Zhurong

CNSA, via China News Service.

Overview

Zhurong was delivered to Utopia Planitia by the Tianwen-1 entry module on 15 May 2021 and reached the surface on 22 May at 10:40 Beijing time, the first Chinese rover to operate on Mars [1]. The spacecraft comprised an orbiter and an entry module of back shell, landing platform and outsole, carrying the rover; descent ran approximately 3.5 h from separation through multi-stage deceleration to ramp mechanism expansion and rover egress. The rover operated about a year, roughly twice its design life, and entered hibernation on 18 May 2022 without waking again [2]. Through sol 300 it had traversed over 1800 m [2].

Specifications

Parameter	Value	Source
Dimensions	approximately 3.3 x 3.2 x 1.85 m	[3]
Power source	solar, deployable panels	[1]
Suspension	active, main and auxiliary rocker arms with a releasable clutch
Payload	six instruments

Rover mass is not published. The panel count of four is visible in the photograph above and is not given in any published text.

Mission profile

Parameter	Value	Source
Landing	15 May 2021, Utopia Planitia	[1], [9]
Rover egress from the platform	22 May 2021
First images released	11 June 2021	[9]
Planned mission	90 Martian days, completed 15 August 2021
Traverse through sol 300	over 1800 m	[2]
Traverse to 5 May 2022	1921 m over 347 Martian days	[9]
Data returned by rover and orbiter to 5 May 2022	about 940 gigabytes
Relay test with ESA Mars Express	November 2021
First solar conjunction outage	mid September to late October 2021
Status	did not wake from hibernation in May 2022	[1]

The program page gives 1921 m over 347 Martian days to 5 May 2022 [9], which extends the over 1800 m through sol 300 recorded in the literature [2], and adds the 940 gigabytes returned jointly by rover and orbiter and the November 2021 relay test through ESA’s Mars Express.

Mobility

Rock coverage at the Martian surface is approximately twice that of the Moon, which set the obstacle-clearing requirement [1]. The suspension is active, built on a main and auxiliary rocker arm arrangement with a clutch at the main rocker arm connecting point. Releasing that clutch converts the passive linkage into a commandable mechanism with four functions: controlled lifting, controlled lowering, wheel lifting, and suspension contraction.

Failure condition	Recovery action
Single wheel sunk	lift that wheel
All wheels caught	contract the suspension
Body in contact with a rock	raise the suspension to clear it

Recovery actions from [1].

Suspension contraction with sequential wheel lifting produces a walking gait, which extracts the vehicle from soft ground by changing which wheels carry load rather than by increasing drawbar pull. That addresses regenerative slip-sinkage directly: a wheel that is unloaded and repositioned does not have to develop thrust against soil whose shear strength has already been exceeded. Martian sand has a cohesion at or below 1 kPa and a friction angle near 30 degrees, and drift and crusty-to-cloddy soils reach 11 kPa, so the strength available to a loaded wheel varies by an order of magnitude across the surface types the rover crosses [7].

Terrain along the traverse is flat and covered by reddish soils and dust, with dark-toned material exposed where wheels or wind removed the dust layer [2].

Power and energy

Solar radiation intensity at Mars orbit is approximately 43 percent of that near Earth, and atmospheric dust raises the energy cost of operation on top of that deficit [1]. Background column optical depth over the aphelion half of the year sits below 1 and regional activity recurs at L_s 210 to 240 and 320 to 340, so array output has a seasonal floor independent of deposition [5], [6]. Two measures respond to it. Maximum power point tracking improves conversion efficiency from the cells. An ultra-thin solar film with an anti-dust coating gives a dust removal efficiency over 86 percent [1], which addresses deposition rather than suspension.

A dormancy and wake-up mode covers the range of surface lighting conditions [1]. On the onset of a dust storm the rover powers off to prevent battery drain and remains asleep until generated power and temperature reach their thresholds simultaneously. That coupling, requiring both conditions rather than either, is what makes the mode a survival state rather than a low-power state.

Thermal

Surface temperature below -100 C sets the design case [1]. Measured air temperature at landed sites spans 140 to 300 K, with a seasonal amplitude near 20 K at low latitude and 60 K at 47.9 N, and a diurnal range large enough that the vehicle crosses most of that span every sol [5]. The architecture combines active and passive control.

Element	Function
Solar window	collects heat during the day, raises cabin temperature at night
Aerogel plus CO2 isolation	passive insulation: reduces conduction, isolates radiative leakage, eliminates in-cabin convection
Active heating at night	brings in-cabin equipment to its required ambient temperature
Active control on external equipment	navigation and obstacle avoidance cameras, multispectral cameras

Thermal elements and their functions from [1].

The passive layer is what makes the active budget affordable: with limited active thermal resources, leakage is attacked on all three transfer paths at once rather than compensated by heater power [1]. Other extravehicular equipment is qualified to withstand the ambient extremes without active control.

