Starship Asterisk*

http://antwrp.gsfc.nasa.gov/apod/ap060328.html

any scale to the width of the " picture " ??? like how long would it take to cross the frame ?

For the first ~3 months of the animation, there are 30+ objects in the picture at a time. Then the number of objects ramps down and for most of the second half of the year, there are less than 5 objects.

Any particular reason for this large disparity?

Anyone ever discuss a weakness of using apparent optical motion to identify NEOs?

If the initial apparition of a long-period or parabolic object was on a collision course, it would exhibit NO apparent motion and would not be detected until its change in apparent magnitude became obvious. (Anything not moving relative to the cockpit glass and getting larger is a bad thing)

Is anyone testing for non-stellar objects (ID spectrographically?) with no apparent motion and violet-shifted spectra? Once all the short-period NEOs have been catalogued, these will be the real impact threat.

Looking for better ideas.

Randall

That was my experience watching a rocket launch from Vandenberg, it was getting brighter and bigger and not really moving its position, and I thought it was headed straight for me. I did not know what I was seeing for over 10 seconds, and several ideas went by while I was 'deer in the headlights'. It wasn't till a minute later that I did know for certain what I had been seeing, by then it was all over.

There's no substitute for experience. Thanks Randall, I had not thought about (focused on) the 'not moving' aspect.

Something one mile in diameter will make one hellofa bang when it lands at 11 miles per second; and we have a hard time seeing things that small ten million kilometers away, or the time to look for them.

It's kind of a numbers game and we are counting on probabilities to save our collective asses, I presume.

This is similar to JohnD's post of busy solar system.
Orin

Hey, I sent my question to NASA and got an expert reply (quoted below) many thanks to Dr. Donald K. Yeomans, NASA/NEO program manager at JPL:

Long-period comets in the near-Earth space represent only 1% of the population of near-Earth objects. The other 99% are near-Earth asteroids. While comets do arrive at Earth with higher relative velocity, they are also far less dense so the energy at impact is not much larger than a similarly sized asteroid.

NASA's goal is to discover almost all of the Near-Earth Asteroids
(NEAs) well in advance of a potential threat. For long period comets (LPC), this is not possible of course but then they only represent 1% of the threat and NASA plans to address the issue of NEAs first and, when suitable technology is available, then focus upon the LPCs. The optimal discovery detector for LPCs would be a wide field optical or infrared search instrument in the asteroid belt.

As you say, once an object is close and on an Earth impacting trajectory, the motion is all along the line of sight rather than the plane of sky but there would be tell tale motion prior to the final approach (due to Earth's parallax) so there should be some time for risk reduction (e.g., evacuation of affected locations on Earth etc.).

Using Doppler observations of LPCs requires more light than a standard astrometric clear filter observation and would further increase the necessary brightness at which a LPC could be detected - thus reducing the warning time. As noted, the problem of LPCs will require substantially more resources for near-Earth asteroid/comet discovery than is currently available.

At least we know they have worked the problem.

Randall

and so this ends up locked. thanks orin