New Horizons

[Camacha]

I really doubt Pluto will look that interesting, all though I would be glad to be wrong. Really, really looking forward to this encounter.

Even if it turns out to be the most boring and uninteresting object ever, that will make it interesting in its own right That is the amazing thing of sending probes to unknown bodies - pretty much everything is new, useful information.

67P, Ceres, Pluto - what an exciting time we live in!

[Frida Space]

On Tuesday morning (in the US I guess) New Horizons will cross 1 AU to Pluto, and will fire its engine for a 96 sec burn, the 1st Pluto homing maneuver.

[Streetwind]

Go go little space piano!

[Frida Space]

New Horizons is as far from Pluto as the Earth is from the Sun! (that's 1 Astronomical Unit obviously) and 32+ AUs from Earth.

At 11:20 UTC it completed a 93 second burn which changed her velocity by 1.14 m/s. Confirmation of the burn arrived around 16:30 UTC.

[MoeKitsune]

New Horizons is an Interplanetary space piano. Kinda. Anyways, This is kinda like what an Eeloo encounter by me would be like: whizzing right by.

[smjjames]

I don't get the space piano reference though.

I wonder if New Horizons will reach the edge of the Heliosphere sooner than it took the Voyager probes?

[Nicholander]

I don't get the space piano reference though.

New Horizons is about the size of a grand piano.

[Albert VDS]

Happy 1 AU day!

[Bill Phil]

If Pluto is so inclined, then how are they absolutely sure it has cleaned it's entire orbit? Or are they just guessing?

Anyhow, the distance from Earth is going to vary by a few AUs... Every year, that is.

[andrewas]

It hasn't cleared its orbit. Thats why its a dwarf planet and not a planet.

[Technical Ben]

http://pluto.jhuapl.edu/whereisnh/sideview/nhsv20150301_0234.jpg

New Horizons is as far from Pluto as the Earth is from the Sun! (that's 1 Astronomical Unit obviously) and 32+ AUs from Earth.

At 11:20 UTC it completed a 93 second burn which changed her velocity by 1.14 m/s. Confirmation of the burn arrived around 16:30 UTC.

I knew the distances were large, but never knew they were to such an exponential degree out that far!

If Pluto is so inclined, then how are they absolutely sure it has cleaned it's entire orbit? Or are they just guessing?

Anyhow, the distance from Earth is going to vary by a few AUs... Every year, that is.

It varies by exactly 2 AU every year for me. In the summer it's +1 AU (up), and in the winter it's -1 AU (down)... from my perspective. [/trollscience]

Edited March 10, 2015 by Technical Ben

[Hcube]

At 11:20 UTC it completed a 93 second burn which changed her velocity by 1.14 m/s

Wait... A 93 second burn only changed its velocity by 1.14 m/s ??? Given the power of the average hydrazine thruster and the mass of New Horizons, something must be wrong here... o.O

Did you rather mean 114m/s ? That would be a more plausible Delta-V for a final course correction to pluto...

Please tell me if im wrong !

(EDIT: typo.)

Edited March 10, 2015 by Hcube
Typo

[Bill Phil]

Wait... A 93 second burn only changed its velocity by 1.14 m/s ??? Given the power of the average hydrazine thruster and the mass of New Horizons, something must be wrong here... o.O

Did you rather mean 114m/s ? That would be a more plausible Delta-V for a final course correction to pluto...

Please tell me if im wrong !

(EDIT: typo.)

you don't need much Dv that far anyways. A little bit can go a long way!

Plus, maybe the probe is super massive? Or it was specifically made to not have a lot of acceleration...?

- - - Updated - - -

It hasn't cleared its orbit. Thats why its a dwarf planet and not a planet.

Neptune isn't part of it's orbit... Or if it is, it isn't much of a part. So, how do they know about all the other masses that are basically invisible? They can't know. And other TNOs aren't exactly in the same orbit. So, how do they know?

- - - Updated - - -

It varies by exactly 2 AU every year for me. In the summer it's +1 AU (up), and in the winter it's -1 AU (down)... from my perspective. [/trollscience]

Not quite...

It depends on where an AU is measured. The surface, the center, the other surface? Plus, earth's distance varies by about 1% of an AU.

[KerikBalm]

Neptune isn't part of it's orbit... Or if it is, it isn't much of a part. So, how do they know about all the other masses that are basically invisible? They can't know. And other TNOs aren't exactly in the same orbit. So, how do they know?

Ummm... What?

The orbits of Neptune and Pluto do cross. Sometimes Pluto is farther out, sometimes Neptune is....

[Bill Phil]

Ummm... What?

The orbits of Neptune and Pluto do cross. Sometimes Pluto is farther out, sometimes Neptune is....

Have you seen Pluto's inclination? It's huge compared to Neptune...

And it is possible for objects to cross orbits from the perspective of a plane, but they wouldn't necessarily cross the same point. This is because orbits can be... weird. And, the smallest seperation possible is pretty big, bigger than the sepeartion of Mars and Earth at closest approach. So, using Neptune against Pluto's planet-hood isn't quite correct. So I ask how they know that it hasn't cleaned it's orbit?

[Owen5595]

Edit: Forum Glitch

[Kryten]

And it is possible for objects to cross orbits from the perspective of a plane, but they wouldn't necessarily cross the same point. This is because orbits can be... weird. And, the smallest seperation possible is pretty big, bigger than the sepeartion of Mars and Earth at closest approach. So, using Neptune against Pluto's planet-hood isn't quite correct. So I ask how they know that it hasn't cleaned it's orbit?

