AIRCRAFT ELECTRIC-FIELD MEASUREMENTS - CALIBRATION AND AMBIENT FIELD RETRIEVAL

An aircraft locally distorts the ambient thundercloud electric field. In order to determine the field in the absence of the aircraft, an air craft calibration is required. In this work a matrix inversion method is introduced for calibrating an aircraft equipped with four or more e lectric field sensors and a high-voltage corona point that is capable of charging the aircraft. An analytic, closed form solution for the es timate of a (3 x 3) aircraft calibration matrix is derived, and an abs olute calibration experiment is used to improve the relative magnitude s of the elements of this matrix. To demonstrate the calibration proce dure, we analyze actual calibration data derived from a Lear jet 28/29 that was equipped with five shutter-type field mill sensors (each wit h sensitivities of better than 1 V/m) located on the top, bottom, port , starboard, and aft positions. As a test of the calibration method, w e analyze computer-simulated calibration data (derived from known airc raft and ambient fields) and explicitly determine the errors involved in deriving the variety of calibration matrices. We extend our formali sm to arrive at an analytic solution for the ambient field, and again carry all errors explicitly.