Running the systemp_w_calibration.grc Program

The video shown here explains the features in this program.

Before Starting The Program

The video here explains how set up the horn and make adjustments to the user-defined settings referred to below.

• Check the user-defined settings illustrated below. These are the Variable blocks in the upper right corner of the Gnuradio canvas.

  

  • To change a value, double click on the box and then type the value in the Value box and hit OK.

  • integration_time1 is the short integration time, and integration_time2 is the long integration time. These can be changed to any value at 0.4 s or above.

  • Be sure that the file path in the prefix box is correct. This is the folder where the data files will be saved.

    Hints on setting the file path correctly: (These steps are explained in the setting up the horn video.)

    1. Open the File Navigation window (folder icon).
    2. Navigate to the folder to which you want to save the spectrum files.
    3. Right click on the folder.
    4. Select Properties.
    5. Double click the Parent folder: path and copy it to the clipboard.
    6. In the prefix variable box paste the path name inside quotes in the Value box. (Delete any existing path name.)

    7. Then append the actual folder name to the end of the parent path. Be sure to separate folder names with / and end with /.

       EXAMPLE:

       Parent folder: home/Jansky/radio_astronomy

       data folder name: horn_data_2020

       Value to put into the prefix variable box:
       “home/Jansky/radio_astronomy/horn_data_2020/” (Include the quotes)

• CAUTION: If you run the program on a laptop without the power cord plugged in, the computer may go into a sleep mode and stop running the program, depending on the length of the run. Change the power settings on your computer so that it never suspends or goes to sleep.

After Starting The Program

• The first screen that appears looks like the following:

• This display is used for most observations that are uncalibrated.

• Adjust the ymin and ymax values to scale the graph as desired.

• Fill in the azimuth, elevation, and location, if desired.

  • NOTE: When entering these values, you must hit ENTER after each entry in order for it to get recorded by the program.

  • These parameters are included in the title, as described in the Saving a Spectrum to a Data File section below. This is also demonstrated in this video..

• The Short Integration option is good for quick observations and demonstrations. Switch to Long Integration for smoother data when a pointing is settled on and you are ready for a longer run.

• The Clipped Spectrum is the better selection for most viewings. The Full Spectrum is good for demonstrating how the signal processing affects the spectrum. It also might be useful for the expert user who wants the full spectrum for some reason.

Saving a Spectrum to a Data File

• Video - describes how to save data

• The spectrum that is currently being displayed on the screen can be written to a .csv data file by clicking the Capture Current Spectrum button. The data file is written to the folder under the path in the prefix Variable box.

• When Writing to file is selected under the Write to csv File window, a data file will be written to a new file in the data folder each time an integration time elapses. For instance, if Long Integration is selected and is 10 s, then every 10 s a new file is written. So for a 20 minute run, a total of 120 files will be written to the data folder.

This option is useful when running a drift scan or for when the user sets the telescope to collect data at a later time when the user is not able to be present.

• Data File Format:

  • The .csv format is a .txt data file that can be opened in any spreadsheet.

  • When opened in a spreadsheet, the data will appear in 2 columns. The first columns contains the frequency, in MHz, from 1414 MHz to 1424 MHz. The second column is the signal.

  • A graph of Signal vs. Frequency can easily be created after opening a file in a spreadsheet.

  • The file name has a format that contains the date, time, location, azimuth, and elevation, with “_spectrum” at the end. The location, azimuth, and elevation are recorded with the values in the corresponding fields on the spectrometer inferface screen.

  • As an example, the filename 2020-07-15_Morgantown_200_30_spectrum.csv contains data that was collected on July 15, 2020 in Morgantown with the telescope pointed at an azimuth of 200 degrees and an elevation of 30 degrees.