The Yale, AURA, Lisbon, Ohio State partnership (YALO) to refurbish and operate the Yale 1-m telescope at CTIO (NOAO Newsletter No. 52, page19) saw first light in early June 1998. This note is to alert the community to the availability of time on this telescope for the next observing period and to invite submission of observing proposals. The operating mode of this telescope is well suited to synoptic programs, targets of opportunity, or acquisition of small data sets. The single fixed instrument is an optical-IR camera, ANDICAM, providing imaging in standard bands from 0.4 µm to 2.2 µm.
Caption:
I-band frame of the Type I SNe 1998bu taken with the YALO Telescope some 45
days after maximum, when the SNe had faded by about 2.4 magnitudes to I =
13.2. This SNe is interesting, as it occurred on M96 (NGC 3368), a Leo-I
Group Galaxy with a Cepheid distance from HST data. This 40s exposure with a
FWHM of 1.5" shows also some of the cosmetic details of the CCD (picture
courtesy of Ricardo Covarrubias and Nick Suntzeff.)
The telescope, the new imaging system, and a new commercial Telescope Control System have been in use for a commissioning and science verification period. This process will ensure that, when the instrument becomes available to the NOAO user community later this year, it will be stable and reliable. Most of the commissioning and science verification has been performed under Yale and Ohio State management, while work on the telescope has been performed on a labor-charge basis by CTIO mountain staff.
As of mid-July, about 25 Gbytes of data have been obtained on programs including bulge micro-lensing photometric follow-ups (Ohio State), low-mass X-ray transients, and globular cluster monitoring (Yale). All observations are being performed on a queue-scheduling basis by two observers provided by CTIO working on one-week shifts. The scheduling has proved to be flexible and efficient enough to respond to short-notice events. This has been operationally tested on several targets of opportunity: The gamma-ray burst 980703 (http://cfa-www.harvard.edu/iauc/06900/06966.html) for Yale, the micro-lensing event 98-SMC-01, detected by the MACHO collaboration, (http://cfa-www.harvard.edu/iauc/06900/06935.html) for Ohio State, and SN 1998bu in NGC 3368 for CTIO staff (http://cfa-www.harvard.edu/iauc/06800/06899.html).
The new imaging system ANDICAM was built at Ohio State by a group led by Darren DePoy; for details, see: http://www-astronomy.mps.ohio-state.edu/~depoy/research/instrumentation/andicam/andicam.html. Because of delays in the procurement of an array for the IR channel, it has been commissioned with only the optical CCD channel operating. Some performance features are as follows:
1) The sensitivity curve of the CCD can be found on ANDICAM's home page. The count rate, and color terms from standard stars, are being determined and will be posted on the YALO web pages at CTIO in the near future.
2) There is significant fringing in the R band---therefore special calibration plans are needed to remove this effect.
3) The total overhead (readout time plus clearing the chip and starting the next integration) is about 50 seconds.
The telescope presently slews very slowly, about 1 minute per 10 degrees. Therefore, programs with widely separated targets, or which need frequent standard stars, will be very inefficient. We plan to change the gear train late this year to achieve about 0.6 deg/s.
Vendor information on the new TCS system can be found at http://www.primenet.com/~comsoft/.
It is expected that by December 1998, the IR array will be installed and ANDICAM will have both channels fully functional and characterized. Proposers for semester 1999A can assume the availability of the complete imaging system with 0.4-2.2 µm coverage.
ANDICAM has a ten position filter wheel in its optical channel. Five of these positions hold 50 mm filters that allow unvignetted imaging over the entire 2048 × 2048 CCD (10' field-of-view). The other five positions are 25 mm filters that will vignette part of the CCD (a 1024 × 1024 section in the middle will remain unvignetted). The full field-of-view positions will have the set uBVRI, while the restricted field-of-view positions will hold Strömgren filters vby plus Hb. In the IR channel the standard J, H, and K broadband filters will be available; the possibility of additional narrowband filters is under discussion. Any one of the optical filters and any one of the IR filters can observe the same telescope's field of view simultaneously and independently. A dithering capability is provided for the IR channel by an internal chopping mirror. For performance estimates, we suggest that ANDICAM's IR performance be scaled from CIRIM, considering telescope aperture and pixel size. Pixel size on the sky for both the optical and the IR channels will be 0.3".
Changing either filter complement involves opening the dewar and it is not expected to be done more than once a year. NOAO users should restrict their filter choices to the above sets.
All observations will be performed on a queue-scheduling basis by two CTIO mountain staff observers. Queue management will rotate among the partners. The queue manager on duty is charged with monitoring the short-term performance of the queue, and with all communication with the observers. No direct communication between the time grantees and the observers is allowed. The long-term monitoring of the queue, as well as the balance of the distribution of time among the partners, is performed by a management committee having partner representatives.
Under AURA's operating agreement in Chile, 10% of the science time is allocated to Chilean astronomers. NOAO users also receive a 10% time share, allocable during the non-Bulge season. This restriction arises from the science interests of the Ohio State group. This amounts to about eight dark and eight bright nights for next semester depending on the exact request for engineering nights. It is vital that science proposals provide accurate estimates of total telescope time per program (including general overheads, time on standards, slewing time, readout time, etc.). Time spent on standard stars will be counted against the observing program. If two or more programs can share standards during a particular night, they will be charged proportionally. Observed time is logged from an archive that stores all the (raw) data on local disks, which are subsequently transferred to two data tapes (one remaining at CTIO). These data are then sent to the proposer via express-delivery; receipt within four weeks of data taking is the goal. Custom-made IRAF scripts and translation files are being written at CTIO by S. Heathcote for NOAO users, that they can reduce their frames using quadproc just as with any other detector at CTIO.
Since the YALO telescope provides a unique queue/service observing capability not available on other CTIO telescopes, preference will be given to (a) proposals for synoptic programs where a few frames/night will yield significant scientific results, or (b) proposals that require less than 10 hours total observing time. Consistent with this policy, target-of-opportunity as well as long-term (i.e., multi-year) programs will be considered. Successful proposals should avoid duplication with programs being pursued by other YALO partners (see http://www.ctio.noao.edu/yale/yale.html for a list of Yale and Ohio-State observing programs). Proposals for YALO time should be submitted by 30 September using the standard NOAO electronic form, and will be evaluated in the same way as all other proposals submitted to NOAO. Because of the queue/service observing mode, it is important to include a target table at the end of the standard form, as is done for proposals submitted for the WIYN telescope (see ftp://ftp.noao.edu/noaoprop/wiyn_info.txt, especially Section 2.2 of that document.)
Proposers with time granted on YALO should expect a "Phase II" communication in order to provide, on a standard template, the basic information needed by the queue-manager and the observers to complete the program. This is an important step, as no communication between the NOAO user and the observer will be allowed prior to, or during the observations; remaining details can be dealt with through the CTIO liaison astronomer René A. Méndez (rmendez@noao.edu). The contents and layout of the Phase II form are being worked out at this moment; it will probably be a simple ASCII form distributed via e-mail.
For general information on the YALO project, please take a look at: http://www.ctio.noao.edu/yale/yale.html. For other information, please contact the undersigned.
René A. Méndez, CTIO-YALO liaison (rmendez@noao.edu)
Darren DePoy, Ohio-State University (depoy@rosse.mps.ohio-state.edu)
Charles Bailyn, Yale University (bailyn@astro.yale.edu)