ORBIT DESIGN AND ANALYSIS FOR THE ASTROD MISSION CONCEPT

Abstract

The ASTROD (Astrodynamical Space Test of Relativity using Optical Devices) mission concept is to conduct high-precision measurement of relativistic effects, better determination of the orbits of major asteroids and other solar system parameters, improvement in the measurement of [Formula: see text], measurement of solar angular momentum via Lense–Thirring effect, and the detection of low-frequency gravitational waves and solar oscillations in a single mission. It will be realized by placing a fleet of drag-free spacecraft in solar orbits together with an Earth reference system. Two spacecraft launched into separate solar orbits, as a simple implementation, can reach the opposite side of Sun after traveling about 2.5 years. In this paper, we describe the orbit design process for this simple implementation including the two-body model, initial velocity determination, and optimization consideration. Through fine tuning of the initial velocity, we can have the two spacecraft nearly return to the 2.5 years positions at 7.5 years mission time, which means that the ASTROD mission can have a second good chance to observe Shapiro time delay precisely and to measure the solar Lense–Thirring effect if the mission lasts over 7.5 years. We also calculate the light traveling time and the Shapiro time delay.