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Seminar Report GPS based debris removal system
BRECW,Hyderabad Page 1 of 32
CONTENTS
Content Page No
List Of Figures ii
List Of Tables iii
Acknowledgement
Abstract
1. Introduction 1
1.1 Aim 1
1.2 Objective 1
1.3 Literature Survey 1
1.4 Applications 2
1.5 Organisation of Project 2
2. Space Debris 2
2.1 Introduction 4
2.2 Defination 4
2.3 space debris events and its environment 5
2.4 space surveillance network (ssn) 6
2.5 Conclusion 7
3. Types of Orbits 8
3.1 Introduction 8
3.2 Types of orbits 8
3.3 Low Earth Orbit(LEO) 9
3.3.1 Advantages of LEO 10
3.3.2 Disadvantages of LEO 10
3.4 Medium Earth Orbit(MEO) 10
3.4.1 Advantages & Disadvantages of MEO 11
3.5 Geostationary Orbits (GEO) 12
3.5.1 Applications of GEO 12
3.5.2 Adavntages & Disadvantages of GEO 13
3.6 Highly Elliptical Orbits (HEO) 13
3.6.1 Applications of HEO 16
3.7 Conclusion 16

4. Approaches to Active Debris Removal 17
4.1 Introduction 17
4.2 Electro-dynamic tethers 17
4.3 Laser Brooms 19
4.3.1 Ground Based Laser Technique 20
4.3.2 Space Based Laser Technique 22
4.4 Solar sails 22
4.5 Space Network 23
4.6 Collector Satellites 24
4.7 Conclusion 25
5. Conclusion 26

LIST OF FIGURES
2.1Tracked Orbital Debris Population 4
3.1 LEO 8
3.2 HEO 13
3.3 HEO with two satellites 13
3.4 Constellation of satellites 14
3.5 HEO orbit 14
4.1 Electro-Dynamic Tethers Create a Force by Interacting 17
with Plasma in the Earth’s Atmosphere
4.2 Ground Based Laser 20
4.3 De Orbiting By Laser 20
4.4 Space based Laser 23
4.5 Deployed solar sails in space 24
4.6 Orbit debris capture using a space net 24
4.7 TAMU Sweeper with Sling-Sat 25

LIST OF TABLES
1. Estimated amount of orbital debris

ABSTRACT
The wireless communication and networking on a large scale is carried out
through satellites. Inter planetary communication is also made possible due to satellite
technology. The various kinds of space debris or space junk that are revolving around
our earth in an orbit possess a threat to the satellite communications. Infact, these
particles whether tiny or big are on their way to destroy the whole system of satellites
and space stations orbiting around our globe in the near future. This deadly debris
must be eliminated in order to have a complete access to our earth orbiting satellites.
The concept of light pressure exerted by laser beams provides a valuable tool to
eliminate these particles.
In the modern era, communication plays a significant role in human life, a
country’s economy and further development in science and technology. The
communication system has developed to an extent that information exchange across
any part of the blue planet is very easy. This is possible due to the satellites revolving
around us. Every nook and corner of the earth can be accessed via satellites.
The development in the satellite technology heads in one direction launching
many satellites and the debris created due to these satellites possess a threat of
destroying the satellites and heads in the opposite direction. In the next 100 years,
man’s thirst for wider and better universal communication will lead in launching of
many satellites which in turn produces huge amount of debris. The space around the
earth would get so congested that it needs to be cleaned. We have discussed about the
various proposals that are made to clean the space junk. We have also suggested
methods, which use the radiation pressure exerted by high intensity lasers and
sunlight in removing space debris.

CHAPTER-I
INTRODUCTION
1.1 AIM:
To reduce the risk of satellites being hit by debris.
1.2 OBJECTIVE:
The various kinds of space debris or space junk that are revolving around
our earth in an orbit possess a threat to the satellite communications. This debris
has to be eliminated to maintain the satellite communications.
1.3 LITERATURE SURVEY:
The review of the literature will briefly explore the statistical methods and the
neural networks methods.
Statistical methods have traditionally built a linear or a non-linear
model, based on the historic traffic data, to predict the travel time on freeway or
arterial streets. H. M. Zhang1 use the historic critical v/c ratio, occupancy from
the loop detector to build up a non-linear model named “the journey Speed
Model” to predict the travel time on arterial streets. The journey speed is
represented as the weighted sum of the historic speed and the current speed
from the Where qi is the flow rate detected by the detector and oi is the detected
occupancy for time interval i. u f is the free-flow speed, a and β are model
parameters and γ is a weighting factor. However, this statistical method is
peculiar to the network under study and is not generic and transferable to other
traffic networks for other cities.
Neural networks are models designed to imitate the human brain
through the use of mathematical models. Similar to statistical methods, Neural
Networks are built using previous existing data. However, neural networks can
perform better than statistical methods in mapping the relationships between the

