LIVE: Chang'e-3 lunar probe and rover, CZ-3B - Xichang - December 1, 2013

[Blackstar]

I am actually quite amazed that very few mainstream news outlets are following the story. I honestly (naively?) expected the first Moon landing of the 21st century to be creating a much bigger stir. Sure, tomorrow evening there will be a headline or two, but I expected (or hoped) for more, even though it's not a manned landing.

Not surprising. For one thing, it's not really news until it actually happens. LADEE got covered after the launch, but primarily because it was so visible along a very populated coast. MAVEN got some coverage, but not much. And American media doesn't really care about what happens in China, or much of the rest of the world, for that matter. You can watch CNN for days and most of their coverage is domestic, or about 3-4 countries that are currently experiencing turmoil.

[jumpjack]

Long english post about landing site with plenty of images:
http://lunarnetworks.blogspot.ca/2013/12/quick-glance-at-change-3-sinus-iridum.html

"Fresh" image: sun raised, ready for landing"! :-)


Landing now scheduled for 1 orbit earlier, at 13:40 UTC (~8:40 am EST/5:40 am PST/9:40 pm in Beijing).

i would have supposed they would have DELAYED landing time, they would have actually landed at previously scheduled time, would have spent two hours checking/cutting/editing images and footage and would have "declared" all happened two hours later! 

[Galactic Penguin SST]

Probably the best annotated diagrams of the lander and rover I have seen so far. 

(source)

[veblen]

I am actually quite amazed that very few mainstream news outlets are following the story. I honestly (naively?) expected the first Moon landing of the 21st century to be creating a much bigger stir. Sure, tomorrow evening there will be a headline or two, but I expected (or hoped) for more, even though it's not a manned landing.

Not surprising. For one thing, it's not really news until it actually happens. LADEE got covered after the launch, but primarily because it was so visible along a very populated coast. MAVEN got some coverage, but not much. And American media doesn't really care about what happens in China, or much of the rest of the world, for that matter. You can watch CNN for days and most of their coverage is domestic, or about 3-4 countries that are currently experiencing turmoil.

Well, apart from the launch vids, what coverage has been provided for people to look at? Images of the earth/moon while on the journey would have been nice, but we didn't get any. Chang'e-3 has been orbiting the moon for several days, and now at a pretty impressively low altitude. But no vids/pics available.

With a safe landing on Luna that will all change of course.

[savuporo]

Well, apart from the launch vids, what coverage has been provided for people to look at?

Apparently the official mission blog on Sina Weibo has been pretty active with updates.

[Apollo-phill]

I think members of the forum will find the following information of direct interest to the Change'3 mission lunar soft landing that is due to take place tomorrow (14th December 2013)

The following is text taken from the paper called:-

AUTONOMOUS NAVIGATION AND CONTROL FOR PINPOINT LUNAR SOFT LANDING
by Xiangyu Huang, Dayi Wang, Yingzi He, Yifeng Guan

which was presented at the:-

International ESA Conference on Guidance, Navigation & Control Systems
2-5 June 2008, Tralee, County Kerry, Ireland


A LUNAR SOFT LANDING SCENARIO

In the Fig.1, the lunar soft landing process is divided into four phases. The first phase is the powered descent phase, from 15km altitude above the lunar surface to 2km altitude above the landing zone. In this phase, the relative velocity of the spacecraft to the Moon will drop from 1714m/s to 0m/s. The second phase is the approach phase, from 2km to 100m altitude above the landing zone. The landing attitude should be adjusted to be vertical to lunar surface in a period as short as possible. During this phase, a thrust engine will be used to counteract lunar gravity. In this way, the spacecraft could slowly descend in variable velocity. The third phase is terminal landing phase from 100m to 4m altitude above the landing site. The velocity caused by lunar gravity should be cancelled to make the terminal velocity
reduce to 0m/s. During this phase, lunar imaging sensor is used to explore the terrain of landing zone. The spacecraft could perform the horizontal displacement to choose appropriate landing site. The fourth phase is the free descent phase from 4m to 0m altitude above the landing site.

[Fig.1 Schematic of lunar soft landing process]

AN INITIAL GNC SYSTEM SCHEME FOR PINPOINT LUNAR SOFT LANDING
The attitude control system for pinpoint lunar soft landing is a 3-axis stabilized system. Attitude control and orbit maneuver are achieved by a set of thrusters and a main throttleable thrust engine. A parameterized approach to attitude control system design [1] is applied for pinpoint lunar soft landing. Attitude & orbit determination and hazard detection are performed by star sensors, Inertial Measurement Unit (IMU), altimeter, velocimeter, sun sensors, and lunar imaging sensors. The main operation modes of GNC include powered descent, approach, hovering & hazard avoidance, and terminal landing. Orbit control adopts a throttleable thrust explicit guidance and the gravity turn guidance. The GNC system configuration for pinpoint lunar soft landing is shown in Fig. 2.

