Leonard David's INSIDE OUTER SPACE

Credit: CNSA

Now circuiting Mars, China’s Tianwen-1 spacecraft is slated to perform systematic checks of onboard equipment. The craft used its 3000 newton engine on February 15 to place it into a polar orbit around the Red Planet.

Credit: CCTV/Inside Outer Space screengrab

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.

Pre-selected candidate landing area on Mars. Area 1 is located on the Chryse Planitia plain, the pre-selected landing area 2 is located on the Utopia Planitia.
Credit: Zou Yongliao, et al.

Roughly two to three months later, the Mars orbiter will be briefly placed in a deorbit and entry arc to release the landing capsule replete with a 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, the rover will conduct high resolution, on-the-spot surveys of Mars.

Credit: CCTV/Inside Outer Space screengrab

Comprehensive study of Mars

The first mission of China’s deep exploration plan, Tianwen-1 will carry out a comprehensive study of Mars by orbiting, landing and roving, conducting studies of Mars’ magnetosphere and ionosphere, surface and sub-surface, according to Zou Yongliao of the National Space Science Center, Chinese Academy of Sciences in Beijing.

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).
Credit: Zou Yongliao, et al.

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.

Rover-carried instruments.
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. “Considering the unpredictability of the Martian atmosphere, there will be a lot of uncertainty and risks,” Tan told China Central Television (CCTV) in a recent interview.

Credit: CCTV/Inside Outer Space screengrab

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

“The process will take about 80 to 100 seconds. When reaching [328 feet] 100 meters 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 mark to assure the landing spot is safe.

Credit: CCTV/Inside Outer Space screengrab

Past mishaps

The entire landing process will take about nine minutes, during which the probe should slow its speed from 4.9 kilometers per second to zero.

Miao Yuanming, deputy chief designer of Mars probes with the China Aerospace Science and Technology Corporation, cautioned 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 in a CCTV interview 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.

Tianwen-1 orbiter. Credit: Zou Yongliao, et al.

China’s Mars rover. Credit: Zou Yongliao, et al.

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