China lands Chang'e-4 on far side of Moon
planetary.org
planetary.org
Perhaps interesting to note the origin of this name for spacecraft. The legend "Chang'e flies to the moon" (嫦娥奔月) lies behind the Mid-Autumn Festival (featuring mooncakes, as it were). Point is, the names of Chinese space missions are every bit as carefully steeped in tradition as, say, Mercury/Gemini/Apollo.
Chang'e stole the Immortal Pill, and eat it alone without her husband knowing. After she ate it, her body became to float and she flied to the moon, to live there alone forever as her punishment, with only one rabbit being her companion.
Sounds familiar? Yep I believe if you are a Naruto fan, you can make a lot of connections.
So that's why one of their rovers was called "Jade Rabbit"
Japanese/Korean people believe the rabbit is pounding the ingredients for rice cake.
Pollon[0], for example, focuses on a daughter of Apollo. I didn't even know the "man on the moon" thing was called Apollo until I was in high school.
The People's Republic of China doesn't think of itself as a "Nation State." Instead, it thinks of itself as a "civilization state." A part of PRC's self appointed charge is to prevent the marginalization of Chinese civilization.
https://www.youtube.com/watch?v=imhUmLtlZpw
When I was working in Houston, it was a regular occurrence for me to meet yet another Chinese born employee of whatever corporation I was in, who would soon after ask me if I could read Chinese characters, then say it was a "shame" I couldn't. I'm not even Chinese, so I find this a bit parochial. I'm aware of the importance of Chinese characters in the culture of East Asia, but still, there's something a bit too self important about it.
Now, many years later, I'm married to a Chinese woman. Even she gives me this guff! It's like they're trying to match the attitude level of the French.
(EDIT: If you know of something wonderful more people should know about, most of the time, you should try to share it as a direct experience. That way, you're more likely to get across the magic and you're less likely to come across as a lecture.)
My experience is that attitudes are often quite different if you look like a Chinese person.
So after about the 5th time like that, we had the argument. It turns out that she was just being scared and telling me to be careful, not knowing how an English speaker would take that contextually.
You should also keep in mind that the people that are saying this to you have already learned a complete another language and alphabet (since they are presumably communicating with you in English).
Asking someone to be ashamed of not having entirely elective knowledge isn't "live and let live." Nor would that strike me as being likely to be productive. Instead, you should describe how desirable and rewarding that knowledge is.
Maybe my interpretation isn't that common? (pause to google)
Apparently it is the common accepted meaning:
https://www.ldoceonline.com/dictionary/it-s-a-shame-what-a-s...
[0]: https://en.wikipedia.org/wiki/The_Cowherd_and_the_Weaver_Gir...
So confusing to put it that way. No one has caught anything with a rope or a cable, as far as I know. Basically, they are orbiting a relay satellite around the L2 Lagrange point so that the relay has line of sight with both the landing point and Earth. Obviously, if it just sat at L2, the moon would be in between the relay and the Earth. Orbiting around Lagrange points has been known about for a long time. If you want to cite something more recent and innovative pertaining to Lagrange points, astronomers, rocket scientists, and engineers have been working on fuel saving chaotic trajectories through the Lagrange points.
Arguably, the fact that they are the first to implement the L2 halo does win the Chinese space agency some innovation points.
Indeed, so a choice of words that indicates this was going on in this instance is all the more confusing.
Never got around to Titan. I really liked Seveneves. I think Sonar Taxlaw is the most perfect woman, next to my wife. Nothing wrong with referring to L2, L4, L5...
I called it a lasso because, if you look at the diagram, it literally looks like a lasso.
Arrgh! That would be like when my grade school teacher called the LEM the "moonwalker" because it looked like it could walk around on the moon.
Come to think of it, saying "Lagrangian" wouldn't have prevented my confusion - not that there's anything wrong with the terminology in OP. I'm reminded of a passage in Cryptonomicon, which I've been rereading:
"Newton wrote a *different* book, *also* called *Principia Mathematica*, which isn't *really* about mathematics at all; it's about what we would todaycall physics."
"Then why did he call it Principia Mathematica?"
