The infrared astronomy group at the Universite de Montreal has been involved in building instruments for the past 20 years, to support its own research projects or under contract with the Canada-France-Hawaii Telescope Corporation and the National Research Council. A camera for the detection of faint objects around nearby stars, a multiobject spectrograph for the 0.8pm to 2.5pm spectral range, and a wide field camera, funded by the Natural Sciences and Engineering Research Council and the Canadian Foundation for Innovation, have been designed recently and are described below. The triple-imager Trident
Direct exoplanet detections are limited by the speckle noise of the point spread function (PSF). This noise can
be reduced by subtracting PSF images obtained simultaneously in adjacent narrow spectral bands using a multichannel
camera (MCC). Experiments have shown that speckle attenuation performances are severely degraded
by differential optical aberrations between channels that decorrelate the PSFs of the different spectral bands.
We present a new technique which can greatly alleviate this problem: the introduction of a holographic diffuser
at the focal plane of the MCC. The holographic diffuser converts the PSF image into an incoherent illumination
scene that is then re-imaged with the MCC. This imaging process is equivalent to a convolution of the scene
with the PSF of each channel of the MCC. The optical aberrations in the MCC then affect only the convolution
kernel of each channel and not the PSF globally, resulting in more correlated images. We report laboratory
measurements with a dual channel prototype (1.575 μm and 1.625 μm) to validate this approach. We achieved
a speckle noise suppression factor of 12-14, which is ~4-6 times better than what has been achieved by existing
Direct exoplanet detections are currently limited by speckle noise arising from residual atmospheric wavefront errors and optical aberrations. Simultaneous spectral differential imaging (SSDI) is a high contrast imaging technique that aims at reducing this noise by the subtraction of images obtained simultaneously in adjacent narrow spectral bands. SSDI performances are severely degraded by differential optical aberrations between channels. We discuss two novel approaches to implement SSDI in which there are no differential aberrations. The first uses a microlens array at the focal plane to sample the point spread function (PSF) and micro-filters on the backside of each microlens to separate colors. The micropupils are immediately imaged on the detector. The second preserves the microlens array at the focal plane but re-images the array of micropupils through a beam-splitter on the detector. In both concepts the PSF measurement is made at the microlens array, so all optics is common prior to the PSF measurement in all colors. A simple prototype was used to test the concepts; preliminary results yield noise attenuation of ~10-2.
CPAPIR is a wide-field infrared camera for use at the Observatoire du mont Megantic and CTIO 1.5 m telescopes. The camera will be primarily a survey instrument with a half-degree field of view, making it one of the most efficient of its kind. CPAPIR will provide broad and narrow band filters within its 0.8 to 2.5 μm bandpass. The camera is based on a Hawaii-2 2048x2048 HgCdTe detector.
Detecting and characterizing exoplanets is one of the main science drives for extremely large telecopes. It requires a high-order (extreme) adaptive optics (ExAO) system combined with a coronagraph and a science camera optimized for efficient attenuation of point spread function (PSF) residuals induced by atmospheric speckles and high-frequency quasi-static aberrations. Spectral differential imaging is a very promising technique for attenuating PSF residuals. High-contrast imaging observations with the TRIDENT camera at the AO focus of the Canada-France-Hawaii Telescope (CFHT) have shown that companion detection using differential imaging is seriously compromised by very small amount of non-common path wave front errors between the different optical channels of the camera. Such problems can be eliminated with a new type of detector assembly: a multi-color detector assembly (MCDA). This paper describes the MCDA concept along with numerical simulations predicting the combined performance of an ExAO system with a Lyot coronagraph and an MCDA on a segmented 20m telescope.
The Laboratoire d'Astrophysique Experimentale (LAE) at the Universite de Montreal has designed and built several near-infrared cameras/spectrometers in the last decade for the Observatoire du Mont-Mégantic (OMM), the Canada-France-Hawaii Telescope (CFHT) and the Herzberg Institute of Astrophysics (HIA). These instruments have required innovative solutions for cryogenic electro-mechanical controls. This paper presents cryogenic motors, bearings, gears, epoxies and positioning/sensing devices at the heart of these cryo-mechanisms. In particular, the paper will focus on a new ball plunger with integrated Hall effect sensor, which can be used both as a mechanical detent and analog position encoder.
A wide-field near-infrared (0.8 - 2.4 μm) camera for the 1.6 m telescope of the Observatoire du mont Megantic (OMM), is currently under construction at the Universite de Montreal. The field of view is 30' × 30' and will have very little distortion. The optics comprise 8 spherical cryogenic lenses. The instrument features two filter wheels with provision for 10 filters including broad band I, z, J, H, K and other narrow-band filters. The camera is based on a 2048 × 2048 HgCdTe Hawaii-2 detector driven by a 3--output SDSU-II controller operating at ~250 kHz.
