Using and Modifying the SRTN Sofware - BenningtonCS/Telescope-2014 GitHub Wiki

Basic Usage (Running SRTN, Pointing Telescope)

  • To run srtn, first cd to the directory it is located, which is srtnver3. Then, turn on the rotor controller and make sure it is in AUTO mode, signified by an A in the leftmost display window on the controller. If it is not already in AUTO mode, push the F button until you see an A. Once the controller is on, execute the command ./srtn to run the program.
  •   With SRTN open and running, you may now begin to point the telescope at objects of interest and observe. In the skymap below the graphical power display, you can click on any of the objects presented in it to command the telescope to point there. When using this method, it is important to note that you cannot just click anywhere on the skymap to point the telescope there; if you click on an empty space on the skymap, it will guide the telescope to the object closest to where you clicked. The nice thing about using the skymap, however, is that it tracks whatever object you're looking at.

  •   To direct the telescope without using the skymap, click on the "azel" button on the top of the SRTN window and enter in your azimuth and elevation coordinates, separated by a space, and press enter. SRTN will not track a position if the telescope is pointed with the "azel" button.
  • Each time you use the telescope, it is wise to calibrate it within the software, which is described in the following section.
  •   Before exiting SRTN, you must return the telescope to the Stow position, which you can do by pressing the "stow button" on the top of the SRTN window, or by entering 0 0 in the "azel" command.

Making Edits

  • To modify the srt.cat file on the machine in the physics stockroom, you will need to know a little about the text editor vi. To open a file in vi, cd into the directory of the file you want to edit, and execute a command like vi srt.cat. vi initially opens in command mode, which does not allow edits. To edit the file, press i to enter insert mode. Once you are done editing your file, press esc to exit insert mode. Then, enter :w to write (save) your file, and then :q to quit out of vi. Before you relaunch srtn, you must recompile the software by executing the command ./srtnmake. It will take a few seconds, so don’t freak out when your command line disappears for a bit. Once it does reappear, you are ready to launch srtn with your new edits.
  • The srt.cat file is the closest thing srtn has to a config file. Within srt.cat, one may change the tuning of the telescope, the system temperature, the latitude/longitude coordinates, and a host of other variables (that I do not recommend changing).
  • In srt.cat, the keyword for frequency is FREQUENCY, the keyword for lat/long coordinates is STATION, the keyword for system temperature is TSYS, and the keyword fot command files is COMMAND. A full description of srt.cat keywords and what they're for can be found in the srt.hlp file.

The Command Buttons of SRTN (top of the GUI) and What They Do

Clear

  • As the label implies, the clear button will clear the control console display of accumulated spectral-line data, 25-point scan data. This function is useful if the user is accumulating multiple spectra from different sources or galactic coordinates. The system will treat new source spectra as additions to the accumulated spectrum. (Taken from MIT SRTN user manual).

Stow

  • Brings telescope back to stow position.

azel

  • Refer to "Basic Usage" section above.

npoint

  • Initiates a 25-point scan/map of the source selected. The map is 1/2 beamwidth spaced and when finished displays a false-color, gaussian plot to the left of the accumulated spectrum plot. (This plot will clear when the clear button is enabled). The resulting maximum T(ant) (with associated offset) is displayed under scan results in the information sidebar. The color plot will NOT refresh if the SRT window is reduced then refreshed. (Taken from MIT SRTN software manual)

beamsw

  • Initiates a continuous "off/on/off " beamswitched comparison observation of the selected source at the frequency settings entered with "freq". The off/on/off measurements are a set and are complimentary, meaning that the two off-source positions switch sign within each set. The off-source measurements are spaced at +/- 1 beamwidth in azimuth (offset = +/- beamwidth/cos EL). "BEAMWIDTH" is set in the srt.cat file A left mouse click on the bmsw button after the scan has started will abort the beamswitch operation. Basically what this mans is if you do a beamswitch on a source object, the telescope will slew a beamwidth over from the source, come back to the source, then slew a beamwidth to the other side of the source. This method is used to tease out signals from faint radio sources.

freq

  • Enter a frequency in MHz that you want to tune the telescope to. It will accept nearly anything, but that doesn't mean you will get good data out of observations at a frequency that isn't around 1420 MHz.

offset

  • Enables the user to enter any az/el offset pair desired. Left click the offset button and enter the offsets in the command entry box.

record

  • Toggles output file recording on and off. Output data files are labeled in the form:
    yydddhh.rad
    Record also allows the user to enter a filename. RECORD 10 SPEC in srt.cat sets interval to 10 averaging periods where SPEC records spectrum. Without the keyword SPEC on the power is recorded. (Taken from srtn [the c version] help file).

cmdfl

  • Allows you to input a command file that you've written (that has the suffix .cmd) to tell SRTN to execute a series of commands seamlessly, rather than inputting every command manually. The following are instructions from the c version of the SRTN help file.

"Command file rules: (default filename srt.cmd)

1] reads one line at a time skipping blank lines, and lines which start with * and lines with past times

2] stops at and executes any line with current or future time

time format: line starts with yyyy:ddd:hh:mm:ss and is followed by cmd
alternate format: LST:hh:mm:ss cmd
current time format: : cmd
current time plus n seconds format: :n cmd
each line MUST start with time or : or * for comment

command keywords: items in [ ] are optional
sourcename,mode,radec,azel,galactic,offset,stow,calibrate,noisecal,record,freq,roff
sourcename (any name in catalog) [mode]
mode n(for 25_point scan) b(for beamswitch)
radec hh:mm:ss [sign]dd:mm:ss [epoch] [mode]
azel az_deg el_deg
galactic glat_deg glon_deg
offset azoff_deg eloff_deg
stow
calibrate
record [optional filename]
roff (turns off record)
freq frequency [bandwidth]num

Note that 25_point scan runs only once while beamswitch until next cmd
For example:

: Sun
:60
:600 Sun n
: stow

goes to the sun,waits 60 seconds,does 25 point
and after 600 seconds goes to stow.
Note that the seconds to wait is right next to the ":"
and otherwise there is a space before the command.

A command file can be checked by running in simulate mode -see help on cmdline options another name for a command file can be entered by clicking on the text area."

  • To run a command file other than the stock command file, write your command file in a text editor, and save it as a .txt file, NOT a .cmd file. Then go into srt.cat and on one line write "COMMAND yourcommandfile.txt" and recompile srtn with ./srtnmake. The command file will be executed automatically when you run srtn.

cal

  • This button runs the automated calibration procedure. We want "CALMODE 20" in the srt.cat file for the procedure with an absorber. When you hit cal, a text box will pop up in srtn that says "place absorber enter." When you have placed an absorber in front of the feed, hit enter. When data starts to flow again, the procedure is over.

  • Refer to the page "Calibrating the Telescope" for the true calibration procedure. The automated procedure is but one part of a larger scheme.