The Keck Planet Imager and Characterizer (KPIC), a series of upgrades to the Keck II Adaptive Optics System and Instrument Suite, aims to demonstrate high-resolution spectroscopy of faint exoplanets that are spatially resolved from their host stars. In this paper, we measure KPIC’s sensitivity to companions as a function of separation (i.e., the contrast curve) using on-sky data collected over four years of operation. We show that KPIC is able to reach contrasts of 1.3 × 10−4 at 90 mas and 9.2 × 10−6 at 420 mas separation from the star, and that KPIC can reach planet-level sensitivities at angular separations within the inner working angle of coronagraphic instruments such as GPI and SPHERE. KPIC is also able to achieve more extreme contrasts than other medium-/high-resolution spectrographs that are not as optimized for high-contrast performance. We decompose the KPIC performance budget into individual noise terms and discuss limiting factors. The fringing that results from combining a high-contrast imaging system with a high-resolution spectrograph is identified as an important source of systematic noise. After mitigation and correction, KPIC is able to reach within a factor of 2 of the photon noise limit at separations < 200 mas. At large separations, KPIC is limited by the background noise performance of NIRSPEC.
The Keck Planet Imager and Characterizer (KPIC) combines high contrast imaging with high resolution spectroscopy (R∼35,000 in K band) to study directly imaged exoplanets and brown dwarfs in unprecedented detail. KPIC aims to spectrally characterize substellar companions through measurements of planetary radial velocities, spins, and atmospheric composition. Currently, the dominant source of systematic noise for KPIC is fringing, or oscillations in the spectrum as a function of wavelength. The fringing signal can dominate residuals by up to 10% of the continuum for high S/N exposures, preventing accurate wavelength calibration, retrieval of atmospheric parameters, and detection of planets with flux ratios less than 1% of the host star. To combat contamination from fringing, we first identify its three unique sources and adopt a physically informed model of Fabry-Pérot cavities to apply to post-processed data. We find this strategy can effectively model the fringing in observations of bright stars, reducing the residual systematics caused by fringing by a factor of 2. Next, we wedge two of the transmissive optics internal to KPIC to eliminate two sources of fringing and confirm the third source as the entrance window to the spectrograph. Finally, we apply our previous model of the Fabry-Pérot cavity to new data taken with the wedged optics to reduce the amplitude of the residuals by a factor of 10.
Vortex fiber nulling (VFN) is a single-aperture interferometric technique for detecting and characterizing exoplanets separated from their host star by less than a diffracted beam width. VFN uses a vortex mask and single-mode fiber to selectively reject starlight while coupling off-axis planet light with a simple optical design that can be readily implemented on existing direct imaging instruments that can feed light to an optical fiber. With its axially symmetric coupling region peaking within the inner working angle of conventional coronagraphs, VFN is more efficient at detecting new companions at small separations than conventional direct imaging, thereby increasing the yield of on-going exoplanet search campaigns. We deployed a VFN mode operating in K band (2.0 to 2.5 μm) on the Keck Planet Imager and Characterizer (KPIC) instrument at the Keck II Telescope. We present the instrument design of this first on-sky demonstration of VFN and the results from on-sky commissioning, including planet and star throughput measurements and predicted flux-ratio detection limits for close-in companions. The instrument performance is shown to be sufficient for detecting a companion 103 times fainter than a fifth magnitude host star in 1 h at a separation of 50 mas (1.1 λ / D). This makes the instrument capable of efficiently detecting substellar companions around young stars. We also discuss several routes for improvement that will reduce the required integration time for a detection by a factor >3.
The Keck Planet Imager and Characterizer (KPIC) is a series of upgrades for the Keck II Adaptive Optics system and the NIRSPEC spectrograph to enable diffraction-limited, high-resolution (R>30,000) spectroscopy in the K and L bands. KPIC’s use of single-mode fibers provides a substantial reduction in sky background as well as an extremely stable line-spread function. In this paper we present the results of extensive system-level laboratory testing and characterization of Phase II of the instrument and each of its modes. We also show early on-sky results from the first few months of commissioning with these upgrades along with the next steps for the instrument.
KPIC (Keck Planet Imager and Characterizer) is a series of upgrades to Keck II adaptive optics and the NIR-SPEC spectrograph enabling K-band diffraction-limited high-resolution spectroscopy. KPIC’s single-mode fibers provide a substantial reduction in sky background as well as an extremely stable line-spread function. In this paper we present the on-sky performance of KPIC phase I and lessons learned from calibration and operation of the system, including procedures for maximizing throughput and assessments of long-term line-spread and calibration stability. During phase I, KPIC successfully detected 23 exoplanets and brown dwarfs, with separations from 200 to 3600 mas and K-band magnitudes up to 17.
