Microsatellite market requires high performance while minimizing mass, volume and cost. Telescopes are specifically targeted by these trade-offs. One of these is to use the optomechanical structure of the telescope to mount electronic devices that may dissipate heat. However, such approach may be problematic in terms of distortions due to the presence of high thermal gradients throughout the telescope structure. To prevent thermal distortions, Carbon Fiber Reinforced Polymer (CFRP) technology can be used for the optomechanical telescope material structure. CFRP is typically about 100 times less sensitive to thermal gradients and its coefficient of thermal expansion (CTE) is about 200 to 600 times lower than standard aluminum alloys according to inhouse measurements. Unfortunately, designing with CFRP material is not as straightforward as with metallic materials. There are many parameters to consider in order to reach the desired dimensional stability under thermal, moisture and vibration exposures. Designing optomechanical structures using CFRP involves many challenges such as interfacing with optics and sometimes dealing with high CTE mounting interface structures like aluminum spacecraft buses. INO has designed a CFRP sandwich telescope structure to demonstrate the achievable performances of such technology. Critical parameters have been optimized to maximize the dimensional stability while meeting the stringent environmental requirements that microsatellite payloads have to comply with. The telescope structure has been tested in vacuum from -40°C to +50°C and has shown a good fit with finite element analysis predictions.
The adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). Recently, INO has been involved in the optomechanical design of several subsystems of NFIRAOS, including the Instrument Selection Mirror (ISM), the NFIRAOS Beamsplitters (NBS), and the NFIRAOS Source Simulator system (NSS) comprising the Focal Plane Mask (FPM), the Laser Guide Star (LGS) sources, and the Natural Guide Star (NGS) sources. This paper presents an overview of these subsystems and the optomechanical design approaches used to meet the optical performance requirements under environmental constraints.
The early-light facility adaptive optics system for the Thirty Meter Telescope (TMT) is the Narrow-Field InfraRed Adaptive Optics System (NFIRAOS). The science beam splitter changer mechanism and the visible light beam splitter are subsystems of NFIRAOS. This paper presents the opto-mechanical design of the NFIRAOS beam splitters subsystems (NBS). In addition to the modal and the structural analyses, the beam splitters surface deformations are computed considering the environmental constraints during operation. Surface deformations are fit to Zernike polynomials using SigFit software. Rigid body motion as well as residual RMS and peak-to-valley surface deformations are calculated. Finally, deformed surfaces are exported to Zemax to evaluate the transmitted and reflected wave front error. The simulation results of this integrated opto-mechanical analysis have shown compliance with all optical requirements.
This paper describes the current opto-mechanical design of NFIRAOS (Narrow Field InfraRed Adaptive Optics System) for the Thirty Meter Telescope (TMT). The preliminary design update review for NFIRAOS was successfully held in December 2011, and incremental design progress has since occurred on several fronts. The majority of NFIRAOS is housed within an insulated and cooled enclosure, and operates at -30 C to reduce background emissivity. The cold optomechanics are attached to a space-frame structure, kinematically supported by bipods that penetrate the insulated enclosure. The bipods are attached to an exo-structure at ambient temperature, which also supports up to three client science instruments and a science calibration unit.
This paper reports on the deposition of vanadium oxide thin films with sheet resistance uniformity better than 2.5% over a 150 mm wafer. The resistance uniformity within the array is estimated to be less than 1%, which is comparable with the value reported for amorphous silicon-based microbolometer arrays. In addition, this paper also shows that the resistivity of vanadium oxide, like amorphous silicon, can be modeled by Arrhenius' equation. This result is expected to significantly ease the computation of the correction table required for TEC-less operation of VOx-based microbolometer arrays.
In carbon fiber reinforced plastic (CFRP) optomechanical structures, particularly when embodying reflective optics, angular stability is critical. Angular stability or warping stability is greatly affected by moisture absorption and thermal gradients. Unfortunately, it is impossible to achieve the perfect laminate and there will always be manufacturing errors in trying to reach a quasi-iso laminate. Some errors, such as those related to the angular position of each ply and the facesheet parallelism (for a bench) can be easily monitored in order to control the stability more adequately. This paper presents warping experiments and finite-element analyses (FEA) obtained from typical optomechanical sandwich structures. Experiments were done using a thermal vacuum chamber to cycle the structures from −40°C to 50°C. Moisture desorption tests were also performed for a number of specific configurations. The selected composite material for the study is the unidirectional prepreg from Tencate M55J/TC410. M55J is a high modulus fiber and TC410 is a new-generation cyanate ester designed for dimensionally stable optical benches. In the studied cases, the main contributors were found to be: the ply angular errors, laminate in-plane parallelism (between 0° ply direction of both facesheets), fiber volume fraction tolerance and joints. Final results show that some tested configurations demonstrated good warping stability. FEA and measurements are in good agreement despite the fact that some defects or fabrication errors remain unpredictable. Design guidelines to maximize the warping stability by taking into account the main dimensional stability contributors, the bench geometry and the optical mount interface are then proposed.
We provide an update on the development of the first light adaptive optics systems for the Thirty Meter Telescope
(TMT) over the past two years. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO
System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star
(LGS) multi-conjugate AO (MCAO) architecture will provide uniform, diffraction-limited performance in the
J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as
is required to support TMT science cases. Both NFIRAOS and the LGSF have successfully completed design
reviews during the last twelve months. We also report on recent progress in AO component prototyping, control
algorithm development, and system performance analysis.