Communications

Link	Parameter	Value
X-band direct	Rover-to-Earth visible arc	approximately M04:30 to M16:00 each sol [1]
X-band direct	Uplink rate to the omnidirectional antenna	as low as 7.8125 bps [1]
UHF relay	Architecture	loop relay mode inherited from Chang’e-4, two-way [1]
UHF relay	Near-Mars arc pass around noon	approximately 10 min [1]
UHF relay	Martian night pass	approximately 5 h [1]
UHF relay	Near-Mars arc rate	Mbps class [1]

The 7.8125 bps direct uplink is a command channel, not a data path, so the relay carries everything of volume: real-time and delayed telemetry, images, detection data, and the follow-up work instructions for the rover, all within the same near-Mars pass [1].

Modes of operation

The rover is in standby by default, with computers on and other equipment operating intermittently [1]. A mission cycle template is run onboard against the arc of visibility, and the measurement and control equipment is switched on and off independently. Standby rather than sleep is affordable because the passive thermal stack holds cabin temperature without continuous heater draw. The diurnal ground temperature cycle the schedule is written against has an annual amplitude of about 20 K in its daily mean at low latitude, so the template is stable across most of the year and shifts only near the solstices [5].

Interval	Action
Martian afternoon, approx 10 h	X-band omnidirectional receiver on, holding a basic uplink channel
Martian noon, approx 1 h	UHF receiver on for the near-Mars arc
Martian night, approx 5 h	UHF receiver on for the remote arc
M11:00 to M15:00	primary work period, ambient temperature highest and no additional heating needed

Daily template from [1].

Scheduling the work period against temperature rather than against illumination is a direct consequence of the thermal budget: heating an actuator costs energy that the arrays would otherwise deliver to the activity itself.

Ground operations

Delayed instructions are uplinked each Martian morning via the orbiter, relayed to the rover by UHF around noon for execution, and telemetry is returned through the orbiter by UHF during the Martian night [1]. The cycle is therefore one command load per sol with a single execution window and a single return window, rather than the multiple tactical passes available to the NASA rovers through the Mars Relay Network.

Payload and instruments

Six instruments are carried [1]. Four of them measure the environment described on the martian environment page rather than the rover’s own state, and the meteorology package is the Chinese counterpart to REMS and MEDA [5].

Instrument	Measurement	Source
Navigation camera	surface morphology, driving	[1]
Multispectral camera	mineral and rock types, material type distribution
Subsurface detection radar	soil structure, soil type, weathering and deposition characteristics, water and ice content, stratification
Surface composition detector (MarSCoDe)	LIBS for quantitative chemistry, short-wave infrared spectroscopy for mineralogy and rock identification	[1][4]
Magnetic field detector	magnetic field index, variation field, inverted ionospheric current	[1]
Meteorological instruments	temperature, pressure, wind speed and direction, and sound

MarSCoDe is built as an optical head, a calibration target assembly, a spectrometer module and a payload controller [4]. Its LIBS laser is a passively Q-switched 1064 nm unit at 23 mJ per 4.5 ns pulse, firing at 1 to 3 Hz, with fixed energy and no adjustment mechanism because the output already exceeds the ablation threshold. A 106 mm Ritchey-Chretien telescope [4] both focuses the beam and collects the plasma emission at ranges of several meters, pointed by a worm-gear beam pointing mechanism driven by two stepping motors, with autofocus off a 1550 nm laser diode through the same path [4]. Emission is dispersed across three LIBS channels covering 240 to 340, 340 to 540 and 540 to 850 nm, while the short-wave infrared channel covers 850 to 2400 nm in a selectable 64 or 330 bands, and a remote micro imager at 2048 x 2048 pixels and approximately 45 urad resolution records the target before and after each shot.

MarSCoDe measured 38 targets by LIBS and short-wave infrared in the first 300 sols [2]. The magnetometer campaign returned vector measurements at 16 sites along a 1089 m track [3]. The measured field is weaker than orbital mapping had inferred, and the two candidate explanations are demagnetization of the entire Utopia Basin or of the 5 km radius ghost crater in which the rover landed. The discrepancy is partly a sampling-geometry effect: an orbital measurement averages over an area of radius comparable to its altitude, from 185 km or 400 km, whereas a ground measurement samples an area of radius comparable to the source depth [3].

End of mission

Zhurong entered hibernation on 18 May 2022 and did not re-establish contact [2]. Orbital imagery subsequently showed it stationary. Dust accumulation on the arrays is the assumed cause, against an 86 percent dust removal efficiency demonstrated for the coating and a wake logic requiring both power and temperature thresholds to be met at once [1]. Removal of deposited dust by wind requires a surface shear stress at or above the saltation threshold, which is not a schedulable event, and column optical depth during a global storm reaches a global mean near 4 with local values of 5 to 10, so a storm subtracts from generation at the same time as it adds to deposition [6].

Technologies developed

The active suspension is the one mobility capability on Mars that no NASA rover has carried. Its value is not obstacle clearance, which rocker-bogie already provides, but a recovery mode that does not depend on developing thrust: lifting a sunk wheel, or contracting the whole suspension, changes the load distribution instead of demanding more shear from soil that has already failed. The thermal architecture pairs a passive stack that attacks conduction, radiation and convection simultaneously with a solar window that stores daytime heat for night use, which converts part of the survival heating load from an electrical draw into a thermal one. The 86 percent dust removal coating is the first flight demonstration of a passive array dust mitigation measure on Mars [1], against cumulative deposition that is monotonic absent a wind event at or above the saltation threshold [6].