APOD: Farther Along (2011 May 06)

Comments and questions about the APOD on the main view screen.
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APOD: Farther Along (2011 May 06)

Post by APOD Robot » Fri May 06, 2011 4:06 am

Image Farther Along

Explanation: What is humanity's most distant spacecraft? Launched in 1977, Voyager 1 now holds that distinction at 17.5 billion kilometers from the Sun. That corresponds to 16 light-hours or 117 Astronomical Units (AU). This graphic shows the position of Voyager 1 relative to the outer solar system (top and side views) along with other distant spacecraft contenders. Next most distant, Pioneer 10 is about 15.4 billion kilometers from the Sun, though on the opposite side of the solar system from Voyager 1. Voyager 2 and Pioneer 11, both also well beyond the orbit of Pluto, are 14.2 billion and 12.4 billion kilometers from the Sun respectively. Still outbound for Pluto, the New Horizons spacecraft is presently 3 billion kilometers from the Sun and will encounter the Pluto system in July of 2015. All these spacecraft have used sling-shot style gravity assist maneuvers to increase their speeds through the outer solar system. Voyager 1 is moving the fastest though, escaping the solar system at about 17 kilometers per second. Still operational, both Voyagers are headed towards the outer boundary of the solar system, in search of the heliopause and the beginning of interstellar space.

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Re: APOD: Farther Along (2011 May 06)

Post by Boomer12k » Fri May 06, 2011 4:42 am

Very confusing pictures.....

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Re: APOD: Farther Along (2011 May 06)

Post by Ann » Fri May 06, 2011 4:58 am

Interesting graphics. For me, who so rarely keep up with spaceflight news, this was very informative.

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Re: APOD: Farther Along (2011 May 06)

Post by owlice » Fri May 06, 2011 8:58 am

I love this! It is amazing, amazing! to know these are out there, what they do, what they keep doing, and how far they have gone!
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Re: APOD: Farther Along (2011 May 06)

Post by Indigo_Sunrise » Fri May 06, 2011 11:10 am

This is a very awesome representative, indeed! I've always been fascinated with the Voyager missions: the thought of something so far away from our planet still sending us data is just amazing to me. And that it will still take an incredible amount of time for either of them to come anywhere close to another star system.
From here:
Eventually, the Voyagers will pass other stars. In about 40,000 years, Voyager 1 will drift within 1.6 light years (9.3 trillion miles) of AC+79 3888, a star in the constellation of Camelopardalis. In some 296,000 years, Voyager 2 will pass 4.3 light years (25 trillion miles) from Sirius, the brightest star in the sky . The Voyagers are destined—perhaps eternally—to wander the Milky Way.
Boggles my mind...... :shock: But in such a good way!

Great APOD!!!!

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Re: APOD: Farther Along (2011 May 06)

Post by orin stepanek » Fri May 06, 2011 11:32 am

:mrgreen:
Click to play embedded YouTube video.
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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 1:02 pm

Code: Select all

17.5 trillion meters  : Voyager 1
15.4 trillion meters  : Pioneer 10
14.3 trillion dollars : U.S. debt
14.2 trillion meters  : Voyager 2
12.4 trillion meters  : Pioneer 11
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Re: APOD: Farther Along (2011 May 06)

Post by moonstruck » Fri May 06, 2011 1:17 pm

Wow, thanks for the prospective.

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Re: APOD: Farther Along (2011 May 06)

Post by Jim Leff » Fri May 06, 2011 2:03 pm

Apollo 10 hit 11 km/s coming back to Earth from the Moon. Why can't Voyager 1 do a lot better than that, with all its cleverly planned gravitational assists?

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Re: APOD: Farther Along (2011 May 06)

Post by Jim Leff » Fri May 06, 2011 2:10 pm

Also, the fact that something has traveled so incredibly fast for so many years (1/3 of a century) and now seems so very far, yet is still only light hours (not days, let alone weeks, months, or years) away really drives home for me the enormity of interstellar distances.
Last edited by Jim Leff on Fri May 06, 2011 2:19 pm, edited 1 time in total.