The Keck Planet Imager and Characterizer (KPIC) is a novel instrument that combines high-contrast imaging with high-resolution spectroscopy to enable high-dispersion coronagraphy (HDC) techniques that allow us to characterize directly imaged exoplanets at a spectral resolution of R~35,000. At this resolution, individual absorption lines in planetary atmospheres are spectrally resolved, allowing for measurements of molecular abundances to constrain chemical composition, planetary radial velocities to constrain orbital configurations, and planetary spin to constrain angular momentum evolution. I will provide an overview of the instrument, with a focus on its novel fiber injection unit (FIU) and the use of single mode fibers. I will discuss new HDC techniques we are developing that take advantage of the single-mode fibers of KPIC to both spatially and spectrally filter out the bright glare of the host stars to study the faint exoplanets. In particular, we have demonstrated the ability to forward model the high-resolution spectrum of diffracted stellar speckles, allowing us to directly fit our data without the need for cross-correlation functions. I will present some early science observations from KPIC that successfully demonstrate its technical capabilities, with the highlight being the first detection of all four HR 8799 planets at high spectral resolution. I will conclude with future avenues to push the sensitivity of HDC techniques and discuss possible synergies with other exoplanet characterization techniques such as long-baseline interferometry.
The Keck Planet Imager and Characterizer (KPIC) is a purpose-built instrument to demonstrate technological and instrumental concepts initially developed for the exoplanet direct imaging field. Located downstream of the current Keck II adaptive optic (AO) system, KPIC contains a fiber injection unit (FIU) capable of combining the high-contrast imaging capability of the AOs system with the high dispersion spectroscopy capability of the current Keck high resolution infrared spectrograph (NIRSPEC). Deployed at Keck in September 2018, this instrument has already been used to acquire high-resolution spectra (R > 30,000) of multiple targets of interest. In the near term, it will be used to spectrally characterize known directly imaged exoplanets and low-mass brown dwarf companions visible in the northern hemisphere with a spectral resolution high enough to enable spin and planetary radial velocity measurements as well as Doppler imaging of atmospheric weather phenomena. Here, we present the design of the FIU, the unique calibration procedures needed to operate a single-mode fiber instrument and the system performance.
The Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II adaptive optics system and instrument suite with the goal of improving direct imaging and high-resolution spectroscopic characterization capabilities for giant exoplanets. KPIC Phase I includes a fiber injection unit (FIU) downstream of a new pyramid wavefront sensor, coupling planet light to a single mode fiber fed into NIRSPEC, Keck’s high-resolution infrared spectrograph. This enables high-dispersion spectroscopy (HDS) of directly imaged exoplanets at smaller separation and higher contrast, improving our spectral characterization capabilities for these objects. Here, we report performance results from the KPIC Phase I FIU commissioning, including analysis of throughput, stability, and sensitivity of the instrument.
KEYWORDS: Coronagraphy, Device simulation, Planets, Exoplanets, Atmospheric optics, Imaging systems, L band, Image resolution, Visible radiation, Signal to noise ratio
The Keck Planet Imager and Characterizer (KPIC) is a purpose-built instrument for high-dispersion coronagraphy in the K and L bands on Keck. This instrument will provide the first high resolution (R>30,000) spectra of known directly imaged exoplanets and low-mass brown dwarf companions visible in the northern hemisphere.
KPIC is developed in phases. Phase I is currently at Keck in the early operations stage, and the phase II upgrade will deploy in late 2021. The goal of phase II is to maximize the throughput for planet light and minimize the stellar leakage, hence reducing the exposure time needed to acquire spectra with a given signal-to- noise ratio. To achieve this, KPIC phase II exploits several innovative technologies that have not been combined this way before. These include a 1000-element deformable mirror for wavefront correction and speckle control, a set of lossless beam shaping optics to maximize coupling into the fiber, a pupil apodizer to suppress unwanted starlight, a pupil plane vortex mask to enable the acquisition of spectra at and within the diffraction limit, and an atmospheric dispersion compensator. These modules, when combined with the active fiber injection unit present in phase I, will make for a highly efficient exoplanet characterization platform.
In this paper, we will present the final design of the optics and opto-mechanics and highlight some innovative solutions we implemented to facilitate all the new capabilities. We will provide an overview of the assembly and laboratory testing of the sub-modules and some of the results. Finally, we will outline the deployment timeline.
