Royal Greenwich Observatory,
Madingley Road,
Cambridge CB3 0HJ
Telephone (01223) 374000
Fax (01223) 374700
Internet G.Rixon@ast.cam.ac.uk
INT-PF-1
INT Wide-Field Camera:
User Requirements for Controls
Guy Rixon
Issue 3.1; 1997-01-29
Royal Greenwich Observatory,
Madingley Road,
Cambridge CB3 0HJ
Telephone (01223) 374000
Fax (01223) 374700
Internet G.Rixon@ast.cam.ac.uk
Document history
Issue 0.1 1994-03-14 Original document.
Issue 0.2 1994-05-16 Modified to include more description of high-level control and comments on the previous draft.
Issue 0.3 1994-05-18 Changes in light of the general functional specification for the instrument. Pause/continue deleted. The integrated Acquire/set filter/expose operation was removed. A new requirement was added for the maximum readout time.
Issue 1.1 1994-12-22 The same as issue 0.3: declared as 1.1 so that the issue number matches the SID of the copy in SCCS.
Issue 1.2 1995-04-25 The requirement for the content of FITS-headers was added. This changes the numbering of other requirements.
Issue 1.3 1995-08-18 The requirements for commentary in the log were added.
Issue 2.1 1996-07-31 Requirements rearranged as noted in the text: alterations proposed by GTR.
Issue 2.2 1996-08-01 Further alterations requested by PSB.
Issue 2.3 1996-10-02 Enhancements requested by ING were added.
Issue 2.4 1996-10-07 Clarifications requested by MJI were added: see requirements 16 and 76. This issue was signed off by MJI as EGO project-scientist.
Issue 3.1 1997-01-29 The requirement for an Exbyte drive was noted in section 2.4. Requirements 77..81 were added. Various requirements were clarified as requested by ING (requirements 15, 18, 28, 32), extended (requirements 7, 8, 17, 28, 34, 64, 66) or moderated in the light of tests at the telescope (requirements 19, 23, 32, 39). Requirements 42 (logging comments in FITS files) and 51 (deletion of observations reserved to ING staff) were removed. A large number of requirements were noted to depend on ING-wide policy decisions and waivers of these requirements were granted. In particular, the section on reliability is now only advisory.
1 Introduction
1.1 Purpose.
This document describes the requirements, as perceived and stated by astronomers and operations staff, for the software system that will control the imaging camera at the INT Prime Focus. The completeness and validity of the control system should be judged by reference to the following text. The discussion and judgements here recorded are aimed at engineers developing the control system and scientists concerned with its final form and appearance.
Questions of design, development method and underlying technology are not raised here, except where connections with existing technology are required.
1.2 Scope
The Observing System for the INT Wide-Field Camera (WFC), is the set of all software and computing equipment used by observers at the INT to observe with the WFC. It includes the WFC Control-System and the Data-Handling System. The former product allows astronomers to make observations with the camera and to store the resulting data on disk. The latter system assists observers in checking, logging and exporting the observations.
For the purposes of this document, devices such as CCD controllers (and their firmware) are considered part of the new system. Similarly, computer peripherals such as image displays and tape drives, are treated as part of the system, rather than part of its environment, since they will be delivered and installed with the system.
1.3 Sources of requirements
FS Functional specification for the instrument.
GTR Suggestion by G. Rixon.
M1 Meeting between M. Irwin, P. Bunclark and G. Rixon, 4/3/94.
M2 Meeting between P. Bunclark and G. Rixon, 10/5/94.
M3 Review of logging requirements, P. Bunclark, B. Gentles, M. Irwin, P. Rees and G. Rixon attending, 16/09/95.
M4 Review of requirements after tests at the INT, 1997-01-28. Meeting attended by M. Johnson, D. Ives and G. Rixon (RGO project managers), M. Irwin and P. Bunclark (RGO project scientists), N. Walton (INT manager), D. Sprayberry (INT specialist in direct imaging), P. Rees and P. Fishwick (ING S/W-engineering) and C. Hankinson (ING mech.-engineering).
MJI Specified by M. Irwin.
PCTR Specified in email from P. Rees (representing all groups at ING) to G. Rixon on 1996-12-17.
