New Horizons’ first hi-res imagery of Ultima Thule • Hacker News Board

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

#91

Post by lokedhs » Thu, Jan 03, 2019, 1:18 AM UTC

theon144 wrote: post #78

brianpgordon wrote: post #60

Earlier quoted context omitted.

Check out the crazy journey Rosetta took on the way to 67P/Churyumov–Gerasimenko: https://commons.wikimedia.org/wiki/File:Animation_of_Rosetta...

Wow, I actually had no idea; how is this all pre-planned, does somebody at NASA just put "67-P/Churyumov" into a "Orbital Maneuver Planner" and let some computers crunch the possible paths out? Or does someone actually sit down and come up with the possible sequence of orbital assits (to later verify with a computer) with a pencil and paper?

It's a combination of both. They have tools that help worth the trajectory calculations, but they have to manually decide on the basic layout of the path to take.

There is a very interesting interview with Pablo Munoz from the Bepi Colombo team about flight dynamics on the Omega Tau podcast that explains this: http://omegataupodcast.net/295-bepicolombo/

The other interviews on the same episode are also worth listening to. In fact, the entire podcast is great.

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

#92

Post by thereisnospork » Thu, Jan 03, 2019, 1:21 AM UTC

rbanffy wrote: post #86

lisper wrote: post #44

Earlier quoted context omitted.

No, that's actually not true. Hitting Ultima-Thule is much harder. For starters, just figuring out where U-T actually is is very difficult. The observations we have only constrain two of its three degrees of orbital freedom. The third has to be inferred via orbital mechanics. Likewise, figuring out where the spacecraft is is also non-trivial. By way of contrast, figuring out where you are relative to New York to with…

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.

Id guess it could be done for not that much, assuming accuracy can go from a few meters to few thousands of miles. (Someone more versed might be able to give a better oom on accuracy). Just need to launch 4(+) satalites, 2 up and 2 down relative to the orbital plane. So long as a ship isn't hiding behind a planet/sun it should have LOS to all 4 for triangulation.

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

#93

Post by garmaine » Thu, Jan 03, 2019, 1:22 AM UTC

rbanffy wrote: post #86

lisper wrote: post #44

Earlier quoted context omitted.

No, that's actually not true. Hitting Ultima-Thule is much harder. For starters, just figuring out where U-T actually is is very difficult. The observations we have only constrain two of its three degrees of orbital freedom. The third has to be inferred via orbital mechanics. Likewise, figuring out where the spacecraft is is also non-trivial. By way of contrast, figuring out where you are relative to New York to with…

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.

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

#94

Post by JshWright » Thu, Jan 03, 2019, 1:49 AM UTC

remote_phone wrote: post #79

What an astounding feat! I remember reading they were going to aim for 2000 miles from Ultima Thule, was the closest approach revised to 18,000 miles?

No, this photo was taken before the closest approach (note the very high sun angle, there's basically no shadows, so the probe was still inside the orbit of UT when the photo was taken). It's going to be another month before we see the closest/highest resolution photos (and years before all the data is downloaded)

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

#95

Post by peter303 » Thu, Jan 03, 2019, 2:04 AM UTC

ajuc wrote: post #42

We only have 2 examples, but both this and the Rosetta mission object were rubber-duck-shaped. Is this very common?

14 missions to comets, 20 to asteroids, and around 50 planetary small moons imaged well enough to see their shapes. Under a hundred miles in diameter many have irregular shapes. I would guess this shape only occurs a few percent of the time.

Wednesdays news conference speculated UT shape is primordial, while the others may have been carved through four billion years of planetary evolution.

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

#96

Post by raattgift » Thu, Jan 03, 2019, 2:27 AM UTC

lisper wrote: post #44

jdmichal wrote: post #35

Earlier quoted context omitted.

To be fair, while that's an accurate representation of the distances, it's not accurate of the difficulty. They don't have to deal with unpredictable atmosphere. There's reasons laser-guided missiles are about 1-2 meters-ish of accuracy with constant guidance, while we can basically fire-and-forget spacecraft to 4 billion miles away.

No, that's actually not true. Hitting Ultima-Thule is much harder. For starters, just figuring out where U-T actually is is very difficult. The observations we have only constrain two of its three degrees of orbital freedom. The third has to be inferred via orbital mechanics. Likewise, figuring out where the spacecraft is is also non-trivial. By way of contrast, figuring out where you are relative to New York to with…

> two of its three degrees of orbital freedom

Three?

> I know these things because I used to work at JPL

Ok, I don't. What are the three DoFs and how do they relate to 6DoFs or six Keplerian elements? Some background-fixing?

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

#97

Post by lisper » Thu, Jan 03, 2019, 2:35 AM UTC

raattgift wrote: post #96

lisper wrote: post #44

Earlier quoted context omitted.

No, that's actually not true. Hitting Ultima-Thule is much harder. For starters, just figuring out where U-T actually is is very difficult. The observations we have only constrain two of its three degrees of orbital freedom. The third has to be inferred via orbital mechanics. Likewise, figuring out where the spacecraft is is also non-trivial. By way of contrast, figuring out where you are relative to New York to with…

> two of its three degrees of orbital freedom Three? > I know these things because I used to work at JPL Ok, I don't. What are the three DoFs and how do they relate to 6DoFs or six Keplerian elements? Some background-fixing?

Brain wedgie. I meant six. And direct observations give you four of the six. I guess I was just thinking about 3-d location and just forgot about the time derivatives. Sorry.

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

#98

Post by karmakaze » Thu, Jan 03, 2019, 3:02 AM UTC

dekhn wrote: post #25

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?

the development of double precision floating point, and the kalman algorithm, were two major improvements. Basically there is a computer at JPL that, given a location in the solar system and a current location of a ship, will give you instructions on when to burn. After you burn fuel to move, you update based on visual locations of known stars, fit a model, and do incremental burns until convergence. The book Digital…

> the development of double precision floating point

So refreshing to hear that a double is good enough for JPL when repeatedly told it's not good enough for mere dollars and cents.

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

#99

Post by SubMachineGhost » Thu, Jan 03, 2019, 3:09 AM UTC

Avamander wrote: post #89

azernik wrote: post #52

"hi-res" is relative - this is still about 5 times the feature size that was actually captured by the LORRI camera. Going to have to wait at least a few days for the glorious 30m/pixel version.

Some page wrote that it takes more than a year to get every piece of information about the fly-by.

Pluto's flyby generated about 8GB of data and it took about 16 months to get all of it downloaded [1], and this data includes more than just the images, and i read somewhere that the Ultima Thule flyby will generate about 6GB of data.

I think the images are the first thing that get downloaded, so it should not take more than a week to get all high res images.

1 - https://en.wikipedia.org/wiki/New_Horizons#Telecommunication...

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

#100

Post by perl4ever » Thu, Jan 03, 2019, 3:15 AM UTC

jdmichal wrote: post #35

lisper wrote: post #33

Earlier quoted context omitted.

> 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…

To be fair, while that's an accurate representation of the distances, it's not accurate of the difficulty. They don't have to deal with unpredictable atmosphere. There's reasons laser-guided missiles are about 1-2 meters-ish of accuracy with constant guidance, while we can basically fire-and-forget spacecraft to 4 billion miles away.

I believe New Horizons did course corrections, even fairly late.