travel times and the input data. In the past several years, neural networks have
been successfully applied to predict short-term traffic flow and travel time.
1.4 APPLICATIONS:
1. Satellite communiation
2. Space crafts
3. Rockets
1.5 ORGANISATION OF SEMINAR REPORT:
Space debris, also known as orbital debris, space junk, and space waste,
is the collection of defunct objects in orbit around Earth. This includes
everything from spent rocket stages, old satellites, and fragments from
disintegration, erosion, and collisions. Since orbits overlap with new spacecraft,
debris may collide with operational spacecraft.
Since the number of satellites in Earth orbit is steadily increasing, space
debris, if left unchecked, will eventually pose a serious hazard to near-Earth
space activities, and so effective measures to mitigate it are becoming urgent.
Equipping new satellites with an end- of-life de-orbit and orbital lifetime
reduction capability could be an effective future means of reducing the amount
of debris by reducing the probability of collisions between objects, while using
spacecraft to actively remove debris objects and to retrieve failed satellites are
possible measures to address existing space debris. Most space debris is less
than 1cm (0.39in) including dust from solid rocket motors, surface degradation
products such as paint flakes, and coolant released by nuclear power satellites.
Impacts of these particles cause erosive damage similar to sand blasting.
The risk of satellites being hit by debris is increasing at an alarming rate.
The solar panels present in the satellites are very delicate. So even very small
size debris could be a cause for the malfunctioning of the panel, which in turn
may interrupt the efficiency of the data transfer.
In communication systems the satellites usually are grouped into
networks. If a satellite is being hit by big debris then there is every possibility of

it losing its ability to function properly. This may break the communication
network leading to large amount of financial and material loss for a certain
amount of time until a replacement is made.
The most space debris created by a spacecraft's destruction was due to
the upper stage of a Pegasus rocket launched in 1994. Its explosion in 1996
generated a cloud of some 300,000 fragments bigger than 4 mm and 700 among
them were big enough to be catalogued. This explosion alone doubled the
Hubble Space Telescope collision risk. To prove this we have found a ¾ inch
hole in the Hubble.
Currently about 19,000 pieces of debris larger than 5 cm are tracked,
with another 300,000 pieces smaller than 1 cm below 2000 km altitude. For
comparison, ISS orbits in the 300–400 km range and both the 2009 collision and
2007 anti-sat test event occurred at between 800–900 km.

CHAPTER-II
SPACE DEBRIS
2.0 INTRODUCTION:
In this chapter, It is clearly explained about the Space Debris, Space
Debris Events and Its Environent Space Surbiellance Network(SSN).
2.1 DEFINATION:
Satellites have become an integral part of the human society but they
unfortunately leave behind an undesirable by-product called space debris.
Orbital space debris is any man-made object orbiting around earth which no
longer serves a useful function. Non-functional spacecrafts, abandoned launch
vehicle stages mission related objects and fragments from breakups are all
considered orbital space debris. Since the last decade there are growing
concerns that artificial orbital debris generated by space activities is degrading
the near earth space environment. Recent statistical data shows that 70% of the
catalogued objects in Earth orbit, larger than 1 cm size, are in low earth orbit
(LEO). Figure 1 shows the distribution of LEO debris. The increasing threat
posed by space debris to active satellite demands high attention. Collisions and
explosions will proliferate the debris population drastically thereby degrading
the space environment further.
The lifetime of all orbital debris depends on their size and altitude. In
LEO, an object below 400 km will de-orbit within a few months because of
atmospheric drag and gravitational force, whereas, objects above 600 km may
stay in the orbit for tens of years. As the LEO is a limited resource, it is very
important to explore the various space debris mitigation techniques and suitable
measures are to be taken to solve the space debris problem.
Three categories of space debris, depending on their size:
1. Category I (<1cm) - They can make significant damage to vulnerable
parts of a satellite.
2. Category II (1-10cm) - They tend to seriously damage or destroy a