PSB Specified by P. Bunclark (project scientist)
2 General Description
2.1 Product perspective
The imaging camera which the proposed systems will control is a new instrument, using the latest generation of CCD detectors in a mosaic pattern. The camera introduces control problems that have not been approached for any other ING system and the control system is not directly derived from any other ING installation. That said, the astronomical uses of the camera are essentially the same as any other imaging instrument. The control system is the `spiritual descendant' of the Perkin-Elmer ADAM system for the INT prime focus and of the VAX ADAM system for the WHT prime focus.
It is probable that parts of this system will be re-used for other INT instruments and on the JKT and WHT.
2.2 User characteristics and levels of control
Three classes of use require access to the systems.
z Observers undertaking scheduled observations at prime focus. Most observers are visitors to ING and do not have time to learn about the system before observing: they require a simple and intuitive interface to the observing functions which they can pick up easily during their first night of observations. Wherever possible, this interface should be preserved across system upgrades, and should be consistent between ING telescopes, so that skills gained by observers in one visit to the INT remain valid in later visits. Observers may want to construct simple programs to combine observing functions.
z ING support astronomers and telescope operators performing system checks or set-up operations: they will use the same interface as the observers but are assumed to know more about the system.
z ING or RGO staff carrying out repairs, tests or upgrades: they need low-level access to all parts of the system.
All users are assumed to speak English.
There are a number of ways that users can perform or support observing:
z There may be one observer who drives the telescope and instruments and oversees the data handling. This person must be physically present in the INT control-room to ensure the safety of the equipment and to guard against possible injury to staff who enter the dome.
z The observer may be assisted by a telescope operator (TO) who controls the target acquisition and may also (at the observer's request) drive the rest of the observing system.
z A second observer may take over the data-handling duties.
z ING technicians may interact with the system during observing to monitor or cure problems.
z The observers may operate the system remotely with the TO present to ensure safety. The observers run elements of the observing system locally and the observing system handles the network access to the INT.
z The remote observers may submit observations to be executed by the TO or by an ING astronomer. This can be done either through the existing arrangements for service observing or by real-time communication between the observers and ING staff. Both arrangements might be supported by a queuing system in which the observing system selects and executes observations automatically or semi-automatically.
Normal observing should be automated as far as possible. This is much easier to do and more helpful with the WFC than with, say, ISIS since there are fewer options. The ideal is for the observer to be able to schedule observations for some large part of a night and then to intervene only if problems occur or if the scientific priorities change.
`Classical' observing should also be supported in which camera-control and target-acquisition are logically separate and in which the observer starts exposures explicitly. At this level, it is still desirable to automate complex operations like target-acquisition.
At the lowest level, operations affect one distinct item of hardware. It is unlikely that such commands will be needed for observing, but they will be needed by engineers.
2.3 Operational environment
2.3.1 The camera
The WFC is a mosaic of four Loral CCD detectors mounted in the prime focal-plane of the INT. The four CCD chips are to be exposed and read out simultaneously. Each chip has 2048 2048 pixels each 15 mm square.
A fifth Loral CCD is mounted to the side of the main mosaic and serves as an autoguider. This chip is fixed in position relative to the mosaic. Exposure and read-out of the autoguider CCD is independent of the mosaic except for the use of the common shutter and filter. The shutter exposes all the detectors at the same time; as a result, the autoguider is blind when the science CCDs are clearing or reading out.
A filter wheel is provided in the beam-path to the CCDs and it is expected that all observations will use a filter. The wheel has six demountable filter-holders and will generally be loaded with broad-band filters. Each filter holder carries a machine-readable code and the wheel can return to the control system the identity of the filter holder in the beam. For the standard set of broad-band filters the mapping of filters to holders will be fixed (the filters will be glued into the holders) but some empty holders will be provided in which observers can mount their own filters. The filters also cover the beam-path to the autoguider.
The CCDs lie in one plane which is aligned parallel to the focal plane using capstans on the cryostat; this only needs to be done when the cryostat is refitted to the camera after maintenance. The control system cannot drive or sense the capstans. The CCDs are driven into the focal plane using the telescope's focus drive which moves the camera and cryostat as one unit. If filters of different optical thicknesses are used, it is necessary to adjust the focus each time the filter wheel moves.
