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Beijing Institute of Tracking and Telecommunications Technology，Beijing 100094，P.R.China

Abstract: Chang’e-5 mission is China’s first lunar sample return mission.It contains several new flight phases compared with the previous lunar missions，such as the lunar take-off and orbit insertion phase，the rendezvous and docking phase，etc.Chang’e-5 mission is extremely complicated and full of new challenges.This paper sorts out the characteristics and the difficulties in telemetry，tracking，and command（TT&C）of Chang’e-5 mission.The main technical contribution is a reliable general design of the TT&C system，including the application of X-band TT&C in launch and early orbit phase（LEOP），multiple targets simultaneous TT&C in X-band，lunar surface benchmark calibration，high-precision and rapid orbit trajectory determination for the lunar surface take-off，remote guidance rendezvous and docking，the determination of the initial navigational value for the separation point of the Chang’e-5 orbiter and returner，and the design of the reentry measurement chain.Based on this scheme，a global deep space TT&C network and interplanetary reentry measurement chain have been established for China，and near-continuous TT&C support for China’s first extraterrestrial object sampling and return mission has been realized，ensuring reliable tracking，accurate measurement and accurate control.The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administration（NASA）and European Space Agency（ESA）for subsequent lunar and deep space exploration missions.The techniques of rapid trajectory determination of lunar take-off and orbit entry，as well as high precision and remote guidance of lunar orbit rendezvous and docking can lay a technological foundation for the future manned lunar exploration missions and planetary sampling and return missions.

Key words：Chang’e-5；telemetry，tracking and command（TT&C）；the third phase of China lunar exploration program；lunar exploration；system design

0 Introduction

China’s first lunar explorer，Chang’e-1，was launched in 2007 and circled the moon for more than one year.China’s first lunar lander，Chang’e-3，was launched in 2013 and successfully released a rover on the lunar surface.Chang’e-5 mission is the third phase of the China lunar exploration program，the final step of the three-stage“circling，landing and returning”of the China lunar exploration pro?gram［1］.Chang’e-5 explorer was launched in Wen?chang launch site with the Long March-5 carrier rocket on 24 November，2020（Beijing time）.And 23 days later，on 17 December，2020，it carried the lunar samples back to the earth，and fullfilled the first sample return mission of extraterrestrial celes?tial bodies in China.Chang’e-5 mission contains several new flight phases compared with the previ?ous lunar missions，such as the lunar take-off and or?bit insertion phase，the rendezvous and docking phase，etc.These make the mission extremely com?plicated and full of new challenges.It is“the aero?space system engineering with the highest complexi?ty and the largest technical span”［2］in China.

During the implementation of the mission，the telemetry，tracking，and command（TT&C）sys?tem is mainly responsible for TT&C of the Long March-5 rocket，orbit determination，state monitor?ing and flight control of the Chang’e-5 explorer in each flight phase，lunar surface positioning and sam?pling operation control of the explorer after landing on the Moon，and the reentry measurement of the returner.Through the cooperation of the space seg?ment and the ground segment，reliable tracking，ac?curate measurement and accurate control are real?ized.

This paper sorts out the characteristics and dif?ficulties in TT&C of Chang’e-5 mission，conducts a comprehensive analysis and systematic solutions for the key problems，and summarizes the imple?mentation effect of the mission.The practice of the mission shows that the design of the TT&C system is stable and reliable，and can effectively ensure the complete success of the mission，and provide refer?ence for the TT&C scheme design of China’s sub?sequent lunar and deep space exploration missions and manned lunar exploration missions.

1 Overview of Chang’e?5 Mission

1.1 Chang’e?5 explorer

The Chang’e-5 explorer has a total mass of about 8 200 kg and is composed of four parts：An orbiter，an ascender，a lander and a returner.The overall configuration is shown in Fig.1［3］.

Fig.1 Overall configuration and coordinate system of Chang’e-5 explorer

The TT&C subsystem of the orbiter’s ground monitoring and control adopts the unified X-band（UXB）TT&C scheme.There are two groups of frequencies of the orbiter.Each group includes an uplink frequency and a downlink frequency，and the turnaround ratio is 880/749.The high-speed data transmission from the orbiter to the ground adopts X-band suppressed carrier TT&C scheme with only one downlink frequency.The TT&C subsystem of the ascender also adopts UXB TT&C scheme.There are two groups of frequencies of the ascender.Each group includes an uplink frequency and a downlink frequency，and the turnaround ratio is 880/749.The high-speed data transmission from the lander to the ground adopts X-band suppressed carrier TT&C scheme with only one downlink fre?quency.The TT&C subsystem of the returner adopts the unified S-band（USB）TT&C scheme，with only one group of frequency and the turnaround ratio is 240/221.

