Integrated communications and optical navigation system

Abstract

The Integrated Communications and Optical Navigation System (ICONS) is a §exible navigation system for spacecraft that does not require global positioning system (GPS) measurements. The navigation solution is computed using an Unscented Kalman Filter (UKF) that can accept any combination of range, range-rate, planet chord width, landmark, and angle measurements using any celestial object. Both absolute and relative orbit determination is supported. The UKF employs a full nonlinear dynamical model of the orbit including gravity models and disturbance models. The ICONS package also includes attitude determination algorithms using the UKF algorithm with the Inertial Measurement Unit (IMU). The IMU is used as the dynamical base for the attitude determination algorithms. This makes the sensor a more capable plug-in replacement for a star tracker, thus reducing the integration and test cost of adding this sensor to a spacecraft. Recent additions include an integrated optical communications system which adds communications, and integrated range and range rate measurement and timing. The paper includes test results from trajectories based on the NASA New Horizons spacecraft. NOMENCLATUREa planet radius or half distance between landmarks f focal length k 1 ¦rst-order optical distortion coe©cient in the imager focal plane k 2 second-order distortion coe©cient in the imager focal plane l i vector from the Sun to the planet center or the center of a straight line joining two landmarks o x image center x coordinate o y image center y coordinate p c the position in the camera frame p w the position in the world frame R transforms from the world to the camera frame