2.3.2 The TCS
The telescope is controlled by a Perkin Elmer mini-computer. The observing system may only interact with the telescope (adjustments to the telescope pointing or requests for telescope telemetry) through the telescope computer. The TCS is a mature system and may not be modified very greatly to suit the P-F camera. Shortly after commissioning of the WFC, the P-E TCS will be replaced with a system based on the WHT TCS. The observing system will be adapted to suit this new TCS.
For the foreseeable future (about five years at present), the INT will normally be provided with a Telescope Operator who will control the pointing and tracking of the telescope. The TO may use some part of the WFC control-system to do this but may also use a local interface built into the TCS; in the latter case, the WFC control system must continue to operate correctly.
2.3.3 TO's working station
Currently, the TO has a non-windowing terminal to the TCS and a bank of status-display equipment with push-button control over the autoguider. Most or all of this equipment will be taken out of use in the first year of service of the WFC. The WFC control system will provide its own status displays on an X-windows device of some kind. As a general principle, the TO's will be able to view on his/her working station any display available to the observers.
2.3.4 Observer's working station
This station allows the principal observer to drive all parts of the P-F control system and data-handling system. No physical controls will be provided, but sufficient computers displays and terminals must be included to support the various threads of control.
The equipment supplied for this station will also be used for observing with other INT instruments. It is assumed that the system-control computer will be the observer's station.
2.3.5 System computer
One central computer will be provided for data-acquisition and system coordination. This machine will host the disks and tape drives needed for data-acquisition and export and its console will form the observer's working station. The system computer will also be used to observe with other instruments at the INT.
2.3.6 Data-handling station
This station must include computer equipment to allow an astronomer to control the data-handling system and associated data-reduction programs such as IRAF. When two observers are present, the writing of tapes may be controlled from this station.
Since the WFC is a simple imaging instrument, it should be possible to provide a standard reduction-pipeline for the observations. This facility would give the observers reduced data to take home and would allow reduced observations to be stored in the archive. Such a pipeline might be provided inside the data-handling system or the DHS might be arranged to drive an external system.
In principal, the data-handling station could be anywhere on the ING LAN that provided suitable displays and peripherals. In practice, a dedicated workstation will be provided with a fast network-connection to the system computer.
2.3.7 Output on FITS tapes
The end result of the observing is data taken away by the observers for analysis and equivalent data sent to the La Palma archive in Cambridge. In both cases, FITS tapes are required and these will be D-tapes and C-tapes in the normal ING manner. It should be possible to write both tapes onto DAT cartridges in parallel. Observers should also be allowed to make the C-tape on an Exabyte cartridge.
2.3.8 Meteorological instruments
It would be useful to collect meteorological data for each observation. Currently, the INT has met. instruments but these are not readable by software systems. It might be required, at some future date, to provide new met. instruments and to link these into the observing system.
2.4 Assumptions and dependencies.
It is assumed that all external devices to be controlled and all sources and sinks of data are mentioned above. Any new connections of the system to the outside world would require a redesign of the system.
The system computer and its peripherals and the TO's terminal will be delivered as part of the WFC project, together with any other processors and peripherals found necessary during the system design. Any additional equipment (e.g. extra monitors and disks) needed to improve the ease of use will be provided by ING.
ING will provide and install the cabling and network infrastructure needed for the WFC. ING are to provide the Exabyte drive.
2.5 General constraints.
The computer hardware for the system will be installed in the INT control room, where space is limited. The controls for the WFC system must coexist with the controls for other instruments.
Manpower to alter and adapt the TCS will be limited. The interface between the new control-system and the TCS may be required to reuse parts of the existing inter-processor link.
Any systems installed at the INT should be capable of simulation at Cambridge so that RGO can provide support. This may mean buying duplicates of all hardware. However, the delivered systems must be capable of support by ING once development has ceased at Cambridge.
Software provided with the WFC camera will probably be adapted and reused for other instruments and/or telescopes. The analysis and design of the system should take this into account.
3 Specific Requirements.
All requirements are considered essential for first release unless marked as enhancements. The enhancements are candidates for an upgrade programme to begin after the system is commissioned and accepted by ING.
3.1 Operations required during observing
Requirement 14 from M1, M2, WHT, FS; 18/5/94.
The system shall support at least the following operations.