satellite in a collision.
3. Category III (>10cm) – They may completely destroy a satellite in a
collision and can be tracked easily
Fig 2.1: tracked orbital debris population
2.2 SPACE DEBRIS EVENTS AND ITS ENVIRONMENT:
There has been a steady growth of space debris since the launch of
Sputnik in 1957, with jumps following two of the largest debris creating events
in history: the 2007 Chinese anti-satellite (ASAT) test and the 2009 Iridium-
Cosmos collision. The first of these events occurred on January 11, 2007, when
China intentionally destroyed its Fengyun-1C satellite while testing its newly
developed ground-based ASAT system. It was the largest debris-creating event
in history, producing at least 150,000 pieces of debris larger than one centimeter
(NASA 2008, 3). The resulting debris has spread into near polar orbits ranging
in altitude from 200 to 4,000 kilometers. Roughly 80 percent of this debris is
expected to stay in orbit for at least the next one hundred years and threatens to
impact operating satellites (Celes Trak 2009). The test illustrates how a single
unilateral Action in space can create long-term implications for all space-faring
nations and users of satellite services.

The second major space-debris creating event was the accidental
collision between an active Iridium satellite and a defunct Russian military
satellite on February 10, 2009. The collision created two debris clouds holding
more than 200,000 pieces of debris larger than one centimeter at similar
altitudes to those of the 2007 Chinese ASAT test (Johnson 2009b). It was the
first time two intact satellites accidentally crashed in orbit, challenging the
―Big Sky Theory‖.
Currently, the highest spatial densities of space debris are in near-polar
orbits with altitudes of 800 to 1,000 kilometers. These are known as ―critical
orbits‖ because they are most likely to reach the point where the production rate
of new debris owing to collisions exceeds that of natural removal resulting from
atmospheric drag. They exist because several large fragmentation events have
occurred in these regions, such as the two described above, and because debris
lifetimes can last up to decades at these altitudes.
2.3 SPACE SURVEILLANCE NETWORK (SSN):
The United States Space Surveillance Network detects, tracks, catalogs
and identifies artificial objects orbiting Earth, i.e. active/inactive satellites, spent
rocket bodies, or fragmentation debris. The system is the responsibility of the
Joint Functional Component Command for Space, part of the United States
Strategic Command (USSTRATCOM). Space surveillance accomplishes the
following:
1. Predict when and where a decaying space object will re-enter the
Earth's atmosphere;
2. Prevent a returning space object, which to radar looks like a
missile, from triggering a false alarm in missile-attack warning
sensors of the U.S. and other countries;
3. Chart the present position of space objects and plot their

anticipated orbital paths;
4. Detect new man-made objects in space;
5. Correctly map objects travelling in the earth's orbit;
6. Produce a running catalog of man-made space objects;
7. Determine which country owns a re-entering space object;
8. Inform NASA whether or not objects may interfere with
satellites and International Space Station orbits.
The following table shows the estimated amount of debris objects by their size.
Debris Size 0.1-1cm 1-10cm >10cm
Total number
at all altitudes
150 million 780,000 23,000
Debris in low
earth orbit
20 million 400,000 15,000
Table 2.1: Estimated amount of orbital debris
The 2009 satellite collision was the first accidental hypervelocity
collision between two intact artificial satellites in low Earth orbit. It occurred
on February 10, 2009.In that unprecedented space collision, a commercial
communication satellite (IRIDIUM33) and a dysfunctional Russian satellite
(COSMOS 2251) impacted each other above Northern Siberia, creating a
cloud of new debris objects. Till now, over 1719 large fragments have been
observed from this collision.
2.4 CONCLUSION:
From this chapter we get a brief idea about the Space Debris, Space
Surveillance Network and Its environment. How the space derbris is occurred and
number of space debris occurred and the history of space debris.

