Solar TDOA/Doppler Difference Joint Observation Navigation for the Approach Phase of Mars Exploration

The celestial navigation using the difference between the direct and reflected solar light is emerging, as the difference can remove the conjoint bias caused by the instability and unpredictability of sunlight. These navigation methods include the solar Doppler difference and the solar TDOA (time difference of arrival). The solar TDOA measurement has a high positioning accuracy. However, the solar flare is unpredictable, which leads to the instability and randomness of the positioning performance in the approach phase. Fortunately, the solar Doppler difference navigation is stable. However, this navigation system is unobservable. To utilize their advantages and avoid their disadvantages, we combine them and propose the solar TDOA/Doppler difference joint observation. Due to its unobservability, we integrate it with the Mars angle navigation, and develop the solar light joint observation/Mars angle integrated navigation that is completely observable. The simulation results demonstrate the stability and robustness of the solar TDOA/Doppler difference joint observation navigation method. Compared with the celestial navigation using one solar difference observation such as the TDOA or the Doppler, the solar light joint observation/Mars angle integrated navigation can provide higher and more stable navigation accuracy.