Tianwen -1. China wants to take Mars too!
Despite the fact that the Chinese were the first to tinker with rockets a thousand years ago,
although for purposes certainly not peaceful, in the most recent space race China has decided to
get involved only in 1970. A bit out of time, then, when the first men were already walking
on the Moon and the two superpowers USA and USSR seemed to have taken an unbridgeable advantage.
In that year the Chinese launched their first satellite; after that everything seemed to stop
again... until the end of the century, when globalization and political renewal led the
Chinese government to make space exploration a strategic cornerstone of its international
policy. Suffice it to say that in 2020 China spent about 11 billion dollars on space,
making it the second economic power in the sector after the US (22 billion dollar budget). Ranking
in which they have far surpassed Europe (7.5), Russia (2.5), India (1.9) and Japan (1.7).
This commitment led to the first orbital flight of a taikonaut in 2003, which was followed in
2011 by the launch of a space station to which two different missions with three-man crews docked.
Then there was the assault on the Moon, with the first-ever descent of a rover
on the hidden side of the satellite and the mission to bring home lunar samples.
A majestic crescendo, which is being followed by the current attempt to drop
a rover on Mars as well. Will it succeed?
The "Questions to the Sky" (Tian-wen in Chinese) is the name of a text attributed to the poet Qu
Yuan, who lived between the fourth and third centuries BC, a work that takes the form of
a series of questions in verse with which the author questions some fundamental philosophical
and scientific issues. Evidently now China hopes to find the answer to some of these questions,
considering that the space probe currently traveling to Mars has decided to give the name
Tianwen-1. A name that according to the Chinese Space Agency will be given to all of China's
planetary exploration missions, signifying the Chinese nation's perseverance in pursuing truth
and science and exploring nature and the universe. In fact, the mission, whose launch took place in
the early hours of July 23 from the Wenchang space center, is particularly ambitious. If all goes
well, in fact, for the first time in the history of Martian exploration a single spacecraft will
bring to the Red Planet an orbiter, a lander and a rover, with a scientific load of 13 instruments:
seven mounted on board the spacecraft that will enter in orbit around the planet, and six on board
the rover that will be released shortly after the landing module will rest on Martian soil.
Thus, the China National Space Administration, after being the first to place a probe on the
hidden hemisphere of the Moon, also aspires to be the first to successfully complete
a mission of this type, after the failure of the only other mission that attempted to bring
orbiters, landers and rovers on Mars: the Soviet Mars 3, back in 1971.
In fact, China had already tried in 2011 to bring a probe around the Red Planet:
but the orbiter Yinghuo-1 was involved in the failure of the Russian mission Fobos-Grunt,
that once reached the Earth orbit then failed to find the thrust to enter the trajectory to Mars.
Now China tries again, and the objectives of this new triple mission are very clear:
to study the morphology and geological structure of Mars, as well as its evolution and its causes.
To do this, the probe will analyze the topography of the planet,
paying particular attention to features such as dry river beds, volcano reliefs, wind erosion,
glaciers at the poles, etc. And to this purpose are dedicated the two cameras on the orbiter.
They will then be studied the characteristics of the surface and underground layers of the soil
of Mars, as well as the distribution of water ice. This is the task assigned to the georadars
present on the orbiter and the rover. They will analyze the composition and type of rocks,
present on the surface, as well as the carbonate minerals present in the ancient lakes, rivers
and other environments conditioned by the past presence of water on the planet. To this task are
dedicated the spectrometers on board the orbiter and the rover as well as the multispectral camera.
It will also follow the ionosphere, climate, seasons and more generally the atmosphere of Mars.
This is the role of the two-particle detectors on the orbiter and the rover's weather station.
And finally, the internal structure of Mars, its magnetic field, the history of its geological
evolution, the internal distribution of its mass and its gravitational field will be investigated.
Magnetometers, as well as radars present on the orbiter and rover,
are dedicated to this objective. To collect all these data,
the orbiter module and the rover have on board several cameras (at various resolutions,
the highest of 2048x2048 pixels, and for several bands of the electromagnetic spectrum),
a georadar to probe the Martian subsurface up to 100 meters deep, particle analyzers,
mass spectrometers, magnetic field detectors and magnetometers. The orbiter, in addition
to collecting data, will also act as a bridge for communications between the rover and Earth.
Once at its destination, presumably around February 11, 2021, Tianwen-1 will eventually
settle into a very eccentric polar orbit, which will take it 265 kilometers from the surface
at its closest point to 12,000 km at its farthest. The lander-rover pair, on the other hand, will
have to wait until perhaps April 24 before it can undock from the orbiter and face its descent to
the Martian surface. This calculated wait, already used for the American Viking landers in the '70s,
will allow to carefully study the conditions of the Martian atmosphere
before attempting the dangerous descent. "BE sure to join the Insane Curiosity Channel...
Click on the bell, you will help us to make products of ever higher quality!"
To make it touch the ground without problems, the lander has even been
equipped with three braking systems that will be activated in succession: a parachute,
the thrust of the retrorockets and finally the shock absorbers of the support feet.
Some of the technologies required for this type of operation have been adapted from
those used by China in previous lunar missions. In particular, the lander's automatic guidance,
control and navigation system is developed from that of Chang'e 4. This mission successfully
landed a rover on the hidden side of the Moon last year. Since the Martian surface can be
rough and include many rocks that would endanger the mission, the landing system uses a radar
and a camera that compare the images taken during the descent with those of an internal database.
