Gary Muller

What is better than an 8192x8192 CCD Mosaic imager: two Mosaic wide-field imagers, one for KPNO and one for CTIO

A new generation wide-field imager is being developed and will be put into service at sites in North and South America. Driven by the requirement for larger imaging areas and more pixels but limited by manufacturing process constraints, manufacturers are developing 2, 3, and 4-side buttable CCDs that can be tiled to achieve large imaging areas as opposed to developing a single large CCD. NOAO has designed, fabricated, and tested a wide-field imager called Mosaic that tiles 8 CCDs to produce an imaging area slightly greater than 123 mm X 123 mm. Several successful science observation runs have been completed using Mosaic at the KPNO Mayall 4 m and .9 m telescopes. A second Mosaic Wide-Field Imager is presently being manufactured and will be deployed at the CTIO Blanco 4 m telescope early next year. This report will focus on the mechanical design aspects of the Mosaic Imager and the upgrade path to achieve the scientific requirements will be discussed.

Design of the Gemini near-infrared spectrograph

The Gemini Near-Infrared Spectrograph (GNIRS) supports a variety of observing modes over the 1-5 μm wavelength region, matched to the infrared-optimized performance of the Gemini 8-m telescopes. We describe the optical, mechanical, and thermal design of the instrument, with an emphasis on challenging design requirements and how they were met. We also discuss the integration and test procedures used.

Modifying Hydra for the WIYN telescope: an optimum telescope, fiber MOS combination

The KPNO fiber-fed, multi-object spectroscopic instrument, Hydra, is being moved from the Mayall to the WIYN telescope. The WIYN telescope has good concentricity between the focal surface radius and the exit pupil. The primary modification to the instrument will allow the fibers to align with the telescope exit pupil while lying along the curved focal surface. Maximum pupil alignment losses will be reduced from 15% at the Mayall to 5% at the WIYN. The new orientation of the instrument requires a different mechanism for accessing the fiber and focal plate for maintenance. We are also upgrading the manner in which the fibers are held in place around the focal plane in order to reduce neighboring fiber interactions beyond the pivot circle. The wavelength calibration assembly is being modified to take advantage of extra room in the instrument. For guiding, instead of using offset guide probes, we are developing an algorithm which will utilize the field orientation probes. The Bench Spectrograph associated with Hydra is also being moved over to the WIYN, however, we do not discuss the spectrograph in this paper.

iSHELL: a 1-5 micron cross-dispersed R=70,000 immersion grating spectrograph for IRTF

iSHELL is 1.15-5.4 μm high spectral resolution spectrograph being built for the NASA Infrared Telescope Facility on Mauna Kea, Hawaii. Dispersion is accomplished with silicon immersion gratings in order to keep the instrument small enough to be mounted at the Cassegrain focus of the telescope. The white pupil spectrograph is designed to produce resolving powers of up to R=70,000. Cross-dispersing gratings mounted in a tilt-able mechanism at the second pupil allow observers to select different wavelength ranges and, in combination with a slit wheel and dekker mechanism, slit lengths ranging from 5″ to 25″. One Teledyne 2048x2048 Hawaii 2RG array is used in the spectrograph, and one Raytheon 512x512 Aladdin 2 array is used in a slit viewer for object acquisition, guiding, and imaging. About

LSST instrument concept

4 million in funding has been provided by NSF, NASA and the University of Hawaii. First light is expected in about 2015. In this paper we discuss the science drivers, instrument design and expected performance.

