Deep Impact

[bmpbmp]

Hi All,

I have some questions about deep impact.

1- How does NASA really know what the comet is made out of?

2- How does NASA really know the effects of what the impact will cause?

3- How big is the Comet and How big is the probe?
(Space.com references it as comparing a washing machine hit manhatten. Now either it's a big washing machine or manhatten shrunk I think)

Thanks

[A Thousand Pardons]

1- How does NASA really know what the comet is made out of?

2- How does NASA really know the effects of what the impact will cause?

If they really knew the answers, there would be no reason to do the test. They do have reasonable ideas, based upon other pieces of information.

[bmpbmp]

Exactly my point, for all we know the comet could 3explode into 1000 peices> Since they don't know what it's made of and the effect of impact.

[bmpbmp]

Exactly my point, for all we know the comet could explode into 1000 pieces. Since they don't know what it's made of and the effect of impact.

[NEOWatcher]

Exactly my point, for all we know the comet could explode into 1000 pieces. Since they don't know what it's made of and the effect of impact.

It seems like this topic has been clearly covered here, with plenty links to other information. Like...
http://www.badastronomy.com/phpBB/viewtopic.php?t=22578
http://www.badastronomy.com/phpBB/viewtopic.php?t=22465
http://www.badastronomy.com/phpBB/viewtopic.php?t=21571
http://www.badastronomy.com/phpBB/viewtopic.php?t=22461
To give you the benefit of the doubt... Is there something that you're not understanding from the discusions?

[Cl1mh4224rd]

Its size is believed to be 14 by 4 kilometers (8.7 by 2.5 miles) based on measurements taken by the Hubble Space Telescope in visible light and the Spitzer Space Telescope in infrared.

(Source: 9P/Tempel 1)

I can't find dimensions for the impactor, but it weights about 370kg (815 lbs.).

[A Thousand Pardons]

Manhattan is probably longer than that, but a lot narrower. Maybe it averages out. Maybe it depends on how dense Manhattan is.

[Archer17]

There's some info here regarding the impactor. There is no danger to Earth from this mission.

I've heard the Manhattan/washing machine or mosquito-747 analogy used to put the sizes of the impactor/comet into perspective bmpbmp. The impactor is only 1 meter in diameter. Here's two more sites that talk about this mission:

Tempel 1 facts

NASA site on Deep Impact

[Tassel]

Manhattan is probably longer than that, but a lot narrower.

It's close: Manhattan Island is 13 miles long and 2.3 miles wide at its widest point.

[jfribrg]

Exactly my point, for all we know the comet could explode into 1000 pieces. Since they don't know what it's made of and the effect of impact.

Assume for the moment that it does explode into 1000 pieces. All of these pieces would continue to orbit the sun along the same path that it does now. The impactor simply doesn't have nearly enough energy to change the direction of any sizeable chunk of the comet. Maybe some tiny rocks will change direction, but these pose no risk to Earth. Also remember that Venus is closer to Earth than the comet is. It is very far away is is guarenteed to stay that way.

One final comment is that the coma of the comet (the fuzzy part around the nucleus) already contains thousands of tiny comet chunks along with water and other gases. A few thousand more chunks doesn't change things at all.

Just get out there and enjoy the heavens instead of worrying about them.

[bmpbmp]

Yes but the actual impactor itself. How big is it and how much does it weigh.

What chemicals are on board it.

Also you said it's further than venus then how can they be so sure they will actually hit it

[Archer17]

Read my links bmpbmp?

[Musashi]

Also you said it's further than venus then how can they be so sure they will actually hit it

Science.

[ToSeek]

Washing machine v. Manhattan is not an analogy; that's a good approximation of the actual sizes of the probe and of the comet.

[ToSeek]

Cosmic Crash Won’t Destroy Comet or Earth

The event could be visible from backyards. But for some, the novel space shot conjures visions of comet chunks careening into Earth. Is there any chance that Deep Impact will result in icy lumps of the comet splitting off, placing our planet in danger?

Put your crash helmets back in the closest and get some sleep.

[Nergal]

Someone already covered the size of the comet, so...

Yes but the actual impactor itself. How big is it and how much does it weigh.

From Archer17's link:

Spacecraft mass:
Total: 1020 kg
Flyby Spacecraft: 515 kg
Instruments: 90 kg
Fuel: 86 kg
Impactor: 364 kg (49% copper, 24% aluminum)
Impactor fuel: 8 kg
Spacecraft size:
Body: approximately 3.2m (126") long, 1.7m (68") wide, and 2.3m (92") high
Impactor: 1m diameter
Solar panels: about 2.8m square
High gain antenna: 1m diameter

What chemicals are on board it.

Also from Archer17's link:

Impactor: 364 kg (49% copper, 24% aluminum)
Impactor fuel: 8 kg

Also you said it's further than venus then how can they be so sure they will actually hit it

There's always a chance it could miss...however I'm not betting on it.

[Archer17]

Washing machine v. Manhattan is not an analogy; that's a good approximation of the actual sizes of the probe and of the comet.

I heard coffee table and 1/2 the size of Manhattan.

[Hamlet]

Also you said it's further than venus then how can they be so sure they will actually hit it

They continually monitor the spacecrafts trajectory and make adjustments when needed.