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Re: APOD: Farther Along (2011 May 06)

Post by Art Olph » Fri May 06, 2011 2:13 pm

Why not throw pc to wind and include miles in the distances for us olpharts?

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Re: APOD: Farther Along (2011 May 06)

Post by geckzilla » Fri May 06, 2011 2:19 pm

It's not about being PC at all, it's just that meters are a much friendlier way to measure things. They had a few mishaps with their old friend miles and figured the two just couldn't be with one another. :lol:

In any case (miles in parentheses):

http://www.nasa.gov/mission_pages/voyag ... 14112.html
This graphic shows the relative positions of NASA’s most distant spacecraft in early 2011, looking at the solar system from the side. Voyager 1 is the most distant spacecraft, about 17.5 billion kilometers (10.9 billion miles) away from the sun at a northward angle. Pioneer 10, the next most distant, is about 15.4 billion kilometers (9.6 billion miles) away from the sun on the opposite side of the solar system. Voyager 2 is about 14.2 billion kilometers (8.8 billion miles) away from the sun on a southward trajectory, on the same side of the solar system as Voyager 1. Pioneer 11 is about 12.4 billion kilometers (7.8 billion miles) away from the sun. New Horizons is about 3 billion kilometers (2 billion miles) away from the sun, on its way to Pluto.
Miles, kilometers, may as well just say those things are a long damn way out there.
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Re: APOD: Farther Along (2011 May 06)

Post by Chris Peterson » Fri May 06, 2011 2:35 pm

Jim Leff wrote:Apollo 10 hit 11 km/s coming back to Earth from the Moon. Why can't Voyager 1 do a lot better than that, with all its cleverly planned gravitational assists?
Anything from outside the Earth's orbit will arrive at Earth with a minimum velocity of 11 km/s, because that is Earth's escape velocity. Had the Apollo craft swung around the Earth and headed away, most of that speed would have been lost again. Any net gain or loss would be determined by angular momentum transfer from (or to) the orbital velocity of the Earth around the Sun. That's how gravitational assists work. Jupiter's escape velocity is about 60 km/s, so if we had allowed Voyager 1 to crash into that planet, it would have been going very fast indeed! But since we wanted it to survive, no velocity gain could be extracted from Jupiter's gravity well.

Keep in mind that in the Apollo example you give, velocity is with respect to the Earth. The (radial) velocity of the Apollo craft with respect to the Sun was zero. If you want to send something out of the Solar System, you need a high sun-referenced velocity. It is cleverly planned gravitational assists that allow our craft to reach speeds of 10-20 km/s with respect to the Sun- something that we don't have the technology to do with chemical propulsion alone. (The solar escape velocity at Jupiter is 19 km/s; at Neptune it is 8 km/s.)
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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 2:51 pm

moonstruck wrote:
Wow, thanks for the prospective.
  • -------------------------------------------------------------
    PROSPECTIVE, n. [L. prospectivus. See Prospect, n.]

    1. The scene before or around, in time or in space; view.

    2. A perspective glass, a telescope which shows
    objects in the right position.. [Obs.] Chaucer. Beau. & Fl.
    -------------------------------------------------------------
    PERSPECTIVE, n. [F. perspective, fr. perspectif.]

    1. A glass through which objects are viewed. [Obs.]
    Not a perspective, but a mirror." Sir T. Browne.

    2. That which is seen through an opening; a view; a vista.
    "The perspective of life." Goldsmith.

    3. The effect of distance upon the appearance of objects, by
    means of which the eye recognized them as being at a more or
    less measurable distance. Hence, aërial perspective, the assumed
    greater vagueness or uncertainty of outline in distant objects.

    4. The Art and the science of so delineating objects that
    they shall seem to grow smaller as they recede from the eye.

    5. A drawing in linear perspective.
    -------------------------------------------------------------
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Re: APOD: Farther Along (2011 May 06)

Post by Jim Leff » Fri May 06, 2011 2:52 pm

Thanks. Curious: is the solar escape velocity from earth greater than the escape velocity of earth?

