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Fraser
2005-Jun-10, 04:20 PM
SUMMARY: NASA's Deep Impact is now only a few weeks away from its target, Comet Tempel 1, which it's due to strike on July 4. During the morning of July 3, the spacecraft will deploy its 1 metre (39 inch) impactor which will then guide itself to collide with the comet. Deep Impact will fly 500 km (310 miles) below the comet and capture every moment of the collision with its instruments. The spacecraft will have 13 minutes to take pictures and transmit them back to Earth before it enters a hail of particles from the comet's nucleus.

View full article (http://www.universetoday.com/am/publish/deep_impact_nearing_target.html)

What do you think about this story? Post your comments below.

Guest_curious
2005-Jun-10, 05:54 PM
What does it mean for the flyby craft to be "below" the comet and impactor? Above and below
are not orbital mechanics concepts.

antoniseb
2005-Jun-10, 06:08 PM
Originally posted by Guest_curious@Jun 10 2005, 05:54 PM
What does it mean for the flyby craft to be "below" the comet and impactor? Above and below
are not orbital mechanics concepts.

The impactor will head into the comet and the flyby craft will pass approximately 500 kilometers (310 miles) below.

I'm not sure what the writer was thinking. The sentence probably should have been:
the flyby craft's nearest approach will be approximately 500 kilometers (310 miles) away.

Generally, Deep Impact is a fairly cheap, simple, but exciting mission. I'm looking forward to seeing the results.

om@umr.edu
2005-Jun-10, 06:29 PM
I agree, that sentence is unclear.

Let's hope there are no serious mistakes in the closing moments, like those that plagued the auto-parachute system that was designed to deploy as samples were returning from the Genesis mission.

"The autonav is like having a little astronaut on board," Grammier said. "It has to navigate and fire thrusters three times to steer the wine cask-sized impactor into the mountain-sized comet nucleus closing at 23,000 miles per hour."

This is an important mission.

I agree with the assessment by the Deep Impact P.I., Dr. Michael A'Hearn. "With the information we receive after the impact, it will be a whole new ballgame. We know so little about the structure of cometary nuclei that almost every moment we expect to learn something new."

With kind regards,

Oliver
http://www.umr.edu/~om

John L
2005-Jun-10, 07:48 PM
The spacecraft going below the comet is proabably either relative to the comet's orbital path or the ecliptic, with above being what we would call North and below being south - relative to Earth.

My name is on the disc attached to the impactor. I wonder if they made any provisions to try to help that disc survive the impact? I'd like to know that a billion years from now a freighter will stop off to fill its water tanks and find a little round disc with my name on it.

om@umr.edu
2005-Jun-11, 12:22 AM
Interesting, John L.

What is the impactor made of?

The comet is probably very friable, at least the outer layers, so survival of the impactor seems like a reasonable possibility.

Do you work at NASA’s Jet Propulsion Laboratory in Pasadena?

With kind regards,

Oliver
http://www.umr.edu/~om

alfchemist
2005-Jun-11, 12:02 PM
Does anybody have an idea if the impact will or will not alter, even very slightly, the comet's orbit/path?

aeolus
2005-Jun-11, 01:36 PM
Originally posted by alfchemist@Jun 11 2005, 12:02 PM
Does anybody have an idea if the impact will or will not alter, even very slightly, the comet's orbit/path?
The impact will alter the comet's orbit slightly. The comet currently comes as close as about 50 million kilometers from Earth at it's closest approach. This impact might allow it to approach closer in the future: by a few hundred metres. No worries.

Guest
2005-Jun-12, 09:37 PM
Here is an alternate theory on comets.
http://www.thunderbolts.info/tpod/2004/arc...ions-comets.htm (http://www.thunderbolts.info/tpod/2004/arch/041229predictions-comets.htm)
Keep this in mind when you see the results from Deep Impact.
If there is no icy core then the whole theory for comets needs to be revised.

antoniseb
2005-Jun-12, 09:44 PM
Originally posted by Guest@Jun 12 2005, 09:37 PM
Here is an alternate theory on comets.
Hi Guest,

There is a fair amount of discussion about this alternate theory in the "Alternate Theories" section of this forum in the "Electric Universe" thread. This idea is far enough from main stream astronomy that we'd prefer to limit discussion of it here in the Current Stories section of the forum.

Please note that some other alternative theories are making some interesting predictions about what the results of Deep Impact will be. Some or all of these alternative theories will need some revising after this mission, since they don't all agree on what the results should be. At most, one can be right.

Svemir
2005-Jun-13, 05:31 AM
The impactor is made of copper (AFIR), ca. 600 kg.
Some consequences:
1) If the comet desintegrate and reveal it's core that would mean Tunguska meteorite was an asteroide and not a comet, since eyewitnesses saw just one trace on the sky.
2) If the comet desintegrate in rather spectacular way, very easy, it will mean that it was not 1 object, but several loosely connected chunks, as someone suggests all comets are in nature (Levy-Shoemaker included)
3) If Deep Impact registers even a photon of x-rays from impact, we can expect 2000 more posts in EU thread

aeolus
2005-Jun-13, 02:17 PM
Originally posted by Svemir@Jun 13 2005, 05:31 AM
3) If Deep Impact registers even a photon of x-rays from impact, we can expect 2000 more posts in EU thread
Or maybe the deletion of the EU thread...and the creation of the EU forum??? :lol:

antoniseb
2005-Jun-13, 04:05 PM
Originally posted by aeolus@Jun 13 2005, 02:17 PM
Or maybe the deletion of the EU thread
For the record, some x-rays are to be expected if the comet nucleus is made largely of Carbon compounds. The hunk of copper will be hitting the object with enough kinetic energy to blast a sports-stadium sized crater (if the nucleus is made of porous ices).

So what do you think are the chances that there will be some triply ionized Carbon recombining with electrons during this blast? Yes these are very soft xrays, but they will be xrays. There are likely to be some harder xrays than that from the Oxygen and Silicon in the blast materials.

As it happens, there are xrays being given off by comets all the time from their interactions of coma material with the solar wind.
http://www-personal.engin.umich.edu/~mcombi/xray/

VanderL
2005-Jun-13, 06:34 PM
Hi Antoniseb,

Yes, X-rays are produced by comets, but the explanation that solar ions are responsible is contradicted by the finding of Deep Space 1 during it's flyby of Comet Borrelly. Ironically the action of ions "scavenging" electrons from the comet would constitute a current.

Here (http://www.holoscience.com/news/comet_borrelly.html) is the link (it's the bottom part of the page), if you want to move it to the EU thread I don't mind, but I felt it appropriate to post it here in reply to your post.

Cheers.

antoniseb
2005-Jun-13, 06:57 PM
Originally posted by VanderL@Jun 13 2005, 06:34 PM
if you want to move it to the EU thread I don't mind, but I felt it appropriate to post it here in reply to your post.
Yes, please move further discussion of this to the EU thread. I posted my post in part because there had been a succession of several EU related posts here in this thread.

VanderL
2005-Jun-13, 07:51 PM
I posted my post in part because there had been a succession of several EU related posts here in this thread.

Yeah, and some funny ones too! :D

Cheers.

dazza
2005-Jul-04, 07:50 AM
Bang on!

http://dazza101.blogspot.com/2005/07/deep-...hits-comet.html (http://dazza101.blogspot.com/2005/07/deep-impact-hits-comet.html)