CHAPTER-III
TYPES OF ORBITS
3.1 INTRODUCTION:
Since the launch of the first satellite in 1957 humans have been placing
an increasing number of objects in orbit around the Earth. This trend has
accelerated in recent years thanks to the increase in number of states which have
the capability to launch satellites and the recognition of the many
socioeconomic and national security benefits that can be derived from space.
There are currently close to 1000 active satellites on orbit, operated by dozens
of state and international organizations. More importantly, each satellite that is
placed into orbit is accompanied by one or more pieces of non-functional
objects, known as space debris. More than 20,000 pieces of space debris larger
than 10 cm are regularly tracked in Earth orbit, and scientific research shows
that there are roughly 500,000 additional pieces between 1 and 10 cm in size
that are not regularly tracked. Although the average amount of space debris per
cubic kilometer is small, it is concentrated in the regions of Earth orbit that are
most heavily utilized…and thus poses a significant hazard to operational
spacecraft.
The artificial satellites are classified for the size (large >1000 kg, medium
size 500 –1000kg, small (mini satellites 100-500 kg, microsatellites 10-100 kg,
nano satellites 1-10 kg, pico satellites 0,1-1 kg and femto satellites <100 g)); for the
applications (exploration, communications, navigation and observation); for the
character (military, civil and dual); and for the orbital height (LEO, MEO,
HEO,GEO).
3.2 TYPES OF ORBITS:
 Low Earth Orbit [LEO]
 Medium Earth Orbit [MEO]
 Highly Elliptical Orbits [HEO]
 Geostationary Orbit [GEO]

3.3 LOW EARTH ORBIT ( LEO ):
LEO (Low Earth Orbit, which means low orbits). Orbiting the Earth at a
distance between 500 and 2000 km of and its speed allows them to fly around
the world in 2 hours approximately, with a velocity between 20000 and 25000
km/h. They are used to provide geological data on the movement of Earth's
plates, remote sensing, spatial investigation, metereology, vigilance and the
phone industry satellite. Allow the determination of space debris and the
utilization of the electromagnetic spectrum.
Fig. 3.1 LEO
Most satellites, the International Space Station, the Space Shuttle, and
the Hubble Space Telescope are all in Low Earth Orbit (commonly called
"LEO"). This orbit is almost identical to our previous baseball orbiting example,
except that it is high enough to miss all the mountains and also high enough that
atmospheric drag won't bring it right back home again.
Every satellite, space probe and manned mission has the potential to
create space debris. Any impact between two objects of sizeable mass can spall
off shrapnel debris from the force of collision. Each piece of shrapnel has the
potential to cause further damage, creating even more space debris. With a large
enough collision (such as one between a space station and a defunct satellite),

the amount of cascading debris could be enough to render Low Earth Orbit
essentially unusable.
3.3.1. Advantages of LEO:
Low Earth Orbit is used for things that we want to visit often with the
Space Shuttle, like the Hubble Space Telescope and the International Space
Station. This is convenient for installing new instruments, fixing things that are
broken, and inspecting damage. It is also about the only way we can have
people go up, do experiments, and return in a relatively short time.
3.3.2 Disadvantage of LEO:
The first is that there is still some atmospheric drag. Even though the
amount of atmosphere is far too little to breath, there is enough to place a small
amount of drag on the satellite or other object. As a result, over time these
objects slow down and their orbits slowly decay. Simply put, the satellite or
spacecraft slows down and this allows the influence of gravity to pull the object
towards the Earth.
3.4 MEDIUM EARTH ORBIT ( MEO):
MEO (Medium Earth Orbit, stockings orbits). Are satellites moving on
orbits close moderately of about 20000 km. Its use is intended for mobiles
communications, navigation (GPS), measurements of space experiments and
effective use of the electromagnetic spectrum.
A medium earth orbit (MEO) satellite is one with an orbit within the
range from a few hundred miles to a few thousand miles above the earth's
surface. Satellites of this type orbit higher than low earth orbit (LEO) satellites,
but lower than geostationary satellites.

