[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.