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New Horizons’ first hi-res imagery of Ultima Thule

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Re: New Horizons’ first hi-res imagery of Ultima Thule

#131

Post by hyperpallium »

tempestn wrote: post #119
hyperpallium wrote: post #108

Earlier quoted context omitted.

It's easier to observe bigger objects than smaller objects. Bigger objects have greater gravity than smaller objects, therefore are more spheroid. As we get better at observing, we'll see more objects that are less spheroid.

At least in the case of Oumuamua though, being non-spheroid wasn't really the weird thing about it. It was that it exhibited comet-like acceleration, without any visible off-gassing, and without breaking up as it passed the sun, as a comet would be expected to do. Also the fact that from our current understanding, it is much more likely for a comet to be ejected from a solar system than an asteroid, so it's surprisin…

Fair enough!

Re: New Horizons’ first hi-res imagery of Ultima Thule

#132

Post by mpweiher »

weavie wrote: post #45
jameskilton wrote: post #5

Earlier quoted context omitted.

Actually doing the fly-by is less impressive (the fly-by was planned and programmed a while ago) than the fact that we were able to line up Horizons to an object like this at all! https://twitter.com/Alex_Parker/status/1077986070128668674

I find it more impressive and awe inspiring that stuff in space is so predictable that we can actually program the fly by such a long time in advance and get such a high degree of accuracy.

I also find this somewhere between impressive and amazing. However...

...after watching the Dragon/ISS docking manoeuvre for quite a bit longer than I probably should have, I think I now understand this precision better. When we think of "flying" including flying in space, we automatically have an image of something that's a bit unstable, always being buffeted a little, because that's how all the flying we are familiar with is.

Actually seeing that docking manoeuvre, you get a feel for just how stable things are in space. When the Dragon is parked in its relative position (10m?) it is just there, rock solid, as if attached with steel beams. No, better, as if both parts are part of a single piece of granite. No quivering, nothing.

Of course this is intellectually clear/obvious, but seeing it in practice is something different.

https://www.youtube.com/watch?v=ysyK-J0tkEk

Re: New Horizons’ first hi-res imagery of Ultima Thule

#133

Post by atq2119 »

JoeSmithson wrote: post #124
tempestn wrote: post #27

Earlier quoted context omitted.

What's exciting to me is, both the first interstellar object we've observed visiting our solar system (Oumuamua) and the first Kuiper Belt Object we've visited have been "unusual". That strongly suggests to me that the unusual is more usual than we would have suspected, which means there's probably a great deal of opportunity to increase our understanding of the universe!

They deliberately picked targets that seemed unusual from initial readings.

Oumuamua was literally the only extra-solar object known. There was nothing to be picked.

Similarly for Ultima Thule. They may have been able to find a different target, but it was very difficult to find any target at all in the first place (lots of Kuiper belt objects are known; the difficulty was finding one that could be reached by New Horizons). See this Twitter thread that was linked elsewhere: https://twitter.com/Alex_Parker/status/1077986070128668674

Re: New Horizons’ first hi-res imagery of Ultima Thule

#134

Post by rbanffy »

toomuchtodo wrote: post #118
rbanffy wrote: post #86

Earlier quoted context omitted.

I wonder how much would it cost to build a GPS-like network for the whole solar-system... The good thing is that, for such a thing to be really useful, we'd have to invent better propulsion systems which would, in turn, make the network much cheaper to build.

Pulsars can be used to arrive at celestial positioning accurate to ±5 km. There is a test rig on the ISS that has validated this. No need to build human made beacons when the universe has so graciously provided us with them. https://en.m.wikipedia.org/wiki/X-ray_pulsar-based_navigatio...

They plan to get within 1km, which is quite impressive for one system alone. Thanks for the pointer (after reading it, I remember having read about NICER, but didn't remember the precision they got)

Re: New Horizons’ first hi-res imagery of Ultima Thule

#135

Post by jcims »

6nf wrote: post #117
tomerico wrote: post #116

Earlier quoted context omitted.