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Re: APOD: Farther Along (2011 May 06)

Post by Chris Peterson » Fri May 06, 2011 3:01 pm

Jim Leff wrote:Thanks. Curious: is the solar escape velocity from earth greater than the escape velocity of earth?
The escape velocity from the Earth with respect to the Earth (the velocity needed to ensure that Earth won't ultimately pull you back) is 11 km/s. The solar escape velocity at the Earth's distance from the Sun is 42 km/s.

There is no way with current technology that we could simply blast off the Earth into a trajectory that would ultimately escape from the Sun without adding velocity along the way using gravitational assists.
Chris

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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 3:13 pm

Jim Leff wrote:
Curious: is the solar escape velocity from earth greater than the escape velocity of earth?
Escape Velocity from Earth = 11.186 km/s

Orbital speed around Sun = 29.78 km/s

Total speed needed to escape from the Sun = 29.78 * sqrt(2) = 42.12 km/s

Added velocity needed to escape from the Sun in the direction of orbit = 42.12 - 29.78 = 12.34 km/s

Actual Escape Velocity from Earth plus Sun (without planetary assists) = sqrt [(11.186)2 + (12.34)2] = 16.66 km/s
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Re: APOD: Farther Along (2011 May 06)

Post by biddie67 » Fri May 06, 2011 3:15 pm

Fascinating APOD!!

Question based upon Jim Leff''s comment above :: if there is a component of the Sun's escape velocity that has to be dealt with during a spacecraft's lift through Earth's escape vlocity, is it great enough that there is a difference whether the launch site on Earth is facing the Sun or away from the Sun?

Question based upon Chris's comment above :: is the lack of current technology to overcome the Sun's escape velocity without the aid of gravitational assistance the reason that there isn't any space probes launched that are perpendicular to the solar plane?

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Re: APOD: Farther Along (2011 May 06)

Post by biddie67 » Fri May 06, 2011 3:24 pm

Also-- What does "round trip light time" mean?

Is the New Horizons spacecraft to go into orbit around Pluto -or- flyby?

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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 3:36 pm

biddie67 wrote:
if there is a component of the Sun's escape velocity that has to be dealt with during a spacecraft's lift through Earth's escape vlocity, is it great enough that there is a difference whether the launch site on Earth is facing the Sun or away from the Sun?
Because the Earth is in free fall only (second order) tidal effects are important.
Since tides run only about one meter high it would be roughly equivalent to launching from a meter high platform.

Much more important would be to launch from a mountain top (or from the equator which is 22.7 km higher than the poles).
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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 3:43 pm

biddie67 wrote:
What does "round trip light time" mean?
"Round trip light time" is important for communications.

If a Mars rover sees something unexpected (an avalanche, an alien ray gun, etc.)
its response by way of ground control involves "round trip light time."
biddie67 wrote:
Is the New Horizons spacecraft to go into orbit around Pluto -or- flyby?
Flyby.
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Re: APOD: Farther Along (2011 May 06)

Post by Chris Peterson » Fri May 06, 2011 3:57 pm

biddie67 wrote:Is the New Horizons spacecraft to go into orbit around Pluto -or- flyby?
A flyby, for the simple reason that there is no way to slow it down once it gets there. And it would have to slow down a LOT to remain in orbit around Pluto. It's going to zip by Pluto very fast- a short encounter after a long trip.
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Re: APOD: Farther Along (2011 May 06)

Post by Matt » Fri May 06, 2011 4:33 pm

Chris Peterson wrote:
biddie67 wrote:Is the New Horizons spacecraft to go into orbit around Pluto -or- flyby?
A flyby, for the simple reason that there is no way to slow it down once it gets there. And it would have to slow down a LOT to remain in orbit around Pluto. It's going to zip by Pluto very fast- a short encounter after a long trip.
Do you think we'll be able to gather enough information that we're looking for in just a flyby? What then, it just keeps going like the Voyager missions?