The orbital periods of MEO satellites range from about two to 12 hours.
Some MEO satellites orbit in near perfect circles, and therefore have constant
altitude and travel at a constant speed. Other MEO satellites revolve in
elongated orbits. The perigee (lowest altitude) of an elliptical-orbit satellite is
much less than apogee (greatest altitude). The orbital speed is much greater near
perigee than near apogee. As seen from a point on the surface, a satellite in an
elongated orbit crosses the sky in just a few minutes when it is near perigee, as
compared to several hours when it is near apogee. Elliptical-orbit satellites are
easiest to access near apogee, because the earth-based antenna orientation does
not have to be changed often, and the satellite is above the horizon for a fairly
long time.
A fleet of several MEO satellites, with orbits properly coordinated, can
provide global wireless communication coverage. Because MEO satellites are
closer to the earth than geostationary satellites, earth-based transmitters with
relatively low power and modest-sized antennas can access the system. Because
MEO satellites orbit at higher altitudes than LEO satellites, the useful footprint
(coverage area on the earth's surface) is greater for each satellite. Thus a global-
coverage fleet of MEO satellites can have fewer members than a global-
coverage fleet of LEO satellites.
3.4.1 ADVANTAGES & DISADVANTAGES:
ADVANTAGES:
1. Compared to LEO systems, MEO requires only dozen satellites.
2. Simple in design.
3. Requires only few handovers.
DISADVANTAGES:
1. Satellites require higher transmission power.
2. Special antennas are required.

3.5 GEOSTATIONARY ORBITS(GEO):
As the height of a satellite increases, so the time for the satellite to orbit
increases. At a height of 35790 km, it takes 24 hours for the satellite to orbit.
This type of orbit is known as a geosynchronous orbit, i.e. it is synchronized
with the Earth.
One particular form of geosynchronous orbit is known as a geostationary
orbit. In this type of orbit the satellite rotates in the same direction as the
rotation of the Earth and has an approximate 24 hour period. This means that it
revolves at the same angular velocity as the Earth and in the same direction and
therefore remains in the same position relative to the Earth.
GEO satellites provide the kind of continuous monitoring necessary for
intensive data analysis. By orbiting the equatorial plane of the Earth at a speed
matching the Earth's rotation, these satellites can continuously stay above one
position on the Earth's surface. Because they stay above a fixed spot on the
surface, they provide a constant vigil for the atmospheric "triggers" for severe
weather conditions such as tornadoes, flash floods, hail storms, and hurricanes.
When these conditions develop these GEO satellites are able to monitor storm
development and track their movements.
3.5.1 APPLICATIONS OF GEOSTATIONARY SATELLITES:
Geostationary satellites have modernized and transformed worldwide
communications, television broad casting, and meteorological and weather
forecasting. They also have a number of significant defense and intelligence
applications

3.5.2ADVANTAGES & DISADVANTAGES:
ADVANTAGES:
1. It is possible to cover almost earth by with just 3 Geo satellites
2. Antennas need not be adjusted every now and then can be fixed
permanently.
3. The life time of Geo satellites is quite high usually around 15 years.
DISADVANTAGES:
1. Larger antennas are required for northern/southern regions of earth.
2. High building in a city limit the transmission quality.
3. High transmission power is required.
4. These satellites can’t be used for small mobile phones.
5. Fixing a satellite at Geo Stationery orbit is very expensive.
3.6 HIGHLY ELLIPTICAL ORBIT (HEO):
HEO (Highly Elliptical Orbit, highly elliptical orbits). These satellites
do not follow a circular orbit, but its orbit is elliptical. This implies that much
greater distances reached at the point furthest from the orbit. They are often
used to map the surface of the Earth, as they can detect a wide angle of Earth's
surface. The perigee about 500 km and apogee of 50000 km, your orbit is tilted,
the period varies from 8 to 24 hours, used in communications and space
surveillance and very sensitive to the asymmetry of the Earth (the orbit is
stabilized if i=63.435°).
Remember Kepler's second law: an object in orbit about Earth moves
much faster when it is close to Earth than when it is farther away. Perigee is the
closest point and apogee is the farthest (for Earth - for the Sun we say aphelion
and perihelion). If the orbit is very elliptical, the satellite will spend most of its
time near apogee (the furthest point in its orbit) where it moves very slowly.
Thus it can be above home base most of the time, taking a break once each orbit
to speed around the other side.

Fig. 3.2 HEO
With the highly elliptical orbit described above, the satellite has long dwell time
over one area, but at certain times when the satellite is on the high speed portion
of the orbit, there is no coverage over the desired area. To solve this problem we
could have two satellites on similar orbits, but timed to be on opposite sides of
the orbit at any given time. In this way, there will always be one satellite over
the desired coverage area at all times.
Fig. 3.3 HEO with two satellites
If we want continuous coverage over the entire planet at all times, such
as the Department of Defense's Global Positioning System (GPS), then we must
have a constellation of satellites with orbits that are both different in location
and time.

