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发帖数: 6889 | 1 http://gbtimes.com/china/china-racing-make-2020-launch-window-m
Andrew Jones
2016/02/22
Mars Exploration Rover Spirit captures a stunning view as the sun sank below
the rim of the Gusev crater on Mars on May 19, 2005.Mars Exploration Rover
Spirit captures a stunning view as the sun sank below the rim of the Gusev
crater on Mars on May 19, 2005. (Photo: NASA/JPL/Texas A&M/Cornell)
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China's space programMarsNational Space Science CenterChina Aerospace
Science and Technology CorporationEuropean Space AgencyNASAYinghuo-1Chang'e
3Chinese space programWu JiPietro Baglioni
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Nasa’s Mars 2020 mission may well have company along the way, with teams in
China working urgently to ready their first independent mission to the Red
Planet.
“We are aiming to use the launch window of 2020,” says Dr Wu Ji, director-
general of the National Space Science Centre (NSSC) in Beijing. “If we miss
that window, it will be 2022. So it is quite urgent.”
The NSSC is managing the development and integration of all the science
payloads for China’s Mars Mission, which will, ambitiously, combine an
orbiter, lander and a rover.
This effectively means China will be integrating two steps into one. For its
Moon exploration program, the Chinese first launched orbiters before
attempting – successfully – to soft-land its Chang’e-3 probe on the lunar
surface.
Wu, speaking to gbtimes about China's space science ambitions, revealed that
the orbiter will have on board space particle detectors and cameras capable
of detecting methane – the presence of which may indicate biological
processes occurring on Mars.
The orbiter will also have radar sensor equipment allowing it to observe the
Martian surface and ionosphere.
A model of China’s Martian probe unveiled by CASC in November 2015 in
Shanghai (Credit: China Daily/Long Wei).
Above: A 1:3 scale model of China’s Martian probe unveiled by CASC in
November 2015 in Shanghai (Credit: China Daily/Long Wei).
Down on the surface the rover will carry a ground-penetrating radar that
could reveal a lot about the past and present of Mars.
The same instrument allowed China’s Yutu rover to image around 400m below
the lunar surface, making intriguing discoveries about the composition and
history of the Moon, such as evidence of volcanic floods.
China's Yutu rover, part of the Chang'e-3 mission that soft-landed on the
Moon in 2013 (Chinese Academy of Sciences).
Above: China's Yutu rover (Credit: Chinese Academy of Sciences).
Other scientific payloads will include particle detectors to measure
radiation and may involve international cooperation.
As well instruments, China has less than five years remaining to develop and
master the technologies required for deep space travel and communications,
landing, power and navigation and locomotion on the Martian surface.
The minimum-energy launch windows for a Martian expedition, which allow the
largest mass payload for least energy needed, occur at intervals of
approximately two years and two months due to the respective orbits of Earth
and Mars around the Sun. Thus even small delays on the ground can result in
long waits.
The launch vehicle, likely a new Long March 5 heavy lift rocket which is set
to debut this year, and the spacecraft will be developed by the China
Aerospace Science and Technology Corporation (CASC) and subsidiaries.
Notably however, while China's 2020 Mars mission is bold, it will amount to
a demonstration of technology needed for even more ambitious outlined deep
space projects, including a ground-breaking Mars sample return mission
around 2030.
From the Moon to Mars
China succeeded in soft-landing on the Moon in 2013, becoming only the third
country to do so, but Mars presents another challenge altogether.
The country will be attempting its first independent interplanetary mission,
requiring months of travel through deep space before attempting orbital
insertion around Mars.
The lander and rover will then face a thin but significant atmosphere that
does not much allow parachutes to slow craft, but could destroy them. What
awaits then is a unique gravitational and surface environment.
Self-portrait of Nasa's Curiosity Mars rover at the "Mojave" site (Credit:
NASA/JPL-Caltech/MSSS).
Above: Self-portrait of Nasa's Curiosity Mars rover at the "Mojave" site (
Credit: NASA/JPL-Caltech/MSSS).
