[X] My Assistant

[gndonald]

The most recent (Nov/Dec 2006) issue of 'Australian Sky & Telescope' has an article discussing the possible impact of the asteroid 'Apophis' in 2036. One thing mentioned in the article caught my eye.

This was that NASA had been ordered to plan a mission to asteroid launching sometime in 2013, with the intention of planting a radio tracking beacon on it, so that it's orbit could be plotted as accurately as possible.

Has anything official been released about this and does anyone have information on just what sort of a mission they are looking at. Are they just going to send a tracking beacon or are they considering getting some science out of this as well?

(I know that the Wikipedia article states that the risk is 'minimal' but I'm still interested in knowing what, if anything was (or still is) being planned.)

[climber]

gndonald,

Quite some infos there : http://www.planetary.org/programs/projects...is_competition/
TPS is involved there.

[Paolo]

gndonald,

Quite some infos there : http://www.planetary.org/programs/projects...is_competition/
TPS is involved there.

See also http://www.b612foundation.org/press/press.html

[tasp]

The laser ranging experiments done with the retroreflectors left by the Apollo and Lunakhod missions have been quite interesting and successful. We also have 30 years more experience in building more powerful lasers and telescopes.

Would it be worthwhile to put a retroreflector on Apophis? Granted, we couldn't track it all the way around the sun, but we might get some very precise measurements over a reasonable arc of its' orbit.

Might be useful in some affiliated research too, we would have optical and radio nav info to input into relativity confirmation experiments (we still do those, right?) and maybe gravity wave research, too.

[Comga]

Would it be worthwhile to put a retroreflector on Apophis?

Losses for retroreflectors go up as the distance to the fourth power. If Apophis were to come as close as 10^7 km, the returns would be 1/400 of those from the ALSEP retros. Even 30 years of progress wouldn't be enough. How close does it get to Earth before 2029?

Besides, those Apollo arrays were heavy. How would you land them on Apophis?

Being on the moon, the Apollo retros always pointed at the Earth. Can't guarantee that for Apophis, and retros have limited acceptance angles. Then there are velocity issues, which can be viewed as a case of special relativity. The light doesn't come back along the vector to the source if the relative velocities are sufficient, and even Earth orbital speeds meet that criterion. At best, this introduces another loss term.

I have actually flown retros in space. They are really great for the right applications. This is probably not one of them.

[SigurRosFan]

New article:

- Planetary Society Offers $50,000 Prize for Asteroid Tagging Designs

[Guest_PhilCo126_*]

Tagged or untagged, I guess astronomers all over the world will be ready to see this Asteroid passing near Earth in 2029

[Comga]

Tagged or untagged, I guess astronomers all over the world will be ready to see this Asteroid passing near Earth in 2029

By 2029 it will be too late do deal with Apophis easily. It will either go from Tortino (Danger to Earth) scale 1 to zero or >5. That's the point of getting a better handle on its orbit and makeup well before that date.

[nprev]

Actually, the current data indicates that the most risky encounters occur in 2036 & 2037:

http://neo.jpl.nasa.gov/risk/a99942.html

Good idea to keep an eye on it, but as time goes by the projected miss distances will in all probability increase. Anywhere within the diameter of the Earth is a pretty small target to hit at these scales with this much statistical variation... In fact, if worst came to worst, we could probably wing something of this size & in this orbital situation with a nuclear weapon or even a kinetic impact at short notice & impart enough momentum to prevent a direct collision (an atmospheric graze would be fine).

[Comga]

Actually, the current data indicates that the most risky encounters occur in 2036 & 2037:

Yes, but the effort to divert the asteroid goes up by several orders of magnitude after 2029. To cause a miss in 2036, you only have to shift the asteroid's trajectory by 320 meters at the 2029 Earth encounter, assuming near perfect trajectory knowledge and an aim point at the center of the Earth. This knowledge is the point of the beacon missions. After the encounter, the asteroid may need to be shifted by 3000 km!

[nprev]

I didn't mean to imply that a beacon mission shouldn't be flown; at the very least, the data acquired about the true orbital dynamics of such objects (to say nothing of very thoroughly reality-checking our modeling methods, esp. w/r/t large inputs like the Earth's actual influence on trajectory) would be invaluable. I merely meant to point out that the impact risk is still small, and in all probability will get smaller over time.

