Jan

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South Africa's powerful new telescope can detect "city killer" asteroids

The National Research Foundation's South African Astronomical Observatory (SAAO) in Sutherland in the Northern Cape now hosts one of four telescopes that form part of the Nasa-funded Atlas asteroid alert system.

Atlas, or Asteroid Terrestrial Impact Last Alert System, is specially designed to detect objects that approach very close to Earth — closer than the distance to the Moon, up to about 240,000 km away.
 
Point the thing to JHB CBD and Lootfreely House must surely ping it?
 
It's good news, and an interesting story, though the telescopes are relatively small:
The full ATLAS concept consists of eight 50-centimeter diameter f/2 Wright-Schmidt telescopes, spread over the globe for full-night-sky and 24h/24h coverage, and each fitted with a 110 Megapixel CCD array camera. The current system consists of four such telescopes, two operating 160 km apart on Haleakala and Mauna Loa in the Hawaiian Islands, ATLAS1 and ATLAS2, the third telescope at the South African Astronomical Observatory and a fourth in Chile. These telescopes are notable for their large 7.4° field of view — about 15 times the diameter of the full moon — of which their 10 500 × 10 500 CCD camera images the central 5.4° × 5.4°. This system can image the whole night sky visible from Hawaii with about 1000 separate telescope pointings. At 30 seconds per exposure plus 10 seconds for simultaneously reading out the camera and repointing the telescope, each ATLAS unit can therefore scan the whole visible sky a little over once each night, with a median completeness limit at apparent magnitude 19. Since the mission of the telescope is to identify moving objects, each telescope actually observes one quarter of the sky four times in a night at approximately 15-minute intervals. The four exposures allow to automatically link multiple observations of an asteroid into a preliminary orbit, with some robustness to the loss of one observation to overlap between the asteroid and a bright star, and to predict its approximate position on subsequent nights. Apparent magnitude 19 is classified as "respectably but not extremely faint", and is approximately 100 000 times too faint to be seen with a naked eye from a very dark location. It is equivalent to the light of a match flame in New York viewed from San Francisco. ATLAS therefore scans the visible sky in much less depth, but much more quickly, than larger surveying telescope arrays such as University of Hawaii's Pan-STARRS. Pan-STARRS goes approximately 100 times deeper, but needs weeks instead of half a night to scan the whole sky just once. This makes ATLAS better suited to finding small asteroids which can only be seen during the just few days that they brighten dramatically when they happen to pass very close to the Earth.
 
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