New Near-IR Observing Capability for KPNO

A near-IR imager with low-dispersion spectroscopic capability is likely to be available on a shared-risk basis to KPNO users starting spring semester. Subject to successful operation on the 2.1-m telescope this fall, it will be offered there for the full spring semester, and probably on the 4-m later in the semester. The instrument was developed by Ohio State University for use on the MDM Observatory telescopes. NOAO is providing a two-quadrant ALADDIN InSb array for the instrument, and by mutual agreement among MDM Observatory, OSU Astronomy, and NOAO, the instrument will be made available to KPNO users. The early use of an array from the ALADDIN development program was graciously agreed to by our partner in that program, the US Naval Observatory Flagstaff Station.

The active array format is 1024 x 512 pixels. There is a choice of two image scales through cold interchangeable cameras: 0.35" and 0.18"/pixel at the 2.1-m, and 0.18" and 0.09"/pixel at the 4-m. J,H, and K filters are provided; user-supplied filters in 38 mm square format can be accommodated on request. The read noise is anticipated to be ~55 /pixel for a single read, with multiple low-noise reads possible to reduce the noise. Performance of this array under lab conditions has yielded a dark rate of < 0.1 ; performance in the instrument will be demonstrated in September. The anticipated system throughput for direct imaging should be significantly greater than 30%. In addition to the filters, a grism can be inserted into the beam, giving a spectral resolution of ~1400 for 2 pixels FWHM. The slit width is 0.7" on the 2.1-m, and 0.35" on the 4-m; the slit length covers the full format. Spectroscopy is performed in one band at a time by using the appropriate combination of grism and filter.

OSU is currently retrofitting the instrument with a larger chip mount and associated cryo-cooler, and modifying their controller electronics for the ALADDIN array. It is scheduled for Test and Engineering time on the 2.1-m on 18-22 September, and again on 18-21 November. The results of those runs relative to the potential scheduling of the instrument in the spring 1997 semester will be available through the NOAO Web page.

We are optimistic about the performance and schedule of the OSU/MDM instrument, but it will have completed its first telescope run in this new configuration immediately prior to the deadline for spring semester proposals. Proposals will therefore be accepted on a shared risk basis. Because the instrument is shared with the MDM Observatory, it will not be available at every lunation. The minimum guaranteed availability to KPNO would allow scheduling during only two lunations. More time may be provided depending on semester-by-semester arrangements with the MDM Observatory. IRIM and CRSP will therefore still be scheduled to meet the total demand for time. Successful operation at the 4-m will depend on at least one engineering run, which has not been scheduled yet, to verify the interfaces. It is likely that any scheduled time on the 4-m will be late in the spring 1997 semester. For these reasons, please specify on your observing form the advantages of the larger instrumental format for your program, and the level of acceptability of IRIM or CRSP as backup. For the 2.1-m, you can assume that the instrument will be available any time during the semester, but specify as broad a range of acceptable dates as possible. For the 4-m, available dates will be limited to the period of May-July 1997; again, it will be advantageous to specify the broadest possible choice of runs. The name of the instrument is MOSAIC (MDM-Ohio State Active Infrared Camera), but we fear potential confusion with the new large-format CCD imager. For the purposes of your NOAO proposal, please designate the instrument as OSU-IRIS (IR Imager + Spectrograph). Proposals for projects that can be accomplished only with the new instrument will be scheduled after the instrument has been proven in successful operation during the fall T&E time.

Ian Gatley, Darren DePoy, Rick Pogge, Richard Green