The VLT Real Time Display Software
Contents
1. Although it is part of the VLT control software the RTD is an independent software package and does not require any other VLT software components external packages such as MIDAS or any commercial products Functionality The core of RTD is an image dis play widget which supports two image sources cameras and FITS files The camera is either a technical CCD or scientific detector which provides the image data in shared memory The RTD widget is notified via an image event mechanism by the camera that a new image is available See below for more about real time images Figure 1 shows atypical screen layout when working with the RTD widget The application shown was designed for demonstration purposes and shows an image loaded from a FITS file The user can change the magnifica tion of the displayed image zooming in to get a close up view of a section of the image or zooming out to get an overall view of a large image A panning window supports navigation on the image and a zoom window enables the targeting of a single pixel The RTD widget supports a basic set of colour scaling algorithms linear All documents are available from the VLT Archive or directly via the ESO home page of the World Wide Web main documents Meeting with Consortia and Contractors A two day meeting on the VLT control software was held at ESO on June 19 20 1995 Software representatives of about 10 external Consortia and Contrac tors we2. memory as recom mended by the real time extension standard POSIX 4 The display on X terminals is support ed although for very fast image display frequencies workstations are recom mended In addition on workstations the X11R5 extension for X Shared Memory is supported giving the final boost for passing the scaled pixmap to the X Server The software has been ported and tested on the following workstation platforms HP HP UX and Sun SunOs amp Solaris 2 3 j Big Bang Rescheduled Because of a possible uncertainty in the manpower available in 1996 for the implementation of the new VLT like con trol system the date when the imple mentation will start has been shifted from April 1 to July 1 1996 This means that the operation of the NTT will continue unchanged through June 30 Final ad justments will take place after field tests in December 1995 Telescope Control System and February 1996 EMMI control software of two critical compo nents Observers who might get time after June 30 will be informed about the allocation of observing time if any after the evaluation of the test results This change in schedule does not seriously compromise the NTT s ability to provide useful feedback to the VLT project Further announcements will be made in The Messenger and on the World Wide Web see below The NTT on the World Wide Web As part of ESO s efforts to make more extensive use of the World Wi
3. the first release is available on the July 95 release of the VLT SW For people interested and not receiving the VLT control software the RTD user manual is accessible on anonymous ftp via the following WWW reference _ftp te1 hq eso org vit pub doc rtd_sum1 0 ps qz For more information on the RTD software please contact Thomas Herlin ESO VLT SW group preferably via e mail therlin eso org With this periodically compiled collection of short notes the NTT Team intends to keep the community informed about changes in performance configuration and operation of the NTT and its subsystems guide star catalog and a new server on one of the workstations in the NTT building The performance is for a number of reasons vastly superior to the previous temporary solution which depended on STARCAT in Garching Guide stars are now on a routine basis automatically supplied for every new preset First attempts to acquire also the guide star in a fully automatic way with the guide probe have been very successful Since the light of the guide stars is via a beam splitter also used for parallel image analysis efforts to adjust the exposure times with the image analyser according to the magnitude of the star are under way Graphical Log of Image Analysis Data With the implementation of the cyclic image analysis in parallel mode the self diagnosing capabilities of the NTT can now be much better exploited In order to ena
4. CCS lite does not require HP RTAP and therefore does not allow to access the workstation based real time data base It allows though to easily imple ment user interfaces to LCU software providing access to LCU databases and support at the workstation level for passing messages errors and logs It represents also an easily portable plat form to any users who will be able to prepare an Observing programme ahead of time on a generic UNIX workstation Some developments like the Real time display although part of the VLT control software have been implemented in a fully portable way and can run completely independent of the VLT soft ware see following article Documentation and Standards A complete set of specifications and user manuals exists for the VLT software The VLT Real Time Display Software and for the VLT common software in particular In spite of the large number of documents there exist obvious access roads to documentation So if you are interested in instrumentation software you should simply start reading one document VLT Instrumentation software specification Please refer to latest issue of 12 4 95 If instead the point of interest is telescope subsystems the access specification is VLT software Tele scope Control system functional specifi cation These two documents can also be used as references to any other docu mentation if deeper understanding is required The general requi
5. TD Application T e ae a e o o Workstation F 2 T E ee T P7 aar aar an a ia aa a a Figure 2 RTD high demand on the CPU and the network For some images the variation between exposures is only interesting ina small area In this case a rapid frame can assist the selection of a specific area for example around a star This typically small frame can be updated faster than the rest of the image while the user still sees the complete picture By using rapid frames an image update frequency of more than 10 Hz is expected to be possible Detailed performance meas urements will be done based on the first release of RTD Implementation The RTD widget is implemented as a Tcl Tk Tk 4 0 widget using C The RTI library is also implemented in C but as an independent library In order to support fast application development with the RTD widget a large set of incr Tcl widget classes is provided for managing among other things a zoom window a panning window and a line graphics tool box Although Tcl Tk code is interpreted the performance of the RTD widget when updating images in real time is not degraded This is due to the fact that all image related operations are implement ed entirely in C C Only the user interface parts of the software such as buttons and menus are actually interpret ed at run time The image event mechanism uses standard UNIX IPC and image data is passed using shared
