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DEEP SPACE
COMMUNICATION

PRESENTED BY:
P.MOHANA SAI GEETHA , K.GOWTHAMI,

III/II E.C.E dept, III/II E.C.E dept.,

J.B.WOMEN’S ENGINEERING COLLEGE, J.B.WOMEN’S ENGINEERING COLLEGE,

EMAIL ID: geethageetha16@gmail.com. EMAIL ID: konangigowthami@gmail.com.

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ABSTRACT: Deep space challenging environment for data

exploration and utilization are all along communications. The radio frequency
the dreams of human beings. The
exploration and utilization of the deep channel predominantly used for
space are all along the dreams of human communication typically operates under the
beings.
following constraints.
Deep Space Communication Long Distance
transmits the information obtained by the High Signal Propagation Delays
probe to the ground and processes and High Data Corruption Rates
analyzes it. Deep space usually refers to the Disruption Events
outer space more than 2 million kilometers Complex Geography Environment
away from the earth. And deep space
communications is referred to as SPACECRAFTS:
communication between the earth and other
Spacecraft is the destination system of the
planets. Now spacecrafts are send to the
deep space communication. spacecrafts are
farthest planet Pluto called Newhorizons
launched for scientific study, the launch cost
which will enter into Pluto’s orbit in 2015.
is higher as the spacecraft become bigger so
Among them, the explorations to the Mars
we use light weight systems and equipments
and moon are more frequent. In recent forty
so we cannot incorporate large antennas or
years, Russia, United State and several
powerful communication systems. The
Europe countries have made explorations to
spacecraft's small, light communications
the Mars more than thirty times and sent
equipment consequently transmits at very
probes to the Moon. European Space
low power, typically limited to 20 watts,
Agency (ESA), Japan, China and India also
about the same as a refrigerator light bulb.
have their own Moon exploration probes
Signal power arriving at the antenna can be
right now.
as weak as one 100-millionth of one 100-
Comparison with Normal
billionth of a watt - 20 billion times less than
Communication Compared with common
the power required for a digital wristwatch.
terra and satellite communications, deep-
To "hear" the whisper of a signal from a
space communications presents more
spacecraft at planetary distances, receiving

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antennas on Earth must be very large and be • The Madrid Deep Space
equipped with highly sensitive receivers. Communication Complex, 60
The two main antennas in a spacecrafts are kilometers (37 miles) west of
high gain antenna and a low gain antenna. Madrid, Spain; and
• The Canberra Deep Space
• Low Gain Antenna Communications Complex (CDSCC)
• High Gain Antenna in the Australian Capital Territory,
40 kilometers (25 miles) southwest
DEEP SPACE NETWORK:The of Canberra, Australia near the
NASA Deep Space Network - or DSN - is Tidbinbilla Nature Reserve.
an international network of huge antennas
that allows people on the ground to Each facility is situated in semi-

communicate with satellites and other mountainous, bowl-shaped terrain to

spacecraft missions, as well as providing shield against radio frequency

radio and radar astronomy observations for interference. This strategic placement

the exploration of the solar system and the permits constant observation of

universe. It is best known for its large radio spacecraft as the earth rotates, and helps

antennas. The network also supports to make the DSN the largest and most

selected Earth-orbiting missions. DSN is sensitive scientific telecommunications

part of the NASA Jet Propulsion Laboratory system in the world.

(JPL).

Present Condition:DSN currently consists

of three deep-space communications
facilities placed approximately 120 degrees
apart around the world. They are:

• The Goldstone Deep Space

Communications Complex outside of
NASA's scientific investigation of
Barstow, California, United States;
the Solar System is being accomplished
mainly through the use of unmanned

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spacecraft. The DSN provides the vital two-

way communications link that guides and
controls these machines, and brings back the
images and new scientific information
they collect. All DSN steerable, high-gain,
antennas are parabolic

The antennas and data delivery systems

make it possible to:

• Acquire telemetry data from

spacecraft.
• Transmit commands to spacecraft.
• Track spacecraft position and
velocity.
• Perform Very Long Baseline
Interferometry observations.
• Measure variations in radio waves
for radio science experiments.
• Gather science data.
• Monitor and control the performance
of the network. FUNCTIONS OF DSN:

1. Telemetry: Telemetry data consists

of science and engineering information
modulated on radio signals transmitted from
the spacecraft. The Telemetry System
performs three main functions: Telemetry
data acquisition, telemetry data conditioning
and transmission to projects and telemetry
system validation.two types of telemetry,
science data and engineering data. science