(i) Acquisition of a target from the catalogue.
(ii) Selecting a new filter.
(iii) Observing the current target through the current filter for a specified exposure and archiving the data.
(iv) Observing as above but storing the data in a scratch file.
(v) Observing as above but without saving the data.
(vi) Setting the best focus for the telescope.
(vii) Setting binning factors.
(viii) Setting the readout speed.
The detailed requirements for these operations are given below.
Requirement 15 from M2; 10/5/94. Clarified on 1997-01-29. Waivers granted for catalogue handling by M4 on 1997-01-28.
Acquisition of a named target shall be available as a single logical operation. When commanded to acquire a target from the catalogue described above, the system shall slew the telescope to the correct position.
If the catalogue entry for this object includes a guide star the system shall find this star and adjust the position of the telescope to bring the guide star onto its predicted position (thus removing pointing errors). The system shall then close the guide loop and keep it closed.
If the catalogue entry indicates that no guide star is required, the telescope shall be left tracking in the position it reached at the end of the slew.
If the catalogue entry indicates that the system should find its own guide star, an area of sky at least 400 288 CCD pixels shall be searched and a suitable point-source chosen using algorithms that perform at least as well as at the WHT. The guide loop shall then be locked to keep the telescope in the position it reached at the end of the slew; there is no potential here to remove pointing errors.
The catalogue handling features may be provided as later enhancements.
Requirement 75 from MJI 1996-10-07.
The system shall assist the observer in moving the target in the focal plane from the nominal pointing position to the centre of any one of the SCCDs. This shall be done by one command and the observer need specify only the number of the SCCD and not the distance of the offset.
Requirement 16 from GTR 18/5/94; partly replaced by requirement 76 1996-10-07.
When a target and guide star have been acquired, the system shall keep the telescope at its nominal pointing position both during and between exposures. Where necessary and appropriate, the system shall open the shutter between exposures to allow the autoguider to see the sky.
Requirement 17 from FS; 18/5/94.
When the shutter opens for an exposure, the telescope must track in its current position, even if it has drifted away from its nominal pointing while the shutter was closed. The system must not trail the CCD image by trying to move the telescope back to its previous position.
Requirement 77 from PCTR 1996-12-17
When searching for guide stars, the system shall reject objects that are too malformed or too close to the edge of the ACCD for reliable guiding.
Requirement 76 from MJI 1996-10-07.
When the shutter is open between exposures, and when the autoguider is active, the pointing shall be adjusted to bring the guide star back to the position at which it was first acquired and to keep it there. This applies even if a slightly different pointing was maintained during the previous exposure, as required by requirement 17.
Requirement 18 from FS; 18/5/94.
The system shall prevent cross-talk between the CCDs.
Requirement 19 from M1; 4/3/94. Modified by M4 on 1997-01-28.
Moving a filter into the beam shall be a single logical operation. It must be possible to specify the filter by its name or by the numeric position in the wheel. The system shall be aware of the optical thickness of each filter in the wheel and shall adjust the focus of the telescope accordingly.
Each movement of the filter wheel shall take no more than 15 seconds to move between positions, this being the time between the observer entering a command and being notified of completion of the movement.
Requirement 20 from M1; 4/3/94.
If users are allowed to mount their own filters, the system shall be capable of mapping the names of these filters to names of their filter holders. It must be possible for the observers to change this mapping during the night. However,it is the responsibility of the observers to notify the system of a change of name mapping. When standard filters are used, the system must map their names correctly with no intervention by the observers.
Requirement 21 from WHT; 10/5/94.
The system shall provide a logical operation to make an exposure at the current position of the telescope and with the current filter. Each such operation shall expose all the science CCDs at once, producing four CCD frames which are stored and logged separately. The data shall be passed to the data-handling system for archiving and export. When the exposure time is specified as less than 1 ms, the system shall take bias frames. This operation shall have an option to produce dark frames, which the system must log accordingly.
Requirement 22 from FS 18/5/94; altered by RR 1996-03-04 and 1996-09-30
The length of exposures shall be measured and recorded to an accuracy of at least 0.01 second. The start-time of exposures shall be measured and recorded in UTC to an accuracy of at least 0.1 second.
Requirement 23 from WHT, FS; 14/3/94, modified 18/5/94. Modified by M4 on 1997-01-28.
