Tutorial 6: Radon Stripping – Over-Water Calibration

Database Setup

This tool calculates the c1 coefficient required by the spectral-ratio method for estimating atmospheric radon background. It also calculates the TC, K and Th radon stripping coefficients, and the upward-detector au coefficient (if required).

The tool requires access to lines flown over water in the presence of radon. After removing aircraft and cosmic backgrounds, the resulting spectrum should be a radon spectrum. The c1 coefficient is the ratio of counts in the low-energy 0.609 MeV window (above the Compton Continuum) to the counts in the conventional U window.

Use either Intrepid or Oasis Montaj to set up all the input database fields required by the tool. You will see which fields are required at Step 3 below. Of course, for an Intrepid database, the line number, flight number and fiducial fields must also always be present in the database – with prescribed names as indicated in the "Preparing The Database" section. 

Processing Steps

    1. Open a database from the Main Window – File|Open. For the demonstration dataset select "demo_data\airborne_spectrometry\radon_stripping_overwater\RADON_STRIPPING_OVERWATER..DIR" (or the Oasis Montaj equivalent).
    2. Launch the tool – Calibration|Spectral-Ratio c1.
    3. Set the database aliases and tool parameters – File|Set Aliases and Parameters. Click the Load From File button and select the "aliases_and_params_radon_strip_overwater.pc" control file from the working directory. For an explanation of the aliases and parameters click the Help button. Click Save And Return.
    4. Select the calibration lines from the database. Do this by selecting each of the Select buttons next to the Line Select textBoxes. Click the file icon next to the top-most Line Select textBox and select line 60. Repeat for lines 90, 120, 150, 180, 210, and 240.


Tool Tip:  You can use the following shortcut to select lines: The top Line Select button has the focus (after setting aliases and parameters), so pressing Done on the keyboard brings up the Line Select window. Select the line with the mouse, then press Done on the keyboard to exit the window. Now the second Line Select button will have the focus, so repeat for each line.


    1. Read the aircraft and cosmic spectra from file – File|Read Aircraft And Cosmic Spectra. Select the file "aircraft_and_cosmic_spectra.txt" in the working directory.
    2. Click the Calculate button to estimate the c1 coefficient. If the ratio for an individual line appears to be an outlier, then exclude the line from the analysis using the Include checkBoxes. On completion, the tool displays the TC, K and Th radon stripping coefficients, the c1 coefficient and the upward-detector au coefficient (if the upward-detector option was selected in the Set Aliases And Parameters window) .
    3. View the log file – File|View User Log File to see the full results.
    4. Click Save to save the stripping ratios to a temporary file in a form suitable for cutting/pasting into a control file for airborne processing.