Frankly, this whole issue would be a lot less controversial if we had a more precise value of G as well as a more definitive (and predictible) model of the Earth's exosphere and of course a very precise estimate of the mass of Apophis. Those seem to be the most influental factors beyond traditional orbital computations in my estimation, and I still think the smart money's on a miss by a long shot...

[Thu]

I'm really interested in the competition and I sent a Notice of Intent email to Dr Bruce Betts of The Planetary Society this Monday but haven't got any feedback from him yet. The registration deadline March 1 is coming fast so I'm a little worried

Could anybody help me on this? I'm writing to him via the email address bruce.betts@planetary.org and I also wonder if it is correct or not?

Btw, is there anybody out there having an interest on the Apophis tracking competition?

Thanks,
Thu

[dilo]

Frankly, this whole issue would be a lot less controversial if we had a more precise value of G as well as a more definitive (and predictible) model of the Earth's exosphere and of course a very precise estimate of the mass of Apophis.

I'm not sure of this, IMHO.
In my understanding, what is used in purely gravitational calculations is the relative mass ratios (or the product Gm, which is well known for major solar systems members).
Abolute value of G becomes important when we have to take in account some non-gravitational effects, but I suspect that main error sources arises from other uncertains, like the ones you mentioned. Anyway, the non-linearities of such a system would makes very hard to predict an impact risk.
Let's consider also uncertain in the interplanetary medium and in the Earth exosphere density related to almost-unpredictible solar activity...

[ngunn]

Btw, is there anybody out there having an interest on the Apophis tracking competition?

I'm interested. I made a small donation to the prize fund.

[Pavel]

By 2029 it will be too late do deal with Apophis easily. It will either go from Tortino (Danger to Earth) scale 1 to zero or >5. That's the point of getting a better handle on its orbit and makeup well before that date.

It will go from Tortino to Tortissimo
Seriously, it's called Torino scale.

[tty]

an atmospheric graze would be fine

I'd rather not. It could break up and some of the pieces might impact. It might even go bang like the Tunguska body though that's unlikely (probably not enough volatiles). Also the IR radiation from an atmospheric graze is fierce. A small body like Apophis would not be too bad, but a graze from a kilometer-size object can incinerate half a continent.

[Thu]

Finally, I'm done!

Just submitted the Apophis mission proposal to The Planetary Society. Anybody has an interest can see my proposal from here http://rapidshare.com/files/52591111/Apoph...rsion_.pdf.html

Wish me luck

[nprev]

Congrats on your proposal, Thu! Unfortunately, I got kind of lost in the pay-me portion of your document hosting service; can you perhaps post a more direct link?

TTY: Do you have any data for the IR effects of a graze? I and many others experienced a very small one (many, many orders of magnitude smaller than Apophis) on Aug 10, 1972. There was no detectable heat, but one hell of a double sonic boom: http://www.youtube.com/watch?v=vBu-yUzWXqg

[Paolo]

Finally, I'm done!

Just submitted the Apophis mission proposal to The Planetary Society. Anybody has an interest can see my proposal from here http://rapidshare.com/files/52591111/Apoph...rsion_.pdf.html

Wish me luck

Great job! I had seen other proposals, but yours until now is the most complete and professional-looking!

[nprev]

Sorry, Thu; I was stuck in stupid mode all day yesterday. Got it downloaded, and it does indeed look terrific; you certainly did your research, and it's incredibly detailed. I hope that your proposal wins, you deserve it!!!

[Phil Stooke]

tty said: "Also the IR radiation from an atmospheric graze is fierce. A small body like Apophis would not be too bad, but a graze from a kilometer-size object can incinerate half a continent."


Can you put any numbers to that? I would think that the flyby would be brief enough that the problem is less severe than you suggest, but the numbers could prove me wrong (as usually happens).

Phil

[tty]

TTY: Do you have any data for the IR effects of a graze?

www.lpi.usra.edu/meetings/impact2000/pdf/3103.pdf


You have to consider that the stagnation temperature for a typical meteorite is actually higher than the the surface of the Sun. Try to visualize a bit of the sun about a kilometer across passing maybe 50 km overhead and staying in sight for perhaps 20 seconds....

[Thu]

Thank you nprev and Paolo for your praise. Initially I planned to design a very simple but a little "dumb" s/c that would carry a lot of chaff (as those used in many fighter aircrafts) and spray over Apophis. That would effectively "paint" the asteroid with radar reflecting material and make it more detectable with radar. But later with more research, this approach turned out to be totally wrong but I still kept the idea of designing the s/c small and simple, but not too dumb like before

[ngunn]

Thu, I enjoyed reading your proposal, which seems full of sensible ideas. Having made a small contribution to the Planetary Society's prize fund I am very interested in the progress of the project. I haven't heard much about how it's going so far. Perhaps Emily can tell us how many submissions have been received to date?