The time taken to read out the CCDs at the standard rate (and with no binning) shall be no more than 210 seconds. The additional dead time in each observation (for clearing the array and saving the data, and for the reactions of the control system) must be no more than 10 seconds.
Requirement 24 from GTR; 16/5/94.
It must be possible to take data from a sub-set of the science CCDs. Ideally, there should be an operation that makes one or more of the CCDs invisible to the system until further notice. In any case, events on `disabled' CCDs should not be visible to the observer and should not delay observing on the enabled CCDs.
In addition, if one or more CCDs fails the system must retain the images from the remaining detectors and should allow observing to continue without delays.
Requirement 25 from WHT 10/5/94.
There must be a logical operation that exposes the CCDs as in requirement 21 but stores the observations as scratch files that the observer can access with data-reduction tools. A second operation is required to promote a scratch file to an archived observation at some later time.
Requirement 26 from WHT 10/5/94.
The observer must be able to expose the CCDs without storing or logging observations, as in the glance command of the WHT system. An operation shall be provided to save the resulting images if they appear useful.
Requirement 27 from WHT and FS; 16/5/94, modified 18/5/94.
The system shall allow the observer to change the outcome of the current observation by finishing it early (either saving the data or discarding them), or by retiming it. A pause facility is not required.
Requirement 28 from M1; 16/5/94. Augmented by PCTR on 1996-12-17. Clarified on 1997-01-29.
The system shall provide an operation that determines the best focus for the telescope by exposing in one CCD frame several images of a star taken at different focal positions with a small sp[spatial offset between each.
Ideally, this operation should include code to analyze the CCD frame, find which focal position gives the smallest image-width, and to drive the focus to that position.
An option to estimate a number of profiles across a field for capstan adjustment (suggested capstan movement reported) would be ideal. This feature may be deferred to a separate enhancements-project.
Requirement 29 from M1; 16/5/94, modified 18/5/94.
The system shall provide an operation to set the telescope's focus to a specified value.
Requirement 31 from WHT; 14/3/94. Augmented by PCTR on 1996-12-17.
At the end of each exposure the images shall be automatically displayed at either the observing station or the data-reduction station. The display sub-system must not reuse the SRTD software from the WHT.
Requirement 32 from WHT; 16/5/94. Clarified 19967-01-29. Range of binning factors reduced by M4, 1997-01-28.
The system shall allow the observers to set the binning factors for the science CCDs. Binning factors may be integers from one to four inclusive; higher factors are not needed. The binning factors may be different in the x and y directions but the same pair of factors, set in one operation, must apply to all the science CCDs.
Requirement 72 from RR 1996-09-30 (enhancement).
The system should allow the science CCDs to be windowed. Following practice on the WHT, there may be from one to four windows, and the user may specify the size and origin of each. The windows may be enabled and disabled in the readout without changing their definition. It is recognized that a window defined on one of the science CCDs appears in the equivalent place on the other three: this is a limitation of the CCD controllers and is accepted.
Requirement 33 from WHT; 14/3/94.
The system must allow the observer to select any readout speed which the CCD controller can provide; the five speeds used at the WHT are expected to be available.
Requirement 30 from M1; 16/5/94; altered 1996-07-31. Reclassified as an enhancement by M4 on 1997-01-28.
The system shall provide an operation which does a full observation including filter selection, target acquisition, shutter control and data acquisition.
Requirement 13 from M2: 10/5/94. Reclassified as an enhancement by M4 on 1997-01-28.
The observer must be able to programme sequences of basic observations described in requirement 30. The system must allow the sequences to be programmed before or during observing and to be stored on disk for later reuse. Ideally, the sequences should be recorded in simple text files that the observer can create or modify with a text editor.
3.2 Data handling
Requirement 37 from M1; 4/3/94.
The data-handling system shall preserve all data passed to it and shall protect the data from accidental deletion and corruption at least until they have been written to tape.
Requirement 38 from GTR; 16/5/94.
The system shall be able to store at least 1000 CCD frames each 2048 2048 pixels.
Requirement 64 split from requirement 38 1996-07-31. Augmented by M4 on 1997-01-28.
