Yes as Michael Busch said, because it's small and came from the day side. We can't look with optical telescopes in that direction from the Earth.
There are many near Earth asteroids that spend most of their time inside of Earth's orbit between Earth and Venus. Others may be phased to spend most of their time on the other side of the sun right now. These are easy to miss because we haven't been searching for them for long.
And the smaller ones are only visible when fairly close to Earth. They are usually spotted only when they do close flybys of Earth. For instance right now there are probably is a temporary extra "moon" of the Earth about 1 meter in diameter in and many smaller ones, just here for a few months then the go away again Earth's Many Moons - Astrobiology Magazine - Claimed moons of Earth - temporary satellites - but we can't see them because our telescopes aren't sensitive enough. Further away then even a 10 meter or larger asteroid is invisible to us.
With a long enough observation time, like many decades, we'd spot them eventually from the Earth, as they would do close flybys of Earth from time to time - but we have only been looking for asteroids with these super sensitive full sky searches like Pan Starrs for a few years Pan-STARRS started operations in 2010.
As you can see from this plot, our search for near Earth asteroids started to really take off about 2000.
We have already mapped out all the asteroids of 10 kilometers or larger. out to the outer edge of the asteroid belt. We could be surprised by an asteroid of one kilometer in diameter in an unusual orbit, like the Halloween asteroid that was spotted with only three weeks notice. It did its last flyby in 1975 when we weren't doing these all sky searches for asteroids. ‘Spooky’: the 1,300ft-wide asteroid to hurtle close to Earth on Halloween
But we have found 90% of those also and expect to find 99% by the 2020s.
And - this search is just for the population of NEOs. We could be surprised by an object coming in from beyond Jupiter too, one in a Jupiter crossing orbit. But we'd have lots of notice of a really big 10 km sized or more one from out there, like years of notice.
Pan Starrs can detect asteroids of up to 300 meters in diameter to the outer edge of the asteroid belt. And 100 meters or larger in the inner asteroid belt.
That leaves the smaller ones closer to the sun, and those are harder to spot.
I think the most sensitive telesope to look for asteroids like the Chelyabinsk impactor proposed is the Sentinel telescope proposed by the private B612 foundation. It is designed and they reckon they could fly it by 2019 if they had the funding. But so far they've raised only a tenth of the funding by private donations that they hoped to get, so can't fly it.
Idea is that it would find nearly all potential impactors down to 40 meters diameter. And recently announced, that it should be able to spot them down to 20 meters diameter.
They originally hoped to launch it in 2017 to 2018 on a Falcon 9. And to find 90% of NEOs down to 140 meters within ten years and a significant proportion of all NEOs down to 20 meters.
The total cost is $450 million. Low enough so that an interested multibillionaire could fund the whole thing. And far less than sums that governments sign off for defence projects. E.g. the UK nuclear weapons carrying Trident submarines will cost our government $200 billion. For that much, you could have 200 of these Sentinel space telescopes.
They predict that Sentinel could find most of the smaller asteroids within six and a half years of the launch.
NASA was never going to fund it, just provide support. But it has dropped this support now because of the funding gap. NASA drops partnership with private asteroid hunt.
NASA might possibly fund the less capable Near-Earth Object Camera which will be positioned at the L1 position between Earth and sun instead of an orbit close to Venus. This will help with asteroids of 140 meters diameter or larger. It is competing with other non asteroid related projects, so I wouldn't pin our hopes on it quite yet. And though certainly a major step forward, it won't find the more numerous, and still dangerous, 100 meter diameter or smaller asteroids.
So, it's basically a matter of funding. So far nobody has ponied up the half billion dollars needed to spot these things well in advance. If we had Sentinel operating then we'd know about it many decades in advance.
Meanwhile, then the best we can do is to get early warning.
This is the graph of early warning times for ATLAS using random simulated asteroids
ATLAS - How Atlas works
So most 50 meter diameter asteroids are found at least 3 days in advance, and most 140 meter asteroids are found at least 10 days in advance. But still, a very few could slip through even on the day of impact.
At latitude 21 degrees North, a telescope at Hawaii can't spot anything that is within 21 degrees of the South pole, for instance, or in practice, a bit more than that. About a quarter of the Southern sky is invisible to it. It's got a permanent blind spot in the sky towards the South.
Also, though probably less important, it can only observe for less than half of the 24 hour day.
Also a quarter of the sky, close to the sun, is also out of reach. That's true for all of our terrestrial telescopes, that they can't observe close to the sun. So in total it can see about half of the sky.
As well as ATLAS, the ESA is currently exploring the idea of a network of these, low cost 1 meter telescopes, which together cover the entire night sky, and give three weeks warning for objects of 40 meters in diameter. It splits the images into 16 smaller sub images to expand the field of view, similar approach to a fly's compound eye.
ESA’s bug-eyed telescope to spot risky asteroids
As optical telescopes, they still couldn't observe in daytime, so there'd still be that area around the sun which can't be seen in night time conditions from anywhere on the Earth.
But it could make a big difference for the smaller ones from most directions, several weeks instead of a day or two if that. And having lots of telescopes like this spread out over the Earth at different latitudes gives you a wider spread of the sky to look at, so it could spot asteroids not currently visible from Hawaii. And for very close ones that slip through the net, then it could make a difference to be able to spot them right away when it is daytime in Hawaii.