1.2 Flight process of the mission

The Chang’e-5 explorer was launched by Long March?5 rocket to an Earth-Moon transfer orbit with a perigee of 200 km and an apogee of 380 000 km.After separating from the rocket，the explorer，with the support of ground TT&C，carried out midcourse correction，implemented orbit insertion at the near-Moon point，and entered the orbit around the Moon.During the circumlunar phase，the land?er-ascender and the orbiter-returner were separated.The orbiter-returner continued in orbit around the Moon，while the lander-ascender made a soft land?ing in the predetermined area on the lunar surface af?ter two orbital maneuvers and dynamic descent flight.After landing，lunar surface samples were col?lected and encapsulated during the lunar surface op?eration phase.During the circumlunar flight and the lunar surface operation phase，the orbiter-returner completed four orbit maneuvers for phase adjust?ment and orbit change.Then the ascender took off from the lunar surface and entered the rendezvous and docking orbit.After the rendezvous and docking with the ascender，the lunar samples were trans?ferred from the ascender to the returner，and then the ascender was separated from the orbiter-return?er.At a predetermined time，the orbiter-returner en?tered the Moon-Earth transfer orbit，and at an alti?tude of about 5 000 km from the earth，the returner and the orbiter were separated and reentered the at?mosphere，and finally returned to the landing site in Siziwang Banner，Inner Mongolia.

The schematic diagram of the whole mission flight process and the reentry phase are shown in Figs.2，3.

Fig.2 Schematic diagram of the whole mission flight process

Fig.3 Schematic diagram of the reentry section

2 Difficulties and Challenges of TT&C System

Compared with the previous Chang’e missions（from Chang’e-1 to Chang’e-4），The TT&C sys?tem of Chang’e-5 mission faces many new challeng?es.These challenges can be divided into three cate?gories：The requirements of the new X-band TT&C for launch and early orbit phase（LEOP），the requirements of the new multi-target TT&C and its coverage，and the new requirements brought by the new mission phases.

2.1 Requirements of the new X?band TT&C for LEOP

The previous Chang’e missions used S-band TT&C for LEOP.In order to optimize the weight of the explorer，Chang’e-5 mission adopts X?band TT&C scheme.The TT&C system needs to be able to support X-band TT&C in the launch phase and meet the mission requirements of the explorer system to quickly capture and issue commands.

2.2 New requirements of the multi?target TT&C and its coverage

In the previous Chang’e missions，there was only one TT&C target before landing on the Moon.However，Chang’e-5 mission needs to carry out re?liable X-band TT&C for at most three targets and six frequencies at the same time in the lunar orbit.This needs the TT&C system to simultaneously handle TT&C of multiple targets and multiple fre?quencies（Fig.4）and meet the requirements of highprecision orbit determination.The previous Chang’e-5 mission required a TT&C coverage rate of up to 60%.This can be achieved by China’s two deep space stations in Jiamusi and Kashi.However，since Chang’e-5 mission is required to complete the key tasks such as lunar surface sampling，rendezvous and docking，the TT&C coverage requirement is 90%.It is necessary to build a TT&C network that meets the coverage requirements.

Fig.4 Diagram of multi-target TT&C requirement in X-band

2.3 New requirements of the new mission phases

Compared with the previous missions，Chang’e-5 mission has added new flight phases such as lu?nar take-off and orbit insertion phase，rendezvous and docking phase，waiting around the moon phase，Moon-Earth transfer phase and reentry phase.In order to realize the accurate orbit insertion of ascender，it is necessary to study the high-preci?sion calibration technology of lunar take-off datum.In order to ensure the successful completion of lunar orbit rendezvous and docking，it is necessary to study the multi-target high-precision remote guid?ance method.In order to ensure the accuracy of the initial navigational value of the returner，it is neces?sary to ensure that the accuracy of the orbit determi?nation before the separation of the orbiter and the re?turner meets the interface requirements.In order to ensure the reliable capture and tracking the returner of the reentry process，it is necessary to support the construction of the USB TT&C equipments and ra?dar equipments with a larger scanning range.

3 Scheme Design of TT&C System

In Chang’e-5 mission，the TT&C system in?cludes launch phase TT&C chain，ground based TT&C network，very long baseline interferometry（VLBI）observation network and reentry measure?ment chain.In regard of the aforementioned difficul?ties，the TT&C system has bean carried out the de?sign demonstration，problems in key technologies，and the scheme design.