Fig. 3.4 constellation of satellites
In this way, there is a satellite over every part of the Earth at any given
time. In the case of the GPS system, there are three or more satellites covering
any location on the planet.
s
Fig. 3.5 Highly elliptical satellite orbit, HEO

3.6.1 HIGHLY ELLIPTICAL ORBIT APPLICATIONS:
The highly elliptical satellite orbit can be used to provide coverage over
any point on the globe. The HEO is not limited to equatorial orbits like the
geostationary orbit and the resulting lack of high latitude and polar coverage.
As a result it ability to provide high latitude and polar coverage,
countries such as Russia which need coverage over polar and near polar areas
make significant use of highly elliptical orbits, HEO.
With two satellites in any orbit, they are able to provide continuous
coverage. The main disadvantage is that the satellite position from a point on
the Earth does not remain the same.
3.7CONCLUSION:
In the chapter III, We have discussed about different types of orbits their
advantages, disadvantages, and applications.

CHAPTER 4
APPROACHES TO ACTIVE DEBRIS
REMOVAL
4.1 INTRODUCTION:
Various approaches to remove debris from space have been proposed, and
some seem more technologically feasible than others. Techniques range from
attaching tethers, solar sails, or solid rocket motors to debris objects, to active
capture via nets followed by removal to other orbits. Of these techniques, one
seems particularly feasible and is selected for use in the study presented herein.
4.2 ELECTRO-DYNAMIC TETHERS:
In general, a tether is a long cable (up to 100 km or longer) that connects
two or more spacecraft or scientific packages. Tethers in space can be used for
variety of applications such as power generation, propulsion, remote atmosphere
sensing, and momentum transfer for orbital maneuvers, microgravity
experimentation, and artificial gravity generation. Electro-dynamic tethers are
conducting wires that can be either insulated or bare, and that makes use of an
ambient field to induce a voltage drop across its length.
Electro-dynamic tether moves in the Earth’s magnetic field and is
surrounded by ionospheric plasma. The solar arrays generate an electric current
that is driven through the long conductor. The magnetic field induces a Lorentz
force on the conductor that is proportional to length, current, and local strength
and direction of the magnetic field. Electrons are collected from the plasma near
one end of the bare conductor, and are ejected by an electron emitter at the other
end.
The use of Electro-Dynamic Tethers (EDTs) takes advantage of the effect of
placing a conductive element in the Earth’s magnetic field. The object to be de-

orbited is connected via a tether to a de-orbiting element, and both ends have a
means of providing electrical contact to the ambient ionospheric plasma. The
interaction of the conducting tether moving at orbital speeds induces current
flow along the tether, causing a Lorentz force due to the interaction between the
tether and the Earth’s magnetic field; this causes an acceleration on the object to
which the tether is attached. Figure shows a notional EDT system and the
resulting force on the spacecraft to which it is attached.
Fig.4.1 Electro-Dynamic Tethers Create a Force by Interacting with
Plasma in the Earth’s Atmosphere
A tether made of conductive aluminum and massing only 2 to 2:5% of
the mass of the object to be de-orbited is sufficient to provide significant
deceleration and speed up the de-orbit process.8 Studies have shown that for
high-inclination, low-altitude LEO satellites (e.g., Iridium constellation), the
time required for de-orbit from a 780 km altitude orbit can be reduced from 100
years to 1 year. The technology constraints involve potential difficulty in
attaching the tether, but this could be done via a harpoon, a hooked net, or an
adhesive suction cup. The cross-sectional area and possibility of conjunction
collisions with other objects is also increased with the use of the tethers, but less
so than with other proposed methods. This approach is the preferred method that
our analysis adopts for removal of debris objects from low-Earth orbit.