[nprev]

Initially I planned to design a very simple but a little "dump" s/c that would carry a lot of chaff (as those used in many fighter aircrafts) and spray over Apophis. That would effectively "paint" the asteroid with radar reflecting material and make it more detectable with radar.

Interesting idea, but you're right. Not only would that have been horrendously complex in terms of mechanics, but just getting stuff to stick on Apophis would be a major challenge...

Your ranging technique is sound. Thinking in terms of passive backups here (like those that might be desirable in the event of premature EOM), what if the vehicle bus was designed for the best possible radar reflectivity? I doubt if this could add enough to do better ground-based reads during periapsis passes (your LIDAR data was sobering indeed), but perhaps it's still worth a quick thought; maybe it would!

[elakdawalla]

Perhaps Emily can tell us how many submissions have been received to date?

I'm afraid I don't know the number any more exactly than "quite a few." I'll probably be the one posting the next project update, though, so I'll make sure to mention it here when that happens.

--Emily

[ngunn]

That would be great, thanks Emily. I'm glad quite a few people have risen to the challenge and I look forward to reading the update.

[Thu]

Thinking in terms of passive backups here (like those that might be desirable in the event of premature EOM), what if the vehicle bus was designed for the best possible radar reflectivity? I doubt if this could add enough to do better ground-based reads during periapsis passes (your LIDAR data was sobering indeed), but perhaps it's still worth a quick thought; maybe it would!

@nprev, since the idea is only good for periapsis passes which unfortunately happen only once in Jan-2013 during the period till 2017 mentioned in the mission design competition rules.

However, looking further I agree that this is a good idea and it worths a more detailed analysis if we are to send a s/c to Apophis.

[Thu]

A quick update for anybody interested in the Apophis mission design competition by TPS, the judging is going to be a little longer and the current plan calls for an announcement in January 2008. More detail here http://planetarydefense.blogspot.com/2007/...-planetary.html

By the way, based on my proposal Brian Jones from London, UK had made a beautiful animation of the ART s/c mission to Apophis which I uploaded to YouTube http://www.youtube.com/watch?v=mLp3JtrbJsM
May be next time I'll ask for his cooperation in visualizing space missions

[nprev]

Great video, Thu!!! You're rapidly becoming the center of a small-business version of NASA...keep up the terrific work! Will you also submit this vid as part of your proposal package to TPS? I would; it's most compelling.

[Guest_PhilCo126_*]

TPS talked about an announcement in January 2008... well it's February

[elakdawalla]

Sorry about the delay; we want to make sure the judges have the time they need to make good decisions. Expect an announcement this month.

--Emily

[elakdawalla]

Planetary Society Names Winners of $50,000 Asteroid Tagging Competition

[djellison]

Ahh - great reading. I'm particularly interested in the student efforts - lots of creativity in there!

Doug

(PS - I think the Houyi pdf link is wonky)

[nprev]

Absolutely. As an incipient geezer, it's all too easy to believe that the world is going to hell because the kids don't give a damn about anything but computer games & fashion...then you see something like this.

I am a little disappointed that Thu did not make the cut; thought his proposal was quite well done.

[elakdawalla]

(PS - I think the Houyi pdf link is wonky)

Thanks, fixed. --Emily

[As old as Voyage...]

Looking at the graphic on Emily's TPS blog, Apophis should pass relatively close to the Moon after its near miss of Earth. (Its orbit having been deflected by terrestrial gravity).

Does anyone know how close it could get to the Moon and if there is any chance of an impact?

[DDAVIS]

Does anyone know how close it could get to the Moon and if there is any chance of an impact?
[/quote]

I may be doing an animation of the asteroid encounter(s) in the months ahead, so any data on the path-time-approach distances within the Earth-Mon system would come in very handy.

Don

[Thu]

I am a little disappointed that Thu did not make the cut; thought his proposal was quite well done.

Thank you nprev for your interest on my proposal. In an email from Dr Bruce, the ART spacecraft mission made it to what might be called a semi-finalist level, which is not too bad for the first try at all

[nprev]

No, it's not at all, especially considering the competition you were up against! Congratulations for that, man, and glad to hear that you received some positive feedback from the judges!

