Jerry Allan Mason

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.

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.

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.

KOSMOS and COSMOS: new facility instruments for the NOAO 4-meter telescopes

We describe the design, construction and measured performance of the Kitt Peak Ohio State Multi-Object Spectrograph (KOSMOS) for the 4-m Mayall telescope and the Cerro Tololo Ohio State Multi-Object Spectrograph (COSMOS) for the 4-m Blanco telescope. These nearly identical imaging spectrographs are modified versions of the OSMOS instrument; they provide a pair of new, high-efficiency instruments to the NOAO user community. KOSMOS and COSMOS may be used for imaging, long-slit, and multi-slit spectroscopy over a 100 square arcminute field of view with a pixel scale of 0.29 arcseconds. Each contains two VPH grisms that provide R~2500 with a one arcsecond slit and their wavelengths of peak diffraction efficiency are approximately 510nm and 750nm. Both may also be used with either a thin, blue-optimized CCD from e2v or a thick, fully depleted, red-optimized CCD from LBNL. These instruments were developed in response to the ReSTAR process. KOSMOS was commissioned in 2013B and COSMOS was commissioned in 2014A.

The aluminizing system for the 8.4 meter diameter LBT primary mirrors

The recently commissioned system for aluminizing the 8.408 meter diameter Large Binocular Telescope mirrors has a variety of unusual features. Among them are aluminizing the mirror in the telescope, the mirror is horizon pointing when aluminized, boron nitride crucibles are used for the sources, only 28 sources are used, the sources are powered with 280 Volts at 20 kHz, high vacuum is produced with a LN2 cooled charcoal cryo-panel, an inflatable edge seal is used to isolate the rough vacuum behind the mirror from the high vacuum space, and a burst disk is mounted in the center hole to protect the mirror from overpressure. We present a description of these features. Results from aluminizing both primary mirrors are presented.

Ohio State University Imaging Sciences Laboratory (ISL)

The ISL is a successful astronomical instrumentation program that has completed three major instruments and many smaller projects since 1987. We have developed the capabilities to perform all aspects of instrument design and construction and a range of unique skills and methods. We maintain a permanent staff that currently consists of two scientists specializing in optical design and detector systems, a seniors mechanical engineer, a programmer, an electronic engineer, a mechanical designer, two machinists, and a lab assistant. Instrumentation projects also draw upon faculty and graduate student effort.

A SIMPLE TECHNIQUE FOR THE SUPPRESSION OF LINE FREQUENCY NOISE IN IR ARRAY SYSTEMS

A description of a simple system to suppress low levels of line frequency noise in data taken with IR array cameras is given. Dark frames taken with the MDM/Ohio State infrared camera (MOSAIC) are shown to illustrate the effectiveness of the system.