Braking is an important and risky step in the Mars exploration mission that requires a high degree of accuracy. Only when braking is performed with precise timing and duration can the probe successfully penetrate the planet’s orbit.
BEIJING, Feb. 11 – Accurate braking near Mars successfully launched the Chinese probe Tianwen-1 into orbit around the red planet on Wednesday, according to the country’s space scientists.
Yang Yuguang, a researcher at China Aerospace Science and Industry Corporation Limited, told the Science and Technology Daily that braking is an important and risky step in the Mars exploration mission that requires a high degree of accuracy.
When a probe is set to be captured by a planet’s gravity, the lower its orbit, the more fuel the engine will conserve. But if Tianwen-1 brakes in orbit too close to Mars, the probe could collide with the planet’s surface, as minor errors may exist in its position measurement and control, Yang said.
If the braking time is too long, resulting in excessive braking force, the probe will also be at risk of crashing, he said.
“Only when braking with precise timing and duration can the probe successfully penetrate the planet’s orbit,” said Pang Zhihao, an expert in deep space exploration technologies.
The Tianwen-1 deceleration began with a 3000N engine ignited at 7:52 PM (Beijing time) on Wednesday. After about 15 minutes, the spacecraft, including an orbiter, lander, and rover, had slowed down enough to be captured by Mars’ gravity and was going into an elliptical orbit around the red planet, its closest distance from the surface of Mars at about 400 km, according to the China National Space Administration.
Braking near Mars is different from braking near the moon, which the Chinese lunar probes have successfully accomplished in previous lunar missions.
The average distance between the Earth and the Moon is about 384,400 km, and the communication delay is only about a second. But the distance between Earth and Mars is more than 180 million km, and the one-way communication delay is more than 10 minutes.
“In this case, the ground cannot track the spacecraft in real time. Instructions had to be sent in advance and performed independently by the spacecraft,” explains Yang.
But minor deviations in the engine’s thrust and various variables related to the spacecraft’s position, speed, and attitude will all add to the complexity of achieving autonomous control, he said, adding that Tianwen-1 is equipped with multiple sensors to enable smooth autonomous control. for accurately measuring flight conditions.
Weighing in at over 5 tons, Tianwen-1 is one of the heaviest planetary probes in the world. But scientists and engineers have managed to equip it with a relatively small motor to leave more weight and space for payloads. To make up for the small thrust, they increased braking time to meet braking requirements, Yang said.