[dilo]

Does anyone know how close it could get to the Moon and if there is any chance of an impact?

From the recent JPL article published on Icarus (a must-see masterpiece of planetary mechanics!) Apophis will closely approach Moon on 2029 Apr 14.60586 (almost 17 hours after Earth closest approach) at 0.000641 AU (about 94000 Km from surface), with no impact risk at this date (3-sigma uncertain is less than 4000 Km).

[akuo]

Strange news article about 99942 Apophis circulating now. This is what wikipedia quotes, though I read it initially from a local news source:
http://www.smh.com.au/articles/2008/04/16/1208025229770.html

A 13-year-old German schoolboy corrected NASA's estimates on the chances of an asteroid colliding with Earth after spotting the boffins had miscalculated, a German newspaper reported. Nico Marquardt used telescopic findings from the Institute of Astrophysics in Potsdam (AIP) to calculate that there was a one in 450 chance that the Apophis asteroid would collide with Earth, the Potsdamer Neuerster Nachrichten reported. ...
NASA had previously estimated the chances at only one in 45,000 but told its sister organisation, the European Space Agency (ESA), that the young whizz-kid had got it right.

All this sounds very unlikely to be true. Anybody know about the alleged confirmation by NASA or ESA? Anyway it should be the NEO people in Minor Planet Center doing these calculations, and not NASA.

[nprev]

Hmm...dunno, sounds screwed up to me. Looks like he added the probability of the asteroid smacking into "a satellite" during its C/A, and that's certainly not the same thing as an impact on the surface of the Earth (the effects of which the article goes on to describe in gory detail, so it's obvious that the author(s) are trying to, uh, how do I say it...scare the crap out of their readers).

Another weird thing is that the article mentions 40K sats as potential targets, and C/A for Apophis dips just inside the geosynchronous orbit radius; pretty sure we don't have 40K comsats or whatevers (plus associated junk of significant size) in the Clarke Belt. Let's see the math and the assumptions.

Hopefully the rest of the newsnet won't spin up over this...

[mps]

It's in the news in Estonia already... Why don't they talk about real space news? (yes, actually I know why, but it's still depressing)

[jamescanvin]

<Sigh> This story still seems to be popping up on news sites all over the place even though it's clearly rubbish. At least a corrected story is out there:

Schoolboy's asteroid-strike sums are wrong

I guess 'Kid proved NASA wrong' is a better headline than 'Kid gets sums wrong', why let the truth get in the way.

[nprev]

Looks like this story is dying on its own...no mention of it on the major US venues, nor Google news. Dare I say that common sense has prevailed, for once?

[ngunn]

Dare I say that common sense has prevailed, for once?

They must've started checking here first.

[nprev]

Oh, if only sense was that common, Nigel...

[Pavel]

NASA Statement on Student Asteroid Calculations
http://www.spaceref.com/news/viewpr.html?pid=25232

[nprev]

Thanks, Pavel.

Trying to figure out why the exceedingly remote possibility of a satellite collision was even a part of the problem here. Apophis wouldn't care; would not change its momentum in any significant way, certainly.

I get the uncomfortable feeling that this poor kid did something pretty ambitious & ingenious considering his age, and teachers and/or parents who don't fully understand his work (much less the issue) trumpeted it to the press...hope he's gonna be okay.

[dmuller]

Phew ... well we can trust NASA on that, can't we ... I hope it wasn't them who posted a picture of Phobos above Mars in the article, possibly suggesting that it was Phobos that has a 1 in 45,000 chance of hitting Earth

[Guest_PhilCo126_*]

So we had three winners in the Apophis tracking mission contest:
1. Foresight by US Space Engineering Inc
2. ? by Spanish Deimos Space
3. Apophis Explorer by British EADS AStrium

Any idea which name was given to the 2nd mission?

[elakdawalla]

A-Track. See
http://www.planetary.org/programs/projects...on/winners.html
Note the full proposals are also available linked to from that page in PDF format.

--Emily

[Guest_PhilCo126_*]

Thanks Emily, I surely hope that The Planetary Society will be able to raise the necessary funds in order to realize the winning proposal !

[elakdawalla]

I'm afraid that wasn't the point of this competition (and sadly we are not capable of raising the funds for even the winning proposal, which, though a bargain compared to many space missions, is still more than 30 times the price of the largest project we have ever funded). The point was to give NASA (or ESA) a kick in the pants and some ideas to help stimulate planning for such a mission.

