China successfully launches first Mars mission

[LKJ86]

A review of China’s Tianwen-1 Mars exploration mission

 

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Update: Xi extends congratulations on China's first Mars landing - Xinhua | English.news.cn

Xi extends congratulations on China's first Mars landing
Source: Xinhua | 2021-05-15 14:12:18 | Editor: huaxia

The graphic simulated image taken on May 15, 2021 shows China's probe landing on Mars. The lander carrying China's first Mars rover has touched down on the red planet, the China National Space Administration (CNSA) confirmed on Saturday morning. It is the first time China has landed a probe on a planet other than Earth. (Xinhua/Jin Liwang)

BEIJING, May 15 (Xinhua) -- Chinese President Xi Jinping on Saturday extended congratulations on the successful landing of China's first probe on Mars.

On behalf of the Communist Party of China (CPC) Central Committee, the State Council and the Central Military Commission (CMC), Xi, also general secretary of the CPC Central Committee and chairman of the CMC, extended warm congratulations and sincere greetings to all members who have participated in the Mars exploration mission, Tianwen-1, in a congratulatory message.

Xi said in the message that the landing marks an important step in China's interstellar exploration and a leap from the exploration of the Earth-Moon system to interplanetary exploration.

"The landing left a Chinese mark on Mars for the first time. It is another landmark progress in China's space industry development," said Xi.

"Thanks to your courage in face of challenges and pursuit of excellence, China is now among the leading countries in planetary exploration," Xi said in the message. "The country and people will always remember your outstanding achievements."

Xi stressed organizing and implementing the roving and scientific exploration on Mars carefully, adhering to the self-reliance in sci-tech development, and pushing forward major space projects including planetary exploration.

He also called for boosting China's strength in space technology and making new and greater contributions to exploring the mysteries of the universe and promoting the noble cause of peace and development of humanity.

Vice Premier Han Zheng, also a member of the Standing Committee of the Political Bureau of the CPC Central Committee, witnessed the landing at the Beijing Aerospace Control Center.

Vice Premier Liu He, also a member of the Political Bureau of the CPC Central Committee, read out the congratulatory message.

Tianwen-1, consisting of an orbiter, a lander and a rover, was launched from the Wenchang Spacecraft Launch Site on the coast of southern China's island province of Hainan on July 23, 2020, with the aim of completing orbiting, landing and roving on the red planet in one mission.

The spacecraft entered the Mars orbit in February 2021 and spent about three months surveying the planet.

The successful landing marks China's first landing on an extraterrestrial planet and makes it the second country of a successful Mars landing.

The China National Space Administration has cooperated with international space organizations like European Space Agency and the national space agencies of Argentina, France and Austria.

 

[LKJ86]

China Selects Mars Probe's Landing Site for Easy Landing and Communication Set-Up
China chose Utopia Planitia on Mars as the landing site of its first Mars probe Tianwen-1 by the country's first-hand data research, according to an expert, who further explains why this site is chosen.

 

[FOOLS_NIGHTMARE]

Congratulations China.

https://twitter.com/x/status/1393419029361020929

https://twitter.com/x/status/1393448992902586368

 

[Dalit]

Well done Chinese friends. We don't expect any less. Proud to have such a role model and brotherly nation as our neighbor. China will go from strength to strength Congrats!

 

[FOOLS_NIGHTMARE]

China in world’s leading position on interplanetary exploration: Xi

China in world’s leading position on interplanetary exploration: Xi - Global Times

www.globaltimes.cn

 

[LKJ86]

Designers unveil process of China's first Mars probe’s 9-minute landing
Designers of China's first Mars probe Tianwen-1, whose lander just touched down on the surface of the red planet on Saturday morning, unveiled the crucial nine minutes when the craft reduced its speed from about 4.8 kilometers per second to zero and made a safe landing all on its own.

 

[LKJ86]

China's First Mars Rover Zhurong to Transmit Data Back to Earth Through Orbiter
The lander of China's first Mars probe Tianwen-1 has touched down on the red planet on Saturday morning and the rover Zhurong will begin to explore Mars and transmit data back to Earth.