From here:

Spacecraft optical navigation and conventional ground-based navigation will facilitate maneuvering the flyby spacecraft as close as possible to the collision course with comet Tempel 1.

During the last 24 hours before collision the impactor is on its own but it also has navigation ability and thrusters to make small course corrections.

From here:

Targeting and hitting the comet in a lit area is one of the mission's greatest challenges since the impactor will be traveling at 10 km per second and it must hit an area less than 6 km (3.7 miles) in diameter from about 864,000 km (536,865 miles) away. To accomplish this feat, the impactor uses a high-precision star tracker, the Impactor Target Sensor (ITS), and Auto-Navigation algorithms (developed by Jet Propulsion Laboratory for the DS-1 mission) to guide it to the target. Minor trajectory corrections and attitude control are available by using the impactor's small hydrazine propulsion system.

There are no guarantees, but it's not exactly "fire and forget".

[PatKelley]

Early on in the project, they released a simulation program that has the course-correction algorithms that keep the projectile on target--- it should be a neat view if they get transmitted! The projectile, based on that simulation, will probably make several hundred small course corrections to keep it on trajectory, as it uses navigation similar to the "star finding" navigation to keep the camera dead center of the target, and fires boosters if there is too much of a drift.

[Peter B]

Hi All,

*waves*

Hi bmpbmp.

I have some questions about deep impact.

1- How does NASA really know what the comet is made out of?

Well, it's not just NASA - astronomers around the world have a theory on the composition of comets - they're generally referred to as "dirty snowballs." That is, they consist mostly of water ice, with dusty impurities.

How do we know? There's an instrument called a spectroscope which can be used to determine the composition of objects which shine (like stars) or reflect light (like comets). The spectroscope produces an image of the colours of the rainbow, but with occasional black lines through the rainbow. These lines correspond to different elements. By comparing the lines with records, we can work out which elements are present in the object we're looking at. In the case of comets, they contain lots of hydrogen and oxygen, which are the constituents of water.

2- How does NASA really know the effects of what the impact will cause?

We know the comet's orbit. We know roughly how large it is. Because we know it's mostly water ice, we know roughly what it weighs (all right, we roughly know its mass). We can then calculate roughly what the effect of the impact will be. Even though it's only a rough calculation, even the wildest estimates fall *far* short of the comet being shattered altogether.

3- How big is the Comet and How big is the probe?
(Space.com references it as comparing a washing machine hit manhatten. Now either it's a big washing machine or manhatten shrunk I think)

Thanks

Why do you say that? As others have said, the comet is, what, about 14 km long and 4 km wide. That's about the size of Manhattan, isn't it? And the impactor is a roughly cube-shaped object about 1 metre on a side. That's about the size of a washing machine, isn't it?

(Edited to add) Oh Good Lord, you've looked at the picture in the Space.com article and saw the impactor was the same size as the comet, haven't you! [-X You *do* realise that the for the purposes of the picture, we're very close to the impactor and a long way away from the comet.

[mickal555]

We better not let bmpbmp see this link:
http://www.badastronomy.com/phpBB/viewtopic.php?t=22578

[collegeguy]

We better not let bmpbmp see this link:
http://www.badastronomy.com/phpBB/viewtopic.php?t=22578

That's funny. Hope Zarkov doesn't see it though. Or he will start to claim that he was right all along and the comet can be diverted to earth.

[bmpbmp]

Anyone know what caused this

http://www.nasa.gov/mpg/119586main_m...rst_lin_x3.mpg

[R.A.F.]

Anyone know what caused this.

Archer linked to the NASA site on Deep Impact and if you go to the "related story", you'll see that the outburst was simply a pocket of ice sublimating...a completely natural occurrence.

[Maksutov]

Face it, bmpbmp, it's going to be the end of the world as we know it.* I hope you've made the necessary preparations. You know what the fate of the unprepared typically is, right?

Now is the time for everyone to remember the world as it is, and soon, as it once was, before the impact. Ah, such simple times those were. How little we appreciated what we had.

And we thought of comets as pretty-tailed things up there in the sky, having no idea that...well, it's too late now.

Why does mankind always want to go where it shouldn't and try to comprehend things it was never meant to know?

This would be a better world for children if the parents had to eat spinach.

The gods look down and laugh...
























*The world as we know it being that which doesn't know much about the interior of comets. We have a pretty good idea of what the surface composition is, but until now we've not had the opportunity to get in deep, so to speak. Once Deep Impact does its job, we'll have much better information about the composition of cometary interiors. Such new knowledge will mean our world will have changed in its understanding of comets.

[bmpbmp]

What if the comment was actually made of anti-matter what would be the outcome.

[mickal555]

The statement would be in for it.

[bmpbmp]

What do you mean Mick

[mickal555]

nothing....


If the comet was made out of antimatter- we would know about it.

Any tiny fragment that smashed into it would create heaps more energy than a H-bomb. It would turn completly into energy. No- it ain't made of anti-matter. Bit of a shame really....

[bmpbmp]

I read alot of websites stating that it could be that comets are anti-matter. Is that a proven fact or has it been proven against.