Optimizing the night time is essential on a site like Maunakea. The mountain offers excellent weather conditions that can be used to observe more programs than most sites in the world. CFHT has been making significant efforts toward optimal usage of the night time, starting in 2000 with the implementation of the Queued Service Observing (QSO) system followed by the installation of the dome vents in 2012 and lastly, the implementation of the Signal to Noise Ratio (SNR) observing mode in 2013. The QSO-SNR mode is now used by default at CFHT for two of our instruments: MegaCam, a one square degree imager, and ESPaDOnS, a high resolution spectropolarimeter. This paper describes the implementation strategy for each instrument as well as the time saved using this observing mode.
Proc. SPIE. 9910, Observatory Operations: Strategies, Processes, and Systems VI
KEYWORDS: Signal to noise ratio, Signal to noise ratio, Point spread functions, Astronomy, Sensors, Spectroscopy, Interference (communication), Imaging spectroscopy, Coronagraphy, Signal detection, James Webb Space Telescope
In an effort to optimize the night time utilizing the exquisite weather on Maunakea, CFHT has equipped its dome with vents and is now moving its Queued Scheduled Observing (QSO)1 based operations toward Signal to Noise Ratio (SNR) observing. In this new mode, individual exposure times for a science program are estimated using a model that uses measurements of the weather conditions as input and the science program is considered completed when the depth required by the scientific requirements are reached. These changes allow CFHT to make better use of the excellent seeing conditions provided by Maunakea, allowing us to complete programs in a shorter time than allocated to the science programs.
OPERA is a Canada-France-Hawaii Telescope (CFHT) open source collaborative software project currently under
development for an ESPaDOnS echelle spectro-polarimetric image reduction pipeline. OPERA is designed to be
fully automated, performing calibrations and reduction, producing one-dimensional intensity and polarimetric
spectra. The calibrations are performed on two-dimensional images. Spectra are extracted using an optimal
extraction algorithm. While primarily designed for CFHT ESPaDOnS data, the pipeline is being written to be
extensible to other echelle spectrographs. A primary design goal is to make use of fast, modern object-oriented
technologies. Processing is controlled by a harness, which manages a set of processing modules, that make use
of a collection of native OPERA software libraries and standard external software libraries. The harness and
modules are completely parametrized by site configuration and instrument parameters. The software is open-
ended, permitting users of OPERA to extend the pipeline capabilities. All these features have been designed to
provide a portable infrastructure that facilitates collaborative development, code re-usability and extensibility.
OPERA is free software with support for both GNU/Linux and MacOSX platforms. The pipeline is hosted on
SourceForge under the name "opera-pipeline".
ESPaDOnS is an ongoing project for a cross-dispersed echelle spectrograph/spectropolarimeter, for general community use at the Canada-France-Hawaii Telescope. This instrument will provide: (1) a complete optical spectrum from 370 to 1,000 nm in a single exposure, with a variable resolution between 50,000 and 75,000, (2) all polarization components of the stellar light, and (3) 20% peak total throughput. The wide spectral coverage will maximize the multiplex gain associated wtih multi-line techniques. The high resolution will give sufficient spatial resolution for Doppler and Zeeman-Doppler imaging of rapid rotators, increasing the sensitivity of the observations to small-scale structures. It will also allow accurate brightness, abundance and magnetic field mapping of moderate rotators, and help study stellar pulsations, abundances, and extrasolar planets. The possibility of recording two interleaved spectra will be very useful in polarimetric mode, and very convenient for faint object spectroscopy in non-polarimetric mode, where the spectrum of the adjacent sky will be recorded along with that of the target. The spectrographic is bench-mounted and fed by low-OH H-treated Ceram-Optec optical fibers from a Cassegran module containing all calibration and polarimetric facilities, making it possible to have extremely good wavelength stability and minimal instrumental polarization. The achromatic polarimeter includes one quarter-wave and two half-wave Fresnel rhombs coupled to a removable Wollaston prism. ESPaDOnS will be a unqiue instrument worldwide in polarimetric mode, competitive wiht similar instruments on 8-m class telescopes in non-polarimetric mode. Astronomers will be able to address with unprecedented details a broad range of important issues in stellar physics, circumstellar environments, and extrasolar planets.