We know Pluto hasn't cleared it's orbit because Pluto has itself been cleared by a planet, Neptune. The reason it doesn't approach it isn't because 'the inclination is huge', it's because it's been forced into 2:3 orbital resonance-as have dozens of other objects, the 'plutinos'.

[Bill Phil]

We know Pluto hasn't cleared it's orbit because Pluto has itself been cleared by a planet, Neptune. The reason it doesn't approach it isn't because 'the inclination is huge', it's because it's been forced into 2:3 orbital resonance-as have dozens of other objects, the 'plutinos'.

It can be in 3:2 (or 2:3) resonance and still come closer than it does. The reason it doesn't come that close is its inclination. A resonance as such is only considering orbital period. Not considering anything else. So, therefore, the inclination can mean that close encounters are only possible where the relative inclinations are zero. This reduces the part of the orbit where they can come close to a few spots, and then due to the 3:2 resonance they do not come very close to one another.

Plus, the Plutinos are, for the most part, much less massive and in very different orbits. There are some exceptions...

[Frida Space]

Wait... A 93 second burn only changed its velocity by 1.14 m/s ??? Given the power of the average hydrazine thruster and the mass of New Horizons, something must be wrong here... o.O

Did you rather mean 114m/s ? That would be a more plausible Delta-V for a final course correction to pluto...

Please tell me if im wrong !

Nope, it's really 1,14 m/s It's actually a really big maneuver: from 1 AU of distance, it can change the flyby trajectory by a lot.

By the way, forgot to mention that today's maneuvre was the most distant by any spacecraft in history!

EDIT: There's finally a press release for today's maneuver. Can't post the link from my phone, but it should be on New Horizons website.

EDIT #2: from the press release:

The maneuvre moved its July 14 arrival time back on schedule with a change from the pre-burn course of 14 minutes and 30 seconds. It will also shift the course “sideways†(if looking from Earth) by 3,442 kilometers (2,139 miles) by July 14, sending the spacecraft toward a desired flyby close-approach target point. The shift was based on the latest orbit predictions of Pluto and its largest moon Charon, estimated from various sources, including optical-navigation images of the Pluto system taken by New Horizons in January and February.

Edited March 10, 2015 by Frida Space

[KerikBalm]

It can be in 3:2 (or 2:3) resonance and still come closer than it does.

Guess what... Resonances form because of gravitational interactions...

Just because Pluto and Neptune don't have the same orbit does not mean much.

[Hannu]

Wait... A 93 second burn only changed its velocity by 1.14 m/s ??? Given the power of the average hydrazine thruster and the mass of New Horizons, something must be wrong here... o.O

New Horizons does not have "average" thrusters because there is no time critical high dv burns during a flyby mission. Typically only orbit insertion burn need larger thrust. New Horizons has only very small attitude control thrusters. Low thrust is good because it gives very accurate control. Probes can make corrections of just few millimeters per second or follow some point of target body with some instrument by rotating exactly right way.

[Bill Phil]

Guess what... Resonances form because of gravitational interactions...

Just because Pluto and Neptune don't have the same orbit does not mean much.

It means that using Neptune to argue against planethood shouldn't count. So, what about other objects? How do they know their masses?

You see... Jupiter is so massive it pulls the barycenter of the solar system outside the sun. So in reality, nothing quite orbits the sun. So we have zero planets. Yet, that gravitational thing isn't counted for some silly reason, and everything else is a planet.

[Frida Space]

The New Horizons propulsion system includes 16 small hydrazine-propellant thrusters mounted across the spacecraft in eight locations, a fuel tank, and associated distribution plumbing. Four thrusters that each provide 4.4 newtons (1 pound) of thrust will be used mostly for course corrections. The spacecraft will use 12 smaller thrusters – providing 0.8 newtons (about 3 ounces) of thrust each – to point, spin up and spin down the spacecraft. Eight of the 16 thrusters aboard New Horizons are considered the primary set; the other eight comprise the backup (redundant) set.

At launch, the spacecraft will carry 77 kilograms (170 pounds) of hydrazine, stored in a lightweight titanium tank. Helium gas pushes fuel through the system to the thrusters. Using a Jupiter gravity assist, along with the fact that New Horizons does not need to slow down enough to enter orbit around Pluto, reduces the amount of propellant needed for the mission.

[Nikolai]

It depends on where an AU is measured. The surface, the center, the other surface?

Technical note that makes little difference: As of 2012, the AU is no longer defined in terms of the distance between any two bodies. It is, by definition, exactly 149 597 870 700 meters. (The new definition also points out that this new definition relegates the AU to matters of convenience.)

http://www.nature.com/news/the-astronomical-unit-gets-fixed-1.11416

[KerikBalm]

It means that using Neptune to argue against planethood shouldn't count.

How do you figure that?

They don't cross each other due to orbital resonances, which is due to a gravitational interaction.

The same cannot be said of any other planet.... I don't see your point here.

"two bodies are defined to share an orbital zone if their orbits cross a common radial distance from the primary, and their non-resonant periods differ by less than an order of magnitude. The order-of-magnitude similarity in period requirement excludes comets from the calculation, but the combined mass of the comets turns out to be negligible compared to the other small Solar System bodies, so their inclusion would have little impact on the results."

"a large body will tend to cause small bodies either to accrete with it, or to be disturbed to another orbit, or to be captured either as a satellite or into a resonant orbit. As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence. This latter restriction excludes objects whose orbits may cross but which will never collide with each other due to orbital resonance, such as Jupiter and the Trojan asteroids, Earth and 3753 Cruithne, or Neptune and the plutinos"