Re: Pictures of Pluto
 

Is it a surprise to us that Pluto is so perfectly spherical? In many of my astronomy books from when I was a kid it is depicted as an irregularly shaped rock?

BB

Re: Pictures of Pluto
 

Don't think so, it's well big enough to have it's gravity turn it into a sphere - it's not far off the size of the moon. So's Charon (excepting some dings). You may find that in the dim and distant past (when you went to school) was before they knew Pluto was a binary with Charon. Once you can see two planetoids you can work out much more about size/shape, etc. Otherwise you are saying "ice = white thus for that brightness it would be this size = guessing"

Re: Pictures of Pluto
 

When I was your age Pluto was a planet!

BB

Re: Pictures of Pluto
 

When this probe was launched, Pluto was a planet. 10 years ago.

Basically in 1985-90 the orbit of Charon and Pluto around each other was edge on to us, and they could see transits and eclipses, which meant they knew it was a binary system. Before that they could determine it was 'irregular' in its light pattern - which may be where your school text book got its non-sphere from.

Re: Pictures of Pluto
 

And its phoned home successfully, meaning it didn't get crunched during the encounter. 10 hours till 3 more images, then another 9 hours till 2 more.

Re: Pictures of Pluto
 

It still is a planet. A rose by any other name...

Re: Pictures of Pluto
 

It should really set itself up with an Instagram account so we can see these pictures with trendy filters and witty captions

Re: Pictures of Pluto
 

The images looks awesome so far. :thumbup:

Re: Pictures of Pluto
 

Not sure if you were being sarcastic or not but....

https://instagram.com/nasa/

Re: Pictures of Pluto
 

I was, but that's very cool.

Re: Pictures of Pluto
 

Will xkcd do ?

http://imgs.xkcd.com/comics/pluto.png

Re: Pictures of Pluto
 

I agree with the OP. It will take about 7 minutes for the signal to reach the probe to position to camera, position the antenna, and start taking pictures and then 7 minutes to start receiving the pictures back on earth.

The beam has to be extremely narrow and accurate since the probe doesn't have that much power available. It is likely that the probe can only transmit at a few watts of power but with a very narrow beam, the effective transmitting power could be effectively increased to millions of watts so by the time the signal reaches earth, it will likely be in the micro watts which may be enough to receive the picture.

Re: Pictures of Pluto
 

Actually its 4.5 hours there, 4.5 back.

So all activities are preplanned in advance and run off a queue that's uploaded ahead of time.

Signal bandwidth is ~ 1-4 kbit/s

Signal strength at Earth is 0.00000000000000000004 watts ........

Re: Pictures of Pluto
 

You are correct. I miss calculated.

Re: Pictures of Pluto
 

That appears to be 40 zepto-watts. I suppose with a large enough dish, that little bit of power can be received.

https://en.wikipedia.org/wiki/Zepto-

Re: Pictures of Pluto
 

:eek:

Re: Pictures of Pluto
 

At least we know how to destroy it if the Plutonians attack us.

Re: Pictures of Pluto
 

Can anyone help a simpleton like me understand how the pictures get back to us? Is it just like an interstellar version of wi-fi? And how does New Horizons know where to send the pictures to, given that Earth will be a miniscule dot 1 gazillion miles away.

BB

Re: Pictures of Pluto
 

The New Horizons probe knows roughly where the Earth is, and the small dish that it has has quite a wide beam. So it aims roughly in the right direction and transmits the radio signal, complete with a metric ton of error correction codes. Datarates are about 1kbit/s.

Much bigger dishes on Earth also know where the probe is (clue, it's where Pluto is) and use lots of smart techniques to pull the very faint signal out of the background. Those error correcting codes then correct for noise, and check there's no corruption.

Unlike with wifi, if there is a dodgy packet you can't really easily ask for a retransmit (9 hours for a reply) so there's much more emphasis on error correction.

Oh, and because New Horizons was done on the cheap, the camera is fixed to the probe body, not movable. Therefore to direct the camera it has to move the entire probe to point in the right direction. Downside of that is the dish is then not pointed at earth and it can't transmit. So it's only either gathering data or communicating, not both at the same time. That also means Earth can only talk to the probe when it knows the probe is listening.

Oh, and for knowing what angle you are at there are INS units, and at a pinch, star trackers - that can orientate the probe relative to known star positions.

Re: Pictures of Pluto
 

It's one of those questions like 'Why is our galaxy named after a bar of chocolate?' No-one knows.

Re: Pictures of Pluto
 

I would think quite a wide beam would probably be about a million miles in diameter when it hits the area near earth. However that would be less than a 0.1 degree beam.

Re: Pictures of Pluto
 

Think it's wider than that, about a degree IIRC (if I had the frequency and dish size I could probably work it out). Which would make it about 80 million miles wide at Earth - enough that aim need only be "aim at the sun, then move a bit left or right as needed (the earth's orbit is only 93 million miles).