The EDT captures as pace junk in a net the size of a house. The lifespan
of EDT is not limited by the size of its fuel tank. That’s because this junk capturer
is powered not by liquid fuel, but by a long conducting wire that generates
electricity through as it moves through the earths magnetic field. So an EDT
vehicle could operate indefinitely. It could target a piece of debris capture it in a
net, deliver it into the earths atmosphere and then turn around and start over
again. On average it takes 10 days to remove an object, so each EDT vehicle
could remove 36 objects per year.
4.3 LASER BROOMS:
Lasers in space raise romantic notions of efficiently vaporizing debris
material that could pose a risk to other objects in orbit. The use of lasers for
ADR activities is questionable at best, partially due to a requirement to keep a
very focused beam pointed at a rapidly and arbitrarily moving target for a long
period of time, such that the surface can be ablated enough to induce an
acceleration. Moreover, generating adequate levels of power for a space-based
laser is beyond our current space power generation capabilities. Additionally,
the use of such lasers in space could be problematic with respect to existing
international weapons treaties and UN regulations. Also, many of the objects
that could be removed may contain unspent propellant that could explode if
heated by a laser, thus causing more debris. While lasers may be of some use in
removing smaller debris objects, they are not relevant to the study presented
herein.
A high power pulsed laser is used to ablate the layers of the
dysfunctional satellite thereby producing enough cumulative thrust to deorbit
the spacecraft. This laser can be either ground based laser or space based laser.
In this technique, the surface material of the debris becomes the propellant i.e.
the intensity of the laser must be sufficiently high to cause the material on the
surface of the debris to form vapour and this expansion of the vapour imparts a

thrust to the object. The limitation of this technique is that it requires precise
orbital parameters of the target spacecraft and laser should have high
illumination power. Mainly the laser based techniques are two types:
1. Ground based laser technique
2. Space based laser technique
4.3.1 GROUND BASED LASER TECHNIQUE:
Lasers are designed to target debris between one and ten centimeters in
diameter. Collisions with such debris are commonly of such high velocity that
considerable damage and numerous secondary fragments are the result. The
laser broom is intended to be used at high enough power to penetrate through
the atmosphere with enough remaining power to ablate material from the target.
The ablating material imparts a small thrust that lowers its orbital perigee into
the upper atmosphere, thereby increasing drag so that its remaining orbital life is
short. The laser would operate in pulsed mode to avoid self-shielding of the
target by the ablated plasma. The power levels of lasers in this concept are well
below the power levels in concepts for more rapidly effective anti-satellite
weapons.
NASA research in 2011 indicated that firing a laser beam at a piece of
space junk could alter velocity by 0.04 inches (1.0 mm) per second. Persisting
with these small velocity changes for a few hours per day could alter its course
by 650 feet (200 m) per day. While not causing the junk to reenter, this could
maneuver it to avoid a collision.

Fig.4.2 Ground based laser
Some of the major advantages of ground based laser are that they
provide very high power and technology is much mature. But the Energy lose is
significantly much higher due to atmospheric absorption and they cannot be
moved freely in a huge range.
Fig.4.3Deorbiting by laser

4.3.2 SPACE BASED LASER TECHNIQUE:
This technique is similar to the ground based laser technique. The only
difference is that the laser beam is produced by a service satellite. This avoides
the limitations seen from the ground based laser technique. The major
advantages are that
1. There is no negative atmospheric effects
2. be able to track and target debris with a much larger field of view
3. focus on targets for longer periods of time
But the main disadvantages of the space based laser techniques are the
cost is much larger to build, lunch and operate and it can be used as a space-
based antisatellite weapon system.
Fig.4.4 Space based laser
4.4 SOLAR SAILS:
Solar sails have gained some attention as a possible debris removal
technique. Basically, the concept is simple: a reflecting material, which may be
very thin, is deployed from an orbiting body and solar photons that strike the
material are reflected, imparting acceleration to the orbiting body. Solar sails are

more useful for orbit modifications in which there is no net exchange of energy
and are therefore particularly suitable for altering orbital eccentricity. The
largest contribution to altitude lowering or de-orbiting actually comes from an
increased atmospheric drag rather than the solar/photon effect.
Some of the major advantages of solar sails are
1. It is an effective option for disposal of objects in very high orbits
2. require no propellant or engines
But the only disadvantage is that it is hard to deployment and control
Fig.4.5 Deployed solar sail in space
4.5 SPACE NETS:
The capture by means of a net device is based on its deployment around
the debris being targeted as shown in Fig. Once the debris is surrounded, the net
is closed and the debris is captured. The net is considered as a one shot device
that cannot be ground-tested before operation. Capturing objects with the net is
still considered to be a relatively new form of ADR, which requires further
assessment. Net technology is inherently complex, and best suited for targeting
debris with no breakable parts in medium and high orbits.

