Next: Handling Chunks of Image Data in the Gemini Data Handling System
Up: Data Pipelines
Previous: Interfacing with the Gemini Data Handling System
Table of Contents -
Subject Index -
Author Index -
Search -
PS reprint -
PDF reprint
Hill, N., Gaudet, S., Dunn, J., Jaeger, S., & Cockayne, S. 1999, in ASP Conf. Ser., Vol. 172, Astronomical Data Analysis Software and Systems VIII, eds. D. M. Mehringer, R. L. Plante, & D. A. Roberts (San Francisco: ASP), 163
The Gemini Quick Look System
Norman Hill, Séverin Gaudet, Jennifer Dunn, Shannon Jaeger, Steve Cockayne
National Research Council Canada/Herzberg Institute of Astrophysics,
5071 West Saanich Rd. Victoria B.C. Canada, V8X 4M6
Abstract:
The Gemini Data Handling System (DHS) developed by the Canadian Astronomy
Data Centre (CADC) is required to provide a ``Quick Look'' display system that
allows near real-time display of image data collected by the instruments of the
Gemini Telescopes.
The Gemini Quick Look System allows data to be displayed on multiple
display tools, possibly on different systems,
allows the display of data from multiple data streams,
and allows images to be sent incrementally (in chunks).
The Quick Look Tool is based on the European
Southern Observatory (ESO) Skycat display tool, and expands on the
functionality provided by Skycat.
This paper describes the design and function of the Gemini Quick Look System.
The Quick Look System of the DHS is intended to
provide a near real time display of data collected
by the Gemini instruments, and to
display data produced by the DHS Data Processing system.
The initial version of the DHS, including a working version of the
Quick Look System was accepted by the International Gemini Project Office
in August, 1998. A second version of the DHS is tentatively scheduled
to be delivered in May 1999. This will include some of the enhancements
to the Quick Look System described section 3.
Other aspects of the Gemini DHS are described in Dunn et al. (1999),
Gaudet (1996), Gaudet et al. (1999), Hill et al. (1999), and Jaeger et al. (1999).
Figure 1 depicts the data flow through the Quick Look System.
The components that manipulate the data are divided into three sections:
- Data Sources are the sources for the original data which are all
external to the DHS. Data sources may include all Gemini instruments,
the Gemini Observatory Control System (OCS), and may include non-science
instruments like the Guide Camera.
Data for a single dataset may be sent by more than one data source and
each source
may send the data for a single dataset in more than one chunk. It is also
possible several data sources to be simultaneously sending data to the DHS.
The data structure is described in detail in Dunn et al. (1999).
- Data Handling System are the subsystems of the DHS which
run on the DHS computers at the summit.
All data received by the DHS Data Server are forwarded to the
Quick Look Server
for display, and to the DHS Data Processing system for pre-arranged data
reduction. Data created by the
Data Processing system may be sent back to the Data Server for archival
storage or to be forwarded to the Quick Look Server.
- The Remote Quick Look components are the parts of the
DHS which would run on any remote computer system that is
displaying Quick Look data.
These systems may be computers dedicated to Quick Look,
or they may be computers primarily used for other Gemini functions,
which have Quick Look as a secondary function (the systems running the OCS
for example).
Figure 1:
Quick Look Data Flow.
|
The master Quick Look Server receives data from the Data Server and
routes the data to appropriate Quick Look Tools
and slaved Quick Look Servers. Data routing is based on Quick Look
stream names, which are assigned to a dataset by one of its data sources
(see section 2.3.).
Data is sent
to Slave Quick Look Servers using the IMP (Shortridge 1997)
message passing system,
and to the Quick Look Tools using memory mapped files.
If Quick Look data is to be displayed on computer systems other than
the one running the master Quick Look Server, a slave Quick Look Server
must be run on the second system. The master Quick Look Server transfers
only one copy of each dataset to each slave Quick Look Server,
and so even if more than one Quick Look Tool is displaying a dataset,
only one copy of the data will be transferred over the network.
Having a separate Quick Look Server on each computer also allows memory mapped
files to be used to transfer data between Quick Look Server and Quick Look
Tools, and avoids having to transfer the entire image over the network each
time a chunk is received, which maximizes Quick Look Tool display speed.
2.2 The Quick Look Tool
The DHS Quick Look Tool is a Tcl/Tk program based on the ESO Skycat
display tool (Albrecht et al. 1997). It uses the OcsWish Tcl/Tk interpreter
provided by the Gemini Project (Walker & Gillies 1998).