--Emily

[Guest_PhilCo126_*]

O.K. anyway Apophis has already lost its "doomsday" scenario image, which doesn't mean it isn't an interesting object for scientific research

The future for Apophis on Friday, April 13 of 2029 includes an approach to Earth no closer than 29,470 km (18,300 miles, or 5.6 Earth radii from the center, or 4.6 Earth-radii from the surface) over the mid-Atlantic, appearing to the naked eye as a moderately bright point of light moving rapidly across the sky. Depending on its mechanical nature, it could experience shape or spin-state alteration due to tidal forces caused by Earth's gravity field.
30,000 km is within the distance of Earth's geosynchronous satellites. However, because Apophis will pass interior to the positions of these satellites at closest approach, in a plane inclined at 40 degrees to the Earth's equator and passing outside the equatorial geosynchronous zone when crossing the equatorial plane, it does not threaten the satellites in that heavily populated region.

Using criteria developed in this JPL research, new measurements possible in 2013 (if not 2011) will likely confirm that in 2036 Apophis will quietly pass more than 50 million km (31 million miles; 0.32 AU) from Earth on Easter Sunday of that year (April 13).

[ups]

Any new information on a possible mission to Apophis? Sounds like the project might be far on the back burner right now with all the budget issues.

[hendric]

Could Apophis be imaged by any of the geostationary satellites? It seems like it might be too fast to be captured, but hopefully someone will try!

[nprev]

I dunno, man. Most if not all spacecraft in GEO that have cameras are staring right down the nadir plane, so you'd have to do a major attitude shift to image this rock, which is an expenditure in propellant that the operators would definitely prefer to avoid. Station-keeping capability is one of the major operational lifetime limiting factors.

Maybe we'll get lucky & somebody's weather satellite will be on its last legs & in the right place during the C/A; they might be amenable to rolling the dice if for no other reason than the coolness factor!

[Paolo]

Russia may send spacecraft to knock away asteroid
I have mixed feelings about this. I think a deflection mission is really not needed now. A tagging mission would be far more useful, even if the threat from Apophis seems to be drastically reduced

[hendric]

While a tagging mission tells us where Apophis will be in the future, I think that information can be just as easily acquired by telescopes during the close approaches. We've already landed on two asteroids (Hayabusa and NEAR Shoemaker), so I'd consider a "tagging" mission to not gain us any ability or knowledge we don't already have. A redirection mission lets us get experience doing deflections, and gives us the opportunity to learn about the gotchyas before they happen during a critical encounter. For instance, I'm wondering how much a "gravity tractor beam" mission would need to worry about heat exposure from the asteroid, a la Chandrayaan-1, esp. since many Earth-crossers go significantly closer to the Sun. Or how hard would station-keeping be near a giant rotating potato? Etc.

[Holder of the Tw...]

Apophis is schedueled for additional radar ranging by Goldstone, and probably Aricebo, in January 2013. Everyone is keeping a close eye on it. The threat in 2029 is gone, and the one in 2036 is one chance in 250,000.

Sending a deflection mission out to it, at this time, is a very bad idea. We need to know more about the asteroid itself before you could even start to plan a mission. The potential for making the situation worse, instead of better, exists if you don't have this rock thoroughly studied and modeled.

[nprev]

I can see some rationale for this mission as a technology demonstrator. However, yeah, it'd be much more prudent to try this on a rock that's not an Earth-crosser (& make sure that the experiment didn't subsequently make the target a new Earth-crosser!)

[vjkane]

I can see some rationale for this mission as a technology demonstrator. However, yeah, it'd be much more prudent to try this on a rock that's not an Earth-crosser (& make sure that the experiment didn't subsequently make the target a new Earth-crosser!)

C'mon. You don't want experimental validation for whether an impacting asteroid could have killed off the dinosaurs?

[ElkGroveDan]

C'mon. You don't want experimental validation for whether an impacting asteroid could have killed off the dinosaurs?

There are no dinosaurs on the Moon, and look at all the evidence of impacts. That's good enough for me.

[vjkane]

There are no dinosaurs on the Moon, and look at all the evidence of impacts. That's good enough for me.

No one doubts that impacts happen, just whether the global effects are dino-strophic enough to kill off lots of species and families of species. Still lots of arguments on that one.

I sort of view it like the hole in the wing of Columbia. Until they did the test that proved that foam could bust a hole, there were lots of doubters despite the loss of the shuttle. So a good asteroid strike could settle this other debate. If there are any sentient survivors, of course.