Aligning INU and Pedestal for Shipboard Use

To align the Inertial Navigation Unit (INU) and pedestal for shipboard use, you must enter the following parameters in RCP8:

  • Azimuth Axis Input offset from true orientation.
  • Elevation Axis Input offset from true orientation.
  • INU Roll offset from true orientation.
  • INU Pitch offset from true orientation.
  • INU Heading offset from true orientation.
  1. Set the INU Heading offset to 0.

    Define this as the pedestal 0 azimuth.

  2. Get a rough azimuth axis offset by manually pushing the antenna to point in the direction of the ship's heading.
  3. Adjust the offset until the pedestal azimuth reads 0 on the Antenna utility.
  4. Set the elevation angle:
    1. Make sure the INU stabilization is turned on in the RCP.
    2. In the Antenna utility, set the elevation angle to 0°.
    3. Place a digital level on the waveguide feed in front of the dish in a place parallel to the transmitted beam.
    4. Slowly sweep the antenna 360°, recording the tilt approximately every 30°.

      Monitor the sweep to make sure RCP maintains the earth elevation angle near zero.

      The recorded table should also show the pedestal azimuth. Check this in the Antenna utility by selecting Options > Stable Platform Params.

    5. Plot the resulting data and fit to a sine wave with offset.

      The fit offset gives you a rough elevation axis offset. It is not the exact offset because the beam pattern may not be exactly aligned with the feed waveguide.

      • The sine wave amplitude at 0° gives you the INU Pitch offset.
      • The sine wave amplitude at 90° gives you the INU Roll offset.
  5. When you have finished adjusting the offsets, repeat the stabilization measurement scan to check that the corrections are complete.

    You may need to repeat this many times because of operator mistakes, sign confusions, and cross term contributions.

  6. Run a sun calibration.
  7. Use the results of the sun calibration to fine-tune the pedestal elevation offset, and pedestal azimuth offset.

    Check that the signs are correct.