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China's Tianwen 1 Mars orbiter changes orbit to begin planetary survey

An artist's illustration of China's Tianwen-1 spacecraft entering orbit around Mars.
An artist's illustration of China's Tianwen-1 spacecraft entering orbit around Mars. (Image credit: CCTV/CNSA)

China's Tianwen 1 Mars orbiter has changed its orbit to begin a remote sensing survey of Mars after months of supporting the Zhurong rover.

The spacecraft has been orbiting Mars since February, and in May Tianwen 1 released the Zhurong rover for its successful landing attempt in Mars' Utopia Planitia. Tianwen 1's orbit saw it circle Mars three times every Martian day, or sol, including one pass overhead of the six-wheeled vehicle in order to relay data from Zhurong to Earth using its much larger antennae. 

Tianwen 1 fired its engines for 260 seconds on Monday (Nov. 8) increasing its speed by 256 feet (78 meters) per second, according to the Shanghai Academy of Spaceflight Technology (Chinese). This shifted the spacecraft from orbiting once every 8 hours and 12 minutes, with a closest approach of 248 miles (400 kilometers) and highest point of 7,456 miles (12,000 km), to orbiting once every 7 hours and 5 minutes with a periapsis of 165 miles (265 km) and apoapsis of around 6,500 miles (10,700 km).

Related: China's Tianwen 1 Mars mission in photos 

The original plan for Tianwen 1's science phase involved an orbit with a period of 7 hours and 48 minutes. However, as Zhurong continues to function well beyond its three-month primary mission, the mission's scientists devised the new orbit to both allow Tianwen 1 to achieve its objective of conducting a global survey of Mars and still assist with relaying data from Zhurong to Earth.

Tianwen 1 carries seven science payloads, including medium- and high-resolution cameras for both mapping large areas of Mars and returning sharper, more focused images of the planet's surface. The Mars Orbiter Subsurface Investigation Radar (MOSIR), a sounding radar, will meanwhile scout for water ice beneath the surface. Targets of particular interest include impact craters, volcanoes and canyons.

Tianwen 1 also carries a mineralogical spectrometer for detailing surface composition, particle analyzers for atmospheric studies and a magnetometer. Its orbit passes over the poles meaning that, over time as the spacecraft orbits and the planet rotates, Tianwen 1 will be able to survey the entire surface of the planet.

This image released Nov. 8, 2021 shows a driving map for China's Zhurong rover on Mars as part of the Tianwen-1 mission. (Image credit: Beijing Aerospace Flight Control Center (BACC))

The spacecraft has a design lifetime of two (Earth) years, but Tianwen 1 could be set for extended activity. "At the end of next year when the orbiter's design lifetime comes to an end, we'll design new missions based on the specific conditions of the orbiter, and will then lower its orbit ... for closer observation of Mars and obtain more exploratory data," Zhu Xinbo, deputy chief designer of the orbiter, told CCTV.

The data from Tianwen 1 will also be used for informing and planning future Mars missions, including an ambitious Chinese Mars sample return attempt that could launch as soon as 2028.

Zhurong meanwhile is continuing its journey south from its landing platform, and has covered a total of 4,111 feet (1,253 meters), meaning the roughly 530-pound (240 kilograms) solar-powered vehicle has covered 233 feet (71 meters) since resuming activity after the recent Mars communication blackout caused by a solar conjunction.

Zhurong is now approaching a sediment-filled trough after making a close approach to a small dune, according to a new route map released by the China National Space Administration (CNSA).

On Sunday (Nov. 7) ESA's Mars Express made its first attempt to receive data from Zhurong and then retransmit the information to Earth as part of a set of five such tests with Zhurong. A technical review session was set for Wednesday (Nov. 10) to assess the performance of the first data transmission trial.

Tianwen 1 and Zhurong launched together on July 23, 2020. The pair entered orbit Feb. 10 this year, with Zhurong landing on May 14 and rolling down from its landing platform to the Martian surface on May 22.

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Andrew Jones covers China's space industry for SpaceNews. He is based in Helsinki, Finland.