This document discusses space debris and various approaches to tracking and removing it. It begins with an introduction and overview of different orbit types including low Earth orbit, medium Earth orbit, geostationary orbit, and high Earth orbit. It then discusses sources of debris and challenges posed by debris in different orbits. The document outlines methods for tracking debris using radar, optical detectors, and radio waves. It also summarizes different proposed approaches for debris removal such as tug-like satellites, electrodynamic tethers, laser brooms, solar sails, and space nets.

1. V.CHANDRAKALA

2. 1) Introduction
2)Types of orbits
3) Sources of debris
4) Tracking and Measurement of debris
5) Clearance of space debris
6) References

3.  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 , fragments from
disintegration , erosion and collision.

4.  Debris poses a growing threat to satellites and
could prevent the use of valuable orbits in the
future.
Many pieces of debris are too small to monitor
but too large to shield satellites against.

5. 1. Low Earth Orbit
2. Medium Earth Orbit
3. Geostationary Orbit
4. High Earth Orbit

6.  Situated at an altitude between 160km and 2000km from Earth’s surface.
 It has a time period of about 127 minutes.
 Objects below approx. 160km will experience very rapid orbital decay and
altitude loss.
 It is the simplest and most cost effective orbit for a satellite placement.
 Currently , NASA tracks more than 8,500 objects larger than 10 cm in LEO.

7. Situated from 2000 km to
36,000 km above Earth’s
surface.
The most common use
for satellites in this region
is for navigation ,
communication and space
environment science.
Has an orbital period of
12 hours .

8. It is a circular orbit at 35,786 km
above Earth’s surface and following the
Earth’s rotation .
An object in such an orbit has an
orbital period equal to the Earth’s
rotational period .
This makes them useful for
communications , as receiver on Earth
can always point in the same direction.

9.  Situated at above 36,000 km.
 Little used by satellites .
 Orbital periods of such orbits are greater than 24 hours.
Hence , satellites have an apparent retrograde motion .

10.  Satellites in LEO are in many different orbital
planes providing global coverage and the 15
orbits per day typical of LEO satellites result in
frequent approaches between object pairs.
 After space debris is created , the orbital
plane’s direction will change over time , and
thus collisions can occur from virtually any
direction . This leads to a cascading effect.

11.  At higher altitudes , where atmospheric drag is less significant ,
orbital decay takes much longer .
 This issue is especially problematic in the valuable GEO orbits
where satellites are often clustered to share the same orbital paths .
 It has been estimated that at least one close approach ( within 50
metres ) takes place every year .
 On a positive note , relative velocities in GEO are low , compared
to LEO (about 1.5 kmps ).
 This means that the debris field from such a collision will not
have the drastic effects as that of LEO , atleast over a short term .

12.  Dead spacecrafts
Boosters
Lost equipment

13.  Radar and optical detectors such as LIDAR
are the main tools used for tracking space
debris.
 Radio waves have been recently used.
These waves are transmitted into space and
they bounce off of space junk back to the
origin that will detect and track the object.
 Ground based radar facilities and space
telescopes are also used to track the debris.

14.  Returned hardware of space debris is a valuable source of
information of the environment .
 Close examination of its surfaces allows an analysis of the
directional distribution and composition of the debris flux .
 Some of the modules used were :
 LDEF (Long duration exposure facility ) satellite
 EURECA ( European Retrievable carrier )
 STS-61 Endeavour
 STS-109 Columbia

16.  Tug-like satellites
 Electro dynamic tethers
 Laser brooms
 Solar sails
 Space nets and collectors

17.  The tug like satellites drag the debris to a safe altitude
in order for it to burn up in the atmosphere .
 It creates an electron emission to create a difference in
potential between the debris as negative and itself as
positive .
 The satellite then uses its own thrusters to propel itself
along with the debris to a safer orbit .

18.  An electro-dynamic tether
provides a simple and reliable
alternative to the conventional
rocket thrusters .
 It works on the basic principle of
Lorentz force and Fleming’s Left
hand rule .
 Magnetic force is exerted on a
current carrying wire in a direction
perpendicular to both the flow of
current and the magnetic field .

19.  The laser broom uses a powerful ground based laser to
ablate the front surface off of debris and thereby produce a
rocket like thrust that slows the object .
 With continued application the debris will eventually
decrease their altitude enough to become subject to
atmospheric drag .
 Additionally , the momentum of photons in the laser beam
could be used to impart thrust on the debris directly.
 The current technology used is the Hydrogen fluoride
chemical energy powered laser.
…contd

20.  Although this thrust would be tiny , it may be enough to
move small debris into new orbits that do not intersect those
of working satellites.

21. The Solar sails uses the pressure
from sunlight to navigate an object,
just like a naval sail uses wind.
This way debris can be navigated
out of orbit and burn into the
atmosphere.
The only problem with the solar
sail is that its very hard to navigate
the junk into the ocean and hence
might be pretty dangerous.

22. Space nets or umbrellas are satellites which eject a huge net that ‘fishes’ or
collects the debris and is later disposed off into a graveyard orbit .

23. The most commonly used collector satellite is the Sling Sat .
It has two extended arms which collect the debris as it is in
motion .

24.  Donald Kessler (Kessler 1981), "Sources of
Orbital Debris and the Projected Environment
for Future Spacecraft“
 www.wikipedia.com
 www.nasa.gov
 www.isro.org
 www.nationalgeographic.com

25. Thank you…