Development of GMT Fast Steering Secondary Mirror Assembly

The LSST Instrument is a wide-field optical (0.3 to 1um) imager designed to provide a three degree field-of-view with better than 0.2 arcsecond sampling. The image surface of the LSST is approximately 55cm in diameter with a curvature radius of 25 meters to flat. The detector format is currently defined to be a circular mosaic of 568 2k × 2k devices faceted to synthesize this surface within the constraints of LSSTs f/1.25 focal ratio. This camera will provide over 2.2 Gigapixels per image with a 2 second readout time. With an expected typical exposure time of as short as 10s, this will yield a nightly data set on order of 3 terapixels. The scale of the LSST Instrument is equivalent to a square mosaic of 47k × 47k. The LSST Instrument will also provide a filter mechanism, as well as optical shuttering capability. Imagers of this size pose interesting challenges in many design areas including detectors, interface electronics, data acquisition and processing pipelines, dewar construction, filter and shutter mechanisms. Further more, the LSST 3 mirror optical system places this instrument in a highly constrained volume where these challenges are compounded. Specific focus is being applied to meeting defined scientific performance requirements with an eye to total cost, system complexity, power consumption, reliability, and risk. This paper will describe the current efforts in the LSST Instrument Concept Design.

The WIYN one degree imager: project update 2010

The Giant Magellan Telescope (GMT) is one of Extremely large telescopes, which is 25m in diameter featured with two Gregorian secondary mirrors, an adaptive secondary mirror (ASM) and a fast-steering secondary mirror (FSM). The FSM is 3.2 m in diameter and built as seven 1.1 m diameter circular segments conjugated 1:1 to the seven 8.4m segments of the primary. The guiding philosophy in the design of the FSM segment mirror is to minimize development and fabrication risks ensuring a set of secondary mirrors are available on schedule for telescope commissioning and early operations in a seeing limited mode. Each FSM segment contains a tip-tilt capability for fine co-alignment of the telescope subapertures and fast guiding to attenuate telescope wind shake and mount control jitter, thus optimizing the seeing limited performance of the telescope. The final design of the FSM mirror and support system configuration was optimized using finite element analyses and optical performance analyses. The optical surface deformations, image qualities, and structure functions for the gravity print-through cases, thermal gradient effects, and dynamic performances were evaluated. The results indicated that the GMT FSM mirror and its support system will favorably meet the optical performance goals for residual surface error and the FSM surface figure accuracy requirement defined by encircled energy (EE80) in the focal plane. The mirror cell assembly analysis indicated an excellent dynamic stiffness which will support the goal of tip-tilt operation.

Large Synoptic Survey Telescope mount final design

The One Degree Imager will be the future flagship instrument at the WIYN 3.5m observatory, once commissioned in 2011. With a 1 Gigapixel focal plane of Orthogonal Transfer Array CCD devices, ODI will be the most advanced optical imager with open community access in the Northern Hemisphere. In this talk we will summarize the progress since the last presentation of ODI at the SPIE 2008 meeting, focusing on optics procurement, instrument assembly and testing, and detector operations.

EXPRES: A Next Generation RV Spectrograph in the Search for Earth-like Worlds

This paper describes the status and details of the large synoptic survey telescope1,2,3 mount assembly (TMA). On June 9th, 2014 the contract for the design and build of the large synoptic survey telescope mount assembly (TMA) was awarded to GHESA Ingeniería y Tecnología, S.A. and Asturfeito, S.A. The design successfully passed the preliminary design review on October 2, 2015 and the final design review January 29, 2016. This paper describes the detailed design by subsystem, analytical model results, preparations being taken to complete the fabrication, and the transportation and installation plans to install the mount on Cerro Pachón in Chile. This large project is the culmination of work by many people and the authors would like to thank everyone that has contributed to the success of this project.

Design of the Giant Magellan Telescope

The EXtreme PREcision Spectrograph (EXPRES) is an optical fiber fed echelle instrument being designed and built at the Yale Exoplanet Laboratory to be installed on the 4.3-meter Discovery Channel Telescope operated by Lowell Observatory. The primary science driver for EXPRES is to detect Earth-like worlds around Sun-like stars. With this in mind, we are designing the spectrograph to have an instrumental precision of 15 cm/s so that the on-sky measurement precision (that includes modeling for RV noise from the star) can reach to better than 30 cm/s. This goal places challenging requirements on every aspect of the instrument development, including optomechanical design, environmental control, image stabilization, wavelength calibration, and data analysis. In this paper we describe our error budget, and instrument optomechanical design.