[Fig.2 Schematic diagram of GNC system configuration for lunar landing spacecraft ]


Sensors
(1) Sun sensors and star sensors
There are three kinds of sun sensors, which are digital sun sensors, analog sun sensors and 0-1 sun sensors, used for three different kinds of operation conditions. The three star sensors are used to guarantee global acquisition and tracking capability.
(2) IMU
IMU includes gyros and accelerometers and is used for attitude and orbit measurement for spacecraft, which is one of the key units of GNC system. IMU is the major measurement element particularly during orbit maneuver and soft landing phases. Gyro cluster includes six single degree of freedom rate integrating gyros and is used for measuring the three-axis attitude angular relative speed of spacecraft wrt inertial space. Any three of the six gyros could form an operation mode to complete the attitude measurement mission independently.
There are four accelerometers. The gauging axes of three accelerometers are parallel to three spacecraft principal axes of inertia, respectively. One accelerometer is equipped slantingly.
(3) Altimeter
Altimeter is used to measure the distance between spacecraft and lunar surface along its line-of-sight direction during soft landing phase. The other related position information could be obtained according to the attitude.
(4) Velocimeter
Velocimeter is used to measure the velocity of spacecraftalong its line-of-sight direction during the soft landing phase. The other related velocity information could be obtained according to the attitude.
(5) Lunar imaging sensor
Lunar imaging sensor is used to obtain the image of lunar surface during soft landing phase. Then the data will be transmitted to GNC computer, which will process, judge and choose the proper landing site. Lunar imaging sensor includes three-dimensional imaging sensor and optical imaging sensor.
Actuators
(1) Orbit control thruster
A throttleable thrust engine with the range of thrust from 1500N to 7500N is selected.
(2) Attitude control thruster
Bi-propellant  thrusters  are  used.  16×150N thrusters will be equipped. The 12×150N thruster is used for attitude control during orbit maneuver period, forming the double branches as redundancy each other. The other 4×150N thruster provides the horizontal maneuver capability.
GNC Computer
GNC computer will collect and process the data from all the sensors and actuators, perform GNC calculation and issue control signals to actuators, etc.
Operation modes
(1) Powered descent
The brake engine fires at perilune to cancel the initial velocity of the lander. Explicit guidance method is used in powered descent phase. The main thruster in landing propulsion system operates. Attitude control is achieved by a 150N thruster. Attitude determination is achieved by making use of gyro prediction method. Autonomous navigation based on measurement-updated IMU is used.
(2) Approach
Landing attitude will be adjusted to be vertical to the landing surface in quite a short time. During this period, the increment in vertical velocity caused by lunar gravitational acceleration should be removed. The thrust is required to be almost equal to the lunar gravity of the lander. At the same time, the horizontal velocity will be reduced continuously.
(3) Hovering and hazard avoidance
In order to keep the spacecraft hovering, the thrust of the engine is requiredto be almost equal to the lunar gravity of the lander. Attitude stabilization should be kept by 10N attitude thruster. Lunar imaging sensor should be ensured to operate normally. Lunar imaging sensor in the state of hovering is used to acquire the information of lunar surface altitude and images. GNC computer will detect hazard and choose safe landing site based on the information. The 4×150N thruster is used to perform horizontal movement to avoid hazard.
(4) Terminal landing
The lander will perform soft landing on the moon in verticalattitude. Gravity turning guidance is applied to reduce the velocity. Attitude control is achieved by a 150N thruster. Attitude determination is achieved by gyro prediction. Autonomous navigation based on measurement-updated IMU is used.


Phill Parker

Please see the full excellent paper called :-

AUTONOMOUS NAVIGATION AND CONTROL FOR PINPOINT LUNAR SOFT LANDING
by Xiangyu Huang, Dayi Wang, Yingzi He, Yifeng Guan

for the full text and illustrations.I fully recommend it:-))

[Blackstar]

Well, apart from the launch vids, what coverage has been provided for people to look at? Images of the earth/moon while on the journey would have been nice, but we didn't get any. Chang'e-3 has been orbiting the moon for several days, and now at a pretty impressively low altitude. But no vids/pics available.

