Solar Flare TDOA Navigation Method Using Direct and Reflected Light for Mars Exploration

In the capture period of deep space exploration, three traditional celestial navigation methods including the direction, velocity, and distance measurements cannot completely meet the requirement of navigation accuracy due to ephemeris errors. To solve this problem, considering the fact that some impulses exist in solar light irradiance profile due to solar flares, we propose the solar flare time difference of arrival (TDOA) measurement method, which exploits these impulses to measure the position of the spacecraft. As the time of arrival (TOA) of solar flare cannot be predicted, we cannot use the solar flare TOA directly. The Mars light irradiance variation is related to the solar one, as the Mars light is the solar light filtered by the Martian atmosphere absorption filter. Based on this theory, the solar flare TDOA measurement method using direct and reflected light is developed. In this method, two solar flare TOAs are obtained by the spacecraft. One is from the sun directly. The other is the corresponding TOA reflected by Mars. Their difference is the TDOA measurement. In addition, we also propose two alternative schemes. One uses the solar light instead of flare if solar flares do not occur in the capture period, and the other adopts Phobos as the reflected point instead of Mars to solve the Martian atmospheric absorption. The traditional direction measurement-based navigation method can provide highly accurate navigation information at the tangential direction in the capture period. However, its accuracy at the radial direction is very low. Fortunately, the solar flare TDOA measurement method offsets this problem. To get highly accurate navigation information, the solar flare TDOA measurement and the Mars direction measurement are coupled into the solar flare TDOA/Mars direction integrated navigation system. We present simulation results that demonstrate the feasibility and effectiveness of the solar flare TDOA measurement method. Compared to the traditional direction measurement-based navigation method, the solar flare TDOA/Mars direction integrated navigation can provide higher positioning accuracy, especially the radial component.