The Keck Planet Imager and Characterizer (KPIC) is a purpose-built instrument to demonstrate new tech- nological and instrumental concepts initially developed for the exoplanet direct imaging field. Located downstream of the current Keck II adaptive optic system, KPIC contains a fiber injection unit (FIU) capable of combining the high-contrast imaging capability of the adaptive optic system with the high dispersion spectroscopy capability of the current Keck high resolution infrared spectrograph (NIRSPEC). Deployed at Keck in September 2018, this instrument has already been used to acquire high resolution spectra (R < 35, 000) of multiple targets of interest. In the near term, it will be used to spectrally characterize known directly imaged exoplanets and low-mass brown dwarf companions visible in the northern hemisphere with a spectral resolution high enough to enable spin and planetary radial velocity measurements as well as Doppler imaging of atmospheric weather phenomena. Here we present the design of the FIU, the unique calibration procedures needed to operate a single-mode fiber instrument and the system performance.
The Keck Planet Imager and Characterizer comprises of a series of upgrades to the Keck II adaptive optics system and instrument suite to improve the direct imaging and high resolution spectroscopy capabilities of the facility instruments NIRC2 and NIRSPEC, respectively. Phase I of KPIC includes a NIR pyramid wavefront sensor and a Fiber Injection Unit (FIU) to feed NIRSPEC with a single mode fiber, which have already been installed and are currently undergoing commissioning. KPIC will enable High Dispersion Coronagraphy (HDC) of directly imaged exoplanets for the first time, providing potentially improved detection significance and spectral characterization capabilities compared to direct imaging. In favorable cases, Doppler imaging, spin measurements, and molecule mapping are also possible. This science goal drives the development of phase II of KPIC, which is scheduled to be deployed in early 2020. Phase II optimizes the system throughput and contrast using a variety of additional submodules, including a 952 element deformable mirror, phase induced amplitude apodization lenses, an atmospheric dispersion compensator, multiple coronagraphs, a Zernike wavefront sensor, and multiple science ports. A testbed is being built in the Exoplanet Technology Lab at Caltech to characterize and test the design of each of these submodules before KPIC phase II is deployed to Keck. This paper presents an overview of the design of phase II and report on results from laboratory testing.
The Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II adaptive optics system enabling high contrast imaging and high-resolution spectroscopic characterization of giant exoplanets in the mid-infrared (2-5 microns). The KPIC instrument will be developed in phases. Phase I entails the installation of an infrared pyramid wavefront sensor (PyWFS) based on a fast, low-noise SAPHIRA IR-APD array. The ultra-sensitive infrared PyWFS will enable high contrast studies of infant exoplanets around cool, red, and/or obscured targets in star forming regions. In addition, the light downstream of the PyWFS will be coupled into an array of single-mode fibers with the aid of an active fiber injection unit (FIU). In turn, these fibers route light to Keck's high-resolution infrared spectrograph NIRSPEC, so that high dispersion coronagraphy (HDC) can be implemented for the first time. HDC optimally pairs high contrast imaging and high-resolution spectroscopy allowing detailed characterization of exoplanet atmospheres, including molecular composition, spin measurements, and Doppler imaging.
We will provide an overview of the instrument, its science scope, and report on recent results from on-sky commissioning of Phase I. We will discuss plans for optimizing the instrument to seed designs for similar modes on extremely large telescopes.
The Keck Planet Imager and Characterizer (KPIC) is an upgrade to the Keck II adaptive optics system that includes an active fiber injection unit (FIU) for efficiently routing light from exoplanets to NIRSPEC, a high-resolution spectrograph. The second phase of this upgrade, beginning at the end of 2019, will add a suite of new coronagraph modes as well as a 1000-actuator deformable mirror. One of these modes, operating in the K-band (2.2µm), will be the first Vortex Fiber Nuller (VFN) to go on sky. Vortex Fiber Nulling is a new interferometric method for suppressing starlight in order to spectroscopically characterize exoplanets at angular separations that are inaccessible with conventional coronagraph systems. A monochromatic starlight suppression of 6x10^{-5} has already been demonstrated with a VFN in the lab, thereby exceeding our goal performance, and a polychromatic demonstration is underway. Here we describe the new KPIC coronagraph modes and present the expected performance of the VFN mode using realistic parameters determined from on-sky tests done during the KPIC commissioning. We will also present the latest experimental results of the system using a laboratory replica of the KPIC instrument.
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