Bug-eyed telescopes could search for threatening near-Earth objects - Sen.com
On asteroid detection generally, see my:
which I've made into a kindle book and available for free online:
Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them
There are many near Earth asteroids that spend most of their time inside of Earth's orbit between Earth and Venus. Others may be phased to spend most of their time on the other side of the sun right now. These are easy to miss because we haven't been searching for them for long.
And the smaller ones are only visible when fairly close to Earth. They are usually spotted only when they do close flybys of Earth. For instance right now there are probably is a temporary extra "moon" of the Earth about 1 meter in diameter in and many smaller ones, just here for a few months then the go away again Earth's Many Moons - Astrobiology Magazine - Claimed moons of Earth - temporary satellites - but we can't see them because our telescopes aren't sensitive enough. Further away then even a 10 meter or larger asteroid is invisible to us.
With a long enough observation time, like many decades, we'd spot them eventually from the Earth, as they would do close flybys of Earth from time to time - but we have only been looking for asteroids with these super sensitive full sky searches like Pan Starrs for a few years Pan-STARRS started operations in 2010.
As you can see from this plot, our search for near Earth asteroids started to really take off about 2000.
We have already mapped out all the asteroids of 10 kilometers or larger. out to the outer edge of the asteroid belt. We could be surprised by an asteroid of one kilometer in diameter in an unusual orbit, like the Halloween asteroid that was spotted with only three weeks notice. It did its last flyby in 1975 when we weren't doing these all sky searches for asteroids. ‘Spooky’: the 1,300ft-wide asteroid to hurtle close to Earth on Halloween
But we have found 90% of those also and expect to find 99% by the 2020s.
And - this search is just for the population of NEOs. We could be surprised by an object coming in from beyond Jupiter too, one in a Jupiter crossing orbit. But we'd have lots of notice of a really big 10 km sized or more one from out there, like years of notice.
Pan Starrs can detect asteroids of up to 300 meters in diameter to the outer edge of the asteroid belt. And 100 meters or larger in the inner asteroid belt.
That leaves the smaller ones closer to the sun, and those are harder to spot.
I think the most sensitive telesope to look for asteroids like the Chelyabinsk impactor proposed is the Sentinel telescope proposed by the private B612 foundation. It is designed and they reckon they could fly it by 2019 if they had the funding. But so far they've raised only a tenth of the funding by private donations that they hoped to get, so can't fly it.
Idea is that it would find nearly all potential impactors down to 40 meters diameter. And recently announced, that it should be able to spot them down to 20 meters diameter.
They originally hoped to launch it in 2017 to 2018 on a Falcon 9. And to find 90% of NEOs down to 140 meters within ten years and a significant proportion of all NEOs down to 20 meters.
The total cost is $450 million. Low enough so that an interested multibillionaire could fund the whole thing. And far less than sums that governments sign off for defence projects. E.g. the UK nuclear weapons carrying Trident submarines will cost our government $200 billion. For that much, you could have 200 of these Sentinel space telescopes.
They predict that Sentinel could find most of the smaller asteroids within six and a half years of the launch.
NASA was never going to fund it, just provide support. But it has dropped this support now because of the funding gap. NASA drops partnership with private asteroid hunt.
NASA might possibly fund the less capable Near-Earth Object Camera which will be positioned at the L1 position between Earth and sun instead of an orbit close to Venus. This will help with asteroids of 140 meters diameter or larger. It is competing with other non asteroid related projects, so I wouldn't pin our hopes on it quite yet. And though certainly a major step forward, it won't find the more numerous, and still dangerous, 100 meter diameter or smaller asteroids.
So, it's basically a matter of funding. So far nobody has ponied up the half billion dollars needed to spot these things well in advance. If we had Sentinel operating then we'd know about it many decades in advance.
Meanwhile, then the best we can do is to get early warning.
This is the graph of early warning times for ATLAS using random simulated asteroids
So most 50 meter diameter asteroids are found at least 3 days in advance, and most 140 meter asteroids are found at least 10 days in advance. But still, a very few could slip through even on the day of impact.
At latitude 21 degrees North, a telescope at Hawaii can't spot anything that is within 21 degrees of the South pole, for instance, or in practice, a bit more than that. About a quarter of the Southern sky is invisible to it. It's got a permanent blind spot in the sky towards the South.
Also, though probably less important, it can only observe for less than half of the 24 hour day.
Also a quarter of the sky, close to the sun, is also out of reach. That's true for all of our terrestrial telescopes, that they can't observe close to the sun. So in total it can see about half of the sky.
As well as ATLAS, the ESA is currently exploring the idea of a network of these, low cost 1 meter telescopes, which together cover the entire night sky, and give three weeks warning for objects of 40 meters in diameter. It splits the images into 16 smaller sub images to expand the field of view, similar approach to a fly's compound eye.
As optical telescopes, they still couldn't observe in daytime, so there'd still be that area around the sun which can't be seen in night time conditions from anywhere on the Earth.
But it could make a big difference for the smaller ones from most directions, several weeks instead of a day or two if that. And having lots of telescopes like this spread out over the Earth at different latitudes gives you a wider spread of the sky to look at, so it could spot asteroids not currently visible from Hawaii. And for very close ones that slip through the net, then it could make a difference to be able to spot them right away when it is daytime in Hawaii.
Bug-eyed telescopes could search for threatening near-Earth objects - Sen.com
On asteroid detection generally, see my:
Giant Asteroid Headed Your Way? - How We Can Detect And Deflect Them
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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