3.1 X?band TT&C in LEOP

For the X-band TT&C in the launch phase，two sets of UXB equipment were mounted on two TT&C ships to support TT&C in the launch phase of Chang’e-5 mission and ensure the transmission of key commands before the explorer-rocket separa?tion.Given the narrow beam of X-band，the X-band equipment of the TT&C ships is equipped with 1.8 m aperture guiding antenna with a beam range of 1.4°to realize the fast acquisition and tracking of the downlink signal of the explorer.

In order to ensure the TT&C coverage and the command requirements of the launch phase，it is considered to deploy the TT&C ships in the waters east of Philippines and the waters of French Polyne?sia.The X-band doppler frequency in the tracking passes of the TT&C ship have a range of 500 kHz and a variation rate of 7 kHz/s，and the doppler fre?quency range was 135 kHz in the previous missions in S-band and a variation rate of 1.9 kHz/s.For the large dynamic signal capture，a two-way acquisition strategy is designed with preset the Doppler frequen?cy，the increased frequency-sweeping rate（from 15 kHz/s to 28 kHz/s）and the reduced frequencysweeping range（from 460 kHz to 300 kHz）［4］.This strategy can greatly reduce the two-way acquisition time and ensure that the TT&C ships could com?plete the system acquisition and start sending the command within 60 s.

Based on the nominal trajectory，the Argentina deep space station begins to track the Chang’e-5 ex?plorer 6 min（10° elevation）after the separation of the explorer and the rocket.The TT&C system needs to capture downlink signals quickly and reli?ably in order to judge the working condition of the explorer.The antenna diameter of the Argentina deep space station is 35 m，and its beam range of Xband is only 0.07°.If the launch vehicle has a large deviation in orbit，the position of the explorer will greatly exceed the beam range of the station，so there is a risk that the signal of the explorer cannot be captured.

In order to ensure the ground TT&C station can quickly and reliably capture the signal of the ex?plorer and monitor the working conditions of it，the European Space Agency（ESA）Kourou station is used as a backup of the 35 m antenna in the Argenti?na deep space station.The Kourou station is located in French Guiana，South America，and its 15 m Xband TT&C equipment has wide beam guiding ca?pability of X-band（equipped with a 1.3 m aperture guiding antenna）.The beam of the 35 m antenna in Argentina deep space station is only 1/27 of that of the 1.3 m guide antenna of the Kourou Station.The Kourou station is used as a backup，which reduces the acquisition risk and enhances the mission reliabil?ity.

In order to verify the interface compatibility be?tween the Chang’e-5 orbiter and the TT&C station affiliated to ESA，China and ESA conducted the TT&C compatibility test at the European Space Op?erations Center（ESOC）in 2017，and conducted a full-loop ground to ground interface test between the Chang’e-5 orbiter to Beijing Aerospace Control Center（BACC）via ESOC［5］.It ensures that the ground to ground interface is matched，and the rele?vant technical characteristics can meet the require?ments of Chang’e-5 mission.

3.2 Multi?target simultaneous X?band TT&C

There is only 48 h for drilling sampling，sur?face sampling，and payload detection in the lunar surface operation phase，which requires a continu?ous TT&C support.In addition，from the separa?tion of the lander-ascender and the orbiter-returner to the completion of rendezvous and docking，it is necessary to track multiple targets and multiple fre?quencies at the same time，i.e.supporting at most three targets and six frequencies at the same time.Before the orbiter-returner separation，it is neces?sary to meet the TT&C requirements of the orbiter in X-band and give consideration to the TT&C of the returner.However，the coverage rate of TT&C in the lunar surface operation phase of Jiamusi and Kashi deep space stations is only 60%，which is not enough for drilling and surface sampling at full term.The two 18 m-antenna stations of Qingdao and Kashi cannot meet the TT&C requirements of the orbiter-returner.In addition，the existing TT&C re?sources connot meet the requirements of the X-band TT&C and data transmission of the orbiter and the S-band TT&C of the returner at the same time be?fore the orbiter-returner separation.

