Author Topic: Chang'e-4 lunar probe and rover - CZ-3B- XSLC - December 2018  (Read 33597 times)

Offline Phil Stooke

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This paper is currently in press in Planetary and Space Science:

Jia, Y., Zou, Y., Ping, J., Xue, C., Yan, J. and Ning, Y., 2018b.  The scientific objectives and payloads of Chang’E−4 mission.  Planetary and Space Science, doi: 10.1016/j.pss.2018.02.011.

It is a translation of a paper in the Journal of Deep Space Exploration a month earlier.

It identifies 9 potential landing areas on the far side, 4 in the north, 5 in the south.  The Von Karman site discussed for the last year or so is approximately in one of those areas.  But this paper favors a site they call S5 which is south of Apollo basin, close to the central SPA region targeted by Moonrise (if it flies). 

Offline zandr

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http://www.xinhuanet.com/english/2018-04/12/c_137106225.htm
Quote
Flowers on the Moon? China's Chang'e-4 to launch lunar spring
BEIJING, April 12 (Xinhua) -- China's Chang'e-4 lunar probe is expected to do many things unprecedented in space history after it launches later this year, such as touching down softly on the far side of the Moon and taking the first flowers to blossom on the lifeless lunar surface.
The probe will carry a tin containing seeds of potato and arabidopsis, a small flowering plant related to cabbage and mustard, and probably some silkworm eggs to conduct the first biological experiment on the Moon.
The "lunar mini biosphere" experiment was designed by 28 Chinese universities, led by southwest China's Chongqing University, a conference on scientific and technological innovation of Chongqing Municipality has heard.
The cylindrical tin, made from special aluminum alloy materials, is 18 cm tall, with a diameter of 16 cm, a net volume of 0.8 liters and a weight of 3 kilograms. The tin will also contain water, a nutrient solution, air and equipment such as a small camera and data transmission system.
Researchers hope the seeds will grow to blossom on the Moon, with the process captured on camera and transmitted to Earth.
Although astronauts have cultivated plants on the International Space Station, and rice and arabidopsis were grown on China's Tiangong-2 space lab, those experiments were conducted in low-Earth orbit, at an altitude of about 400 kilometers. The environment on the Moon, 380,000 kilometers from the Earth, is more complicated.
Liu Hanlong, chief director of the experiment and vice president of Chongqing University, said since the Moon has no atmosphere, its temperature ranges from lower than minus 100 degrees centigrade to higher than 100 degrees centigrade.
"We have to keep the temperature in the 'mini biosphere' within a range from 1 degree to 30 degrees, and properly control the humidity and nutrition. We will use a tube to direct the natural light on the surface of Moon into the tin to make the plants grow," said Xie Gengxin, chief designer of the experiment.
"We want to study the respiration of the seeds and the photosynthesis on the Moon," said Liu.
"Why potato and arabidopsis? Because the growth period of arabidopsis is short and convenient to observe. And potato could become a major source of food for future space travelers," said Liu. "Our experiment might help accumulate knowledge for building a lunar base and long-term residence on the Moon."
The public, especially young people, are being encouraged to participate in the Chang'e-4 mission. The China National Space Administration (CNSA) launched a contest among students across China in 2016, collecting ideas on the design of the payloads.
The "lunar mini biosphere" experiment was selected from more than 200 submissions, according to the CNSA.

Offline Phil Stooke

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This link is to the current issue of China's Journal of Deep Space Exploration:

http://jdse.bit.edu.cn/sktcxben/ch/reader/issue_list.aspx

A very interesting set of papers about the CE4 landing site including several suggestions for landing sites and even rover traverse routes.  Chinese language with English abstract, but Google document translation will help, and the illustrations carry a lot of information even without translation.  Many of these papers will probably appear in English elsewhere at a later date.

