Chapter III

Telescope Control — E. Pazderski

(Last updated: 2004.04.06)

This chapter deals with programming tools developed for steering of the 32 m radio telescope (here referred to as RT32 or RT-4) and its various components as well as for monitoring of their state.

III.1  Controlling the Motion

The c:\rt4\new\rt4.exe program is automatically executed with every start of this main computer. It initiates a communication with the controllers of angle converters of the dish position as well as the controller reading the position of the subreflector, sets proper parameters in the FESTO and Lence drivers controllers, initiates the network communication, starts a user graphical interface, and receives commands sent from the console and from the network.

Entire screen of the operator's monitor

In the control room an HP745i (trao2) computer with the HP-UX 10.01 operating system plays the server role for the steering system. This workstation is connected to a separate branch of the Ethernet network, that links the telescopes with the control room, with an extra Ethernet card (EISA). The comminication with the telescopes is carried on the level of link layer within a seven layer network communication model of the OSI.

The following programs perform specialised tasks.
rt4link — communicates with the RT32. It sends commands to the computer in the electric cabin (the lower one) and receives RT32 control parameters. These parameters are stored in the shared memory of the trao2 computer. From here these data can be accessed by other programs. The rt4link reads only primitives, basic parameters and computes the remaining useful parameters.
rt4win — displays some of the telescope parameters in a scalable window.
rt4gov — is responsible for the user commands delivery to the rt4link program.
rt4load — reads commands from a prepared file and supplies them to the rt4link program.
rt4diag — displays diagnostics.
rt4lenze — displays one of parameters of the Lenze controllers in a window of the X-windows.

Running and closing of the programs

Fig. III.1: Monitoring windows: RT4 with time data, current and preset telescope direction (sky coordinates) and the Cassegrain mirror position (top panel), one of parameters of the Lenze drives (middle panel), and some diagnostics (bottom panel)

• RT4 — shows time and sky coordinates,
• Lenze par. 056 — displays the parameter No 56 (this number is settable) of the Lenze drives,
• RT4 Diagnostics — serves to display requested diagnostic information,
• RT4 Command Module — allows for 'manual' control of the telescope position and motion.

Fig. III.2: RT4 Command Module window is used for keying in of the steering commands

Further to the above, opened are also these windows:
• Signal Monitor — plots the signal from one of eight channels,
• VXI Command Module — allows to send commands to the system of data acquisition,
• Receivers Command Module — with this window one can exercise control over receiver systems.

To close all these control programs one need to execute

kill_all

by keying in this command or clicking on the KILL_ALL icon.

Steering commands

FESTO driver terminal

festo mr0.100=$50	— switch off all movements
festo mr0.100=$52	— X — move to the left
festo mr0.100=$53	— X — move to the right
festo mr0.100=$54	— Y — move to the left
festo mr0.100=$55	— Y — move to the right
festo mr0.100=$5a	— A — move to the left
festo mr0.100=$5b	— A — move to the right
festo mr0.100=$5c	— B — move to the left
festo mr0.100=$5d	— B — move to the right

Logging parameter values

lf file	— open a work file file
no adr par	— save the parameters par from the Lenze drive adr to the work file
nod	— terminate the saving

Using catalogues

ncat n	— make the catalogue No n [0 to 9] current. Presently available are:   n = 0 — general catalogue (assumed at the start)   n = 1 — pulsar catalogue   n = 2 — OH source catalogue
cat sname epoch α δ	— add the source by name sname to the current catalogue
show sname	— display data of the sname
alias sname1 sname2	— add another name (sname2) to the source sname1

Other commands

ct s	— add s seconds to the universal time kept by the system
zo n	— enable (normally blocked) movements in a zone of extreme switch; this allows to position the telescope for maitenance purposes: n = 1 with the dish in the lower extreme position n = 2 with the dish in the upper extreme position n = 3 with the dish in the left of meridian extreme position n = 4 with the dish in the right of meridian extreme position
zod	— disable the movements (enabled by the zo n command)
xzero	— insert the offsets Δa and Δz into a correction register of the base position (normally not to be used!)
lenze n	— display the parameter No n [0 < n < 250] in the Lenze window

III.2  Controlling the Receivers (rec)

In the control room an HP745i (trao2) computer with the HP-UX 10.01 operating system plays the server role for the steering system. This workstation is connected to a separate branch of the Ethernet network, that links the telescopes with the control room, with an extra Ethernet card (EISA). The comminication with the telescopes is carried on the level of link layer within a seven layer network communication model of the OSI.