The system must warn the observer when there is disk-space for fewer than 15 more observations, reporting the remaining space after each subsequent observation. If there is space for fewer than 100 observations when the system is started, then the user must be warned once, but not at each observation.
Requirement 39 from M1; 4/3/94; extended 1996-07-31
The system shall treat the each CCD image as a separate observation (i.e. there will be four `observations' per exposure when everything is working). However, it must always be possible to determine which four observations come from the same exposure. Each observation processed by the system shall be allocated a unique run number.
Requirement 81 from PCTR; 1996-12-17.
Facilities shall be provided for making FITS tapes to ING's normal conventions for D-tapes and C-tapes. D-tapes shall be written on DAT cartirdges. Two DAT drives must be available so that a D-tape and C-tape can be written in parallel. An Exabytes drive must also be provided for making C-tapes.
Requirement 40 from M1; 4/3/94; altered 1996-07-31. Changed to an enhancement by M4 on 1997-01-28.
It shall be possible to set the system to write each observation to tape automatically, or to store the observations so that they may be manually written to tape at some later time. A record of the observations written to each tape shall be maintained; ideally, this should be merged with the the log of observations.
Requirement 43 from M1; 4/3/94 altered 1996-07-31. Clarified on 1997-01-29.
When observations are made available for data reduction they shall be passed as disk-FITS files and shall include FITS headers as for the tape files. At the point that the observations become directly visible to an observer working outside the system, they shall be presented as separate files, one file per CCD chip. The name of each file shall include the run number.
Requirement 41 is absorbed by requirements 43 and 44.
Requirement 44 from MJI; 25/4/95
The content of the FITS header of each FITS-file produced by the system shall be as described in INT-DAS-2.
Requirement 42 was withdrawn by M4 on 1997-01-28. See requirement 67.
Requirement 45 from M1; 4/3/94. Amended by M3, 16/08/95; altered 1996-07-31.
A log of observations shall automatically be kept by the system. The system shall either retain the logged information indefinitely (possibly building an extensive catalogue of past observations) or shall deliver the log to operations staff at the end of each night.
Requirement 65 split from requirement 45 1996-07-31.
The working stations shall be provided at all times with a display of this log. At any time, the observers shall be allowed to extract a report from the log and store it outside the data-handling system.
Requirement 66 split from requirement 45 1996-07-31. Extended by M4 on 1997-01-28.
The content of the log and reports from it is to match previous INT practice; the exact form shall be separately agreed between ING and the developers. It is particularly important that the record for each run indicates which CCD produced the data.
Requirement 67 split from requirement 45 1996-07-31.
The observers shall be allowed to add comments to the log, but shall not be able to revise data collected automatically by the system. The comments may be attached to particular observations or may be entire lines or paragraphs between observations.
Requirement 74 from RR and PSB 1996-10-01 (enhancement)
It should be possible to archive images from the autoguider, giving them the same status as images from the science CCDs. That is:
z each image shall be saved to a FITS file;
z each FITS file shall have header information as specified for science observations;
z the images shall be numbered in the normal sequence of runs;
z the runs shall be logged in the normal log of observations.
The feature may be deferred to a separate enhancements-project.
3.3 Catalogues
The whole issue of catalogue handling is uncertain, pending publications of ING-wide standards. Hence, the requirements in this section are only advisory and non-compliance shall not be ground for ING to reject the system.
Requirement 11 from M2; 10/5/94.
The system shall include a catalogue of targets to be observed, the catalogue being maintained by the observers. This catalogue shall contain for each target:
z a celestial position and equinox;
z optionally, an epoch of coordinates and proper motions;
z the coordinates of a guide star or
an instruction to the system to ignore guiding for this target or
an instruction to the system to find a guide star by searching the available field.
Requirement 68 split from requirement 11 1996-07-31
Ideally, the catalogue will be set up before observing begins, but the observers must be able to add, delete or alter entries while observations are in progress. The catalogue shall include the data needed for the system to acquire automatically a target and guide star. If special tools are provided to generate the catalogue they shall integrate the entry of the target position and the selection of a guide star.
Requirement 12 from M1; 16/5/94.
The system shall either include or provide access to a list of guide stars covering the all the sky that the INT can observe. The HST guide-star catalogue (used with the existing guide-star server) is suitable. The system must be able to predict the position at which guide stars will appear on the autoguider CCD.
