Gregory Barrick

SPIRou: the near-infrared spectropolarimeter/high-precision velocimeter for the Canada-France-Hawaii telescope

SPIRou is a near-IR echelle spectropolarimeter and high-precision velocimeter under construction as a next- generation instrument for the Canada-France-Hawaii-Telescope. It is designed to cover a very wide simultaneous near-IR spectral range (0.98-2.35 μm) at a resolving power of 73.5K, providing unpolarized and polarized spectra of low-mass stars at a radial velocity (RV) precision of 1m/s. The main science goals of SPIRou are the detection of habitable super-Earths around low-mass stars and the study of stellar magnetism of star at the early stages of their formation. Following a successful final design review in Spring 2014, SPIRou is now under construction and is scheduled to see first light in late 2017. We present an overview of key aspects of SPIRou’s optical and mechanical design.

SPIRou @ CFHT: design of the instrument control system

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goals of detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of eight companion papers. In this paper, the means of controlling the instrument are discussed. Most of the instrument control is fairly normal, using off-the-shelf components where possible and reusing already available code for these components. Some aspects, however, are more challenging. In particular, the paper will focus on the challenges of doing fast (50 Hz) guiding with 30 mas repeatability using the object being observed as a reference and on thermally stabilizing a large optical bench to a very high precision (~1 mK).μ

Front end of the SPIRou spectropolarimeter for Canada-France Hawaii Telescope

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a nextgeneration instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low-mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the Front End of the instrument is presented. Positioned at the Cassegrain Focal plane of the telescope, the front end is constituted of an atmospheric dispersion corrector, a field viewer with an image stabilization unit (0.03 arc seconds RMS stabilization goal), a calibration wheel and an achromatic polarimeter unit based on Fresnel Rhombs. The polarimeter permits the circular and linear polarization analysis. The retardance of the Fresnel rhombs is nominal to better than 0.5% in the whole spectral domain. The evaluation and the reduction of the thermal background of the Front end is a challenging part of the instrument.

SPIRou @ CFHT: fiber links and pupil slicer

SPIRou is a near-IR (0.98-2.35μm), echelle spectropolarimeter / high precision velocimeter being designed as a next-generation instrument for the 3.6m Canada-France-Hawaii Telescope on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low mass stars and magnetic fields of forming stars. The unique scientific and technical capabilities of SPIRou are described in a series of seven companion papers. In this paper, the fiber links which connects the polarimeter unit to the cryogenic spectrograph unit (35 meter apart) are described. The pupil slicer which forms a slit compatible with the spectrograph entrance specifications is also discussed in this paper. Some challenging aspects are presented. In particular this paper will focus on the manufacturing of 35 meter fibers with a very low loss attenuation (< 13dB/km) in the non-usual fiber spectral domain from 0.98 μm to 2.35 μm. Other aspects as the scrambling performance of the fiber links to reach high accuracy radial velocity measurements (1m/s) and the design of the pupil slicer exposed at a cryogenic and vacuum environment will be discussed.

Correcting polarization crosstalk in the ESPaDOnS spectro-polarimeter

ESPaDOnS is a high-resolution, cross-dispersed, fiber fed, echelle spectrograph in use at the Canada-France-Hawaii Telescope (CFHT). The light from the telescope passes through a polarimeter stage before being injected into the fibers that feed the spectrograph, so the instrument is capable of determining the polarization of the stellar spectra from 370 - 1000 nm in wavelength. One limit to the accuracy of the polarimetry is the inevitable polarization crosstalk added by all optics prior to polarization analysis. The main source of this crosstalk is stress birefringence in the glass of the optics; either residual from the annealing process or induced by the mounting of the optics. The process by which the crosstalk in ESPaDOnS has been reduced from 5% or more to less than 1% is discussed in this paper.

