Telescope Upgrades and Instrumentation
CTIO made significant progress during FY 1999 on its goal of providing a suite of telescopes and instruments that are scientifically productive in an era of 8- to 10-m telescopes, and complement the capabilities of the Gemini 8-m, by the commissioning of three new instruments on the Blanco 4-m telescope. In addition, significant resources are being directed towards the SOAR project, including work on two of the first-light instruments. Further scientific and technical details of the operation can be accessed via: http://www.ctio.noao.edu/.
The main activity in FY 1999 has been the commissioning of the Hydra multi-object spectrograph, the 8K prime-focus Mosaic II Imager, and OSIRIS, the Ohio State University imaging spectrometer. These provide a wide-field optical capability with Mosaic II and Hydra, and a versatile IR capability with OSIRIS over a smaller field but with very high image quality, using the F/14 tip-tilt system. Both Hydra and Mosaic II were built as collaborations between the Instruments Project Group (IPG) in Tucson and CTIO. For Hydra, CTIO built the bench spectrograph, the F/8 optical corrector assembly, and the atmospheric dispersion corrector (ADC), while for Mosaic CTIO provided the 16-port Arcon CCD controller. Following the commissioning and first visitor use of the Mosaic II Imager in late FY 1999, work is continuing to optimize CCD performance. Much of this work is also relevant to the Mosaic I Imager at KPNO; software and hardware upgrades for this instrument will extend into FY 2000. Hydra is now seeing regular visitor use. An upgrade underway is the construction of a folded Schmidt camera and special dewar for use with a Grade 0 SITe 2K x 4K CCD, obtained as part of the Mosaic CCD procurement. OSIRIS is also in regular visitor use, and has replaced existing CTIO instruments CIRIM and IRS for almost all programs. The 1K HgCdTe array in OSIRIS is performing sub-optimally, and is to be replaced by Rockwell.
We are continuing our program to improve the performance and maintainability of the 4-m telescope. Extensive rewiring took place this year, and further replacement of antiquated electronics will take place as a follow-on from the successful installation of new Delta-Tau drive servos during FY 1999. Development of the F/14 tip-tilt system has continued throughout the year, with the system now ready for installation of a small, high-quantum-efficiency EEV CCD, to replace the present interim device. A new thermal control system for telescope and dome is in the process of installation. This will be used in conjunction with the telescope active optics system to provide image quality that has minimal degradation over that produced by the atmosphere, and will replace the present system, which has limited control capability.
We are actively pursuing collaborations with US universities in order to offer additional state-of-the-art instrumentation that complements our own. At present we have such arrangements with Ohio State University (OSIRIS) and have just concluded highly successful collaborations with Lucent Technologies (BTC Mosaic Imager, from 1996), the University of Florida (Mid-IR imager-spectrometer, from 1997), and Rutgers (Fabry-Perot Interferometer, from 1988).
With the installation of the new Blanco instruments, CTIO Engineering and Technical Services have moved into a new phase of instrument building. Three projects were started in FY 1999: (1) the Wide-Field IR sideport imager (Blanco), (2) the Optical Imager (SOAR) and (3) the Hydra-IFU (Blanco). The IR imager is designed to provide a 10 x 10 arcmin field at the Blanco F/8 focus using a Rockwell 2K x 2K HgCdTe array, exploiting the wide-field capabilities of that telescope. The Hydra-IFU feeds the Hydra bench spectrograph with an Integral-Field Unit that can be swung into the F/8 beam. Apart from providing a new capability of spatially-resolved spectroscopy over a small area of sky, we are also interested in modes that allow us to replace functions presently provided by the RC and, particularly, the Echelle spectrographs. Both these new Blanco instruments can be used together with Hydra and Mosaic II in a configuration that requires no instrument changes, which is an operations model we are planning to implement for this telescope by the time we need to transfer resources to operating SOAR. The SOAR Optical Imager, which includes a linear ADC, an F16:F9 focal reducer, and fast tip-tilt sensor, passed conceptual design review in FY 1999, and is ready for procurement of optics. Both the Blanco IR Imager and the SOAR Optical Imager will use Leach II array controllers, operated in a Linux + LabView environment; these systems were specified in FY 1999.
The 1.5-m telescope continues to be offered with a suite of general-purpose instruments. OSIRIS is now scheduled on the 1.5-m, with IRS no longer offered. The CCD used on the Schmidt telescope was replaced with a thinned SITe 2K, providing much higher quantum efficiency and excellent optical performance over a 67 x 67 arcmin field. The 0.9-m continues to be operated with a SITe 2K CCD-based imager.
The Yale 1-m telescope, now run by the YALO consortium (Yale, AURA, Lisbon, and Ohio State U.), has been back in operation throughout FY 1999, providing optical synoptic observing. The service-observing mode has opened up a unique new opportunity to NOAO users, enabling synoptic observations which do not require complete nights, but rather hours of observations on many nights. NOAO's 10% share of observing time has been used for projects ranging from monitoring variable stars to following supernovae as they fade. Those kinds of observations had been more difficult to schedule on the existing CTIO telescopes. In May 1999, the timesharing agreement was renegotiated, with CTIO providing a 1K x 1K HgCdTe infra-red detector array in exchange for additional time. As a result, the NOAO share of observing time increased to almost 20%. The IR detector was installed in July 1999 by Ohio State University to complete the IR channel in ANDYCAM, the simultaneous IR-optical imager. Simultaneous optical and IR observations are now possible, enhancing the unique aspects of this facility. Further details can be accessed via: http://www.ctio.noao.edu/yale/yalo.html.
Atacama Site Survey
An important component of the NOAO Long Range Plan is the building of the Next Big Telescope (NBT). Although excellent sites have already been identified in northern Chile (Tololo, La Silla, Pachón, Paranal, Chajnantor), we need to identify the best site based on the scientific priorities and technical attributes of the NBT. We began this project in FY 1999 by gathering data from earlier surveys and conducting a preliminary topographical analysis. We have also let a contract for a detailed cloud and water vapor analysis of the GOES-8 satellite data, covering 1995--1999. We hope to have the results of this analysis available by late FY 2000, and then be able to trim the list of possible sites down to 5--6, which will be further reduced to 2--3 sites after on-site weather and geological analyses. These remaining sites will be thoroughly tested. As part of the complement of test equipment, we are assembling three Differential Image Motion Monitors (DIMMs), copies of those developed for site testing by ESO. One DIMM will be permanently installed on Tololo, replacing a less capable equivalent; the others will be used first on Cerro Pachón and then at remote sites during the period of intensive site monitoring.