Analysis of tropospheric time delay effect on in-flight attitude improvement of vehicle using integrated GPS-INS

Abstract

The in-flight attitude improvement for maneuvering vehicle is proposed as a new metric for determining the degree of observation for attitude and other inertial navigational errors over specified flight profile of the vehicle. Guided munitions / projectiles can inherit large alignment errors during initialisation process by the launch platform, which if goes uncorrected, may affect terminal phase circular error probability (CEP) of the weapon. These alignment errors can be removed during flight by using Kalman filter based GPS and INS (Inertial Navigation System) data fusion scheme so as to correct the inertial system navigation errors. In order to achieve the precise navigational accuracy of the GPS-INS system, it is essential to model the ionosphere and troposphere time delays properly as they directly affect the measurement accuracy of the GPS and indirectly affect navigational accuracy of GPS-INS states. It is interesting to simulate the effect of tropospheric time delay for the vehicle being guided through GPS-INS when it is flying below the altitude of 60 km. In this paper, emphasis is given on the modelling of tropospheric delay and its impact on the performance of the GPS and GPS-INS during<b style="mso-bidi-font-weight:normal"> </b>flight.