In response to the need for continuous TT&C support in the whole lunar surface operation phase，the Argentina 35 m-antenna deep space TT&C sta?tion was built in 2017，and is able to work simulta?neously at S/X/Ka frequency bands，in which S/X can work in the uplink and downlink，and Ka band can work in the downlink.The performance indica?tors have reached the international advanced level.In order to meet the TT&C requirements of X-band before and after the separation point of the orbiter and at the same time take into account the TT&C of the returner，Namibia 18 m S/X dual-band TT&C equipment was built.The equipment was completed in 2016 to guarantee the simultaneous TT&C of the orbiter and returner before the orbiterreturner separation and also used for the TT&C cov?erage of the important tracking pass［6］.

Through the supplementary construction de?scribed above，a pattern of“three networks plus”has been formed，namely“deep space TT&C net?work，18 m-antenna TT&C subnetwork and VLBI observation network”plus“TT&C equipment of TT&C ships，TT&C equipment of Sanya station，and TT&C equipments of ESA”.The layout of Chang’e-5 mission TT&C network is shown in Fig.5.

Fig.5 Layout of the TT&C network for Chang’e-5 mission

3.3 Calibration of lunar surface datum and rapid determination of take?off trajectory

The high precision calibration technology of lu?nar take-off datum is the prerequisite for the accu?rate orbit entry of ascender and the successful ren?dezvous and docking.This is because，according to the mission flight procedures，before rendezvous and docking，the orbiter has been operating in the lu?nar orbit for a long time，so it can accurately deter?mine the orbit prediction.After the ascender takes off from the Moon and enters the orbit，it completes four orbit changes according to the rendezvous and docking strategy，and finally enters the short-range guidance phase implemented independently when the ascender is 50 km in front of and 10 km above the orbiter.Due to the limited weight of the ascend?er，the small amount of fuel is carried，so the orbit change capability is limited.It is required that the ac?curacy of lunar launch into the orbit must be accu?rate，so as to reduce the unnecessary orbit change consumption.

In order to calibrate the lunar take-off datum with high precision and quickly determine the trajec?tory of the take-off，a measurement method using“three-way measurement system［7］+VLBI inter?ferometry system”is designed.The domestic big tri?angle composing of Jiamusi deep space station，Kashi deep space station and Sanya station provides the strongest geometric constraint for the ascender within China’s territory.The accuracy of the threeway ranging is 5 m，The accuracy of three-way dop?pler is 1 mm/s.Meanwhile，VLBI is carried out at Beijing，Shanghai，Kunming and Urumqi stations of China’s VLBI network，breaking through the quasi-real-time fast frequency synthesis technology of VLBI multi-channel data，and shortening the lag time of VLBI measurement data from 5 min to 25 s［8］.

Based on this scheme，accurate measurement of the lunar take-off datum and real-time monitoring of the trajectory of the ascender’s lunar take-off pro?cess can be realized，thereby providing an important criterion for judging if the ascender entries into the predetermined orbit.

3.4 High precision remote guidance in the ren?dezvous and docking phase

The Lunar orbit rendezvous and docking of the Chang’e-5 mission adopts the orbiter-returner ac?tively docking with the ascender as the target，and the orbiter-returner is the tracker.The TT&C sys?tem will guide the two targets from thousands of ki?lometers to the transition point of 50 km.At the time，the ascender is in a circular orbit with the height of 210 km and coplanar with the orbiter-re?turner.The ascender is 50 km in front of and 10 km above the orbiter.The orbit determination predic?tion accuracy of the two targets should meet the re?quirements of turning into autonomous guidance control procedure.

The TT&C system only relies on the limited resources of ground-based orbit measurement to re?alize the remote guidance of rendezvous and dock?ing，which faces two challenges.

（1）Short tracking pass of orbit measurement.According to the design of the rendezvous and dock?ing remote guidance strategy，the ascender will complete four orbit changes，including phase adjust?ment maneuver，orbit plane modification，altitude adjustment of the apolune and circular maneuver，within 48 h after taking off from the lunar surface and entering the orbit.Between two orbit changes，the tracking passes can be used for orbital determina?tion are at least one and at most three.

（2）High accuracy requirement for remote guidance.The semi-major axis error is 30 m；the ec?centricity error is 0.000 03；and the orbital plane pointing error is 0.01°.

Therefore，the TT&C system fully optimizes the allocation of existing ground TT&C resources，and designed a comprehensive orbit measurement scheme based on“ranging and doppler measure?ment +VLBI+same beam interferometry（SBI）”.The ascender is tracked and measured by Kashi，Jia?musi，and Argentina deep space stations and four domestic VLBI stations［9］.The Kashi，Qingdao，and Namibia 18 m aperture stations are used to track and measure the orbit of the orbiter，to achieve the 1 m ranging accuracy as well as the 1 mm/s doppler accuracy.Through the technical breakthrough，the high-precision SBI technique for two fast moving targets is realized.When the distance between two targets is within 1 000 km，the relative position can be measured by SBI at four VLBI stations in China.The schematic diagram of SBI measurement is shown in Fig.6.

