Tutorial 5: Aircraft And Cosmic Background Calibration

Database Setup

This tool is for estimating the aircraft and cosmic background spectra, and associated calibration parameters, using data specifically acquired for this purpose. Spectra (lines) are acquired at various heights at hight altitude – typically in the range 1,000 m to 3,500 m. The tool performs linear regression of channel (or window) counts vs cosmic counts to estimate the aircraft and cosmic spectra and their associated window calibration coefficients.

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\aircraft_and_cosmic\AIRCRAFT_AND_COSMIC..DIR" (or the Oasis Montaj equivalent).
    2. Launch the tool – Calibration| Aircraft And Cosmic.
    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_cosair.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 high-altitude 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 1000. Repeat for lines 1500, 2000, 2500, 3000, 3500, 4000 and 4500. The Include checkBoxes indicate that all lines will be included in the regression analysis.


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. Click the Calculate button to do the regressions. 
    2. Toggle through the regression plots by checking the appropriate checkBox for TC, K, U and Th.
    3. The aircraft spectrum doesn't look too good. Exclude lines 4000 and 4500 by unchecking all the checkBoxes next to these two lines. Click Calculate to run the regressions again. That looks better.
    4. View the log file – File|View User Log File to see the full results.
    5. Click Save to save the calibration constants to a file in a form suitable for cutting/pasting into a control file for airborne processing (aircraftBackground_x and cosmicBackground_x for each window). This file also contains the cosmic and aircraft spectra, and will be needed if you use the full-spectrum option for cosmic and aircraft background estimation during processing. So don't edit anything in the rest of the file.