As the northern hemisphere of Mars enters the late autumn, how will the Zhu Rong rover cope with the severe cold and sandstorm?

Caption: It was taken on May, 20265438 19 (the fifth Mars day after landing), and the surface of the rover was not covered with dust. Source/"China Lunar Exploration Project" WeChat official account

Caption: Photographed on June 22nd, 2022 (the 247th Mars Day after landing), the surface of the rover was obviously covered with dust.

A few days ago, the "Tianwen No.1" orbiter passed over the patrol area of the rover again near the fire point, and took a 0.5-meter resolution image of the patrol area of Zhu Rong, in which the driving route of the "Zhu Rong" rover was clear and identifiable. As of March 24th, 2022, Zhu Rong has been working on the surface of Mars for 306 Mars days, with a cumulative driving distance of1784m. Tian Wen 1 orbiter has been in orbit for 609 days, 277 million kilometers away from the Earth. At present, the two rovers are operating normally.

The northern hemisphere of Mars has begun to enter autumn. According to the analysis of previous detection data, autumn is the season of frequent dust weather on Mars, and then Mars will enter a long and cold winter. Sandstorm, dust accumulation and low temperature, how to make the "Zhu Rong" rover "live" in the harsh environment?

The designers of 8 1 1 Institute of the Eighth Institute of China Aerospace Science and Technology Corporation, which is responsible for the development of the power products of the rover, have long thought about the countermeasures. When a huge sandstorm enveloped Zhu Rong in dust, the solar energy it received dropped sharply, Zhu Rong would enter the "sleep" mode, and Zhu Rong would "wake up" when the dust dispersed.

By observing the recent selfies taken from the surface of Mars and comparing the photos taken just after landing, a thin layer of dust has accumulated on the surface of the rover Zhu Rong. Judging from the telemetry information of the rover, although the power generation efficiency of the solar wing is affected by dust coverage, the energy is still sufficient. According to Wang Wenqiang, the solar cell designer of the 8 1 1 Mars probe, they have made a special coating on the glass cover of the solar cell, so that the surface of the solar cell array is not easily polluted by dust. Even if it is contaminated with dust, it can be shaken off by vibration.

It is reported that after the northern hemisphere of Mars enters the late autumn season, the light intensity will continue to weaken. At this time, the solar radiation intensity on the surface of Mars is only about 30% of the surface of the earth and about 20% of the surface of the moon, not to mention the cold winter. The energy acquisition of the rover entered an "emergency" state.

The developer's coping strategy is: let the rover hibernate! 8 1 1 Jin Bo, an expert in deep space exploration at the Institute, revealed that "hibernation" will last until the next spring.

What is the difference between the "sleep wake-up" of a lunar rover and a lunar rover? "The dormant awakening of the lunar rover mainly solves how to spend a long and cold moonlit night in a low temperature environment, while the dormant awakening of the lunar rover is mainly aimed at the Martian sandstorm and the Martian winter environment," Jin Bo introduced. "The dormant awakening of the lunar rover requires manual intervention. The sleep wake-up of the rover is completely autonomous. Dormancy depends on the power supply capacity of solar panels and the remaining capacity of lithium-ion batteries, which can be said to be anytime and anywhere. Wake-up depends on the output power of the solar cell and the temperature of the lithium-ion battery. "

In order to enhance the energy acquisition ability and improve the viability of the rover on Mars, the researchers of 8 1 1 have also done their homework: the maximum power tracking (MPPT) technology has been innovatively used, which is the first on-orbit application of this technology in the domestic aerospace field. Chen Daxing, the power controller designer of 8 1 1 rover, told me, "The tracking accuracy is as high as 98%, which improves the utilization efficiency of solar cells by 20% compared with the traditional circuit, which not only solves the energy shortage problem of the rover, but also reduces the area of solar cell array and the weight of power products."