"Because the distinction between mathematics and physics wasn't especially clear in Newton's day--"
"Or maybe even in zis day," Rudy said.Yeah. It's not the most apt choice of words.
https://en.wikipedia.org/wiki/Philosophi%C3%A6_Naturalis_Pri...
Radio repeating: "[It's]...a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances. A repeater sited at a high elevation can allow two mobile stations, otherwise out of line-of-sight propagation range of each other, to communicate. Repeaters are found in professional, commercial, and government mobile radio systems and also in amateur radio. ..."
In 1999, JPL lost Mars Polar Lander, and didn't have telemetry to know why. One of the major lessons learned from this loss was to always have telemetry of Entry, Descent, and Landing (EDL). This telemetry is usually provided by a relay. So despite the fact that we both like it, using relays is not new.
(See sec. 5.1 of [1]: "The omission of EDL telemetry was justifiable from a project perspective. However, the loss of MPL without yielding any clues as to the cause of the loss jeopardized the potential for success of future Mars landers. Therefore, the decision was not justifiable in the context of MPL as one element of the ongoing Mars exploration program.")
I like that they put it in an orbit about the Earth-Moon L2 point. I think it's the first such satellite there.
[1] https://spaceflight.nasa.gov/spacenews/releases/2000/mpl/mpl...
That may turn out to have more science value than establishing that the far side is old (just joshing ... a bit).
Wikipedia seems to say the rover mission duration is 3 months, yet the previous rover traveled for a year and transmitted a bit longer. The Chinese seemed quite coy about it failing last time (as with many things) so perhaps underpromising in this case?
This all preparation for China's planned permanent radio telescope on the far side which would be a huge boon for astronomers by escaping Earth's EM interference.
Also out left field is the 3kg "self sustaining" biosphere of silkworms and plants with a camera inside. Interested to see how long it survives.
Aw man, that's how you get giant mutant moonworms.
Sounds like Elon Musk's original idea for a greenhouse on Mars, to inspire via realtime cam. Is there any indication they'll have a public cam for it?
> The lander carries a 3kg (6.6lb) container with potato and arabidopsis plant seeds - as well as silkworm eggs - to perform biological studies. The "lunar mini biosphere" experiment was designed by 28 Chinese universities.
(Source for the silkworms, at least. I must confess that giant mutant moonworms are only conjecture... for now...)
There’s plenty of sources to back up what I said previously and here, but this provides a great description of why it’s wrong to say the ISS is in freefall:
https://www.quora.com/Is-ISS-considered-to-be-in-gravitation...
There's an obvious reference to Chinese culture in that one, curious what are the biological reasons to choose that creature over any other.
When you have everyone working on the mission trying to make sure their part isn't the one that causes the mission to end before the 90 days are up, you get a long-lived rover.
If the requirements state 90 days, design for 90 days - even if 180 days is achievable 'for free'. Otherwise there is no feedback loop to inform future requirements and 90 becomes an implicit 2000.b
If JWST was designed for two years and a hard shutdown it would have flown years ago and we'd be on JWST Gen 3 by now, doing actual science.
Planned obsolescence of hardware operating on another planet can be hard, much harder than over-engineering it.
Consider the wheels on the rover as a simple example (Curiosity has had structural issues with those). Next time they can either just say spend an extra 10 kg of payload to make the metal thicker, and be assured that it's "definitely 90, or way more" and move on to the next task.
Or, they can consider them lasting beyond 180 a failure. Then they'll need tens of thousands or hundreds of thousands of hours of design and testing to ensure that various types of Martian terrain wear them out at just the right rate, and no more or no less.
Easier to just say "this isn't worth micro-optimizing", eat the fixed cost of the extra payload, and move on. There's going to be tens of thousands of components on the rover that are like that, e.g. try finding a camera sturdy enough to operate on Mars but just fragile enough to reliably fall apart in 180 days.
In aggregate that's why these rovers are exceeding their life span. If it's truly important that missions are extended for whatever reason that can just be decided as a matter of policy. Stop talking to the rover after 90 days, or hand it over to hobbyists.
I think this demonstrates the risk op was getting at. Designed for 90 and lasting more is not an implicit assurance it will last up to 180. It changes expectations and that always Cascades.
JWST's design lifespan is not significantly driving its cost. Its cost derives from its complexity, and (crudely) its complexity follows from the aperture diameter and temperature it requires to achieve the scientific objectives chosen for it.
