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SPACE.com Columnist Leonard David

China's Tianwen-1 Mars mission adjusts orbit to prepare for a Red Planet landing

An artist's illustration of China's Tianwen-1 mission in orbit around Mars. (Image credit: CNSA)

China's Tianwen-1 spacecraft now orbiting Mars is slated to perform systematic checks of onboard equipment after adjusting its orbit in preparations for the country's first Martian landing attempt later this year. 

The Tianwen-1 orbiter used its 3,000-newton engine on Feb. 15 to place itself into a polar orbit around the Red Planet. Tipping the scales at 5 metric tons, Tianwen-1 — consisting of an orbiter, lander and rover — will perform several more orbital adjustments before placing itself into a parking orbit from which the orbiter will perform an initial survey of candidate landing areas.

Sometime in May or June, the Mars orbiter will be briefly placed in a deorbit and entry arc to release the landing capsule, replete with the as-yet-unnamed Tianwen-1 rover. The rover will egress from the lander onto the Martian surface a few days after touchdown, following an appraisal of the surrounding terrain.

For at least 92 Martian days (or about 95 Earth days), the rover will conduct high resolution, on-the-spot surveys of Mars.

Related: China's Tianwen-1 Mars mission in photos

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Comprehensive study of Mars

The first image of Mars returned by China's Tianwen-1 spacecraft. The China National Space Administration (CNSA) released the image on Feb. 5, 2021, demonstrating that the powerful, high-resolution camera on the Tianwen-1 spacecraft was working properly ahead of its orbit arrival. The greyscale image was captured at a distance of 1.36 million miles (2.2 million kilometers) from Mars, according to CNSA. (Image credit: CNSA/PEC)

The first mission of China's deep exploration plan, Tianwen-1 will carry out a comprehensive study of Mars by orbiting, landing and roving on the Red Planet, conducting studies of Mars' magnetosphere and ionosphere, and studying the planet's surface and subsurface, according to Zou Yongliao, deputy director of the National Space Science Center at the Chinese Academy of Sciences in Beijing, who published a paper in the journal Advances in Space Research last month about Tianwen-1's payloads and science objectives.

Scouting for subsurface water ice on Mars is the duty of Tianwen-1's Mars Orbiter Subsurface Investigation Radar (MOSIR) — a subsurface radar sounder. MOSIR is intended to search for water ice and liquid water that may be associated with signs of life in the polar layered deposits, the Tianwen-1 lander/rover touchdown site and other selected areas.

The lander/rover machinery is expected to land on Mars in May or June. Chinese space engineers and scientists have selected candidate landing zones within the relatively flat region in the southern part of the Utopia Planitia, a large plain.

 The Tianwen-1 mission's preselected candidate landing area on Mars. Area 1 is located on the Chryse Planitia plain; the preselected landing area 2 is located on Utopia Planitia. (Image credit: Zou Yongliao, et al.)

Uncertainty and risks

"When the probe brakes in the Martian atmosphere, it will face a process of high temperature, and deviation of attitude due to aerodynamics, which will have a negative impact on the deceleration," said Tan Zhiyun, deputy chief designer of the Mars probe with the China Aerospace Science and Technology Corporation, told China Central Television (CCTV) in a recent interview. "Considering the unpredictability of the Martian atmosphere, there will be a lot of uncertainty and risks," he added.

Next, the lander/rover entry vehicle deploys its parachute with its speed slowing to less than 100 meters per second (224 mph).

"The process will take about 80 to 100 seconds. When reaching 100 meters [328 feet] above the Mars surface, it will enter a hover stage," Tan said. At that time, a microwave ranging and velocity sensor system is to make a measurement of the surface, he added, and a three-dimensional laser camera will take images of the surface of the landing area. The lander may perform translational motions at the 100-meter (328 feet) mark to assure the landing spot is safe.

Image 1 of 4

Pictures of the orbiter scientific payloads (from left to right, first row: payload-controller on the orbiter, Moderate-Resolution Imaging Camera, High-Resolution Imaging Camera; second row: Mars Mineralogical Spectrometer, Mars Ion and Neutral Particle Analyzer, Mars Energetic Particles Analyzer; third row: Electronic equipment and probes of Mars Orbiter Magnetometer, Master processor of Mars Orbiter Scientific Investigation Radar).

Pictures of the orbiter scientific payloads (from left to right, first row: payload-controller on the orbiter, Moderate-Resolution Imaging Camera, High-Resolution Imaging Camera; second row: Mars Mineralogical Spectrometer, Mars Ion and Neutral Particle Analyzer, Mars Energetic Particles Analyzer; third row: Electronic equipment and probes of Mars Orbiter Magnetometer, Master processor of Mars Orbiter Scientific Investigation Radar). (Image credit: Zou Yongliao, et al.)
Image 2 of 4

Rover-carried instruments.

Rover-carried instruments. (Image credit: Zou Yongliao, et al.)
Image 3 of 4

Tianwen-1 orbiter.

Tianwen-1 orbiter. (Image credit: Zou Yongliao, et al.)
Image 4 of 4

China's Mars rover.

China's Mars rover. (Image credit: Zou Yongliao, et al.)

Past mishaps

The entire landing process will take about nine minutes, during which the probe should slow its speed from 11,000 mph (17,600 kph) to a standstill.

Miao Yuanming, deputy chief designer of Mars probes with the China Aerospace Science and Technology Corporation, cautioned in a CCTV interview that among all the 44 endeavors launched to the Red Planet since 1960, 25 of these explorative activities have resulted in mission mishaps.

Miao added that out of the ten most recent Mars exploration activities since 2006, only one has resulted in failure, he said, showing that great progress has been made.

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