6. ble also Visiting Astronomers to keep track of the performance of the telescope tools have been developed to plot individ ual aberrations as measured before and after the setting of the forces versus time In addition the level to which aberrations should ideally be corrected is indicated
7. de Web to inform the scientific community which was strongly encouraged by the Users 8 Committee NTT pages are under de velopment By the time of publication of this issue of The Messenger they should be accessible from the ESO home page http http hq eso org eso homepage html In addition to general information about the NTT and the NTT Upgrade Project any up to date an nouncements will from now on be made on the Web The previously maintained electronic bulletin board will be discontin ued The Information Desk of the general ESO pages can also be used for inquiries with the NTT Team e mail can as before be sent also directly to ntt eso org Update of EMMI SUSI Manual A major revision is currently under way of the EMMI SUSI manual In order to let prospective applicants for observ ing time with the NTT in Period 57 take advantage of the progress made inter mediate versions will be made available electronically Details will be provided on WWW see above Automatic Guide Star Selection The Data Handling and Observation Support Group has installed the HST For RTD application development the VLT Panel Editor can be used to develop control panels using the RTD widget The VLT Panel Editor supports the interactive placement of GUI components and gen erates panels that comply with the ESO VLT common conventions for GU devel opment Availability The RTD software is part of the VLT control software and
8. on about the image for example data type size and the reference to the shared memory location for the image data The event is sent to an RTD server process which keeps a list of RTD applications regis tered for notification of a specific cam era If there is a match the image event i Par No poe era a ArrowShape N Clase 1 Zoom Window Image scaling limage window select graphics 1 scroll image 2 is dispatched to the corresponding RTD application Figure 2 shows a diagram of the image event architecture The advantage of using this decoupled approach is that the camera subsystems and the RTD applications become inde pendent of each other and several RTD applications can attach to the same camera source Real Time Image Display herin bN Sd Ginitallhbrnddemosnge 2 Agil vi a Maxs 14733 High bate Z 2 Gl 2 t display menu 3 Panning Window single Pixel Value Value 4196 Type short fuito Gut The RTD server will also currently not implemented support eavesdropping which is the multi casting of images to remote machines which could be used for example for remote observing For eavesdropping issues such as network bandwidth and image compression tech niques e g H transform will be investi gated Updating images in real time places a Sample application illustrating the RTD architecture R
9. re present The meeting was Organised around a number of tutorials and demonstrations as most of the software comes with a set of auxiliary tools and user interfaces to facilitate development For more information on the VLT software please use the ESO home page in the WWW Should you have additional questions you can contact by e mail either graffi eso org or other members of the VLT software group square root logarithmic and histogram equalisation MIDAS compatible colour maps are supported by the RTD widget as well as the MIDAS intensity transfer tables The colours can be manipulated by a colour bar rotating the colour map or changing the slope of the intensity via mouse interaction The colour distribution can be changed by either manually setting the cut levels or using automatic cut level calculation The widget supports line graphics so that the user can overlay markers and text on the image This might be used for example to identify interesting areas around a star Standard line graphic components such as line circle and text are available and can be drawn interac tively on the image Line graphic at tributes such as line width colour filling font etc can be set by the user via buttons and menus In addition to the interactive line graphics a programmatic interface is available to support overlay ing of more complex line graphics such as star maps taken from a catalogue Pixel query operations are suppor
10. rements standards and rules for this software have been fixed some time ago although there is a constant evolution in the project by the VLT software group T HERLIN A BRIGHTON P BIEREICHEL ESO Introduction The VLT will contain a large number of technical CCD s which will be used for guiding and slit viewing cameras requir ing real time display facilities The fre quency of image display from these image sources can be several Hz for example while performing tracking For scientific detectors real time display ca pability is equally important In particular requirements for infrared detectors have been a driving force in specifying the functionality for a real time display sys tem The Real Time Display RTD software was developed in order to support image display in real time on the VLT The RTD software provides a tool for users to display video like images from a camera or detector as fast as possible on a workstation or X terminal The RTD is implemented as a package providing a widget and library It is designed to be a building block adding display capabilities to dedicated VLT applications in areas such as telescope and instrument control The intention of RTD is not to provide the image processing functionality al ready existing with image processing packages such as MIDAS Functional overlapping with image processing sys tems is kept to a minimum and confined to the area of on line operations 6
11. ted at various levels e get and or display the value of the pixel directly under the mouse e get and or display a table of pixel values surrounding the pixel directly under the mouse Colormap manipulation _tnage Colors cnomp i Intensity Color Saile Algorithm pastel Linear x Logane Square Roit lt Histogram Equaitaton Lt i eee _ draw Width ATOW Fill Line Graphics suppor Outline Stipple Font spectrum Plot Spectrum Beanie ea Figure 1 Another level of pixel value inspection is supported by a spectrum plot along a cut line drawn interactively on the image The pixel values are displayed in a separate graph window The RTD widget provides a library with basic image handling functionality re ferred to as the Real Time Image RTI library In addition to basic image handling algorithms the RTI library provides a data access framework for application devel opers supported by a well defined appli cation programming interface API This enables developers to contribute to and extend the image handling capabilities of the library Real Time Images In order to use the RTD widget for real time an image event mechanism is provided by the RTD software The image eventis sent by the subsystem controlling the camera device e g CCD subsystem or infrared detector control software The image event contains informati
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