13013

Re: APOD: Farther Along (2011 May 06)

Post by 13013 » Fri May 06, 2011 4:40 pm

What are the chances of any of these probes traveling from interstellar to intergalactic space? How long will that take? Or is it more probable that they will be pulled onto the gravitational fields of another star in our galaxy?

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Re: APOD: Farther Along (2011 May 06)

Post by neufer » Fri May 06, 2011 4:54 pm

Matt wrote:
Do you think we'll be able to gather enough information that we're looking for in just a flyby?

What then, it just keeps going like the Voyager missions?
http://en.wikipedia.org/wiki/New_Horizons#Kuiper_belt_mission wrote:
<<Observations of Pluto, with LORRI plus Ralph, will begin about 6 months prior to closest approach. The targets will be only a few pixels across. This should detect any rings or any additional moons (eventually down to 2 kilometers diameter), for avoidance and targeting maneuvers, and observation scheduling. 70 days out, resolution will exceed the Hubble Space Telescope's resolution, lasting another two weeks after the flyby. Long-range imaging will include 40 km (25 mi) mapping of Pluto and Charon 3.2 days out. This is half the rotation period of Pluto-Charon and will allow imaging of the side of both bodies that will be facing away from the spacecraft at closest approach. Coverage will repeat twice per day, to search for changes due to snows or cryovolcanism. Still, due to Pluto's tilt and rotation, a portion of the northern hemisphere will be in shadow at all times.

During the flyby, LORRI should be able to obtain select images with resolution as high as 50 m/px (if closest distance is around 10,000 km), and MVIC should obtain 4-color global dayside maps at 1.6 km resolution. LORRI and MVIC will attempt to overlap their respective coverage areas to form stereo pairs. LEISA will obtain hyperspectral near-infrared maps at 7 km/px globally and 0.6 km/pixel for selected areas. Meanwhile, Alice :owl: will characterize the atmosphere, both by emissions of atmospheric molecules (airglow), and by dimming of background stars as they pass behind Pluto (occultation).
A simulated view of New Horizons passing Pluto and Charon when it arrives in 2015.

During and after closest approach, SWAP and PEPSSI will sample the high atmosphere and its effects on the solar wind. VBSDC will search for dust, inferring meteoroid collision rates and any invisible rings. REX will perform active and passive radio science. Ground stations on Earth will transmit a powerful radio signal as New Horizons passes behind Pluto's disk, then emerges on the other side. The communications dish will measure the disappearance and reappearance of the signal. The results will resolve Pluto's diameter (by their timing) and atmospheric density and composition (by their weakening and strengthening pattern). (Alice :owl: can perform similar occultations, using sunlight instead of radio beacons.) Previous missions had the spacecraft transmit through the atmosphere, to Earth ("downlink"). Low power and extreme distance means New Horizons will be the first such "uplink" mission. Pluto's mass and mass distribution will be evaluated by their tug on the spacecraft. As the spacecraft speeds up and slows down, the radio signal will experience a Doppler shift. The Doppler shift will be measured by comparison with the ultrastable oscillator in the communications electronics.

Reflected sunlight from Charon will allow some imaging observations of the nightside. Backlighting by the Sun will highlight any rings or atmospheric hazes. REX will perform radiometry of the nightside.

After passing by Pluto, New Horizons will continue further into the Kuiper belt. Mission planners are now searching for one or more additional Kuiper belt objects (KBOs) on the order of 50–100 km (31–62 mi) in diameter for flybys similar to the spacecraft's Plutonian encounter. As maneuvering capability is limited, this phase of the mission is contingent on finding suitable KBOs close to New Horizons's flight path, ruling out any possibility for a planned flyby of Eris, a trans-Neptunian object comparable in size to Pluto.[27] The available region, being fairly close to the plane of the Milky Way and thus difficult to survey for dim objects, is one that has not been well-covered by previous KBO search efforts.>>
Last edited by neufer on Fri May 06, 2011 5:04 pm, edited 1 time in total.
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