The importance of this system lies in the fact that during the descent phase towards
the Martian soil it is impossible to intervene manually to control the descent of the lander.
This fact is due to the enormous distance between Earth and Mars at the time of the operation,
equal to almost 300 million kilometers, from which follows a delay in communication, and therefore
the execution of any correction commands, in the order of 16 minutes. A time completely
incompatible with the duration of the descent, which will be completed in no more than 5 minutes.
But even with the assistance of the Automatic Guidance System used on the Moon, the operation
will certainly not be risk-free: Mars gravity is more than twice that of the Moon and,
unlike the Moon, the planet also has an atmosphere that, although tenuous, has an important role in
the attitude of a probe landing. However, it must be said that the possibility of choosing the best
time for the descent, and the fact of starting it from a known point of the orbit followed at
that time by Tianwen-1, brings considerable advantages over those missions that choose to
descend to the surface coming directly from outer space without passing through an orbital phase.
And this is the case of the Perseverance rover, which will descend on the edge of the
Jezero crater, one week after the entry into orbit of the Chinese spacecraft.
If all goes well, the lander of the Tianwen-1 mission will rest in Utopia Planitia,
which in English means Plain of Utopia, a vast flat region in the northern hemisphere of Mars.
With a diameter of 3300 kilometers, it is in fact one of the largest impact basins in the
solar system... flat, with no large craters or orographic obstacles of any significance.
This area is thought to have been filled with water and therefore may contain
extremely interesting study elements. Photographed from space, this region has
always shown strange features, such as polygonal cracks and pits; all details that on Earth are
associated with the presence of subsurface ice or permafrost. So planetologists began to suspect
that an icy deposit was also hiding on Mars. And in fact, in 2016, thanks to information collected
by the Mars Reconnaissance Orbiter mission, the U.S. space agency announced that it had discovered
a large amount of water in the subsurface in the form of ice at a depth of just a dozen meters.
The peculiarity and the scientific interest of the region is undoubtedly due to the fact that
the most probable landing point of the Chinese lander is located practically halfway between
the landing site of Perseverance and the one where the mythical Viking 2 landed on September 3, 1976.
In any case, once landed without damage, the Chinese lander will release a six-wheeled
rover powered by solar panels, very similar in architecture to the lunar
predecessors Yutu and Yutu 2, and also to NASA rovers Spirit and Opportunity.
Unlike the latter, however, it does not have a robotic arm that allows the positioning of
instruments in contact with rocks or the ground. From that moment, the rover will leave for an
exploration of the surface that will last about 90 Martian days, equivalent to almost 93 Earth days.
Weighing 240 kg, the Chinese rover measures 260 cm in length, 300 in width and 185 in height. A mast
supports the two navigation cameras and the multispectral camera. To move around,
it has six independent 30 cm diameter wheels arranged on an active suspension system; each with
an individual motor and all with an additional motor acting on the steering, which allows the
rover to turn on itself and move sideways. Due to the delay in telecommunications with Earth,
which can be up to 22 minutes, the rover uses an autonomous navigation system.
It has a maximum speed of 200 meters per hour, and a navigation speed of 40 meters per hour.
It can overcome obstacles 30 cm high and overcome slopes with an inclination of 30 degrees...
Note that the rover does not yet have its own name. It will in fact
be assigned one by the end of February following an international competition.
On January 2, 163 days after its launch,
Tianwen 1 was still on its way to Mars, about 130 million kilometers from Earth.
The distance traveled was more than 400 million kilometers after a sequence of
orbital maneuvers was performed as it moved away from Earth orbit and approached the Red Planet.
So far, Tianwen-1 has performed three orbital corrections and equipment checks, according to
the space agency. The probe remained in good condition as it continued its journey to Mars,
still 8.3 million kilometers away. On Feb. 11, when Tianwen -1 is within
9,000 kilometers of the Martian surface, the main engine will be turned on for 14 minutes
to slow the probe down and place it in a very elliptical orbit of 400 × 180,000 kilometers
with an 11-day period. The probe will then perform a series of maneuvers to enter the final orbit,
from where for a couple of months it will try to. to precisely locate the landing
site and complete the necessary preparations for the maneuver of detachment of the lander.
The one developed by the People's Republic of China in the space field is a wide-ranging
and long-term strategy. There are many other objectives set by Beijing for the years to come:
in addition to Tianwen-1, which is only the first of a long series of missions
that will reach the major planets of the solar system, in 2021 the construction of the first
Chinese modular station should begin; by 2025 it is planned instead the shipment into space of
a prototype solar power plant in space; later, in 2028 the second independent mission to Mars
should be launched; and by 2036 China aspires to a first human mission on the Moon.
Exactly like the space race between the United States and the Soviet Union,
the challenge between space programs is anything but purely scientific.
Beyond the effects on the prestige that the nations involved obtain from the demonstration
of their technical capabilities, the development of space technologies has an immediate impact on
industry in general and, above all, on defence. New models of intercontinental missiles, improved
satellite systems for communication, Earth observation and, why not, espionage, are just some
of the most immediate effects of space development on the military capabilities of a country.
It is no coincidence that the United States has hastily created a military branch entirely
dedicated to space. The United States Space Force, beyond the science-fiction references, was
certainly born in part as a response to Beijing's assertiveness in outer space, making Washington's
strategists feel the urgency to take action. Space has become again a frontier land and of clash,
in the middle of a militarization process destined to continue in the next years,
and the clash will see the People's Republic of China among the absolute leaders of the world.