Fair chance this rover can last a while though. Good luck to them.
Love the idea of a dark side telescope!
But I guess the other side would as someone posted no em wave from earth and that help.
With China's ICBMs, aren't they already advanced enough that collaborating on space exploration with NASA won't teach them much ICBM technology that they don't already know?
I think the best cooperation is in terms of emergency rescue, backup communications, and sharing scientific results.
Emergency rescues mean compatible docking systems to that if an opportunity arises technical problems don't stop the rescue. Of course actually catching something in space in time to pull off a rescue is nearly impossible, but just in case the orbits line up...
Emergency rescue also means that moon/mars missions should plan to land ~10km from each other - while the area of exploration is greatly limited it means in the worst case you can walk to the other for safety. It also means a party in the middle one day - moral is itself an emergency.
Backup communication means that radio frequencies are compatible. That way "our relay can't reach our rover" can turn to "but we can - let us control it".
with diminishing returns. Post-Apollo funding was/is but a shadow of NASA's glory days. As soon as the military interest is gone, it's inevitable that a program will lose financial support.
Let's see. From the start of Space Age, October 4th, 1957, to the peak of NASA funding in 1966 - almost 9 years. To the last Apollo flight to the Moon in 1972 - a bit over 15 years. Advancements: unmanned space flight, manned LEO flight, manned flight to the Moon and back (overall manned flights ~43, https://en.wikipedia.org/wiki/List_of_human_spaceflights ).
From the Apollo Soyuz Test Project in 1975 to today in 2019 - 44 years. 3 times as much. Advancements: expanded unmanned space flight, permanent manned LEO outpost, reuseable vehicles (Gemini, STS, TKS, EB, X-37), commercial space flight, international space cooperation (overall manned flights ~270).
Per dollar modern space flights are quite competitive with 1970-s. Manned spaceflight is also safer than it used to be. Per unit of time... Mars flights are quite more robust, but Venus is kinda forgotten. Outer Solar system objects are visited more frequently... Russia retracted from unmanned spaceflight... India, China, Europe are growing...
I don't think funding is the only criteria here. In some aspects Apollo project catapulted humanity to the higher frontiers which are hard to keep, but some other indicators point to steady progress everywhere with way more sustainable longer term approach.
I think we should share our discoveries and knowledge, but we shouldn't be partnering. If we really want space exploration, competition is what is going to drive it.
I doubt it's using open comms and a diginotarencrypt certificate.
Now most if not all satellites use encryption and/or authentication for command and control, but I wouldn't be surprised if some space programs don't bother. With something like the New Horizons, why waste precious CPU cycles with encryption/decryption when it takes such a tremendous effort to communicate with it. The Deep Space Network costs something upwards of $1,000/hour, and requires huge dishes and lots of land.
How constant is the L2 point for the relay satellite's orbit? If I understand correctly, this is the "balance" point between the earth and sun's gravity. Does the moon's gravity affect this? If so the L2 point will shift as the moon moves towards and away from this point?
As the moon orbits the earth, presumably the relay satellite would stay put and not follow the moon in its orbit. This would mean that communication from the lander and rover to the satellite is only possible when the moon is in a particular position (between the earth and the sun), correct?
The Chinese relay satellite is orbiting the L2 point of the Earth-Moon system. That is beyond the Moon on a line which goes from Earth to Moon. Hence, this L2 point orbits the Earth like the Moon does, and the whole system orbits the Sun as well.
Now if the spacecraft would be exactly at that point, the Moon would be blocking communications between the probe and Earth antennas. So instead, it follows a halo orbit which is quite stable around that point, but goes over the Moon horizon so that there is always a direct line of sight between Earth and the spacecraft.
Not a stupid question at all !
The L4 and L5 Lagrange points are the stable ones. Something that finds its way there is going to stick around indefinitely. That's why many planets have asteroids in the L4 and L5 they make with the Sun. These are called Trojan asteroids and the names of the Jupiter-Sun Trojans are taken from the Trojan war.
An Israeli group got pretty far with an entry in the lunar lander XPrize. But the prize reached its deadline dates and expired. I hear they may be shopping for a deep space launch vehicle.
https://www.businessinsider.com/photos-dark-side-moon-china-...
