SPACE DEBRIS!
By: Haripriya J
Pollution
is the most adverse effect which is caused by humans to nature. When we talk
about pollution usually, we think about various kinds such as air pollution,
water pollution, and soil pollution. Along with these we also talk about noise
pollution, radioactive pollution, and light pollution. Our major focus in on
those adverse conditions which we feel only on earth. There are various cases
where we could not guess where all we have done pollution. We never thought
even we can pollute space also! Yes, we have polluted the space around the earth
too.
How it is caused?
Space
is polluted majorly by space debris i.e. the artificial satellite which we have
launched to know about our Earth.
First,
we will know about artificial satellites.
We
have come across the moon, the natural satellite of the earth. Artificial
satellites are those satellites that are man-made. A satellite is an object that orbits another object. Most man-made satellites also orbit the Earth, but
some orbit other planets, such as Saturn, Venus or Mars, or the moon. Satellites are used for many purposes such as Scientific Investigation, Earth observation -
including weather forecasting and tracking storms and pollution, Communications -
including satellite television and telephone calls, Navigation -
including the Global Positioning System (GPS), Military - including reconnaissance photography and communications (nuclear weapons are not allowed
in space), etc., The first satellite,
Sputnik 1, was put into orbit around Earth was launched by
Soviet Union. There are approximately 1,886 artificial satellites orbiting
the Earth.
They are as:
A
geostationary orbit often referred to as a GEO orbit, circles the Earth above
the equator from west to east at a height of 36 000 km. As it follows the
Earth’s rotation, which takes 23 hours 56 minutes and 4 seconds, satellites in
a GEO orbit appear to be ‘stationary’ over a fixed position. Their speed is
about 3 km per second.
Geostationary orbit
As
satellites in geostationary orbit continuously cover a large portion of the
Earth, this makes it an ideal orbit for telecommunications or for monitoring
continent-wide weather patterns and environmental conditions. It also decreases
costs as ground stations do not need to track the satellite. A constellation of
three equally spaced satellites can provide full coverage of the Earth, except
for the Polar Regions.
Geostationary transfer orbit
This
is an elliptical Earth orbit used to transfer a spacecraft from a low altitude
orbit or flight trajectory to geostationary orbit. The apogee is at 36 000 km.
When a spacecraft reaches this point, its apogee kick motor is fired to inject
it into geostationary orbit.
Low Earth Orbits
A
low Earth orbit is normally at an altitude of less than 1000 km and could be as
low as 160 km above the Earth. Satellites in this circular orbit travel at a
speed of around 7.8 km per second. At this speed, a satellite takes
approximately 90 minutes to circle the Earth.
In
general, these orbits are used for remote sensing, military purposes and for
human spaceflight as they offer close proximity to the Earth’s surface for
imaging and the short orbital periods allow for rapid revisits. The
International Space Station is in low Earth orbit.
Medium-low earth
orbits
This
orbit takes place at an altitude of around 1000 km and is particularly suited
for constellations of satellites mainly used for telecommunications. A
satellite in this orbit travels at approximately 7.3 km per second.
Polar orbits
As
the name suggests, polar orbits pass over the Earth’s Polar Regions from north
to south. The orbital track of the satellite does not have to cross the poles
exactly for an orbit to be called polar, an orbit which passes within 20 to 30
degrees of the poles is still classed as a polar orbit.
These
orbits mainly take place at low altitudes of between 200 to 1000 km. Satellites
in polar orbit look down on the Earth’s entire surface and can pass over the
North and South Poles several times a day.
Polar
orbits are used for reconnaissance and Earth observation. If a satellite is in a
polar orbit at an altitude of 800 km, it will be traveling at a speed of
approximately 7.5 km per second.
Sun-synchronous
orbit
These
are polar orbits that are synchronous with the Sun. A satellite in a sun-synchronous
orbit would usually be at an altitude between 600 and 800 km. Generally, these
orbits are used for Earth observation, solar study, weather forecasting, and
reconnaissance, as ground observation is improved if the surface is always
illuminated by the Sun at the same angle when viewed from the satellite.
We, humans, are
always curious to know more things about Earth and other planets. So, we launch
more satellites. The Sun is the main energy source for satellites, which is
why all satellites have solar panel arrays mounted on them.
Each array contains thousands of small solar cells which are made of silicon –
a material that allows sunlight to be turned into electrical current.
What happens to the launched
satellite which is not working?
Satellites which we launch has a time
limit, they will be in working condition for some time. After it stops working,
it forms debris in space which is known as Space debris.
This material can be as large as a discarded
rocket stage or as
small as a microscopic
chip of paint. Much of the debris is
in low Earth orbit, within 2,000 km (1,200 miles) of Earth’s surface; however,
some debris can be found in geostationary
orbit 35,786 km (22,236 miles) above the Equator.
