The way they used the L2 point to lasso a relay satellite so they could transmit information from the rover on the far side is stunning too. This was really brilliant, China's space program has really become something.
The way they used the L2 point to lasso a relay satellite
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.
If you read John Varley's Titan series or Neal Stephenson books like Seveneves they regularly call LaGrange points "L2", "L4", etc. I called it a lasso because, if you look at the diagram, it literally looks like a lasso.
If you read John Varley's Titan series or Neal Stephenson books like Seveneves they regularly call LaGrange points "L2", "L4", etc.
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.
Also interesting is the 'Dutch NCLE' project, which hitched a ride with the relay orbiter to study how hard it will be to do 'low-frequency' radio astronomy (esp. below 30MHz) from behind the moon.
That may turn out to have more science value than establishing that the far side is old (just joshing ... a bit).
It is known as radio repeating. Radio stations use them to boost their signals into new territories. Cell towers too.
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. ..."
This comment threw me for a loop - "L2" and "lasso" triggered the pattern recognition in my head for "regression regularization" and it took a moment to realize the topic was still orbital dynamics.
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.
Off topic: That quotation is a bit strange because the full title is "Philosophiæ Naturalis Principia Mathematica", or "Mathematical Principles of Natural Philosophy", which describes exactly what it is ("Natural Philosphy" basically being "science").
This comment threw me for a loop - "L2" and "lasso" triggered the pattern recognition in my head for "regression regularization" and it took a moment to realize the topic was still orbital dynamics.
For what it's worth, I'm from Texas where I see actual lassos somewhat regularly, and I perfectly understood the phrasing here. Maybe it's just a regional difference in how the word "lasso" is understood.
The use of a relay is something less than "stunning" and "brilliant". The use of relay satellites when ground stations do not have line-of-sight to the primary spacecraft (or, when you have reduced bandwidth or other restrictive conditions) is standard practice. This concept is used to relay telemetry from Mars landers, for instance.
You realize the words "stunning" and "brilliant" are subjective, right? Your "standard practice" here is both incredible AND the first time ever done in this scenario to achieve something brand new in space travel. Not sure why you need to tell people not to like things, but it's a really bad habit you should break.
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.
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.