The reclink program sets up a communication with the computer in the secondary focus cabin, sends commands and receives responses.
The recgov program is responsible for the Receivers Command Module window, where commands can be keyed in and responses are displayed.

Steering commands: frequency sinthesizer, phase calibration signals, and dewars control

Receiver command window

Intermediate frequency distribution

Presently the outputs are settable according to the scheme given below:

0 system L	LCP  i = 0   ř
		output A
1 system K (X)	LCP  i = 1   ö
2 system L	RCP  i = 0   ř
output B
3 system K (X)	RCP  i = 1   ö
4 system C1	LCP  i = 0   ř
output C
5 system C2	LCP  i = 1   ö
6 system C1	RCP  i = 0   ř
output D
7 system C2	RCP  i = 1   ö

Fig. III.3: Block diagram of the intermediate frequency distribution (AKę)

The distribution module amplifies input signals and allows for correction of their frequency passband shape. The amplification can be reduced (by setting the level of attenuation) in the range 0 to -15 dB. The passband shape is modified through change of a varactor capacity done with the voltage generated by an 8-bit DA converter. This procedure effectively reduces the amplification in a lower part of the intermediate frequency band (near 500 MHz).

There are four one-argument commands, and four three-argument commands available for frequency distribution control. These are:

1A   — display current connection of the A output
1B   — display current connection of the B output
1C   — display current connection of the C output
1D   — display current connection of the D output
1A i a s — connect the A output to the i input,
      attenuate the signal by a dB, and set the band slope to s
1B i a s — connect the B output to the i input,
      attenuate the signal by a dB, and set the band slope to s
1C i a s — connect the C output to the i input,
      attenuate the signal by a dB, and set the band slope to s
1D i a s — connect the D output to the i input,
      attenuate the signal by a dB, and set the band slope to s

III.3  VXI Command Module Window

The VXI Command Module window accepts the following commands:

vxical	— perform the internal VXI calibration of converters; use this command in case of weird signal data
range N	— sets the range of voltage; user may enter any number for N, but the VXI will pick one of 2, 4, 16, 32 and 64 V that is closest to the requested value
period Δt	— sets the signal sample spacing to Δt s; user ma enter any number of seconds with the pecision of 0.1 s
cal Δt	— switch the noise diode on for Δt integer seconds (for calibration purposes); cal 0 switches the diode off
offset ΔV	— add ΔV Volts to the signal (default is 0 V)
gain G	— multiply the quantity (signal + ΔV) by G (default is 1)
att [n]	— set the attenuation in the IF path to 0 dB [n dB]
getatt	— display the attenuation in the IF path
trigger 0	— set the signal sampling to the internal VXI clock
trigger 1	— sample the signal synchronously with the power supply (230 V)
spectr 0	— abandon the spectrum analyser
spectr 1	— run the spectrum analyser
fa f	— set the starting frequency f [in MHz] for the spectrum analyser
fb f	— set the end frequency f [in MHz] for the spectrum analyser
vb Δf	— set the video bandwidth Δf [in MHz] for the spectrum analyser
rl p	— set the reference level p [in dBm] for the spectrum analyser

The program that displays graphically the spectrum, spectr, resides in the directory /home/rt4/vxi/analyser/.

III.4  The sigmon Program — R. Feiler

To display a signal (voltage) coming from the antenna and AD converted call:

sigmon

and a window named Signal monitor will open. At its bottom there is a command bar that allows to set various options by clicking the buttons:

• Y–	— move the diagram down
• Y+	— move the diagram up
• Y*2	— double the voltage range
• Y/2	— half the voltage range
• Auto: OFF/ON	— auto (ON) or manual (OFF) scaling of the diagram
• Chan. n	— use channel No n, 0 ≤ n ≤ 7
• Clean spikes: YES/NO	— remove (YES) or do not remove (NO) interference (spikes) from the diagram
• last Δt min./hr	— set the time span for the display (for horizontal axis), where Δt = 1, 2, 5, 15, 30 min. or 1 hr
• Max. v V	— set the voltage range (vertical axis), where v = 4, 8, 16, 32 or 64
• Sample: Δt s	— set the sampling interval to Δt seconds
• Open/Close file	— open or close a file where signal data will be or were written
• Freeze/Unfreeze	— freeze or release the displayed diagram
• Time offset: Δt min.	— show the data displayed Δt minutes previously; 0 ≤ Δt ≤ 60
• No avg. value xxxx     Avg.last n sec/min.	— no averaging      average over n = 5, 10, 15, 30 s, 1, 3 or 5 min.