 

[JSCh]

https://twitter.com/x/status/1393549565719027712

Seger YU @SegerYu

(1/2) This is fun!!
#Tianwen1 #Zhurong #天问一号 #祝融号

Latitude of landing point 　 North latitude 　 25 degrees 　 07 minutes 　 07.7 seconds

Flight control important event plan
05-15 08:01:24　The static attitude of the rover confirmed
05-15 08:14:39　The rover-to-Earth communication begins
05-15 08:32:04　The end of the rover-to-Earth communication
05-15 08:38:04　The rover is unlocked and disengaged, and its body lifted
05-15 08:59:04　The solar wing of the rover deployed
05-15 09:48:39　Orbiter-Z sun-ward attitude adjustment begins
05-15 12:00:39　Fixed telemetry probe data on-demand download
05-15 12:29:39　 Close-range telemetry probe data on-demand download
05-15 13:15:39　lowering orbit, separation data on-demand download

8:51 PM · May 15, 2021

 

[JSCh]

China航天​

今天 16:53​

天问一号环绕器在完成着陆过程的中继通信任务后，在周期为两个火星日的停泊轨道上运行一圈，之后在近火点实施变轨机动，将轨道变为周期为三分之一个火星日的中继轨道，这样一个火星日内，环绕器可为火星车提供一次近火点中继通信和一次远火点中继通信，为后续的巡视探测任务提供信息传输服务O网页链接​

China Aerospace
Today at 16:53

After the Tianwen-1 orbiter completed the relay communication mission during the landing process, it continue its two Martian days parking orbit for a single orbit, it then carried out an orbital maneuver at periareion and the orbit is changed to a communications relay orbit with a period of one-third of a Martian day. That way in within one Martian day, the orbiter can provide the communication relay service for the rover at one periareion point and one apoareion point.

Currently at step no. 6
Would move to step no. 7 tomorrow.

 

[JSCh]

PhilLeafSpace​

今天 07:44 来自 HUAWEI P30 Pro 已编辑​

【祝融号的图像及科学数据传输必须依靠器间通信，故首批图像可能于今晚或明早回传】​

有必要说明一下祝融号的通信与数据传输机制：​

#祝融号#火星车设计了超高频(UHF)、X频段两种不同频率的数传链路。UHF链路作为主用数传链路，实现对环绕器的数据传输，数据率适中，但传输距离有限，只有当环绕器处于近火弧段时才能进行数传。出于简单方便考虑，UHF天线通常设计为固定天线，没有自主指向控制需求。​

X频段链路采用可转动式定向天线，可以实现直接对地传输，但数据率太低，难以满足图像数据传输需求，通常用于应急状态；也可以实现对环绕器的数传，数据率相对较高，但存在天线指向控制需求，当环绕器位于近火弧段时，由于其方位角和高度角快速变化，对火星车定向天线提出了更高的指向控制要求。​

​

根据这两种频段的特性，祝融号设计了两种通信数传机制：一是X频段直接对地通信，二是器间通信（UHF为主，X频段为辅）。​

​

1.X频段直接对地通信：持续时间长，但数传速率极低，仅为16bps，故主要用于传输工程遥测数据以供判断火星车状态，传输图像啥的是不可能的。​

​

2.器间通信(UHF为主，X频段为辅)：持续时间短，但数传速率较高，主要用于传输图像及科学探测数据。环绕器在中继通信轨道运行期间，祝融号每一个火星日(sol)可与处在近火弧段的环绕器进行一次器间UHF双向通信，每次约8～10min，平均数传速率约38kbps，平均数传量20Mbit；受供电约束影响，每3sol才能与处在远火弧段的环绕器进行一次器间X频段通信（单向，只可发送），每次约25min，数传速率约32kbps，数传量约50Mbit。​

​

5月15日7时许，祝融号落火，此后的环绕器在265×65000km×86.9º（轨道周期2sol）的停泊轨道上又飞行1圈。​

5月17日（今天）早上8:15左右，环绕器至近火点，进行第四次近火制动，随后进入265×15000km×86.9º（轨道周期1/3sol）的中继通信轨道。​

​

故在此之前，一直使用X频段直接对地通信的祝融号，其数传下行速率只有16bps(2字节/s)，不可能传输得了图像。​

在此之后，它将每个sol绕飞火星3圈，则每个sol都有一次近火弧段UHF器间通信窗口，也都有一次X频段远火弧段通信窗口，且相邻的近火弧段通信窗口与远火弧段通信窗口间隔为1/2sol。​

