Bruce Atwood

The Multi-Object Double Spectrographs for the Large Binocular Telescope

The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical low- to medium-resolution CCD spectrometers being deployed at the Large Binocular Telescope (LBT). Operating in the 340-1000nm range, they use a large dichroic to split light into separately-optimized red and blue channels that feature reflective collimators and decentered Maksutov-Schmidt cameras with monolithic 8×3K CCD detectors. A parallel infrared laser closed-loop image motion compensation system nulls spectrograph flexure giving it high calibration stability. The two MODS instruments may be operated together with digital data combination as a single instrument giving the LBT an effective aperture of 11.8-meter, or separately configured to flexibly use the twin 8.4-meter apertures. This paper describes the properties and performance of the completed MODS1 instrument. MODS1 was delivered to LBT in May 2010 and is being prepared for first-light in September 2010.

Ohio State Infrared Imager/Spectrometer (OSIRIS)

The Ohio State Infrared Imager/Spectrometer (OSIRIS) is a general purpose near infrared (0.9 to 2.5 micrometers ) instrument that can be used at a wide variety of telescope focal planes. OSIRIS currently uses a 256 X 256 HgCdTe array detector and will accommodate larger arrays when available. OSIRIS has two modes of operation: imaging and spectroscopic. This paper describes the general instrument design and sample scientific results.

A Novel Double Imaging Camera (ANDICAM)

We describe an instrument that is capable of taking simultaneous images at one optical (UBVRI) and one near-infrared (JHK) wavelength. The instrument uses relatively simple optics and a dichroic to image the same field on to an optical CCD and an HgCdTe array. The mechanical and thermal design is similar to previous instruments built by our group and the array controllers are based on the same architecture. The instrument has been in use for the past four years on the CTIO/Yale 1m telescope in Chile and has an excellent operational/reliability record. A number of notable science results have been obtained with the instrument; especially interesting are several photometric monitoring projects that have been possible, since the instrument is available every night on the telescope.

MDM/Ohio State/ALADDIN infrared camera (MOSAIC)

The MDM/Ohio State/ALADDIN IR Camera (MOSAIC) is a general purpose near IR imaging camera and medium-resolution long- slit spectrometer in use on the MDM 1.3-m and 2.4-m telescopes and the Kitt Peak 2.1-m and 4-m telescopes. In cooperation with NOAO and USNO, MOSAIC is one of the first general-purpose near-IR instruments available to the astronomical community that uses a first-generation 1024 X 512 ALADDIN InSb array, with the capability to use a full 1024 X 1024 array once one becomes available. MOSAIC provides tow imaging plate scales, and a variety of long- slit grism spectroscopic modes. This paper describes the general instrument design and capabilities, and presents representative scientific results.

Design of the KMTNet large format CCD camera

We present the design for the 340 Mpixel KMTNet CCD camera comprising four newly developed e2v CCD290-99 imaging sensors mounted to a common focal plane assembly. The high performance CCDs have 9k x 9k format, 10 micron pixels, and multiple outputs for rapid readout time. The camera Dewar is cooled using closed cycle coolers and vacuum is maintained with a cryosorption pump. The CCD controller electronics, the electronics cooling system, and the camera control software are also described.

A multi-object double spectrograph for the Large Binocular Telescope

We are building a Multi-Object Double Spectrograph for the Large Binocular Telescope. The instrument is designed to have high throughput from 320 to 1000 nm, spectral resolutions of 1,000-10,000, and multi-object capability over a 6 arcminute field. The design incorporates a dichroic and splits the science beam into a blue and a red channel, each of which can illuminate an 8,192 pixel long detector (with 15 micron pixels) with good image quality. The highly modular design can hold up to three gratings and an imaging flat and a selection of filters in each channel, all of which are quickly accessible; this allows for substantial observing flexibility. Progress on the construction of the instrument and future plans will be described.

On-sky performance of the Multi-Object Double Spectrograph for the Large Binocular Telescope

The Multi-Object Double Spectrographs (MODS) are two identical high-throughput optical dichroic-split double-beam low- to medium-dispersion CCD spectrometers being deployed at the Large Binocular Telescope (LBT). They operate in the 3200-10500Å range at a nominal resolution of λ/δλ≈2000. MODS1 saw first-light at the LBT in September 2010, finished primary commissioning in May 2011, and began regular partner science operations in September 2011. MODS2 is being readied for delivery and installation at the end of 2012. This paper describes the on-sky performance of MODS1 and presents highlights from the first year of science operations.

Lens mounting system for cryogenic applications

Lens mounts for cryogenic service have many requirements: mitigation of thermal shock on the lens, maintenance of lens centering and spacing, control of mechanical stress on the lens from the cell, reliable connection of the lens to the cell, and applicability to a wide variety of lens materials. This paper describes in detail a lens mounting system successfully used in several cryogenic instruments.

The Ohio State Imaging Fabry-Perot Spectrometer (IFPS)

The Ohio State University Imaging Fabry-Perot Spectrometer (IFPS) is designed for two-dimensional imaging spectrophotometric and kinematic studies in the wavelength range of 3400-10000A. Presently it uses four etalons providing low and medium spectral resolutions (lambda/delta-lambda) of 1200 in the 4500-7500A wavelength range, and lambda/delta-lambda=4500 in three bands covering the 3400-4000A, 4100-5500A, and 6000-7000A wavelength regions. These resolutions make it applicable to a wide range of galactic and extragalactic imaging spectrophotometry problems. The IFPS has also found use as direct imaging focal camera (without the etalons). The instrument development and basic design philosophies are described, and some scientific results from the Fabry-Perot mode of the instrument are presented.

The 123 mm 8kX3k e2v/Ohio State CCD231-68 for MODS

As is only fitting, the largest Optical/Infrared Telescope (the Large Binocular Telescope, LBT) has the two largest telescope-mounted spectrographs (MODS) and the MODSs have the four largest scientific CCDs. We describe herein the design, fabrication and early use of the e2v CCD231-68 8k × 3k 15 micron back-illuminated detector designed specifically for low and intermediate resolution multi-object spectroscopy on large telescopes. The 123 mm length of the CCD231-68 is the largest of any scientific CCD. The device can be read out in full frame mode to cover the whole 6 arc-min slit length of MODS, in full frame mode for multi-object spectroscopy with short slits, or in split frame transfer mode to allow readout while integrating subsequent exposures. The four very low noise (<2 e- RMS at 100 kPixels/second) outputs are located at the ends of the four 4k serial registers. Excellent CTE (five-9s5 per Pixel) insures good photometric accuracy across the device. Backthinned red and blue optimized variants are used on the corresponding channels of both MODS.