There's a lot of animation available. And if a Western network wanted to cover it, they could interview people involved in the mission.

But again, robotic space missions get little coverage in the American press, and foreign subjects get little coverage in the American press. Multiply a small number by a small number and you get a small number.

[savuporo]

Spaceflight101 posts a very detailed summary again about the expected sequence of events

http://www.spaceflight101.com/change-3-mission-updates.html

But again, robotic space missions get little coverage in the American press..

MSL landing was fairly well covered

[Apollo-phill]

Just took this image of Moon ( waxing gibbous ) ( 22:50 GMT 13th December 2013 from mid UK ) using a general digital "tourist camera" . Had a high layer of haze over my region.

[Apollo-phill]

 Previous image not the best since my digital camera fairly old but it shows Moon as "..it was..." for me this evening.

However,here is what the Moon will be like - for those who can view it tomorrow - when Change'3 descends and , hopefully, lands successfully and deploys Yutu rover.

[JimO]

.... And if a Western network wanted to cover it, they could interview people involved in the mission.

We've tried in Beijing, there is a remarkable level of reluctance of officials to go on record about the landing. If you have any names and phone numbers, please share via message.

[savuporo]

With less than 12 hours to go now, flurry of articles now hitting the western media

http://www.dailytech.com/Chinas+Lunar+Rover+Enters+Orbit+Prepares+for+Historic+Sat+Landing/article33930c.htm
http://www.bbc.co.uk/news/science-environment-25356603
http://www.newscientist.com/article/dn24759-chinas-jade-rabbit-kicks-off-next-lunar-space-race.html
http://www.mnn.com/earth-matters/space/stories/why-chinas-moon-rover-mission-matters

New Scientist actually takes up the "Eighth continent" angle

[Blackstar]

MSL landing was fairly well covered

Cause Curiosity was badass.

But most of this stuff gets generally ignored compared to more pressing issues, like the fact that it's winter and it is cold outside.

[Phillip Clark]

Another reason for the low media coverage of Chang'e 3 has to be the death of Nelson Mandela.   That came the day before lunar orbit injection and the landing comes on the day of his funeral.

[Phillip Clark]

Something to consider for today's Chang'e 3 landing on the Moon.   In 1966 the Soviet Union succeeded in its first survivable landing on the Moon with Luna 9 after 11 failed attempts (including launch vehicle failures).   The same year the United States made its first survivable landing on the Moon with Surveyor 1 after three failed attempts.   So the Chinese will be extremely lucky to complete a soft-landing at their first attempt.

[QuantumG]

Something to consider for today's Chang'e 3 landing on the Moon.   In 1966 the Soviet Union succeeded in its first survivable landing on the Moon with Luna 9 after 11 failed attempts (including launch vehicle failures).   The same year the United States made its first survivable landing on the Moon with Surveyor 1 after three failed attempts.   So the Chinese will be extremely lucky to complete a soft-landing at their first attempt.

Lucky.. or they'll have the benefit of hindsight and modern engineering simulation.

[Phillip Clark]

Something to consider for today's Chang'e 3 landing on the Moon.   In 1966 the Soviet Union succeeded in its first survivable landing on the Moon with Luna 9 after 11 failed attempts (including launch vehicle failures).   The same year the United States made its first survivable landing on the Moon with Surveyor 1 after three failed attempts.   So the Chinese will be extremely lucky to complete a soft-landing at their first attempt.

Lucky.. or they'll have the benefit of hindsight and modern engineering simulation.

True, but I can imagine that in some quarters the mission will be ridiculed if it fails to survive the landing attempt.   So i thought it appropriate to highlight that no-one succeeded first time.   Of course the Chinese are by-passing the rough-landing phase of their lunar programme, going straight for a full soft-landing.

[QuantumG]

True, but I can imagine that in some quarters the mission will be ridiculed if it fails to survive the landing attempt.

Fair enough. It's a shame that happens.

[Phillip Clark]

True, but I can imagine that in some quarters the mission will be ridiculed if it fails to survive the landing attempt.

Fair enough. It's a shame that happens.

Plus this mission makes me feel really ancient, since I can remember the Rangers returning their photos as they crashed onto the Moon, the Luna 9 rough-landing and Surveyor 1's soft landing - the latter carried live on TV here in the UK.   The Rangers were pre-INTELSAT 1, so no live coverage for us.   It is hard to realise that there are people who have never followed a lunar landing attempt either "live" or as a contemporary event.

[HappyMartian]

CCTV update coming up soon.