That’s not as scary as it sounds. Deep Impact is a spacecraft that was so successful in its original mission to observe the impact of a 370 kilogram copper block into the comet Tempel 1. That was back in July of 2005. But the spacecraft itself was still operating, so NASA decided to extend its mission, now called EPOXI. It will fly by comet Hartley 2 in 2010, and to get there it needs a little boost. It’ll pass by the Earth tomorrow, on December 31, to steal give us a bit of its orbital energy as we circle the Sun. This will add take away energy from the spacecraft, changing its orbit it a bit (it’ll need two more flybys to put it on the right trajectory).
This is very cool, and lots of people are looking for the tiny spacecraft as it approaches us. It’s faint; at magnitude 20 it’s about 0.000001 as bright as the faintest star you can see with your eyes, so you’ll need a big ‘scope! But it helps to have observatories look, because they can confirm the trajectory of the spacecraft and make sure everything is on track.
Tomorrow I expect some images of the little probe will be online. Stay Tuned.
Tip o’ the Whipple Shield to Emily!
Here are some other Bad Astronomy posts about comet Hartley 2. Use the thumbnails and arrows to browse, and click on the images to go through to the posts with more details and descriptions.
December 30th, 2007 at 1:45 pm
Dangit, what are we going to do to replenish that orbital energy? We’re going to have environmental chaos! Continents will move, volcanoes erupt, earthquakes will happen, tsunamis, global warming… er… oops, we’re having those problems already. Sorry.
December 30th, 2007 at 1:47 pm
EPOXI?
Think that name’ll stick?
J/P=?
December 30th, 2007 at 1:57 pm
Wait! Won’t that energy EPOXI picks up, slow the earth down? Yes, I predict disasters. Tomorrow there will undoubtedly be car accidents, somewhere on Earth. Many people will get drunk because of this event. A giant mirror ball will descend in Times Square. Dick Clark will make an appearance. This will prove I am a psychic! James Randi, prepare to lose a million bucks! Remember you all heard it first right here. These are my predictions for tomorrow!
BTW, my daughters name is somewhere on that ship. They had an email campaign where people could send in their names and have them added to the spacecraft.
December 30th, 2007 at 2:16 pm
Yeaaah! Math! Lots and lots of math!
Really man… It’s always baffled me how those folks can even come close to figuring out how to get things like this little gizmo from one place to another using things like orbital influence (or whatever you call it).
I suppose I’m just guilty of watching too many science fiction movies. I want big, honkin’ engines, and a straight line to Hartley 2 in a couple of minutes.
All this little monkeying around with absolutely no margin of error is impressive, and way, way beyond anything I’m capable of doing, but still… Flames! Straight line! Much easier.
And lasers. Just in case Hartley 2 is a little shady.
What? A guy can dream.
December 30th, 2007 at 2:36 pm
“Wait! Won’t that energy EPOXI picks up, slow the earth down? Yes, I predict disasters. Tomorrow there will undoubtedly be car accidents, somewhere on Earth. Many people will get drunk because of this event. A giant mirror ball will descend in Times Square. Dick Clark will make an appearance. This will prove I am a psychic! James Randi, prepare to lose a million bucks! Remember you all heard it first right here. These are my predictions for tomorrow!”
Deep Impact 2?
December 30th, 2007 at 3:21 pm
Did NASA ask me if I wanted the planet slowed down? They are using my tax dollars after all and I think I should get a say.
December 30th, 2007 at 3:41 pm
Psst, John, nah, it’s New Years Eve, wink, wink, nudge nudge… don’t tell anyone though and I’ll give you a 1% cut of the million.
December 30th, 2007 at 3:43 pm
Hey, won’t this slowing down, slightly decrease the force of gravity, therefore making me lighter? Well, who needs diets.
December 30th, 2007 at 4:19 pm
“Psst, John, nah, it’s New Years Eve, wink, wink, nudge nudge… don’t tell anyone though and I’ll give you a 1% cut of the million.”
What million?
December 30th, 2007 at 4:44 pm
“This is very cool.”
Totally. Way.
December 30th, 2007 at 4:55 pm
John, the million bucks James Randi is offering to anyone that can prove they have psychic powers. See, the way I figure it, all my predictions will come true tomorrow, therefore, I’m rich! Shhhhhhh! Don’t tell anyone!
December 30th, 2007 at 4:59 pm
I had to do it…
December 30th, 2007 at 5:00 pm
Aw, blog doesn’t like img tags. So click here.