As of 2018, the United States Space Surveillance Network
was tracking more than 14,000 pieces of space debris
larger than 10 cm (4 inches) across. It is estimated that there are about 200,000 pieces
between 1 and 10 cm
(0.4 and 4 inches)
across and that there could be millions of
pieces smaller than 1 cm.
Does debris fall to earth?
How
long a piece of space debris
takes to fall back to Earth depends on its altitude.
Objects
below 600 km (375 miles) orbit several years before
reentering Earth’s atmosphere. Objects above 1,000 km (600 miles) orbit for
centuries.
What is the problem with Space debris?
The
amount of debris in space threatens both manned and unmanned spaceflight. The
risk
of
a catastrophic collision of a space shuttle with a piece of debris was 1 in
300. (For
missions
to the Hubble Space Telescope, with its higher and more debris-filled orbit,
the risk
was
1 in 185.) If there is a greater than a 1 in 100,000 chance of a known piece of
debris
colliding
with the International Space Station (ISS), the astronauts perform a debris
avoidance
maneuver in which the ISS’s orbit is raised to avoid the collision. On July 24,
1996, the
first
collision between an operational satellite and a piece of space debris took
place when a
fragment
from the upper stage of a European Ariane rocket collided with Cerise, a French
microsatellite.
Cerise was damaged but continued to function. The first collision that
destroyed
an operational satellite happened on February 10, 2009, when Iridium 33, a
communications
satellite owned by the American company Motorola collided with Cosmos
2251,
an inactive Russian military communications satellite, about 760 km (470 miles)
above
northern
Siberia, shattering both satellites.
The
worst space-debris event happened on January 11, 2007, when the Chinese
military
destroyed
the Fengyun-1C weather satellite in a test of an antisatellite system, creating
more
than
3,000 fragments, or more than 20 percent of all space debris. Within two years
those
fragments
had spread out from Fengyun-1C’s original orbit to form a cloud of debris that
completely
encircled Earth and that would not reenter the atmosphere for decades.
On January
22, 2013, the Russian laser-ranging satellite BLITS (Ball Lens in the Space)
experienced
a sudden change in its orbit and its spin, which caused Russian scientists to
abandon
the mission. The culprit was believed to have been a collision between BLITS
and a
piece
of Fengyun-1C debris. Fragments from Fengyun-1C, Iridium 33, and Cosmos 2251
account
for about one-half of the debris below 1,000 km (620 miles).
What happens if the amount of debris gets increased?
With
the increasing amount of space debris, there are fears that collisions such as
that
between
Iridium 33 and Cosmos-2251 could set off a chain reaction (called the Kessler
syndrome
after American scientist Donald Kessler) in which the resulting space debris
would
destroy
other satellites and so on, with the result that low Earth orbit would become
unusable.
Remedy to get rid of Space debris
To
forestall such a buildup in debris, space agencies have begun taking steps to
mitigate
the problem, such as burning up all the fuel in a rocket stage, so it does not
explode
later
or saving enough fuel to deorbit a satellite at the end of its mission. The
British satellite
Remove
DEBRIS, which was launched in 2018 and deployed from the ISS, has tested two
different
technologies for removing space debris, capture with a net and capture with a
harpoon,
and will test a drag sail, which will slow down a piece of debris, so it
re-enters the
atmosphere.
Satellites in geostationary orbit that are near the end of their missions are
sometimes
moved to a “graveyard” orbit 300 km (200 miles) higher
Role
of India in eradicating space debris:
In an operation
known as, ‘Mission Shakti’, an anti-satellite weapon ‘A-SAT’, successfully
targeted a live satellite on a Low Earth Orbit in under 3 minutes. They are the
fourth nation to be able to do so behind the US, China, and Russia. It was
done in March 2019.
Many countries spending crores together to secure their satellites.
India is one of them. The Centre has proposed Rs 33.3
crore for ISRO's 'Project Netra' for securing Indian satellites from space
debris and other dangers, according to documents related to supplementary
demand for grants.
In Sep,
India launched the early warning system Netra (Network for Space Objects,
Tracking, and Analysis) to secure its satellites and other assets in space at
an estimated to cost Rs 400 crore. Scientists say 50 years of human space
exploration has led to the creation of junk around Earth's orbit, posing
serious traffic risks to man-made satellites.
So, we humans are
responsible for creating debris and harming ourselves and the earth. We have
created a mess on earth and now we have spoiled earth’s atmosphere and entered
space to pollute. So, it confirms human himself is polluted physically and
mentally thereby wherever he enters he is polluting everything and making life
miserable.
Reference:
1.
https://www.esa.int/Our_Activities/Space_Transportation/Types_of_orbits
2.
Article of Space Debris
by Britannica encyclopedia.
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