In this paper we present the development of a CCD imager for the modern 1.2m MERCATOR telescope dedicated to long term monitoring of variable astrophysical phenomena. This instrument is a result of the collaboration of the Observatory of Geneva with the Institute of Astronomy in Leuven. After a technical description of the main components of the CCD camera system, the text will focus on the automatization of the observations and subsequent data reduction. The telescope itself is an altazimuth mounted 1.2 m Ritchey-Chretien telescope and is operated in a semi-automatic mode. The system executes a predefined sequence of observations, that only need
occasional checking of data quality by the astronomer. The observation software is written in a FORTRAN based interpreter language (INTER) running on a UNIX system that communicates with the astronomer via GUIs implemented in Perl/Tk. The data reduction is integrated into one package and includes pre-reduction, photometric and astrometric calibration, extraction, catalogue preparation and archiving. This allows to have a GUI driven reduction that is both flexible and robust. The preliminary reduced data give the astronomers an indication of the quality of their observations, so that they can adjust their program or camera settings during the same night.
We present the Mercator Telescope together with the P7-2000 photometer as its first-light instrument. Mercator is a 1.2-meter Ritchey-Chretien telescope, installed at the Roque De Los Muchachos Observatory on La Palma and fully operational since Spring 2001. The Geneva Observatory developed this telescope and a twin, known as the Euler Telescope, was already inaugurated at the La Silla Observatory in 1998. Mercator is an alt-azimuthal telescope designed for semi-automatic operation and high operational robustness. P7 is a high-precision 2-channel differential photometer, built by the Geneva Observatory and in permanent use for over 25 years on various telescopes. It allows quasi-simultaneous observations in the 7 filters of the Geneva photometric system with a variable sampling rate up to 100 samples per second. This vintage instrument was completely refurbished in 2000 to function in an automatic mode on the Mercator Telescope. Electronics were completely renewed and are now based on a digital signal processor (DSP), which controls the instrument and performs basic data reduction. The optical system was left unmodified, apart from the addition of a field camera that is also used for auto-guiding. We also added instrument temperature control and a mechanical derotator. Since the 7 filters are acquired simultaneously and the absolute calibration of the colors is strictly homogeneous, the Mercator-P7 combination is a unique tool to study stellar variability on many different timescales. The current scientific program focuses on multi-periodic phenomena in early-type stars with the goal to identify the frequency spectrum and to constrain stellar models by asteroseismology studies. More than 43000 observations have been performed since 2001 and a precision of few milli-magnitudes is routinely achieved. Our photometric measurements result in the continuous calculation of the atmospheric extinction coefficients and these data are available online for other observers as well. In this paper, we describe the telescope, the photometer and their software, followed by the presentation of some first results. Finally, we discuss an upcoming upgrade and the complete instrumentation plan for Mercator.
Hermes, a high-resolution fiber-fed echelle spectrograph is currently under development for the 1.2-meter Mercator Telescope at the Roque De Los Muchachos Observatory on La Palma. The optical design is based on a large R2.6 echelle grating, operating in quasi-Littrow and white-pupil configuration, and a double-prism cross-disperser. This instrument records the complete optical spectrum from 380 to 875 nm in one single exposure on a 2k x 4k CCD. Order separation is sufficiently large to record two interleaved spectra simultaneously through two 60-mm core fibers: one spectrum of the object and one of the nearby sky or, alternatively, of a wavelength calibration lamp for high-precision radial velocity measurements. This type of observations also benefits from the high instrumental stability, owing to bench-mounting the spectrograph with a fixed configuration in a precisely temperature and humidity controlled chamber. Modest telescope size calls for high detection efficiency and great efforts in the design of both the fiber link and the spectrograph itself go in that direction. We aim at a peak-efficiency larger than 25% for the complete system. With a large fiber aperture of 2.3 arcsec, the resolving powerλ/ΔλΑ is 50000, a value that can be increased to 90000 with an adjustable slit at the fiber exit. This instrument mounted on a flexible telescope has a wide astronomical scope, going from asteroseismology to binary star research and chemical studies of stars and circumstellar material. We present the spectrograph design and we report on the project status.
A Ritchey-Chretien 1.2 m telescope (EULER) and the High- Resolution echelle Spectrograph (CORALIE), a new Swiss observing facility at ESO La Silla Observatory, are operational and since Summer 1998. The Observatory operation is fully automated and supports the unattended, attended and interactive mode of operation under local or remote control. The control hardware is based on Local Control Units (LCU) built from PC/RedHat Linux computers and a Unix Computing Server. The Operational Software is built around INTER, a command language interpreter featuring communication control, data access, image processing functions and easy access to external resources. The general SW architecture is a non-hierarchical tree of pairs made of hardware- independent interpreters running on the Observing Server and hardware dependent servers running on the LCU's. The Operational Software includes the full access (Creation/Modification/Retrieval) to the input/output databases, telescope, instrument and auxiliary set-up and control files as well as a full data-reduction pipeline. We describe briefly the system architecture, summarize the performances and the experience gained over 18 months of operation and we discuss some critical issues: use of standard components, parallel operation, real-time requirements, system upgrade and maintenance.