From /r/space: Image of the occultation profile vs actual shape: https://i.imgur.com/PNh4nmX.png Each line is the same star viewed from a different point on Earth. They arranged for telescopes in a long line North to South to all observe UT at the same time, just as it was predicted to pass in front of the star. Then they precisely timed the apparent blinks of the star. The North-South offset meant the star bisected…

From that pic it looks like they were able to measure accurately to within meters of the actual shape at this distance! That is incredible

Those streaks in that pic are the path of a star that UT passed. Given they know the velocity, if they time the period where the light from the star is occluded, they get a measure of how wide the object is at that elevation.

This is what an occultation looks like: https://www.youtube.com/watch?v=7Y_qc8Ifhso

Crazy they are able to map a few of those together so precisely to get this data.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#136

Post by dwc »

lisper wrote: post #33
mbrundle wrote: post #2

I find it truly amazing that New Horizons was able to take photos of a 20 mile object whilst flying past at ~8 miles/sec - that’s an incredibly small space and time window within which to capture the images. Does anyone know how NASA manages to pilot spacecraft with this level of precision? What kind of engineering processes do you need to enable this?

> photos of a 20 mile object whilst flying past at ~8 miles/sec Not to detract at all from the astonishing technical achievement, but that's the wrong comparison. You can see the ISS with your naked eye, and it's a Actually, the right comparison is of the closest approach distance (~2000 miles) with the distance from earth (4,000,000,000 miles). That's like launching a missile from Los Angeles to New York and hitting…

> The right comparison is with the distance at which this photo was taken: 18,000 miles, or about half an hour from closest approach.

Implicit in this statement: the camera was pointing close to the direction of travel and the target wasn't moving much within the field of view. Hugely easier than trying to image from the side at closest approach, which at best would have given a smeared image and at worst a complete miss.

It's still impressive and awesome. But always try to skew the odds of success in your favor when dealing with stuff like this. You have one pass and then the opportunity is gone.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#138

Post by Rooster61 »

Kind of sucks that this is the big first picture that is being published. The LORRI, while an impressive piece of hardware in and of itself, is not built for high detail, close-in shots (although it was used some for the Pluto flyby closeups). That's the job of the Ralph telescope on-board the spacecraft.

It's a neat picture, but I fear that any subsequent pictures will have less impact on the public, as many laymen will say "Meh, saw that the other day on . Old news".

I'm really looking forward to the spectacular shots we will get from the close-in imager. New Horizons will be MUCH closer to this object than it was Pluto, so it should really get some fantastic shots of the surface features.

For comparison, just check out the wikipedia pages. They show a pretty solid contrast of the capabilities/uses of the two devices:

https://en.wikipedia.org/wiki/Long_Range_Reconnaissance_Imag...

https://en.wikipedia.org/wiki/Ralph_(New_Horizons)

Re: New Horizons’ first hi-res imagery of Ultima Thule

#139

Post by lisper »

rbanffy wrote: post #134
toomuchtodo wrote: post #118

Earlier quoted context omitted.

Pulsars can be used to arrive at celestial positioning accurate to ±5 km. There is a test rig on the ISS that has validated this. No need to build human made beacons when the universe has so graciously provided us with them. https://en.m.wikipedia.org/wiki/X-ray_pulsar-based_navigatio...

They plan to get within 1km, which is quite impressive for one system alone. Thanks for the pointer (after reading it, I remember having read about NICER, but didn't remember the precision they got)

> quite impressive

Especially when you consider how far away the "beacons" are.

Re: New Horizons’ first hi-res imagery of Ultima Thule

#140

Post by lisper »

garmaine wrote: post #93
rbanffy wrote: post #86

Earlier quoted context omitted.

I wonder how much would it cost to build a GPS-like network for the whole solar-system... The good thing is that, for such a thing to be really useful, we'd have to invent better propulsion systems which would, in turn, make the network much cheaper to build.

We have one--stellar navigation. It's what they use.

Not exactly. You can use star location to determine a spacecraft's orientation (and they do), but its location is determined by measuring the doppler shift of the carrier signal sent from the spacecraft back to earth and running those results through some pretty hairy math. GPS works by having a network of beacons in known locations transmitting signals with known timing. I just learned from a sibling comment in this thread that they're working on using pulsars as the beacons. But building an artificial GPS system for the solar system would require sending out a network of satellites into solar orbit. That might be technically feasible, but not economically feasible.
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