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Both
the IRT and Rigel telescopes utilize the Talon software suite for
Observatory scheduling, telescope control and image analysis tasks.
Talon is an
integrated suite of Linux-based software which includes telescope
scheduling algorithms, observatory instrument control, and image analysis.
It is written primarily in classic ?C?, with some components in Perl and csh script. Most
user-level applications in have a Motif-style GUI interface. Talon is
based on OCAAS, a software suite developed by software engineer Elwood
Downey (Clear Sky
Institute) for use at the University of
Iowa?s first remote facility (the
ATF, or Automated Telescope Facility). Significant enhancements were made
to OCAAS (renamed Talon), especially extending Talon to a web-based
interface, by Steve Ohmert at OMI. A block diagram of the
telescope control for Talon is shown below.
- Telescope Scheduler (Telsched)
The telescope schedule accepts
schedule requests from the web-based observing schedule request interface
and sorts them in an optimal manner based on request time and priority
level. The user interface is shown below.
Talon's Telescope
Scheduler
- XObservatory: Telescope Control
Interface
The program Xobservatory provides a real-time display and control
of the observatory. The telescope can be operated in one of two modes:
real-time or batch (remote scheduling). In real-time mode, the observer
may specify the source to be observed by catalog name or coordinates.
There are also tools for auto-focussing,
re-homing all axes, and control of filer wheel. Xobservatory also display time and weather
information, current telescope position, and current status of filter
wheel, roof, focus position, and camera. The user interface is shown
below.
Xobservatory
- Camera
Camera is a powerful FITS image analysis program that
also provides real-time CCD camera control. It has a large number of
analysis tools, including absolute and differential photometry, a WCS
(world coordinate system) solver, a image ?movie?
tool, in addition to the usual analysis tools, such as magnifying lens,
histogram adjuster, image arithmetic, and FITS header editor. The user
interface is shown below with several tools illustrated..
? 
Camera: Image Analysis and Camera
Control
The table below describes the
Talon system is more detail Layered atop
this are the components of the remote access Internet solution, including
user management, scheduling, remote monitoring, direct remote control,
remote maintenance, and basic user data management.
|
Specification |
Description |
|
Observatory Control
System (OCS) |
The Observatory Control
System of Talon consists primarily of Xobs, the Linux X-Windows based
observatory control program. This program calls upon and
coordinates much of the interrelated portions of the Talon
architecture, and forms the primary control panel for the telescope,
dome, and peripheral systems when used locally.
Remote users accessing
the system will be presented with a web-browser display,
incorporating much of the same information as is found in Xobs, but presented in a somewhat
different style more appropriate to the medium. This
functionality is provided by Claw.
Logging of critical
system functions is performed by Talon for diagnostic and technical
review purposes. This information chronicles the operation of
the observatory subsystems at a component and driver level. |
|
Telescope Control System
(TCS) |
The telescope control
software of Talon supports the controlled, properly accelerated and
damped slewing of the telescope to target (manually or
automatically) and subsequent tracking of the target. Tracking
is supported by a pointing mesh (calibration) that is created by
preparing a survey of the sky and performing precise WCS solutions
at each of these sampled locations. The encoder-to-actual
error is recorded for each position and is then used as
interpolation points for any subsequent pointing operation.
This results in a very good and very repeatable pointing
accuracy |
|
Instrument Control
System (ICS) |
The Instrument Control
System controls the primary CCD camera, filter wheel, guide camera
and focus mechanism.
Access to the controls
for the Instrument Control System is through Xobs as implemented by Talon, and by
similar interfaces in Claw, as well as the scheduling options
available via Claw. Locally, images captured by the
system may be viewed using Camera, a comprehensive CCD camera
controller, image viewer, and analysis tool. Web based users
have the option of downloading their images for offline processing,
or for simple viewing in web-delivery format.
Both standard and
H-compressed FITS files are supported. All relevant FITS
fields are noted for each exposure, including location, time,
exposure, image scale, object, and WCS solution, among others. |
|
Dome Control System
(DCS) |
Documentation for
interface and configuration options to the dome enclosure are provided with Talon. The control system
for the dome is governed by a CSIMC controller, which runs a script
that handles basic dome operational commands. These CSIMC
functions can be easily adapted to control nearly any type of switch
interface to a dome control system.
The Dome Control
Software handles all aspects of the dome function including
rotation, shutter open/close, and rotation
to shutter power. Optical Mechanics has adapted Talon for use
with domes from a variety of manufacturers. |
|
Environmental Control
System (ECS) |
Weather station monitors
for barometric pressure, temperature, humidity, precipitation, wind
speed and direction are standard in Talon. The Davis
Instruments EZ Mount Weather Monitor II or equivalent is
provided. |
|
Scheduler Manager System
(SMS) |
Development of the
Claw product includes creation of a scheduling solution that
addresses most common user needs.
The scheduler as
delivered accepts observing requests from users. The
basic components of an observation request consist of naming the
object or coordinates to view, the equipment to be used including
filter choice, and the exposure time. Other specialized
options, such as scheduling a fixed location (non tracking) exposure, or shutter ?flashing? (used in
determining streak direction) may also be selected. |
|
Direct Internet Control
System |
Users with appropriate
privileges can request direct control sessions and are entered into
the scheduler as fixed blocks of time. The user for whom the
direct control session has become active is allowed to sign into the
system for remote control at any time during this session
block. As with any observation, the system will prohibit the
use of the telescope equipment during unfavorable weather
conditions. Administrators may override a direct session, in
the same way that they might override a scheduled request. | |
