Why 140 m,
I wonderd. In El Reg units this is exactly 1,000 linguini. Coincidence?
Criticised in 2014 for lax control over how it spent its asteroid-detection dollars, NASA has formalised its response, announcing last week the launch of a Planetary Defense Coordination Office. The 2014 audit (PDF) said NASA's asteroid-detection work was “a loosely structured conglomerate of research activities that are not …
Coincidence? I think not!
The limit is really in terms of apparent brightness (magnitude) rather than diameter. You can measure the former quite easily, but the latter is more of a derived quantity. You make an estimate as to how much light the object reflects (its albedo); it could be small and shiny, or huge and very dark (a Stealth asteroid). Saturn's moon Enceladus, for example, reflects about 100% of the light hitting it (it's icy). The moon is somewhere around 7%.
Based on the objects where we _do_ know both how bright they are and how big they are, it looks as if most of these rocks are pretty dark, about 4% IIRC. The folks who came up with that 140 meter limit basically took the brightness limit that was practical to reach, fed it back through the formula with an assumed albedo, and got 140 meters. But be warned: when you're told an asteroid is X meters or km across, there's a _big_ uncertainty in that number (unless the diameter has been measured via other methods: measuring how much infrared radiation it puts out, or seeing it occult a star and timing how long the occultation lasted.)
Yah, yah. them impacts happened a zillion years ago and this shite is all a smokescreen to take the air out of global warming except for a couple of irritating facts: Tunguska 1907, Younger Dryas Event 10,000BC that pretty much wiped out all life on North America and ended the Ice Age thaw for a couple thousand years. Bunk you say? Smack your lazy mouse awake on the below hyper informative links:
The cost of finding one will increase as more and more are discovered and fewer undiscovered ones remain. The relationship will be approximately logarithmic, hence it will be possible to extrapolate both the slope and the total number from the published discoveries and annual cost.
From personal observations of bureaucracies I'd expect the 90% level to be reached when there has been a further increase in costs of somewhere between 20- and 200-fold, though there might be attempts to fudge the lower limit on size before this so as to increase the total number.
We've found 90% of them when each time a "new" object comes into view, we're able to link it to one that's been found before.
The example I've seen given for this is population sampling of fish in a pond. You catch fish, tag them, and throw them back. When (say) 5% of the fish you catch already have tags, multiply the number of tags by 20, and you have a decent idea of how many fish are in the pond. Things are not quite so simple -- perhaps you have a few fish that really like to take your bait, and scads more lurk at the bottom of the pond -- but that's the basic idea.
With asteroids, there are similar complications. Some are in longer-period orbits and don't pass us all that often. Others may pass us at angles that make them tougher to detect. The folks doing asteroid population analysis do a decent job of analyzing and correcting for these biases, but it would be fair to say that completion will be "90%-ish" rather than "90%".
Planetary Defense Coordination Office? They weren't even trying. With that expanded budget the first thing they should have done was hire a decent PR company for some nomenclature-related brainstorming.
Regarding other aspects of this news I'll wait to hear what Tha Trumpinator thinks about it.
There should be a total and complete shutdown of meteors entering the united states...
Until we are able to determine and understand this problem and the dangerous threat it poses, our country cannot be the victims of horrendous attacks by big icy rocks that don't believe in anything and have no sense of reason or respect for human life.
I think they should adopt a sliding scale of objects which they don't find
more than not harmless
definitely not harmless
should be noticed
definitely should be noticed
how on earth did you miss this !!!
just as well it missed us
perhaps it is true, that ignorance is bliss
"For some reason I'm less upset about NASA using / wasting tax dollars than the rest of DC's brain farts."
I agree. Paying scientists and engineers to "waste" time and "play" with their toys is far more likely to produce something useful than paying
wankers politicians to play with their own toys.