Some of the high resolution mosaic stuff came in overnight. Including :

https://www.nasa.gov/sites/default/f...?itok=mudwQRzd

As I said, the surface looked very young, and this shows no impact craters at all. That means despite being -230C, its an active surface, which means its getting heated at least to some degree. And those triangular mountains are going to be causing some scratched heads. They are very different to the orange peel mountains nearby, and very regular in makeup and slope.

Re: Pictures of Pluto
 

The spacecraft uses a giant dish antenna to communicate with NASA’s Deep Space Network. It’s no trivial effort, though; the beam is only 0.3-degrees wide and has to hit Earth from Pluto and, eventually, beyond.

We Reach Pluto Tomorrow! 10 Fast Facts About 'New Horizons' | Mental Floss

Re: Pictures of Pluto
 

Where is it heading after this? Will there be an opportunity to examine any of the extrasolar bodies out there?


S

Re: Pictures of Pluto
 

I don't know.

Re: Pictures of Pluto
 

If the opportunity arose and you were a likely candidate, would you accept the solo mission of flying beyond the solar system with enough supplies to last you 20 years but knowing you'd not be coming back?

It's not a definite no for me. Not meant in a depressing way but an exciting one. If I could record data and send it back to earth, that would surely be making a difference. Obviously there is the scary side to it which would ultimately have me back out.

Re: Pictures of Pluto
 

I probably would if there was a final destination - like a planet to colonise or something. Not sure if I would be so keen if it were just head off in a straight line and keep going. Seems a pretty grim way to live out the last 20 years of your life...


S

Re: Pictures of Pluto
 

There are already people willing to die on Mars.

A Mars One Finalist: Why I’m Volunteering to Die on Mars

Re: Pictures of Pluto
 

Yeah, that i can understand - it's just dying in a spaceship hurtling into the unknown having spent the last 2 years on a spaceship hurtling into the unknown.

It's time we started working on wormhole technology or something


S

Re: Pictures of Pluto
 

Fair call. But accepting a solo mission knowing you'll never see another human again is quite a massive commitment. What would you insist on bringing with you?

Re: Pictures of Pluto
 

A lot of seriously cheerful music. And probably not Alien...


S

Re: Pictures of Pluto
 

Vasoline

Re: Pictures of Pluto
 

We have to figure out how to get someone back from Mars (an extremely complex task) before we spend vast amounts of money investigating a theory that nobody understands.

Re: Pictures of Pluto
 

Mmmm. Perhaps . I would maybe have considered such a thing when I was a lot younger. It's the idea of going where no person has gone before. Seeing what no-one else would see although I suppose the reality could be an awful lot of boredom.

Re: Pictures of Pluto
 

I was having an amusing moment :)



If you're interested in this concept, there is a movie called Astronaut: The Last Push which deals with exactly this scenario. Have a watch of that and then see if it still seems as attractive...

I'd consider signing up if it were a planet though. Provided there were no Ewoks.


S

Re: Pictures of Pluto
 

Right, you're going to make me do this, aren't you.

Half power beamwidth is given by:

https://upload.wikimedia.org/math/a/...518db0f7bc.png

k is typically 70 for a parabolic dish, lambda is 0.0429m (7Ghz), and d is 2.1m. Thus theta = 1.43 deg. Maybe a bit better, since they don't slap these dishes together.

There are two potential Kuiper Belt Objects within the available manoeuvring fuel left. They will probably direct towards one of these in a few months time (if they get given the money).

Re: Pictures of Pluto
 

Apparently the writer of the article misinterpreted the following and assumed that there was a 0.3 degree beam.

The alignment analysis showed that the HGA system could be accurately aligned to within 0.2° of the spacecraft spin-axis. An additional 0.1° misalignment with the DSN ground station pointing due to ephemeris is allowed for a total alignment budget of 0.3°.

The RF Telecommunications System for the New Horizons Mission to Pluto

Re: Pictures of Pluto
 

And this is the release image of Charon, showing what you might expect if the surface weren't quite so young (as it is on Pluto).

https://www.nasa.gov/sites/default/f...?itok=Pt_JfrQR


And this is a 3D animation of the Pluto ice mountains (if your browser is young enough)

http://i.imgur.com/ZiRD56E.gifv

Re: Pictures of Pluto
 

Well, the initial data dump from New Horizons is over, and there will be nothing new for the next few months. However NASA have now released some bits from the last downloads.

A view of the atmosphere of Pluto, illuminated by the sun.

https://www.nasa.gov/sites/default/f...?itok=50hWP1Je


Evidence of flowing nitrogen ice, glaciers, which act to erase parts, and only parts, of the surface over time.

https://www.nasa.gov/sites/default/f...?itok=A4yYLX6Y


And finally, a flyover video of parts of the terrain discovered