It's the original source. I chose to post the BI article because the original source is in Chinese.
There is usually an English version of the website available for important government websites (as with this case, the button is on the top right corner).
https://www.space.com/22743-china-national-space-administrat...
It what way is any part of the moon not "quiet and airless" ?
The amounts are small, but scientific instruments are - by design - quite sensitive.
But in all seriousness, it produces a lot of radio signals. So it is completely accurate to call it loud. The moon doesn't have a magnetic core so it doesn't produce its own noise like Earth does.
Also try not to take this condescending tone with people. Especially when you're wrong.
The far side also has a lot more craters. There are also places in the poles that are always in darkness, but those aren't the best places for observatories.
And the comms to the unmanned missions are mostly for forensics (outside of active science or other active payload functions) -- if a problem arises that the automation on board cannot solve it is highly unlikely that a difference between real-time and an hour later warning would matter.
It's one thing to have to wait 16 minutes to grab telemetry and issue commands to something on Mars, but having only a few seconds lag seems like something mission designers/operators would take full advantage of. The idea of actively controlling a rover rather than having it perform pre-programmed routines seems highly desirable.
Rover, probably (which I considered payload functions). For delivery vehicle during passive parts of the trajectory the value is doubtful.
Plus, the standard way of getting a ground station outside a country's land footprint is to put one on a ship. That's what Soviet Union did and I suspect this is what China is doing now.
Never heard of a ship based ground station, and that's saying something as I'm in the industry. How does that work? I'd imagine the antenna would need to be on a massive gimbal, yeah?
In principle this isn't that different from ships designed to track ICBMs, and I've seen designs both with spinning parabolic radar antennas in radomes and regular antennas on gimbals. In fact many of those tracking ships were used in space programmes, but I'm not certain, whether just for one way telemetry or two-way comms
My guess is that they would need a third location for unbroken 360 degree coverage. I would gues somewhere in Africa would do it. They have lots of development projects ther.
Edit - ok, read up on it and N1 was not indeed flightworthy. There is however little information on the nature of technical issues and how long they would've taken to resolve. The program collapsed first and foremost because of the politics and personnel/finance issues.
No, engines didn't need to operate perfectly. N-1 has less gross liftoff mass (GLOM) than Saturn-5, yet N-1 had higher liftoff trust. That's partially because it was supposed to complete the mission with up to 4 engines out during flight.
On the other hand, it is shielded from radio emissions from Earth and might be a good place for a radio-telescope.
One other advantage would also be the lack of atmospheric scattering, but they have made huge strides with adaptive optics so it might not be worth the extra cost of getting all the components to the Moon and assembling them.
You would also be limited by how close you could point the telescope to the Sun when it's in the sky. I think Hubble isn't allowed to point closer than 50 degrees for fear of damaging its optics/sensors.
The corollary of one side of the Moon always facing the Earth is that the Earth hangs in about the same place in the sky for any given point on the Moon's surface. Over a period of (earth) days the Earth's position would slightly but visibly oscillate due to libration [0]. This might slightly vary the incoming Earthlight (analogous to the Moon's illumination at the horizon vs. at the Zenith).
A much bigger effect, however, would be due to the phase of the Earth. As the Moon orbits it will sometimes be between the Earth and the Sun, sometimes further away. On the sun-side, the Earth would be more 'full' and thus there would be more light to reflect. This would significantly vary the incoming light.
However, counterintuitively, I think you'd be better off with a full Earth and no direct sunlight than a new Earth and full direct sunlight, making the near side a slightly better place for an optical telescope. The near side of the moon even has the opportunity to experience eclipses.
Why so insecure? Not a good look.
[0] https://www.nytimes.com/2019/01/02/world/asia/china-change-4...
sad for those people who read such NYT junk on daily basis.
https://www.spacex.com/news/2017/02/27/spacex-send-privately...
It’s easy to promise. I hope spacex deliver, and I hope it does by 2030. That would be great.
But for now “about to start” is as meaningful as Branson’s statements back in 2003.
This mission wasn't difficult from an astro perspective, and was only moderately challenging from a satellite comms perspective.
It just wasn't that high on the priority list.