There is currently a great deal of IR instrumentation activity at CTIO. The new f/14 tip-tilt secondary is nearly complete and should be installed in the 4-m by September. Following several months of optical polishing and testing in Tucson, the secondary mirror appears to be of excellent optical quality, well matched to the excellent figure of the Blanco telescope primary mirror. Our plan is to carry out the initial on-telescope optical testing of the f/14 secondary in September. The guider box and fast CCD TV camera for the tip-tilt system should be completed in October and initial tip-tilt testing with the Cryogenic Optical Bench will begin in late November. This will be followed by further tip-tilt engineering runs in December and January.
We plan to offer the tip-tilt system to visitors on a shared risk basis during the first semester of 1997. We expect the system to be working reasonably efficiently, although its performance will not be fully characterized and the user interface may not yet be as friendly as a typical NOAO facility instrument. Given that the system has yet to be tested and its actual performance is unknown, a conservative approach is warranted for science proposals. Prospective users should propose projects with bright guide stars (V < 16.5) within a 3' radius of the target object that will produce useful results with modest tip-tilt performance (i.e. 0.4" FWHM images). The experience we gain during the next semester will allow us to better quantify the performance of the tip-tilt system.
The NOAO Cryogenic Optical Bench (COB) is currently being fitted with a 512 x 512 ALADDIN array by the Instrumentation Project Group in Tucson. A mountain-based CTIO electronics technician is spending several weeks in Tucson for familiarization with the instrument. With its new ALADDIN array, COB will provide 0.1" pixels and will become the primary infrared imager at CTIO for high spatial resolution work with the tip-tilt system. The COB will be tested with its new array on the KPNO 2.1-m telescope in late September and will be delivered to CTIO in October. It will have its first engineering runs at CTIO in November and December and its first visitor use in January. COB should be regularly available on the Blanco 4-m during the first semester of 1997.
The CTIO HgCdTe IR imager CIRIM will continue to be available for wide field imaging use on the 4-m (0.4" per pixel, 100" FOV at f/7.5) and on the 1.5-m at f/7.5 and f/13. The image quality in the corners of the f/7.5 field has recently been improved by using Hartmann test results and an optical design program to guide a careful realignment of the optics. The CIRIM user manual and CIRIM performance numbers are available both by anonymous ftp from CTIO and on the CTIO home page.
As reported in past Newsletters, we had planned to convert the CTIO Infrared Spectrometer (IRS) to accept the f/14 beam from the tip-tilt secondary and to add a more efficient pupil stop to improve rejection of stray background radiation. This was scheduled for October and November of 1996. But due to a shortage of engineering and mechanical shop resources we have been forced to postpone this upgrade until March and April of 1997. Thus, the IRS will be available in its current f/30 configuration for use at the Blanco 4-m telescope through February 1997. It will then be unavailable for use during March, April and May of 1997. The IRS will be available for visitor use in the f/14 configuration, with tip-tilt secondary, during June and July of 1997. Using the f/14 tip-tilt secondary should result in lower slit losses and a wider field for guide star acquisition. However, the internal f/ratio (after the slit) remains the same. So for proposal planning purposes the basic performance specifications (slit widths, resolutions, and throughput) will show little change. The IRS user manual and performance specifications are available both by anonymous ftp from CTIO and on the CTIO home page.
Finally, preparations are well underway for receipt and operation of COB, SQIID, and other large, complex IR instruments that may visit CTIO, such as Phoenix. This includes cabling and cryocooler installation, and construction of a modest clean room facility in La Serena to support future maintenance and upgrades on site.
Richard Elston, Brooke Gregory, Ron Probst (relston, bgregory , rprobst@noao.edu)