GRACES: Gemini remote access to CFHT ESPaDOnS spectrograph through the longest astronomical fiber ever made: experimental phase completed

The Gemini Remote Access to CFHT ESPaDONS Spectrograph has achieved first light of its experimental phase in May 2014. It successfully collected light from the Gemini North telescope and sent it through two 270 m optical fibers to the the ESPaDOnS spectrograph at CFHT to deliver high-resolution spectroscopy across the optical region. The fibers gave an average focal ratio degradation of 14% on sky, and a maximum transmittance of 85% at 800nm. GRACES achieved delivering spectra with a resolution power of R = 40,000 and R = 66,000 between 400 and 1,000 nm. It has a ~8% throughput and is sensitive to target fainter than 21st mag in 1 hour. The average acquisition time of a target is around 10 min. This project is a great example of a productive collaboration between two observatories on Maunakea that was successful due to the reciprocal involvement of the Gemini, CFHT, and NRC Herzberg teams, and all the staff involved closely or indirectly.

Experimental results from using two laminated film polarizers to make absolute measurements of polarization crosstalk in an optic

In working with polarimeters, it is useful to be able to analyze the level of stress birefringence in the optics of the polarimeter individually. This birefringence shows up in the polarimeter as a conversion of linear polarization to circular polarization and vice versa. A method has been developed for using two, low-cost, laminated film polarizers to make measurements of linear-to-circular polarization conversion in sample optics. Measurements were made on several optical elements of the ESPaDOnS spectro-polarimeter during the effort to reduce the polarization crosstalk, as well as on a quarter-wave plate in order to calibrate the measurement.

CFHTIR: 1k x 1k NIR Spectro-Imaging Camera for the CFHT

The CFHTIR is a large format near IR camera based on the Rockwell HAWAII Array. CFHTIR is designed for both direct imaging at the f/8 Cassegrain focus, as well as spectroscopy on the OSIS multiobject spectrograph. The camera provides 0.21 inch/pixel sampling in both applications with a single set cold transfer optics and pupil mask. The camera includes two eight-position filterwheels driven by cryogenic stepper motors with position control using a novel Hall effect sensor technique. CFHTIR also uses a novel dewar wiring technique employing flexible circuit vacuum feedthrus. CFHTIR is the second large format IR camera based on the Hawaii array constructed at CFHT, the first being the KIR camera for the CFHT Adaptive Optics Bonnette which was commissioned in 1997. This paper describes the system architecture of the CFHTIR highlighting key design concepts and detailing the physical elements.

VASAO: visible all sky adaptive optics: a new adaptive optics concept for CFHT

VASAO is an ambitious project that explores new conceptual direction in the field of astronomical adaptive optics. In the era of 8 meter and larger telescopes, and their instrument costs and telescope time pressure, there is a natural niche for such ground-breaking conceptual development in the 4 meter class telescope. The aim of VASAO is to provide diffraction limited imaging in the visible with 100% sky coverage; the challenge (but potential rewards) arises from the simultaneity of these requirements. To this end, CFHT is conducting a feasibility study based on the polychromatic guide star concept (Foy et al., 1995 [4]) coupled with a high order curvature AO system, presented in this paper. A number of experiments have been started (or carried out) to study the challenges and limits of the techniques involved in an operational setting; these include the FlyEyes detector, and a polychromatic tip-tilt test on natural stars. Because such a project straddles such a fine line between facility instrument and experimental facility, careful thought has to be given to the balance between modes of operations and potential astrophysical targets.

SPIRou at CFHT: fiber links and pupil slicer

SPIRou is a near-IR (0.98-2.35μm) echelle spectropolarimeter / high precision velocimeter installed at the beginning of the year 2018 on the 3.6m Canada-France-Hawaii Telescope (CFHT) on Mauna Kea, Hawaii, with the main goal of detecting Earth-like planets around low mass stars and magnetic fields of forming stars. In this paper, the fiber links which connects the polarimeter unit to the cryogenic spectrograph unit (35 meter apart) are described. The pupil slicer which forms a slit compatible with the spectrograph entrance specifications is also discussed in this paper. Some challenging aspects are presented. In particular this paper will focus on the manufacturing of 35 meter fibers with a very low loss attenuation (< 13dB/km) in the non-usual fiber spectral domain from 0.98 μm to 2.35 μm. Other aspects as the scrambling performance of the fiber links to reach high accuracy radial velocity measurements (<1m/s) and the performances of the pupil slicer exposed at a cryogenic and vacuum environment will be discussed.