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TheThorn
2005-Feb-04, 01:52 AM
The radio telescope at Arecibo took radar images of 2004 MN4 on Jan 27, 29, and 30:

http://neo.jpl.nasa.gov/news/news149.html

The've improved the orbit enough to say that it will miss us on April 13, 2029 by about 22,000 miles, which puts it inside the geosynchronous satelite belt. It's about 360 meters across, so it will look magnitude 3 or so when it's passing by, but it will be moving VERY fast - 42 degrees per hour.

spacepunk
2005-Feb-04, 03:14 AM
Quoting from the article

Radar observations taken at the Arecibo Observatory in Puerto Rico on January 27, 29, and 30 have significantly improved our estimate for the orbit of asteroid 2004 MN4
This is a great way to locate NEO's much like radar is used to locate planes at an airport, but also detect hazardous asteroids in deep space with an ill trajectory towards Earth.

This same method was also used to detect Pioneer 10 or 11 when that craft was lost, and for a few others too if I remember correctly.

antoniseb
2005-Feb-04, 03:25 AM
Originally posted by spacepunk@Feb 4 2005, 03:14 AM
This same method was also used to detect Pioneer 10 or 11 when that craft was lost, and for a few others too
I doubt that. I think you are misremembering things.

wstevenbrown
2005-Feb-04, 01:38 PM
The first diagram shows the gravitational slingshot past Earth. The moon's orbit is shown, but not its relative position. Presumably it was in the path calculation? The article itself says blandly that there is no danger of the object striking the moon, but-- having the moon in the picture would have been considerate. S

antoniseb
2005-Feb-04, 02:15 PM
Originally posted by wstevenbrown@Feb 4 2005, 01:38 PM
having the moon in the picture would have been considerate.
I think the moon was there all along. You needed to look at the larger version of the first diagram:
http://neo.jpl.nasa.gov/images/2004mn4d4.gif
My question about the diagram about the moon is this.
Does this show the moon's position when the asteroid makes it's closest aproach to the Earth? If so, where will the moon be a day later when the asteroid makes its closest approach to the moon? I think the moon is moving away from the path of the asteroid in this diagram, but I am not certain.

wstevenbrown
2005-Feb-04, 04:07 PM
Depends which (unstated) pole of the Earth we're looking down on, doesn't it? For max clarity, identified moon positions for first lunar orbit crossing, closest approach to Earth, and second lunar orbit crossing. I share your cavil, but apologize to authors/journalists for my previous one-- I didn't realize there was an enlargemenrt option. S

TheThorn
2005-Feb-04, 07:40 PM
The other thing to consider, of course, is that space is 3-d, and that diagram is not. I'd expect that the asteroid will pass above or below the plane of the moon's orbit - it would be quite a co-incidence if it actually hit the plane of the orbit, and an even bigger one if the moon happened to be there at the time.

And, spacepunk, radar is a great way to get very precise location data for a known asteroid, which is what they did in this case, but it's a very poor way to locate NEW near earth asteroids, because the beam is very narrow, and radar echos get weaker as the 4th power of distance. Optical surveys can cover a lot of sky to a lot further distance, a lot cheaper which means that they are still the best way to find new asteroids.

Guest
2005-Feb-04, 10:23 PM
antoniseb @ Feb 4 2005, 03:25 AM

(spacepunk @ Feb 4 2005, 03:14 AM)
This same method was also used to detect Pioneer 10 or 11 when that craft was lost, and for a few others too
I doubt that. I think you are misremembering things.

What about the Clementine probe then? :P Hmmmmmmm ........ perhaps your memory isn't reliable either :lol: :lol: :lol:

Quoting from http://www.spacepub.com/users/data/projects/pro.htm


In an all to familiar story, Clementine was lost shortly after photographing the surface of the Moon due to a malfunction in one of it's thrusters and is now orbiting the Sun.