Offline Galactic Penguin SST

I have found some academic papers regarding the scientific instruments on Chang'e 4 from Chinese forums and other websites. Here's a list and some technical specifications of all of them: (info from JIA Yingzhuo, ZOU Yongliao, XUE Changbin, PING Jinsong, YAN Jun, NING Yuanming. Scientific objectives and payloads of
Chang’E-4 mission
(in Chinese). Chin. J. Space Sci., 2018, 38(1): 118-130.; doi 10.11728/cjss2018.01.118)

Lander:
1. Landing Camera (LCAM)
2. Terrain Camera (TCAM)
3. Low Frequency Radio Spectrometer (LFS)
A. Lunar Lander Neutrons and Dosimetry (LND) (Kiel University, Germany)

Rover:
1. Panoramic Camera (PCAM)
2. Visible and Near-Infrared Imaging Spectrometer (VNIS)
3. Lunar Penetrating Radar (LPR)
B. Advanced Small Analyzer for Neutrals(ASAN) (Swedish Institute of Space Physics)

Relay satellite:
C. Netherlands-China Low-frequency Explorer (NCLE) (Radboud University Nijmegen, Netherlands)

Of the 6 Chinese instruments, 5 of them are apparently the same model as the ones from Chang'e 3. Only the Low Frequency Radio Spectrometer for radio astronomy observations is new.

The specifications of the instruments are as follows (not sure about some of the translations of the technical terms - I did badly with my undergraduate physics!  :P):

Landing Camera (LCAM)

Observation Wavelength - 419-777 nm
Focal distance - 4 m - infinity
Effective pixels - >= 1024 x 1024
Observation field - 45 x 45° (error <5%)
Modulation Transfer Function - >=0.20 (all fields)
Signal to noise ratio - >= 40 dB at highest SNR; >= 30 dB for albedo 0.09 and Sun angle 30°)

Terrain Camera (TCAM)

Observation Wavelength - 420-700 nm (with RGB capability)
Focal distance - 5 m - infinity
Effective pixels - >= 2352 x 1728
Observation field - 22.9 x 16.9° (error <5%)
Modulation Transfer Function - >=0.20 (all fields)
Signal to noise ratio - >= 40 dB at highest SNR; >= 30 dB for albedo 0.09 and Sun angle 30°)

Panoramic Camera (PCAM)

Observation Wavelength - 420-700 nm (with RGB and full color capability)
Focal distance - 3 m - infinity
Observation field - 19.7 x 14.5° (error <5%)
Modulation Transfer Function - >=0.20 (all fields)
Signal to noise ratio - >= 40 dB at highest SNR; >= 30 dB for albedo 0.09 and Sun angle 30°)

Low Frequency Radio Spectrometer (LFS)

Observation frequency - 0.1-40 MHz
Receiver Sensitivity - <= 10 nV·Hz^−1/2
Dynamic Range - >= 75 dB
Frequency resolution - 1-10 kHz for 0.1-1.0 MHz range and 100-200 kHz at 1.0-40 MHz range

Visible and Near-Infrared Imaging Spectrometer (VNIS)

Observation Wavelength - 450-950 nm (visual - NIR channel) & 900-2400 nm (NIR - short wave IR channel)
Spectral resolution - 2-10 nm (visual - NIR channel) & 3-12 nm (NIR - short wave IR channel)
Observation field - >= 6 x 6° (visual - NIR channel) & >= 2 x 2° (NIR - short wave IR channel)
Modulation Transfer Function - >0.1
Signal to noise ratio - >= 40 dB at highest SNR; >= 30 dB for albedo 0.09 (Sun angle 45° for visual - NIR channel & 15° for NIR - short wave IR channel)

Lunar Penetrating Radar (LPR)

Channel 1

Transmitter Voltage - 1000 V (error <5%)
Transmitter Pulse frequency - 0.5, 1, 2 kHz
Transmitter Pulse time of arrival - <= 5 ns
Receiver frequency - 10-175 MHz
Receiver input dynamic range - >90 dB
Antenna central frequency - 60 MHz
Antenna bandwidth - >=40 MHz
Standing wave function - <= 3
Maximum detection depth - >= 100 m
Depth resolution - 1 m

Channel 2

Transmitter Voltage - >= 400 V (error <5%)
Transmitter Pulse frequency - 5, 10, 20 kHz
Transmitter Pulse time of arrival - <= 1 ns
Receiver frequency - 10-1000 MHz
Receiver input dynamic range - >90 dB
Antenna central frequency - 500 MHz
Antenna bandwidth - >=450 MHz
Standing wave function - <= 2.5
Maximum detection depth - >= 30 m
Depth resolution - <= 30 cm

