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 (< 600 K) at bandpasses where these bodies emit most of their radiation while capturing relevant molecular spectral features.
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