Fig.6 Schematic diagram of SBI measurement

3.5 Determination of initial navigation value of orbiter?returner separation point

Before the orbiter-returner separation，the na?dir point of the orbiter-returner is located near 30°south latitude（Fig.7），instead of in the domestic TT&C area.The TT&C stations that can be used include Namibia station built in Walvis Bay，Namib?ia and the Argentina deep space stations built in Neuquen，Argentina.The last mid-course correc?tion（the sixth mid-course correction）of the orbiterreturner only takes about 4.5 h before orbiter-return?er separation，which requires 1 h orbital determina?tion prediction to the separation point by the TT&C system.The position accuracies of three directions（RTN，radial，tangential and normal）are better than 1 000 m（3σ），and the velocity accuracies are better than 0.5 m/s（3σ）.However，the actual mea?surement data that can be used for orbital determina?tion is only 3 h.Through the simulation analysis of orbit measurement and determination，no matter what orbit measurement strategy is adopted in Na?mibia station and Argentina deep space station，it cannot meet the mission requirements.Therefore，the TT&C system proposes the strategy of using ESA’s Maspalomas station，and adopts the threestation three-way measurement，including three-way ranging and three-way doppler，to improve the accu?racy of orbit determination prediction［10］.Located near 30° N，Maspalomas station along with Namib?ia station and Argentina deep space station，form a“grand triangle”，effectively improving the measure?ment geometry.The three-way measurement mode has been successfully applied in the lunar landing process of Chang’e-3 mission［11］，and the data accu?racy is significantly better than the single-station two-way ranging and doppler measurement.Unfor?tunately，through coordination with ESA，the Mas?palomas station is not able to conduct three-way ranging.In view of this situation，a strategy of threestation relay measurement is proposed for the TT&C system，i.e.Argentina deep space station，Maspalomas station and Namibia station carry out two-way ranging and Doppler measurement individ?ually.By evenly distributing available tracking pass resources to the above three stations，the measure?ment geometry can be effectively improved to meet the accuracy requirements of orbit determination pre?diction［12?13］.

Fig.7 Schematic diagram of three-station relay measure?ment

3.6 Design of reentry measurement chain

The returner is small in size and radar cross sec?tion（RCS），and it returns by semi-ballistic jump re?entry with a high reentry velocity and a large ballis?tic dispersion.In order to ensure reliable tracking and a measurement of the reentry process，supple?mentary construction of TT&C system is carried out，and a lunar reentry measurement chain（Fig.8）consisting of“radar equipment+TT&C equip?ment+optical equipment”is constructed.

Fig.8 Reentry measurement chain

The first reentry height of the returner is 120 km，and then the height decreases quickly.The lowest point is about 55 km，and then the altitude increases gradually to the peak.After that the height is again reduced to reentry the atmosphere for the second time.

When the lowest point of the first reentry is reached，the jump height is a key parameter of the process.If the jump height is too high，the returner will fly out of the atmosphere；while if the jump height is too low，the returner will fly directly into the Indian Ocean.The TT&C system needs to en?sure that the returner has a reliable measurement be?fore and after the lowest point of reentry，and deter?mines the jump height reliably.

The whole flight process of the first reentry of the returner is located over the Indian Ocean with?out land-based TT&C stations.The TT&C system solves the limitation of resources without land-based TT&C stations by setting a TT&C ship in the wa?ters east of Somalia［14］.Before entering the black barrier，the TT&C equipment of the ship starts to receive telemetry steadily，providing guidance for radar equipment and optical equipment.After enter?ing the black barrier，reflection tracking by radar equipment and camera shooting by optical equip?ment are carried out.

Given the large range of ballistic dispersion of the returner after it is out of the first black barrier，the Karachi wide beam guiding equipment and the vehicle-mounted multi-beam equipment located in Ali，Tibet are responsible for the capture and track?ing of the returner.The capture range of the Karachi wide beam guiding equipment reaches 18° and that of the vehicle-mounted multi-beam equipment reach?es 20°，both of which can cover the dispersion range of the returner under normal ballistic deviation.Sub?sequently，the radars deployed in Xinjiang，Qing?hai，Inner Mongolia and other places carry out con?tinuous measurement of the returner before the sec?ond entry into the black barrier until the parachute of the returner open，to ensure reliable tracking of the returner.A mobile optical recording equipment is set up in the landing area to record the process of the returner’s parachute open and landing.