3.4 Status displays
Requirement 34 from M1; 4/3/94. Augmented by RR 1996-10-01. Augmented by PCTR on 1996-12-17. Changed radically by PCTR and M4.
Any station which controls the telescope must be provided with status displays of the telescope and autoguider. The displays must include all the information currently shown in the TCS display plus:
(i) the position of the guide star on the autoguider;
(ii) whether the autoguider is obscured by the shutter;
Ideally, the display should also include graphs showing the recent variations of the (x,y) position of the guide-star. These positions should logged be such that the records persist when the observing system is shut down. This feature may be deferred to a separate enhancements-project.
Requirement 35 from M1; 4/3/94. Augmented by RR 1996-10-01. Augmented by PCTR on 1997-12-17.
The observers status shall be provided with displays of
(i) the state of the science CCDs (clearing, exposing, paused, etc.);
(ii) the readout format (size, binning and windowing details) and readout speed of the science CCDs;
(iii) the actual and required temperatures inside the cryostat;
(iv) the state of the shutter;
(v) the position of the filter wheel and detent pin;
(vi) the current contents of the filter-wheel.
Requirement 81 from PCTR; 1996-12-17.
Error messages should only be the result of a failure and should not be produced under normal working conditions.
Requirement 82 from PCTR; 1996-12-17.
All error reporting shall be descriptive and, as far as possible, should be unambiguous and accurately describe the cause of any failure. If a failure is automatically corrected by the system, the content of any error message should indicate that a successful recovery has been achieved. This requirement covers the entire operational system.
Requirement 36 from GTR; 10/3/94.
Any messages from the system to the observer shall be logged. There shall be a message display which shows the most recent messages and which the observer can scroll back to read earlier messages.
3.5 Distributed and remote access
Requirements 60-63 in this issue replace requirements 1-3 in issue 1.
Requirement 60 from GTR; 1996-07-31.
The system shall support distribution of control across two or more working stations. The stations may be anywhere on the ING LAN. As a forcing function, the system may require that one station by the console of the system computer: this prevents the system starting with nobody in the control room.
Requirement 61 from GTR; 1996-07-31.
All control functions and status displays shall be available at all `full' working stations; to qualify, a station must support X-windows. Stations equipped with non-graphical terminals shall have access to all command-line facilities provided for the full stations.
Requirement 62 from GTR; 1996-07-31.
As delivered, the system shall provide full working stations for the TO and one observer; these shall be arranged in the INT control room.
Requirement 63 from GTR; 1996-07-31.
The delivered system shall also provide at least a non-graphical working station on the access walkway in the dome. This will be used when changing filters in the WFC.
Requirement 4 from M1, 4/3/94.
The system shall allow the management of previously-observed data to be done by a second observer at a separate working position. Ideally, this person should be allowed to work from a point on the network outside the INT building.
Requirement 5 from WHT, 14/3/94.
Since the observers may be new to the INT, all observing functions should be available through simple, intuitive interfaces. In particular, it shall be possible for a new observer to explore the full range of control functions without reference to a printed manual. These interfaces may be graphical but need not be.
Requirement 6 from M1, 3/4/94; altered 1996-07-01
All working stations shall provide a command interface though which simple command procedure may be set up and executed. The command-line conventions of IRAF are recommended as an example of good practice.
3.6 Engineering access
Requirement 7 from WHT; 14/3/94
The system shall allow ING staff independent, low-level control of
(i) the science CCDs;
(ii) the autoguider;
(iii) the filter wheel;
(iv) the shutter.
Requirement 8 from WHT; 14/3/94.
This control may be needed during the day, when the observer's control stations are not active, or for emergency repairs at night, when the engineering controls must coexist with the observers' controls. Engineering control of the telescope is to be through the existing TCS.
Requirement 9 from WHT; 14/3/94.
Low-level control of the data-handling functions is assumed to be built into the observers' interface. In general, the system shall provide enough access to engineers that faults can be traced and its performance monitored.
Requirement 78 from PCTR; 1997-01-29.
It must not be necessary to change hardware, e.g. PROMs or PCBs, to allow diagnostics to be run.
Requirement 79 from PCTR and M4; 1997-01-29
Where engineering controls and observing controls are in use at the same time, the engineering must have the option of disabling the observing controls.
