Tianwen-1 launches for Mars.
China’s Tianwen-1 Mars mission launched successfully Thursday, initiating a phase of deep space and interplanetary exploration. A Long March 5 rocket launched the Tianwen-1 orbiter and rover from Wenchang Satellite Launch Center at 12:41 a.m. Eastern. Successful Trans-Mars injection was confirmed around 40 minutes later by the China Aerospace Science and Technology Corporation.
The flight path took the Long March 5 over the Philippines and close to the capital Manila. Spent stages were planned to drop into the surrounding seas. China’s Yuanwang-class tracking ships assisted launch operations, along with support from the European Space Agency’s ESTRACK facilities. First acquisition of the spacecraft as it separated from its Long March 5 launcher was expected to be made by the 15-meter antenna in Kourou, French Guiana. The roughly five metric ton wet mass spacecraft is now on a seven-month journey to the Red Planet.
“The Tianwen-1 mission is a major landmark project in the process of building China’s aerospace power , and a milestone project for China’s aerospace to go further and deeper into space,” mission deputy commander Wu Yansheng said in a CASC statement.
Tianwen-1 is due to arrive at Mars in February 2021, entering a highly elliptical orbit. The spacecraft will then move to a near-polar orbit with a periapsis of 265 kilometers for 2-3 months before the rover landing attempt. The orbiter and rover together carry 13 science payloads for a range of detections of the Martian atmosphere, magnetosphere, surface, subsurface and climate.Tianwen-1 is China’s first independent interplanetary mission. Missions to near-Earth objects, a Mars sample return, possible Voyager-like probes and a Jupiter system orbiter are planned for the decade ahead.
Delayed landing attempt
The delay will allow the orbiter to survey the candidate landing sites with its cameras and provide the lander with the data required to make its landing attempt. China has selected a portion of Utopia Planitia, south of Viking 2, as the landing area for the 240-kilogram rover. The selection was made based on science goals and engineering constraints, which include low elevation to provide more atmosphere and time to slow the lander’s descent as well as the solar power needs of the rover. The landing ellipsis will be 100 by 20 kilometres.
The early part of the lander’s entry and descent will be aided by aeroshell and parachute know-how from the Shenzhou human spaceflight missions. A blunt-body aeroshell will help slow the speed of the entry vehicle from around 4.8 kilometers per second to 460 meters per second over the course of 290 seconds. A disk-band-gap supersonic parachute will then further slow the craft to a speed of 95 meters per second over the next minute and a half. Retropropulsion systems from China’s lunar landers will then do the rest of the work. Technologies proven on the Chang’e-3 and -4 missions China sent to the moon in 2013 and 2019, respectively, will provide altimetry and hazard avoidance.
Tianwen-1 Science goals
The orbiter carries seven science payloads including medium- and high-resolution cameras, the latter comparable to HiRise on NASA’s 2005 Mars Reconnaissance Orbiter mission. It also carries a magnetometer, a sounding radar and instruments for atmospheric and ionosphere detections. The orbiter, which will also perform a relay function, is designed to operate for one Mars year, or 687 Earth days.
The rover, designed to last 90 Mars days, carries six instruments, including a laser-induced breakdown spectroscopy experiment similar to that carried by NASA’s Curiosity rover for detecting surface elements, minerals and rock types. As well as topography and multispectral imagers, the vehicle has payloads related to climate and magnetic field detections. The rover also carries a ground-penetrating radar. Elena Pettinelli of Roma Tre University, Italy, who was involved in the ground-penetrating radar experiments on the Chang’e-3 and -4 rovers, says the instruments on orbiter and rover could potentially provide a lot of new information.
Into deep space
Tianwen-1 is designated as the first in a new series of interplanetary and deep space exploration. The missions build upon on China’s Chang’e lunar exploration exploits and plans. Next is the tentatively named ZhengHe mission, which aims to collect samples from near-Earth asteroid 2016HO3/469219 Kamo’oalewa and return these to Earth before heading to main belt comet 133P/Elst-Pizarro. The mission profile requires launch to take place in 2022.
A mission featuring two “Interstellar Heliosphere Probes” is also being pushed. Two launches would use a Jupiter assist to follow up on the discoveries of the Voyagers. In addition, concepts for missions to Jupiter are being studied for launch in 2030, which could complement the studies of the Jovian system by NASA’s Europa Clipper and ESA’s JUICE missions.