December 30th, 2007 at 5:11 pm
My back-of-the-napkin calculation indicates about an 8′-10′ telescope and good conditions would be required to see it… a bit beyond my little 8″ Celestron.
I wonder if any observatories will be having a public visit night
December 30th, 2007 at 5:39 pm
Can anyone tell me why they used a copper slug to smash into Tempel 1, as opposed to some other material?
BTW: I, too, stand in awe of the folks who can coordinate the orbital gymnastics needed to get extra use out of probes like this.
December 30th, 2007 at 5:46 pm
“John, the million bucks James Randi is offering to anyone that can prove they have psychic powers. See, the way I figure it, all my predictions will come true tomorrow, therefore, I’m rich! Shhhhhhh! Don’t tell anyone!”
I know, I was being sly and incognito.
December 30th, 2007 at 7:18 pm
Michael Lonergan says: “BTW, my daughters name is somewhere on that ship. They had an email campaign where people could send in their names and have them added to the spacecraft.”
Are you sure you’re not thinking of “Dawn”? I was part of that campaign.
- Jack
December 30th, 2007 at 7:23 pm
Shoeshine Boy says: “Can anyone tell me why they used a copper slug to smash into Tempel 1, as opposed to some other material?”
I’m not sure, but I can make an educated guess.
Copper is really dense (denser than steel) so you can get a lot of mass without taking up too much room. Also, it can be made very pure (and thanks to the semiconductor industry, it doesn’t even cost too much for that purity). Also too, it’s a material not likely to be found in a comet nucleus, so they can easily subtract the spectral lines for copper from the resulting flash to figure out what the rest of it is.
- Jack
December 30th, 2007 at 7:43 pm
I thing they attached them to the impactor on the Deep Impact. I know they’ve done it to several missions.
December 30th, 2007 at 7:45 pm
John, that’s okay, I think the secret is safe.
December 31st, 2007 at 12:46 am
EPOXI To Earth: I iz stealin’ ur orbital enurgee
December 31st, 2007 at 1:00 am
But, Deep Impact isn’t going too steal Earth’s orbital energy, it’s going from a slightly higher orbit to a lower orbit, so it’s giving it’s orbital energy to earth.
And yes Squid, they said on the EPOXI site that on perigee it will be visible with an 8” telescope from northern Australia and southeast Asia.
December 31st, 2007 at 7:24 am
Must be brighter than mag 20 when it comes by then. Of course, I doubt I’ll be going to Australia today
December 31st, 2007 at 7:54 am
Celestial mechanics is utterly cool. Of course, you need to know vector math and matrices to actually do it.
Doesn’t whether the Earth gain or lose orbital energy depend on how the flyby goes? I know that at least one astronomer has seriously proposed extending the Earth’s lifetime by using comet bypasses to move it outward over millions of years. Does that mean it would be gaining orbital energy, or losing it? Orbital velocity would be slower, so less kinetic energy, but it would be further from the sun, so more potential energy. Must think about this. I should sit down and do the math. Let me see, can’t do Ep = m g h because solar g isn’t constant over differences of AUs…
December 31st, 2007 at 9:19 am
*PHIL*
SPAM ALERT
The comment from Ereksiyon (two or three comments before this one) is SPAM.
You can delete this one too, if you want.
-Dave
December 31st, 2007 at 3:54 pm
Shoeshineboy, Jack… good guess Jack!
The Deep Impact website had an extensive set of FAQs which included that very question…
http://deepimpact.umd.edu/faq2.html
We are working on the EPOXI FAQs as well…
http://epoxi.umd.edu/8faqs/index.shtml
Elizabeth
EPOXI webmaster
December 31st, 2007 at 6:11 pm
Elizabeth says: “Shoeshineboy, Jack… good guess Jack!”
Wow, I got one right? Cool.
I looked at some of your FAQ’s. With the beryllium added to the copper, it’s the same mix as the Mark 3 reentry body heat shield used on the Poseidon missile.
Also, I love the term “Whipple Shield.” These go back at least to 1951 when he working with von Braun and Ley on their spacecraft concepts for the famous “Colliers” series. He proposed a thin (2 to 3 mm) aluminum shield spaced a few cm off of the surface it was protecting. Any impactor that didn’t just vaporize on the surface would have its energy greatly spread out by having a large number of secondary particles generated, which the lower surface could deal with. This is the basic concept behind segmented armor.
- Jack