Pietro Baglioni, manager of the ExoMars mission rover at the European Space
Agency (ESA), notes that while there are a number of ways it can be
attempted, the challenges of landing and operating on Mars are significant.
“After the atmospheric entry with the heat shield protection and the use of
parachutes necessary to slow down to acceptable descent speeds, one can
choose different landing techniques, depending also on the mass and
configuration of the module you need to land and to the levels of residual
acceleration required at touch down.
"For the final approach, you can land by use of a first parachute of course
to slow down the entry phase, and then using thruster's engines that are
fired few seconds before the final touchdown to decrease the shock at
landing.”
“Or you can land with a system of airbags as NASA did for the Spirit and
Opportunity Rovers. Or finally, you can also use the innovative Sky Crane
system which is what NASA has used for Curiosity.”
Scientific instruments and supporting equipment sent to Mars needs in
general, thermally conditioned and environmental protected to deal with
temperatures from minus 120 degrees at night to 20 degrees plus during the
day.
“They landed a rover on the Moon not so long ago, so they must have
acquired some experience, some know-how also about the operational
philosophy that they can somehow apply also to a mission to Mars,” says
Baglioni, referring to the Chinese mission.
“[But] landing on Mars is different because there is an atmosphere, there
is a different gravity, so the mission scenarios are different.”
China’s first attempt to get to Mars was with its Yinghuo-1 probe, which
piggybacked on the ill-fated Russian Phobos-Grunt mission that did not get
beyond Earth orbit.
This, along with Japan's earlier failure with its Nozomi orbiter, left the
path clear for India to become the first Asian country to get to Mars with
its Mars Orbiter Mission in 2014, sparking a strong reaction in China.
Phobos-Grunt was not an isolated failure, as half of all missions to Mars
have failed for a variety of reasons and at different stages, underlining
the difficulty and complexity of the tasks ahead.
Search for life
Interest in Mars is blooming, with a range of missions looking to build on
previous discoveries and search for evidence that we are, or were, not alone
in the solar system.
Ahead of China's visit to Mars, ESA’s ExoMars mission will, in
collaboration with Russia's Roscosmos State Corporation and Nasa, search for
evidence of traces of past life or even present life.
Split into two missions, the first will consist of the Trace Gas Orbiter,
including a cutting-edge camera, and the ‘Schiaparelli’ lander, which will
demonstrate the technology required to land on Mars.
ExoMars 2016 will launch next month, and will use a landing technology with
a radar Doppler altimeter and dedicated software for the timely activation
and parachute and thruster systems.
The scheduled ExoMars 2018 mission will then use a Russian-built descent
module and landing platform system which will make use of European
technology derived from that tested with Schiaparelli to finally deliver the
rover on the Martian surface.
The ExoMars rover will carry a drill which can retrieve samples from two
metres below the Martian surface where, shielded from the harsh radiation,
traces of past or even present life may be found.
ESA's ExoMars 2018 Rover undergoes egress test in ‘Mars Yard’ of France’s
CNES space agency (Photo: ESA).
Above: ESA's ExoMars 2018 Rover undergoes egress test in ‘Mars Yard’ of
France’s CNES space agency (Photo: ESA).
Terror awaits
The ExoMars mission and those similar need to combine rocketry, surface
mobility and autonomous navigation means with deep space communications,
landing technology, power generation and thermal control capabilities and
highly sophisticated and sensitive instruments to achieve the scientific
goals.
“Altogether it’s a combination of technologies and difficult challenges
that are quite ambitious, of course, and we are trying to implement them
with our mission,” Baglioni says.
With their craft being light minutes away on Mars, back on Earth teams for
the Chinese and European missions will have to go through something like the
‘Seven Minutes of Terror’ experienced by NASA during the entry, descent
and landing of Curiosity Mars rover in 2012.
The Chinese and European missions represent a growing interest and
representation in interplanetary space exploration, which seems set to be
added to by private entities in the future.
And success in these and Nasa’s Mars 2020 mission and their discoveries
could pave the way and provide further impetus for eventual human missions
to Mars. | c***l
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