All existing Skycat functionality is retained.
The Quick Look Tool merges data chunks into a single coherent
image and displays the most recently received dataset and frame.
See Dunn et al. (1999) for more information about chunking.
The control panel shown in Fig. 2 was added to Skycat to
control the new Quick Look functions.
The control panel:
- Shows the list of currently subscribed streams
(see section 2.3.).
- Allows the list of subscribed streams to be modified.
- Displays a list of frames available for the current dataset.
- Allows a frame to be selected for display.
- Allows the Quick Look Tool configuration to be modified.
- Allows a specific dataset to be retrieved from the DHS Data server
and displayed.
- Allows the currently displayed frame to be saved to the Gemini archive.
Figure 2:
Quick Look Control Panel.
|
2.3 Quick Look Streams
Data are directed to appropriate Quick Look Tools based on
Quick Look stream names.
A set of Quick Look stream names are assigned to each dataset by
one of its data
sources. Each Quick Look Tool individually subscribes to a set of Quick Look
streams. The initial list of subscribed streams are determined from the
Quick Look Tool configuration file,
and the user may change the subscribed streams with the control panel
(section 2.2.).
When the Quick Look Server receives data for a dataset, the data is
forwarded only to those Quick Look Tools which have subscribed to at least
one of the Quick Look streams associated with the dataset.
Quick Look streams allow simple and flexible control over the routing of data
to Quick Look Tools.
3. Future Enhancements
There are several enhancements to the Quick Look System which will
be added in the near future:
- The newest version of Skycat allows overlay graphics to be stored in
the input files. This feature will be used to allow data displayed by the
Quick Look System to contain graphics and graphics overlays.
- Simple image processing as data is received. This will allow
removal of flat or bias effect, or application of a bad pixel map.
- The Quick Look control panel will be merged into the Skycat
interface using the Skycat plug-in capability.
- The ability to merge separate frames into a rough mosaic. This will
allow a unified view of images from instruments with multiple detectors.
At the time of writing, there are no operational instruments for the
Gemini telescopes, however we have tested the Quick Look System
with instrument simulators. We have met our throughput requirements of:
- 10 frames per second for 128 x 128 pixel images.
- 1 frame per second for 512 x 512 pixel images.
- .5 frame per second for 1024 x 1024 images.
The Quick Look System is now being used by instrument developers and by
Gemini integration and testing staff for testing and development of
Gemini instruments.
A high frame update rate will allow instruments that collect data continuously
(e.g., the Gemini Guide Camera) to display data with the appearance of
continuous motion.
It is expected that the throughput of the Quick Look System will be high
enough that the Gemini Guide Camera will be able to use the Quick Look System
as a real time display, eliminating the need for a dedicated real time
display system.
References
Albrecht, M. A., Brighton, A., Herlin, T., & Biereichel,
P. 1997, in ASP Conf. Ser., Vol. 125, Astronomical Data Analysis
Software and Systems VI, ed. G. Hunt & H. E. Payne
(San Francisco: ASP), 333
Dunn, J., Jaeger, S., Hill, N., Gaudet, S., & Cockayne, S. 1999,
this volume, 167
Gaudet, S. 1996, in ASP Conf. Ser., Vol. 101, Astronomical Data Analysis
Software and Systems V, ed. G. H. Jacoby & J. Barnes
(San Francisco: ASP), 388
Gaudet, S., Hill, N., Dunn, J., Jaeger, S., & Cockayne, S. 1999
this volume, 3
Hill, N., Gaudet, S., Dunn, J., Jaeger, S., & Cockayne, S. 1999,
this volume, 155
Jaeger, S., Dunn, J., Cockayne, S., Gaudet, S., & Hill, N. 1999,
this volume, 159
Shortridge, K. 1997, Interprocess Message Passing (IMP)
System,
(AAO/IMP_MANUAL_8, Drama Software Report 8) (Sydney:
Anglo-Australian Observatory)
Walker, S. & Gillies, K. 1998, OcsWish Technical Manual,
(ocs.ocs.015-OcsWishTechnical/02) (Tucson: NOAO)
© Copyright 1999 Astronomical Society of the Pacific, 390 Ashton Avenue, San Francisco, California 94112, USA
Next: Handling Chunks of Image Data in the Gemini Data Handling System
Up: Data Pipelines
Previous: Interfacing with the Gemini Data Handling System
Table of Contents -
Subject Index -
Author Index -
Search -
PS reprint -
PDF reprint
adass@ncsa.uiuc.edu