To store the observed signal in a file one need to click the button 'Open file', which will lead to opening of a new window where there the directory (e.g. /temp/dat) and file name (the .dat extension is recommended) are to be keyed in. When accepted, the name is shown on the upper margin of the sigmon window and the fourth button at the bottom gets the 'Close file' inscription. Clicking this buttom closes the file and the registration ends. A user may now transfer the file to another location using the FTP protocol within the LAN. Although due to security reasons there is no direct access to the computer (ask the local staff for current possibilities), the general scheme would look like this:

ftp trao2 login: oper password: *********** cd /temp/dat get filename.dat

Remark: If there are problems during initialization of the sigmon, check the active processes in the hpterm system window. To this end use the Unix command ps -d. Now if more than one VXI process is being run, stop them one by one (beginning with the VXI program, if it is active) using the kill process_No command.

III.5  The track Program — G. Hrynek

Mouse usage
Placing the mouse cursor on an object and clicking the left button causes the name of the object to be displayed. Press the right mouse button to obtain detailed data of the object shown in a separate window.

Steering of the antenna
This program also makes it possible to control the telescope movements. To this end one must mark (enable by clicking) two options (described below) with the same name. A button of one of them can be seen on the right side of the top menu bar and the other is inside the 'Options' menu (on the left of top margin). When both the options are enabled, a blinking 'WARNING' will appear in the center of the window. After the program has issued commands for the telescope to move to a desired source, the options are automatically disabled. This scheme would not work if a user tried to point the antenna any place off source.

Button commands (a button pressed gets enabled)
• Show	— display current antenna state (without sources)
• Calibration Source	— display visible calibration sources
• Blazars	— display visible blasars of the 9 used in an RT4 project
• Pulsars	— display visible pulsars (data base includes all the 88 pulsars observed with the RT4)
• Masers	— display visible masers (selected of about 1300)
• Other	— display visible sources from user's data base (see comments below)
• Move telescope	— point the antenna to the chosen source (one of two options required)
Options (enabled option gets a small square to its left)
• Source name	— add names to the displayed sources
• Move telescope	— the second option (besides the button described above) that enable pointing of the antenna to another source
• Tracking line	— display source positions from its rise to set
• Symulation	— allows for displaying of selected sources for any given date and time
• Show source position	— display the position of a source (defined in a separate window)
• Search source	— find an object among currently displayed
• Make calibration	— allows for carrying out of calibration measurements
• System cooled/not cooled	— allows to select one of two pulsar lists corresponding to cooled (option enabled) and uncooled current receiving system

It is possible to use one's own source data base for displaying on the map. The file name of such data base must not exceed 10 characters and there may be no more than 1500 sources in it. Each source in the data base must consist of the following fields: name RA^h RA^m RA^s Dec° Dec' Dec" epoch, where RA is the right ascension, Dec is the declination and epoch is the epoch of these coordinates. Here is an example:
  w3oh 2 23 17 61 38 58 1950

III.6  Dealing with Problems — M. Gleba

• Commands are still being accepted by the steering program

It may happen so that the system behaves as if the telescope stood still despite commanding it to a source with the ps command. One can find whether it moves or not by checking the RT4 window and paying attention to the time displayed therein. If the reading of time does not change (with about every second) then there is a real problem with the telescope control. Otherwise the system only 'cheats' and the operator should stop the telescope (with the pd command), then move it using the pp A z command and finally repeat the ps α δ command. Similar 'cheating' may happen when a source to be observed lies below the telescope horizon, i.e. when the source altitude is smaller than 3°.

If the described method does not suffice, one may reset the system with the qu command.

• Commands are not accepted

• 1. Check the state of the elevation and azimuth drives — green control lights on (ready)
• 2. Check readings from the Lenze drives:

  — the Slave type drives normally provide the C56 code

  — the Master type drives normally communicate the C51 state

• 3. An ill behaviour of the system may also be caused by an improper communication between the Master and Slave drives (thus check the corresponding cables).
• 4. Check also the state of fuses of brakes (cabinet No 8); the green control lights on the door of the cabinet should be on.
• 5. In the cabinet No 10 the fuses FF33 are permanently switched off.
• 6. Check fuses in the cabinet No 6 and 7.

How to read error codes of FESTO: Under DOS operating system issue the command festo, then type md=h so that what obtains will be hexadecimally coded; now use dr 1.1 to get an error number itself. Such error numbers are to be checked against the tabular listing, that can be found in the electric cabin (next to the computer). Hexadecimal numbers of further possible errors that might have occurred during the start of the system can be displayed by repeted use of the same command, i.e. dr 1.1.

Fig. III.4: FESTO controller