A near-infrared camera in use at the Canada-France-Hawaii Telescope and at the 1.6m telescope of the Observatoire du Mont-Mégantic is described. The camera is based on a Hawaii-1 1024×1024 HgCdTe array detector. Its main feature is to acquire three simultaneous images at three wavelengths (simultaneous differential imaging) across the methane absorption bandhead at 1.6 micron, enabling an accurate subtraction of the stellar point spread function (PSF) and the detection of faint close methanated companions. The instrument has no coronagraph and features a fast (1 MHz) data acquisition system without reset anomaly, yielding high observing efficiencies on bright stars. The performance of the instrument is described, and it is illustrated by CFHT images of the nearby star Ups And. TRIDENT can detect (3 sigma) a methanated companion with Delta H=10 at 0.5” from the star in one hour of observing time. Non-common path aberrations between the three optical paths are the limiting factors preventing further PSF attenuation. Reference star subtraction and instrument rotation improve the detection limit by one order of magnitude.
Affordable adaptive optics on small telescopes allow to introduce the technology to a large community and provide opportunities to train new specialists in the field. We have developed a low order, low cost adaptive optics system for the 1.6m telescope of the Mont Megantic Observatory. The system corrects tip-tilt, focus, astigmatisms and one trefoil term. It explores a number of new approaches. The sensor receives a single out-of-focus image of the reference star. The central obstruction of the telescope can free the focus detection from the effect of seeing and allows a very small defocus. The deformable mirror is profiled so as to preserve a parabolic shape under pressure from actuators located at its edge. A separate piezoelectric platform drives the tilt mirror.
We present the preliminary conceptual design of a Mosaic IR Camera and Multi-Object Spectrography (MIRCAMOS) for the Canada-France-Hawaii Telescope. The instrument houses 4 Hawaii-2 2048 by 2048 HgCdTe detectors sensitive between 0.8 and 2.5 micrometers . The optics is all reflective, featuring a warm corrector with fast tip/tilt capability and 4 cryogenic optical trains. The pixel scale is 0.20 inch/pixel yielding a field of view of 13.7 feet by 13.7 feet. Z, J, H or K band spectroscopy at R approximately 1500 is obtained with a single grating setting. A cryogenic slit wheel unit featuring several positions for multi-object custom masks is mounted within a separate cryostat designed to be thermally cycled within 8 hours for rapid exchange of MOS masks. Each mask can hold up to approximately 300 slitlets distributed over a FOV of 7 feet by 13.7 feet. MIRCAMOS is very competitive compared with similar instruments planned for 8- 10 m telescopes.
One of the major problems in trying to observe a faint companion from the ground comes from atmospheric turbulence. We present here a new camera capable of subtracting the effect of atmospheric turbulence on the PSF by taking simultaneous images of a star at three different wavelengths centered around the 1.6 micrometers methane absorption band typical of brown dwarfs and jovian planets. It is to be used at the adaptive optics compensated foci of the Megantic 1.6m, the CFHT 3.6m and the Gemini 8.2m telescopes. We present its design, which results from experiences at Megantic and CFHT with various techniques. Simulations predict there will be a 15 magnitude increase in sensitivity for detection of faint companions.
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.
KIR is a 1024 by 1024 near-IR camera used with the adaptive optics Bonnette (PUEO) of the Canada-France-Hawaii Telescope. The camera houses a 1024 by 1024 HgCdTe and simple refractive optics providing diffraction-limited images with an image scale of 0.035 inch/pixel. First light was obtained in December 1997. The throughput of the camera, from the top of the atmosphere down to the atmosphere down to the detector including PUEO, is 19 percent, 20 percent and 21 percent at J, H and K, respectively. This project is a collaboration between the Universite de Montreal, the Observatoire Midi Pyrenees and the Canada-France-Hawaii Telescope. The design and performance of the instrument are presented in this paper.
SIMON (`Spectrometre Infrarouge de Montreal') is a near-infrared (1.0 micrometers to 2.5 micrometers ) camera/spectrometer currently under development at the Universite de Montreal. The instrument will be used on the 3.6 m Canada-France-Hawaii telescope (CFHT) and the 1.6 m telescope of the Observatoire du Monte Megantic (OMM). It will house a 1024 MUL 1024 array with an image scale of 0.15" on the CHFT and 0.34" on the OMM. Two long-slit spectroscopic modes will provide resolving powers of 1300 and 5000 from 1.0 micrometers to 2.5 micrometers . The instrument could be interfaced with the adaptive optics system currently under development at the CFHT, providing diffraction-limited images at J, H, and K. This paper describes the general characteristics and the optical design of the instrument.