And here are the specifications of the European instruments:

Lunar Lander Neutrons and Dosimetry (LND)

Detection capability for:
Fast neutrons - 2-20 MeV (32 channels)
Neutron flux rate - 10-104 min^-1
Protons - 7-30 MeV (32 channels)
Electrons - 60-500 keV (32 channels)
Alpha Particles - 7-20 MeV/n (32 channels)
Heavy ions - 10-30 MeV/n (32 x 32 array)
LET - 0.1-430 keV/μm (64 channels)
Time resolution - 1 min for flux rate; 5 min for protons and electrons; 30 min for heavy ions

Advanced Small Analyzer for Neutrals(ASAN)

Observation range - 10 eV - 10 keV
Mass resolution - Neutral atoms - capable of distinguishing H atoms and +ve ions of mass to charge ratio of 1, 2, 4, 8, 16, 32
Energy resolution - 7% (+ve ions) and 30% (Neutral atoms)
Time resolution - 10 s

Netherlands-China Low-frequency Explorer (NCLE)

Observation frequency/Frequency resolution - 100 kHz∼1MHz/1 kHz; 1∼10MHz/10 kHz; 10∼80MHz/100 kHz
Clock stability - <5 x 10^-11
Receiver Sensibility - <-160 dBm.Hz^-1 (10 MHz)
Dynamic Range - >= 84 dB
Interferometer base line - >400000 km
Interferometer resolution - <= 1 Mbit.s^-1

I'll translate other details mentioned in the paper when I have time.
« Last Edit: 05/20/2018 04:50 PM by Galactic Penguin SST »
Chinese spaceflight is a cosmic riddle wrapped in a galactic mystery inside an orbital enigma... - (not) Winston Churchill

Offline EgorBotts

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Thanks for these descriptions.

Does is mean that the Queqiao relay satellite doesn't carry a (even low res) camera? I would have hoped for a good PR that they would embed something on the relay spacecraft: their picture of the moon's far side with the earth on the background taken during Chang'e 5 TI is one of my favorite ever.

Offline Phil Stooke

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There is a small camera on one of the small satellites accompanying the relay satellite.  It was provided by Saudi Arabia, and I don't think we know much yet about how it will be used.

Ive read about this from the Saudi Press Agency just yesterday, it didn't specify the Chang'e-4 mission but these are the specs of the camera. It weighs around 630g, a resolution of 38m at 300km and 88m at 9000km from the lunar surface. They even shared pictures of it on the SPA Arabic twitter account.
Link in Arabic *Didn't use google translate as I am an Arabic speaker
https://www.spa.gov.sa/1768149

Offline Steven Pietrobon

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Here are images of the camera.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Phil Stooke

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"a resolution of 38m at 300km and 88m at 9000km from the lunar surface"

That's not exactly how the text gives those numbers, and they don't sound right - resolution should scale linearly with distance.  So the orbit varies from 300 to 9000 km altitude, and the image resolution may indeed be 38 m (per pixel, presumably) at 300 km, but in that case the 88 m is probably the cut-off resolution beyond which they don't take images (at c. 700 km altitude).   In other words, imaging only near periapsis. 

Offline mcgyver

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I cant'find any info about relay satellite status.
Did it arrive at L2?
Is there any official site/twitterpage?


About resolution:
http://win98.altervista.org/telescopio.html


There is a missing "0" in resolution from 9000 km !

Errata:
"a resolution of 38m at 300km and 88m at 9000km from the lunar surface"


Corrige:

"a resolution of 38m at 300km and 880m at 9000km from the lunar surface"


« Last Edit: 06/13/2018 07:37 AM by mcgyver »

Offline mcgyver

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Offline mcgyver

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Better images from Saudi Arabia camera onboard Longjiang-2 satellite, the only survivor of the two small satellites launched together with Queqiao:








http://www.planetary.org/blogs/jason-davis/2018/20180614-longjiang-2-earth-pics.html

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