4 Mission Implementation Effects

In the mission implementation process，the TT&C system successfully completes the work un?dertaken according to the established plan.Mission practice shows that the TT&C system scheme is re?liable and effective，which ensures the complete suc?cess of Chang’e-5 mission.

During LEOP，the Yuanwang?6 ship was lo?cated in the sea east of the Philippines，which real?ized the tracking pass lap with the mainland TT&C station，ensuring the TT&C coverage during the whole process from the rocket take-off to the first shutdown of the second stage.The Yuanwang?5 ship was located near French Polynesia，which en?sured the telemetry acquisition and command trans?mission before and after the separation of the explor?er and the rocket.In the blank tracking pass be?tween the two ships，space-based telemetry was re?ceived by relay satellites，so as to ensure the contin?uous acquisition of telemetry data of rockets in the whole launch section.In the actual misson，Yuan?wang?6 ship only used 15 s to complete the two-way frequency acquisition.Both the Argentina deep space station and the ESA’s Kuru station success?fully captured the signals from the Chang’e-5 ex?plorer after the separation.

The deep space TT&C network composed of Kashi，Jiamusi and Argentina deep space stations ensured the continuous TT&C during the 48 h lunar surface sampling phase，and the 18 m-antenna TT&C subnetwork composed of Kashi，Qingdao and Namibia stations successfully completed the TT&C work of the orbiter-returner.The difference between the lander’s lunar surface positioning accu?racy and the image data obtained by lunar reconnais?sance orbiter（LRO）is only 60 m［15］，which can be effectively used as the lunar surface liftoff datum mark.The initial orbit was determined by using the measurement data 30 minutes after the ascender was put into orbit.

In the rendezvous and docking phase，the semimajor axis accuracy of the ascender at the remote guided shift point was up to 10 m；the eccentricity accuracy was up to 1e-5，and the orbital plane pointing accuracy was up to 0.005°，which met the mission requirements of the ascender and orbiter-re?turner to transfer to short-range autonomous guid?ance control.

After the fifth midcourse orbital correction of the orbiter-returner，the TT&C system and explor?er system jointly evaluated the correction effect，which met the conditions for canceling the sixth mid?course orbital correction.Therefore，the sixth mid?course orbital correction was not implemented，and the whole 16 h tracking data after the fifth mid?course orbital correction to orbiter-returner separa?tion were used for the high-precision orbital determi?nation.Under the circumstance，the accuracy of track prediction was satisfied without three-station relay measurement.

After the orbiter-returner separation，the re?turner entered the tracking pass of the Karachi wide beam guiding equipment before and after the first black barrier.The tracking state of the equipment was affected by the black barrier at the initial stage of acquisition.Subsequently，Ali vehicle-mounted multi-beam equipment completed the capture of the returner normally，obtained the telemetry data of the returner，and sent the command as planned.Subsequent measurements were carried out by vari?ous radar and USB equipments to ensure the full coverage from the second reentry phase to the para?chute-opening of the returner，and image data were successfully obtained by optical equipments.

5 Conclusions

The successful implementation of Chang’e-5 mission has brought a satisfactory end to the three stages of China lunar exploration program.In the de?sign stage of the mission，the mission requirement analysis，the technical difficulty identification and the system scheme design are conducted according to the actual TT&C requirements of the lunar sam?pling return mission.The main technical problems are solved，including the X-band TT&C in LEOP，the multiple targets simultaneous TT&C in Xband，the lunar surface benchmark calibration，the high-precision and rapid orbit trajectory determina?tion for the lunar surface take-off，the rendezvous and docking remote guidance，the determination of the initial navigational value for the separation point of the orbiter and returner，the design of the reentry measurement chain.A reliable general TT&C scheme has been designed.China’s global deep space TT&C network and interplanetary reentry measurement chain have been established.Near-con?tinuous TT&C support for China’s first extraterres?trial object sampling and return mission has been re?alized，ensuring reliable tracking，accurate measure?ment and accurate control.The global deep space network can provide TT&C support comparable to that of National Aeronautics and Space Administra?tion（NASA）and ESA for subsequent lunar and deep space exploration missions.The techniques of high-precision and rapid orbit trajectory determina?tion for the take-off from lunar surface，as well as rendezvous and docking remote guidance can lay a technological foundation for manned lunar explora?tion missions and planetary sampling and return mis?sions.