China seeks “Heavenly Questions” with ambitious Tianwen-1 mission to Mars

China seeks “Heavenly Questions” with ambitious Tianwen-1 mission to Mars

The Tianwen-1 Orbiter, Lander, and Rover are scheduled to depart for Mars within a three hour launch window extending from 00:00-03:00 EDT (04:00-07:00 UTC) on Thursday, 23 July 2020 from the Wenchang Spacecraft Launch Center in Wenchang, Hainan, People’s Republic of China.

The flight will be the first China-led mission to another planet and seeks to be the first successful Chinese Mars endeavour.  Liftoff of the mission will mark the first time a flight to another planet departs from Chinese soil.

The road to Tianwen-1

The mission follows the failed Fobos-Grunt flight, a joint partnership between China and Russia, which included the Yinghuo-1 craft that was to be China’s first Mars orbiter.

The mission came to an end after Fobos-Grunt itself failed to perform the Trans Mars Injection burn to send itself on its way to Mars from Earth parking orbit.  The entire mission reentered and burned up in Earth’s atmosphere in January 2012.

After that, Chinese authorities began an independent Mars program, and Tianwen-1 was formally approved for flight in 2016 as a three-pronged approach that included an Orbiter, Lander, and Rover.

The three-parts will launch as an integrated stack and remain together through Mars orbit insertion and the first two months of orbital operations at the Red Planet

Artist’s impression of the three spacecraft China will send to Mars. ( Credit: Nature Astronomy, CNSA)

The Lander will then descend to the Martian surface and, if successful, deploy a Rover shortly thereafter.

All three elements of the craft were developed by the China Aerospace Science and Technology Corporation while the overall mission is managed by the National Space Science Center in Beijing.

In order to get the craft to Mars, China will make use of their Chang Zheng 5 (Long March 5) carrier rocket, the nation’s heavy-lift vehicle which had a less-than-stellar debut.

Its first mission resulted in the YZ-2 optional third stage and satellite being placed into an incorrect orbit; however, the YZ-2 stage was able to correct the issue and place the payload into the desired orbit.  The mission was declared a success by Chinese officials, matching what other launch providers around the world would do under similar circumstances.

The second flight encountered an outright failure in July 2017, grounding the rocket for over two and a half years as major upgrades and enhancements were made — including a completely redesigned core stage YF-77 engine, to which engineers traced the failure.

A successful return to flight mission followed on 27 December 2019, and saw the rocket take the Shijian-20 communications satellite into its intended Geostationary Transfer Orbit.

The fourth flight of the Chang Zheng 5 followed on 5 May 2020; the rocket successfully launched China’s future deep space crew capsule on a multi-day Earth orbit test flight. 

As with the previous flight, the fourth mission was a success and largely cleared the way for the rocket’s use on this historic voyage to Mars.

The mission

Launching from the Wenchang Spacecraft Launch Center in Hainan, People’s Republic of China, the mission’s first phase will bring the craft into a stable Earth parking orbit before a short coast phase.

At the end of the coast, the second stage will reignite to perform the Trans-Mars Injection burn to send the craft into a heliocentric (Sun) orbit that will intercept Mars in February 2021.

Assuming a successful launch, the Tianwen-1 stack will spend seven months cruising through the interplanetary void between Earth and Mars before arriving for an orbit insertion no earlier than 11 February 2021.

Upon reaching Mars, the Orbiter’s main engine will fire up to perform the Mars Orbit Insertion burn, slowing the craft just enough to be grabbed by Mars’ gravity and enter a highly eccentric, equatorial orbit of the planet.

The combined stack will then spend two months undergoing initial activations and checkouts in Martian orbit as the Orbiter itself positions itself into its primary science orbit that is far more polar than equatorial.

In April 2021, the Lander, with the Rover inside, will detach from the Orbiter and prepare for Entry, Descent, and Landing on 23 April 2021.

At present, the landing location has been narrowed to two sites, both within Utopia Planitia

The landing sequence will utilize a combination of aerobraking, parachute descent, retrorocket firing, and airbag deployments to achieve a soft and successful touchdown on the Martian surface.

After landing, the Rover will be deployed shortly thereafter — ideally on the same day — to begin a planned 90 Sol (90 Martian day) series of events to categorize the local environment.

The Rover will be powered by solar panels and will perform both radar and chemical analyses of the Martian surface, specifically looking for biomolecules and biosignatures that would indicate the presence of past or current life on Mars.

A paper by Zhou, et al. presented at the 16th International Conference on Ground Penetrating Radar in 2016 revealed the overall mission objectives for the flight.

  1. Search for evidence of current or past life,
  2. Produce Martian surface maps,
  3. Characterize Martian soil composition and water ice distribution, and
  4. Examine the Martian atmosphere.

Additionally, Tianwen-1 serves in part as a technology demonstration flight for a proposed Chinese Mars sample-return mission in the 2030s.

To accomplish these objectives, the Orbiter will carry both medium and high-resolution cameras capable of discerning objects to within 100 m and 2 m, respectively, from a 400 km orbit. 

The Lander and Orbiter separate in Martian orbit ahead of the planned April 2021 landing. (Credit: Mack Crawford for NSF/L2)

The Orbiter also carries a Mars Magnetometer, a Mars Mineral Spectrometer, an Orbital Subsurface Radar, and a Mars Ion and Neutral Particle Analyzer.

For surface operations, the Rover is outfitted with Ground Penetrating Radar capable of seeing 100 m below the Martian surface, a Mars Surface Magnetic Field Detector, a Mars Meteorological Measurement Instrument, a Mars Surface Compound Detector, a Multi-Spectrum Camera, and a Navigation and Topography Camera. 

International Cooperation

While Tianwen-1 is a China-led mission, it is not a solo enterprise and enjoys a range of international support and cooperation.

The European Space Agency’s Estrack ground stations will provide telemetry and communications support during launch, as will the Comisión Nacional de Actividades Espaciales (CONAE), the space agency of Argentina.

CONAE is also expected to assist with long-range and deep space tracking of Tianwen-1 as one of China’s deep space telemetry dishes is within Argentina.

The Austrian Research Promotion Agency, which includes the Austrian Space Agency, partially designed and built the magnetometer on the Orbiter, and the Centre national d’études spatiales (CNES) of France provided build and development support for the spectroscopy camera instrument on the rover.

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