T
he pastel morning sky lights up,
and a few seconds later, a
deafening bang follows. It is
slightly past nine o’clock in the
morning on 15 February 2013,
when a some 20-m-long asteroid explodes in
the sky above the Russian city of Chelyabinsk
on the frontier between the Ural Mountains
and Siberia. The energy discharge injures
1,600 people, damages 3,600 buildings, and
activates car alarms.
The asteroid struck Earth without being
identified by one single telescope. The fear of
an unknown asteroid or comet measuring up to
several km one day striking one of the major
cities of the US have made the American space
agency NASA introduce a 7 stage strategy,
aiming to prepare scientists and authorities
for identifying and destroying threatening
asteroids and comets – and at worst
alleviating the consequences of an impact.EARTH CLOSE TO COLLISION THIS YEAR
NASA is continuously watching out for Near-
Earth Objects (NEOs) via telescopes on Earth
and in space. Whereas the vast majority of
very large asteroids with diameters of 1+ km
have been identified, scientists estimate that
about 300,000 unknown NEOs of 40+ m
exist, which could make up a threat.
The 37-m-long 2000 SG344 asteroid is
an example of how much damage even small
asteroids can cause. The asteroid is one of
those which are monitored by NASA,
because it might strike Earth. If that were to
happen one day, the force would be the
equivalent of about 70 Hiroshima bombs.
The effect of an impact depends on how the
asteroid explodes. The Chelyabinsk(^1) IDENTIFY AND MAP OUT ASTEROIDS
To spot asteroids and comets and determine their sizes,
make-up, and paths, new telescopes must be employed
on Earth and in space in the years to come to identify
yet unknown threats to Earth.
Telescopes, which capture visible
light, have difficulties distinguishing
between a small, light asteroid and a
large, dark one, because light surfaces
reflect more visible light than darks
ones. This is known as albedo. The
NEOCam telescope captures infrared
light, which we normally associate
with heat. Large objects emit more
heat radiation than small ones, and
so, the method is more accurate for
determining size. With an infrared
telescope, it is, moreover, possible to
spot an entirely dark asteroid.
Infrared light reveals size of asteroids
SMALL ASTEROID HUNTER
POWERED BY SUNLIGHT
2018 In 2018, when NASA launches
its new large Space Launch System
rocket, the small NEA Scout (Near-Earth
Asteroid Scout) satellite is included. The
14 kg satellite has a 86 m^2 solar sail,
which will take it close to asteroids by
means of the weak pressure of sunlight.
In this way, the satellite can photograph
them and record their paths.
HUGE DIGITAL CAMERA MAPS
OUT THE NIGHT SKY
2022 The LSST (Large Synoptic Survey
Telescope), built on a mountain peak in
Chile, will be the world's biggest digital
camera with a resolution of 3 GIGApixels.
Every night, the telescope will take 800+
photos of the sky to see how it changes.
NASA expects that over a period of 10 years,
the LSST will be able to spot 62 % of all
potentially hazardous asteroids of 140+ m.
HIGH
ALBEDO
(MUCH
LIGHT
IS
REFLECTED)
HIGH
ALBEDO
(MUCH
LIGHT
IS
REFLECTED)
INFRARED LIGHT
VISIBLE LIGHT
VISIBLE LIGHT VERSUS INFRARED LIGHT
LOW
ALBEDO
(LITTLE
LIGHT
IS
REFLECTED)
LOW
ALBEDO
(LITTLE
LIGHT
IS
REFLECTED)
Objects of different sizes
appear the same due to
different albedos.
The sizes of objects
appear correctly no
matter their albedos.
NASA
JPL-CALTECH/NASA
LARGE SYNOPTIC SURVEY TELESCOPE (LSST)
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