NFIRAOS is the first-light adaptive optics system planned for the Thirty Meter Telescope, and is being designed at the
National Research Council of Canada's Herzberg Institute of Astrophysics. NFIRAOS is a laser guide star multiconjugate
adaptive optics system - a practical approach to providing diffraction limited image quality in the NIR over a
30" field of view, with high sky coverage. This will enable a wide range of TMT science that depends upon the large
corrected field of view and high precision astrometry and photometry. We review recent progress developing the design
and conducting performance estimates for NFIRAOS.
The use of uncooled infrared (IR) imaging technology in Thermal Weapon Sight (TWS) systems produces a unique tool
that perfectly fulfills the all-weather, day-and-night vision demands in modern battlefields by significantly increasing the
effectiveness and survivability of a dismounted soldier. The main advantage of IR imaging is that no illumination is
required; therefore, observation can be accomplished in a passive mode. It is particularly well adapted for target
detection even through smoke, dust, fog, haze, and other battlefield obscurants. In collaboration with the Defense
Research and Development Canada (DRDC Valcartier), INO engineering team developed, produced, and tested a rugged
thermal weapon sight. An infrared channel provides for human detection at 800m and recognition at 200m. Technical
system requirements included very low overall weight as well as the need to be field-deployable and user-friendly in
harsh conditions. This paper describes the optomechanical design and focuses on the catadioptric-based system
integration. The system requirements forced the optomechanical engineers to minimize weight while maintaining a
sufficient level of rigidity in order to keep the tight optical tolerances. The optical system's main features are: a precision
manual focus, a watertight vibration insulated front lens, a bolometer and two gold coated aluminum mirrors. Finite
element analyses using ANSYS were performed to validate the subsystems performance. Some of the finite element
computations were validated using different laboratory setups.
A rugged lightweight thermal weapon sight (TWS) prototype was developed at INO in collaboration with
DRDC-Valcartier. This TWS model is based on uncooled bolometer technology, ultralight catadioptric
optics, ruggedized mechanics and electronics, and extensive onboard processing capabilities.
The TWS prototype operates in a single 8-12 μm infrared (IR) band. It is equipped with a unique
lightweight athermalized catadioptric objective and a bolometric IR imager with an INO focal plane array
(FPA). Microscan technology allows the use of a 160 x 120 pixel FPA with a pitch of 50 μm to achieve a
320 × 240 pixel resolution image thereby avoiding the size (larger optics) and cost (expensive IR optical
components) penalties associated with the use of larger format arrays. The TWS is equipped with a
miniature shutter for automatic offset calibration. Based on the operation of the FPA at 100 frames per
second (fps), real-time imaging with 320 x 240 pixel resolution at 25 fps is available. This TWS is also
equipped with a high resolution (857 x 600 pixels) OLED color microdisplay and an integrated wireless
digital RF link. The sight has an adjustable and selectable electronic reticule or crosshair (five possible
reticules) and a manual focus from 5 m to infinity standoff distance. Processing capabilities are added to
introduce specific functionalities such as image inversion (black hot and white hot), image enhancement,
and pixel smoothing. This TWS prototype is very lightweight (~ 1100 grams) and compact (volume of 93
cubic inches). It offers human size target detection at 800 m and recognition at 200 m (Johnson criteria).
With 6 Li AA batteries, it operates continuously for 5 hours and 20 minutes at room temperature. It can
operate over the temperature range of -30oC to +40oC and its housing is completely sealed. The TWS is
adapted to weaver or Picatinny rail mounting. The overall design of the TWS prototype is based on
feedbacks of users to achieve improved user-friendly (e.g. no pull-down menus and no electronic focusing)
and ergonomic (e.g. locations of buttons) features.
A dual band thermal/visible weapon sight (TVWS) prototype was developed by INO in collaboration with
DRDC Valcartier. The TVWS operates in the 8-12 μm infrared (IR) and 300-900 nm visible wavebands for
enhanced vision capabilities in day and night operations. It is equipped with lightweight athermalized
coaxial catadioptric objectives, a bolometric IR imager operating in a microscan mode providing an
effective resolution of 320 x 240 pixels and a visible image intensifier of 768 x 493 pixels. The TVWS is
equipped with a miniature shutter for automatic offset calibration. Real-time imaging at 30 fps is available.
Both the visible and IR images can be toggled with a single touch button and displayed on an integrated
color micro liquid crystal display (LCD). The TVWS also has a standard video output via a coaxial
connector. An integrated wireless analog RF link can be used to send images to a remote command control. The sight has an adjustable electronic crosshair and two manual focuses from 25 m to infinity. On-board
processing capabilities were added to introduce specific functionalities such as image polarity inversion
(black hot/white hot) and image enhancement. This TVWS model is also very lightweight (~ 1900 grams)
and compact (volume of 142 cubic inches). It offers human size target detection at 800 m and recognition at
200 m (Johnson criteria) with the IR waveband while offering the human recognition at up to 800 m with
the visible waveband. The TVWS is adapted for weaver or Picatinny rail mounting.