Requirement 80 from PCTR; 1997-01-29.
Ideally, engineering facilities should be run via the system computer, i.e. without the need for another terminal. The minimal requirement is that diagnostics must be able to be run over a remote network connection.
Requirement 10 from WHT; 14/3/94; altered 1996-07-31
It shall be possible to run any part, or all, of the system on a spare computer for engineering work; the engineering system must not interfere with the operational system.
3.7 Reliability
The requirements in this section are treated as guide-lines only pending publication of an ING policy on reliability and related issues. Hence, failures in the delivered system shall not be grounds for rejecting the system.
RGO proposes a warranty period of six months from provisional acceptance of the system in which the reliability may be tested and necessary repairs will be made by RGO engineers. After that period, ING must either accept responsibility for the system, demonstrate non-compliance with the requirements in this document, or agree changes with RGO as a separate project. The warranty applies only in respect of requirements agreed by RGO and signed off by ING.
Requirement 46 from WHT; 14/3/94. Altered by RR 1996-10-01. Corrected on 1997-01-29.
Some version of the observing system shall be available for use each night when the WFC is scheduled for observing. The observers require access from 1500 hrs each afternoon until one hour after astronomical twilight on the following morning.
Requirement 47 from WHT; 14/3/94.
The performance of the observing system is unacceptable if, averaged over a week, 5% of the total dark or twilight hours cannot be used for observing due to technical faults.
Requirement 48 from WHT; 14/3/94.
The availability of the data-handling system is unacceptable if the observers are denied access to their observations for 5% or more of observing hours on any night or for 70% or more of non-observing hours in any day.
Requirement 69 from GTR; 1996-07-31
Data recorded in the observation files shall be correct. The performance is unacceptable if more than one CCD frame in 1500 is recorded in the disk-FITS file incompletely or in a corrupt form. This requirement also applies to the header of each FITS file.
Requirement 49 from WHT; 14/3/94.
If observing has to be interrupted to reload control software, the reloading shall take an absolute maximum of 5 minutes (this period should be counted from the point at which the computing hardware becomes accessible; e.g. it does not include rebooting the computers). Reloading times less than one minute are desirable.
3.8 Security
Requirement 50 from GTR; 14/3/94.
The systems should be inaccessible to users not authorized by ING. Specifically, an unauthorized user may not drive the telescope, operate the camera or alter recorded observations.
Requirement 52 from GTR; 14/3/94.
Write access to the operational software shall be reserved to Operations staff.
Requirement 53 from GTR; 14/3/94.
Interruptions of the mains power supply are common on La Palma. Hardware supplied with the systems must not be damaged by interruption of supply. If the systems are crashed caused by lack of power no damage should occur to previously stored data.
3.9 Safety
Requirement 54 from GTR; 14/3/94.
In certain circumstances, unexpected movement of the telescope could cause injury to staff or damage to equipment. The safety of the telescope is normally the TO's responsibility; the TO must be able to isolate all mechanisms so that they cannot be moved via the P-F control system.
Requirement 55 from GTR; 14/3/94.
The moving parts of the camera are not readily replaceable. Where a software system has control of a moving mechanism, safeguards must be built in to prevent mechanical damage.
3.10 Compatibility
Requirement 70 from GTR 1996-07-31
Where functions of the WFC observing system overlap with observing system for other instruments, common conventions should be used. Programs should be made reusable wherever possible.
Requirement 71 from GTR 1996-07-31
Programs developed for the WFC that are made reusable in other observing systems should be designed to work on all ING telescopes.
3.11 Resources
Requirement 56 from M1; 4/3/94.
All programs within the WFC control-system and the data-handling system must run together on the computer provided by the project, which will be a SPARCstation with `at least the power of an IPX'.
3.12 Constraints on hardware
Requirement 57 from GTR; 14/3/94.
All hardware purchased for the delivered system should be suitable for use at mountain-top air pressure (roughly 75% of sea-level pressure). All mains-powered equipment must be suitable for use with a 240V 50Hz supply.
Requirement 72 from PSB 1996-08-01.
Any part of the system which is to be mounted in the dome must be able to operate in the humidity range 0..99% RH and the temperature range -10..+30_C.