​

照此计算，第一个X频段远火弧段通信窗口在O5月17日20点半左右，第一个UHF近火弧段通信窗口在O5月18日早8:50左右，祝融号可能会在这两个时间窗口回传所获取的火星图像。而5月18日早的这一通信窗口，也符合计划中说的“3个火星日后建立UHF器间通信链路”。#微博公开课#​

@China航天 @Steed的围脖 @haibaraemily @航空物语 @NASA爱好者​

参考资料：彭松,尺清,郑旸.火星车自主功能方案设计[J].国际太空,2020(07):14-18.​

PhilLeafSpace
Today at 07:44 from HUAWEI P30 Pro Edited

[Zhurong’s image and scientific data transmission must rely on inter-device communication, so the first batch of images may be returned tonight or tomorrow morning]

It is necessary to explain the communication and data transmission mechanism of Zhurong:

The Mars Rover Zhurong has designed two data transmission links of ultra-high frequency (UHF) and X-band at two different frequencies. UHF link is used as the main data transmission link to realize data transmission to surround device. The data rate is moderate, and the transmission distance is limited. Data transmission can only be carried out when the surround device is in the periareion arc. For the sake of simplicity and convenience, UHF antennas are usually designed as fixed antennas, and there is no need for autonomous pointing control. The X-band link uses a rotatable directional antenna, which can realize direct-to-earth transmission, but the data rate is too low to meet the demand for image data transmission and is usually used in emergency situations; Data transmission to the orbiter can also be realized. The data rate is relatively high, but there is a need for antenna pointing control. When the orbiter is located in the periareion arc, due to the rapid change of its azimuth and altitude angles, a directional antenna for the Mars rover is required with higher pointing control capability.

Based on the characteristics of these two frequency bands, Zhurong has designed two communication data transmission mechanisms: one is X-band direct-to-earth communication, and the other is inter-device communication (UHF is the main and X-band is the secondary).

1. X-band direct-to-earth communication: duration is long, but the data transmission rate is very low, only 16bps, so it is mainly used to transmit engineering telemetry data on the status of the rover. It is impractical to transmit images.

2. Inter-device communication (UHF as main, X frequency band as auxiliary): short duration, but higher data transmission rate, mainly used to transmit images and scientific data. When the orbiter is in the relay communication orbit, Zhurong can perform UHF two-way communication with the orbiter in the periareion arc on each Martian day (sol), each time about 8-10 minutes, and the average data transmission rate is about 38kbps, the average data transmission capacity is 20Mbit; affected by power supply constraints, inter-device X-band communication (one-way, only sending) can be performed with the surround device in apoareion arc section every 3sol, and the data transmission rate is about 25min each time. Rate is about 32kbps, the data transmission capacity is about 50Mbit.

At about 7 o'clock on May 15th, Zhurong begin landing on Mars, after which the orbiter flew one more circle on the parking orbit of 265×65000km×86.9º (orbital period 2sol). At around 8:15 in the morning of May 17 (today), the orbiter reached the periareion point for the fourth periareion braking, and then entered the relay communication orbit of 265×15000km×86.9º (orbital period 1/3sol).

Therefore, before this, the ZhuRong rover, which has been using the X frequency band to communicate directly to earth, has a data transmission downlink rate of only 16 bps (2 bytes/s), and it is impossible to transmit images. After that, it will fly 3 times around Mars each sol, then each sol will have a periareion arc UHF communication window, and a X-band apoareion arc communication window. The interval between periareion and apoareion communication window is 1/2 sol.

According to this calculation, the first X-band communication window for the apoareion arc is around 20:30 on May 17, and the first UHF periareion arc communication window is around 8:50 on the morning of May 18. Zhurong may return the Mars images acquired during these two time windows. The communication window on the morning of May 18 is also in line with the stated plan that "UHF Inter-device communication link will be established after 3 sols".

@China Air Force @Steed的围铃 @haibaraemily @航空物语 @NASAenthusiast

Reference materials: Peng Song, Chi Qing, Zheng Yang. The design of the autonomous function scheme of the Mars rover[J].International Space,2020(07):14-18.

 

[charene514]

This is not china's first Mars mission.

The first mission failed to take off !