Fig 4.6: orbit debris capture using a space net
4.6 COLLECTOR SATELLITES:
TAMU Space Sweeper with Sling-Sat(4S) :
This technique is also about capturing of space debris but with a very
less amount of fuel usage. A university in Texas proposed this idea. The sling
sat will work on swinging capturing an object, then swinging it towards Earth’s
atmosphere to destroy it and then using the momentum to go towards the next
piece of debris for same process. By this technique, the fuel consumption will
be very less as the sling sat will use the momentum gained by throwing the
debris.
To remove the space debris, many ideas have come up from different
parts of the world. But an idea that sounds most technical is to clean the debris
object by object. Obviously to travel for each object (and sometimes very
widely spaced objects) the spacecraft will require loads of fuel making it a much
inefficient project. The 4S system points to correct this flaw. It will trap the
debris at the ends of a spinning satellite, and then throw the object down while
rotating in Earth's atmosphere in order to destroy it. Then it will make use of the
momentum exchanged during the two actions to move towards the next piece to
be captured. This will minimize the fuel usage and extend the operational
lifetime.

Fig.4.7 TAMU Sweeper with Sling-Sat
4.7 CONCLUSION:
Here in this chapter, we have discussed about the collector satellites,
Solar sails, space nets,space based laser technique, ground based laser
technique, laser beams, etc,.

CHAPTER-V
CONCLUSION
There are many methods for active debris removal and some of the
important methods have been listed here. These methods can effectively help in
removing the active debris in space and thus improve operations of satellites by
not interfering in their operation. This will also help in reducing dangers of
satellites collision with space debris. The removal of existing space debris have
been explored to minimize the space debris threat. However, the realistic and
effective method to solve space debris problem is to avoid any new debris
generation.
Studies indicate that usage of propulsion systems by decelerating
spacecrafts is not an effective solution as it increases complexity, mass and cost.
Electro-dynamic tether systems can be considered for removing the spacecrafts
after useful lifetime to greatly increase the orbital decay of the spacecraft.
Numerical analysis indicate that EDT systems massing just 2 to 5% of the total
spacecraft mass can deorbit the spacecraft within few months thus providing
significant mass/cost savings compared to propulsion systems. Electro-dynamic
tether technique has been proposed as an innovative solution to deorbit the
spacecrafts after useful lifetime. So our space exploration agencies like ISRO
and NASA should explore the possibilities to prevent orbital space debris by
using efficient and economic techniques like EDT to keep our space
environment safe for the future scientific space explorations.

REFERENCES
[1] International Journal of Research (IJR) Vol-1, Issue-10 November
2014 ISSN 2348-6848 Space Debris Elimination Techniques.
[2] Robert Osiander and Paul Ostdiek, Handbook of Space
Engineering,
. Archeology.
[3] Marco M. Castronuovo, Active space debris removal-A preliminary
mission analysis and design, Acta Astronautica 69 (2011) 848-859.
[4] Carmen Pardini, Toshiya Hanada and Paula H Krisko, Benefits and
risks of using electrodynamic tethers to de-orbit spacecrafts, Acta
Astronautica 64 (2009) 571-588.
[5] Robert P Hoyt and Robert L Forward, The Terminator Tether:
Autonomous deorbit of LEO spacecraft for space debris mitigation,
AIAA-00—0329.
[6] Holger Burkhardt, Martin Sippel, et, Evaluation of propulsion
systems for satellite end-of-life deorbiting, Germany, AIAA-2002—
4208.
[7] Shin Ichiro Nishida, Satomi Kawamoto, etc. , Space debris removal
system using a small satellite, Acta Astronautica 65(2009) 95-102.
[8] Jonathan W Campbell, Using Lasers in Space: Laser Orbital debris
removal and asteroid deflection
[9] ―Position paper on orbital debris,‖ International Academy of
Astronautics, 8 March 1993.
[10] David S. F. Portree and Joseph P. Loftus, Jr., Orbital Debris and
Near-Earth Environmental Management: A Chronology, NASA
reference publication 1320, 1993.
[11] Patera, R. P., and Ailor, W. H., The realities of re-entry disposal,
AAS Paper 98-174, Feb. 1998.
[12] Vladimir A. Chobotov, Orbital Mechanics, 3rd ed., AIAA
education series, 2002.

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