control software and user interface
Instrument control is operated through the cfht 'director' environment.
Within this environment, line commands are typed and dispatched to the
four agents, each controlling one specific instrument module.
The cassegrain agent controls the cassegrain module and associated motions, lamps
and sensors. This includes in particular moving the atmospheric dispersion corrector prisms
(commands adc, adc1 and adc2), the calibration wheel (command calibwh),
the guider density wheel (command denswh), the halfwave rhombs (commands rhomb1 and
rhomb2), the wollaston slide (command wedwol) and the fabry-perot wheel (command
fabpero). It also involves switching on and off the flat field and thorium lamps
in the calibration box and tuning their fluxes (commands flat, thor, fluxred, fluxblue) and reading the
two temperature sensors (commands temppol and tempcb). It can also display the
status of the cassegrain unit, as shown in the image on the right.
The spectrograph agent controls the spectrograph unit and associated motors,
lamps and sensors. In particular, it operates the camera drive and hartmann mask for focussing the spectrograph
(commands camfocus and hartmann), the slicer rotation and associated motions for setting the
spectrograph configuration (commands slicer, bench and dekker) and the slicer lamp drive (only used
for alignment purposes, command lamp). It can also set the slicer lamp on or off (command halogen),
put the exposure meter on or off (command expometer), open or close the exposure meter shutter (command
exposhutter), read the 4 temperature, the pressure and hygrometer sensors (commands tmp1, tmp2, tmp3,
tmp4, pressure, hygrometry) and launch the associated graphical tools (commands hskgui for
displaying the sensors values and apdgui for
displaying the exposure meter graphs).
The guider agent operates the guiding camera and offers
all usual functionalities, among which acquiring and displaying images from the guiding camera (commands
acquire and visu), changing the position and size of the image (command winsize), updating the zone on which
guiding is active (command gzone), computing the relative position of the guiding star with respect to the
centre of the guiding zone and send corrections to the telescope control system (command autoguide).
It also provides the observer with a number of byproducts, like for instance a graphical window displaying
the magnitude and width of the guiding star as a function of time (command gapgui).
The detcom agent operates the main ccd detector as well as the spectrograph shutter.
It offers the observer all usual explosure handling utilities, like setting the exposure type and time (commands
etype and etime), running exposures (command go) and checking the ccd temperature (command temp).
Individual commands can be chained within shell scripts to automatically run series of
operations that require a large number of low level tasks. With such scripts, observing sessions can be automated
quite easily, provided adequate procedures have been designed for the program being carried out.
Graphical user interface
The alternate option for operating the instrument is the graphical user interface (GUI).
consists in a graphical interface with buttons, checkboxes and popup menus offering all commands
mentioned above with a much more intuitive approach. An example window (for controlling
exposures) is shown on the right. In total, 10 different windows
are accessible (in principle sequentially) from a single menu bar to drive the instrument during
the various stages of an observing night (eg setting the instrument, focussing, taking
calibration exposures, starting guider, running exposures, ending session). Although users
can in principle choose between driving ESPaDOnS directly from a 'director' window or from
the GUI, most prefer to use the GUI thanks to its easier access and intuitive approach.
A full description of the GUI and instructions to operate it safely are available at CFHT.
© Jean-François Donati, last update Nov 16 2005