Dr. David R. Andersen Profile

Dr. David R. Andersen

Scientist at NRC - Herzberg Astronomy & Astrophysics

SPIE Involvement:

Author

Publications (62)

PROCEEDINGS ARTICLE | August 23, 2017

Optomechanical design of TMT NFIRAOS Subsystems at INO

Proc. SPIE. 10371, Optomechanical Engineering 2017

KEYWORDS: Large telescopes, Mirror mounts, Optical mounts, Optomechanical design, Telescopes, Integrated optics, Adaptive optics, Finite element methods, Infrared imaging, Mirrors

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SPIE Journal Paper | June 16, 2017

Quantifying telescope phase discontinuities external to adaptive optics systems by use of phase diversity and focal plane sharpening

Lamb, Masen , Correia, Carlos , Sauvage, Jean-François , Véran, Jean-Pierre , Andersen, David , Vigan, Arthur , Wizinowich, Peter , Van Dam, Marcos , Mugnier, Laurent , Bond, Charlotte

JATIS Vol. 3 Issue 03

KEYWORDS: Error analysis, Telescopes, Adaptive optics, Optical spheres, Image sensors, Image segmentation, Large telescopes, Device simulation, Exoplanets, Image retrieval

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PROCEEDINGS ARTICLE | August 9, 2016

The Infrared Imaging Spectrograph (IRIS) for TMT: multi-tiered wavefront measurements and novel mechanical design

Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI

KEYWORDS: Thirty Meter Telescope, Interfaces, IRIS Consortium, Adaptive optics, Wavefront sensors, Wavefronts, Stars, Real-time computing, Sensors, Imaging systems

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The InfraRed Imaging Spectrograph (IRIS) will be the first light adaptive optics instrument on the Thirty Meter Telescope (TMT). IRIS is being built by a collaboration between Caltech, the University of California, NAOJ and NRC Herzberg. In this paper we present novel aspects of the Support Structure, Rotator and On-Instrument Wavefront Sensor systems being developed at NRC Herzberg. IRIS is suspended from the bottom port of the Narrow Field Infrared Adaptive Optics System (NFIRAOS), and provides its own image de-rotation to compensate for sidereal rotation of the focal plane. This arrangement is a challenge because NFIRAOS is designed to host two other science instruments, which imposes strict mass requirements on IRIS. As the mechanical design of all elements has progressed, we have been tasked with keeping the instrument mass under seven tonnes. This requirement has resulted in a mass reduction of 30 percent for the support structure and rotator compared to the most recent IRIS designs. To accomplish this goal, while still being able to withstand earthquakes, we developed a new design with composite materials. As IRIS is a client instrument of NFIRAOS, it benefits from NFIRAOS’s superior AO correction. IRIS plays an important role in providing this correction by sensing low-order aberrations with three On-Instrument Wavefront Sensors (OIWFS). The OIWFS consists of three independently positioned natural guide star wavefront sensor probe arms that patrol a 2-arcminute field of view. We expect tip-tilt measurements from faint stars within the IRIS imager focal plane will further stabilize the delivered image quality. We describe how the use of On-Detector Guide Windows (ODGWs) in the IRIS imaging detector can be incorporated into the AO correction. In this paper, we present our strategies for acquiring and tracking sources with this complex AO system, and for mitigating and measuring the various potential sources of image blur and misalignment due to properties of the mechanical structure and interfaces.

PROCEEDINGS ARTICLE | August 9, 2016

The Infrared Imaging Spectrograph (IRIS) for TMT: instrument overview

Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI

KEYWORDS: IRIS Consortium, Adaptive optics, Spectrographs, Imaging systems, Thirty Meter Telescope, Galactic astronomy, Sensors, Stars, Wavefronts, Cameras

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PROCEEDINGS ARTICLE | August 9, 2016

Flowdown of the TMT astrometry error budget(s) to the IRIS design

Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI

KEYWORDS: IRIS Consortium, Calibration, Adaptive optics, Thirty Meter Telescope, Picosecond phenomena, Sensors, Error analysis, Point spread functions, Observatories, Data modeling

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PROCEEDINGS ARTICLE | August 9, 2016

Design and analysis of the NFIRAOS thermal optics enclosure

Proc. SPIE. 9908, Ground-based and Airborne Instrumentation for Astronomy VI

KEYWORDS: Finite element methods, Thermography, Infrared telescopes, Adaptive optics, Thirty Meter Telescope, Thermography, Aluminum, Skin, Cladding, Astronomy, Optomechanical components

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The Narrow Field InfraRed Adaptive Optics System (NFIRAOS) will be the first-light facility adaptive optics system for the Thirty Meter Telescope (TMT). In order to meet the optical performance and stability specifications essential to leveraging the extraordinary capabilities of the TMT, all of the optical components within NFIRAOS will be protected within a large thermally-controlled optics enclosure (ENCL). Among the many functions performed by the ENCL, the most critical functions include providing a highly stable, light-tight, cold, dry environment maintained at 243±0.5 K for the NFIRAOS opto-mechanical sub-systems and supporting TABL structure. Although the performance of the ENCL during the science operation of NFIRAOS is critical, the maximum thermal loading will be defined by the cooldown/ warm-up cycle which must be accomplished within a time-frame that will minimize the on-sky operational impact due to daytime maintenance work. This study describes the thermal/mechanical design development and supporting analyses (analytical and finite element analyses (FEA)) completed during the preliminary design phase and through the current progression of the ENCL final design phase. The walls of the ENCL consist of interlocking, multilayered, thermally insulated panels, which are supported by an externally located structural framework which attaches to the NFIRAOS Instrument Support Structure. The regulation of the interior ENCL wall surface temperature to within ±0.5 K requires that the heat flux into the interior of NFIRAOS be eliminated by cooling a thermal conduction plate embedded between multiple layers of insulation. The thermal design of the enclosure was evaluated for both steady-state (SS) performance and transient performance (cool-down and warm-up cycles). The transient analysis utilizes a hybrid of a one-dimensional thermal network approach combined with three-dimensional conjugate heat transfer analyses of explicit opto-mechanical components within the ENCL. Many design-parameter combinations were evaluated to determine the performance impact of cooling power and transient temperature profiles. The results derived from the analyses of these design iterations indicate the multi-layer enclosure wall design will meet all thermal requirements. During SS operation, the interior temperature variation is within ±0.5 K of the target operational temperature, while the heat influx from the exterior TMT environment is 1528 W (extracted by the embedded cold plate). The transient cool-down cycle will take approximately 15 hours to complete and requires the in-situ air handling units to deliver 14KW of cooling power (derated for the TMT site conditions) throughout the interior space of the NFIRAOS ENCL.

PROCEEDINGS ARTICLE | July 27, 2016

NFIRAOS in 2015: engineering for future integration of complex subsystems