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data is the important data because the 5 Radio Science :The field of Radio
mission success depends on this data. Science improves our knowledge of the
engineering data contains the health and solar system and the theory of general
positional information of the spacecraft. relativity through radio frequency
2. Spacecraft Command: The purpose of experiments performed between spacecraft
the Command System is to provide the and the Deep Space Network's (DSN) Radio
means by which a Project controls the Science System. In the past, Radio Science
activities of its spacecraft. Control has performed experiments which have
information (Command Data), provided by allowed scientists to characterize planetary
the Project, is modulated on the RF carrier atmospheres and ionospheres, characterize
and transmitted to a spacecraft by a DSN planetary surfaces, characterize the
station. The Command System functions as planetary rings, characterize the Solar
a transfer medium between the Project corona, confirm general relativity,
Control Center and its spacecraft. characterize interplanetary plasma, search
3 Radiometric Tracking : The for gravitational waves, characterize
purpose of the Tracking System is to planetary gravity , and determine the mass
provide two-way communication between of the planets, moons, and asteroids.
Earth based equipment and spacecraft, to 6 Monitor and Control :The purpose of
make measurements that will allow the state the Monitor and Control System is two-fold:
vector (position and velocity) of spacecraft to provide real time monitor data to projects
to be determined. which reflect the status of project support by

4 Very Long Baseline Interferometry DSN systems, and to provide monitor and
control capabilities to operators of DSN
The purpose of the Very Long Baseline
systems' components.
Interferometry (VLBI) System is to provide
the means of directly measuring plane-of-
WORKING OF DSN:
the-sky angular positions of radio sources
(natural or spacecraft), DSN station The theory and challenges of deep
locations, interstation time and frequency space communications:Distance is the
offsets, and Earth orientation parameters. main problem in space communications,
since the intensity of electromagnetic

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radiation decreases according to 1/r2, that is radiated energy. A low gain antenna radiates
why signals from deep space probes are in a wide angle, while a high gain antenna
usually very weak when they reach the radiates in a narrow beam. On spacecraft
Earth. In order to receive the faint signal high gain antennas are used to send
back on Earth large parabolic disc antennas scientific measurements at high data rates
are used. To collect as much as possible of back to earth as well as receiving steering
the faint signal the antenna dish must be big. commands from earth; these antennas are
Since the electromagnetic radiation cannot highly directional and require very accurate
move faster than the speed of light there are aiming. Spacecraft are always equipped with
considerable time lag introduced in the at least one low gain antenna often two.
communications making real time These low gain antennas are very important
communications impossible. since they can intercept signals from almost
It takes over 5 hours for a signal any direction, this is useful if the spacecraft
from earth to reach the orbit of Pluto in the gets disoriented and the main high gain
outer part of the solar system. In order to antenna doesn’t point towards Earth. If the
communicate with the Earth the spacecraft spacecraft only had a high gain antenna it
must have a free line of sight to the Earth, would then not be able to receive any more
since radio waves cannot pass through large instructions from Earth. The low gain
solid objects such as planets and moons. A antennas are used in these kinds of situations
space probe orbiting a planet will therefore as a backup to receive the appropriate
lose contact with earth every time it gets on commands that will turn the spacecraft so
the far side of the planet. This means that the that the main antenna gets properly aligned
spacecraft will not be able to communicate to earth again. However, the low gain
with the Earth at all times. Even if the probe antenna can only handle a fraction of the
has a free line of sight to the Earth the data rate compared to the high gain antenna.
receiving antenna could be on the wrong Coding used in DSN:
side of the Earth, however by using several Most missions employ error
antennas in different places around the detecting – error correcting codes to
planet that could be solved. substantially improve telemetry link
The gain of an antenna is a measure performance. DSN users are reminded that
of how good the antenna is at focusing the their encoders should conform to the

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CCSDS Telemetry Channel Coding Blue adequacy of the link margin for
Book (CCSDS 231.0-B-1, September 2003. telemetry/dwell, tracking, telecommand
payload data reception. The IDSN station
Acceptable codes include:
has the responsibility of receiving the
1) Convolutional r = 1/2, k = 7 only. spacecraft health data as well as the payload
2) Reed-Solomon 223/255 only. data in real time. Later, conditioning of the
data takes place, before onward transmission
3) concatenated Convolutional / Reed-
of the same to Mission Operations Complex
Solomon at Bangalore. The tracking data
4) Turbo codes with rates: 1/2, 1/3, 1/4, or comprisingRange, Doppler and Angle data
will be transferred to the control center for
1/6, block sizes: 1784, 3568, 7136, and
the purpose of orbit determination. The
8920. payload data will be transmitted to the
INDIAN DEEP SPACE Indian Space Science Data Center (ISSDC)
NETWORK (IDSN):The Indian Deep as and when received by the payload data
Space Network consists of a 18-m and a 32- acquisition system, located at the station
m antennae that are established at the IDSN
campus, Byalalu, Bangalore. The Network is
CCSDS File Delivery Protocol (DSN) to
augmented witha couple of stations in the
western hemisphere in addition to the 64-m improve station utilization efficiency as well
antenna in Bearslake, Russia to improve the as reduce mission risk and costs, all DSN
visibility duration and to provide support
users should employ the CCSDS File
from the antipodal point.
Delivery Protocol (CFDP), to transfer data
The existing ISTRAC (ISRO to and from a spacecraft.
Telemetry Tracking and Command
Bandwidth Efficient Modulation
Network) S-Band Network stations will be
used to support the mission during Launch (DSN):Missions operating in the 2 and 8
and Early Orbit Phase (LEOP) that includes GHz bands, should employ bandwidth
Earth Transfer Orbit (ETO) up to a range of
about 1,00,000 km. Although the 18-m efficient modulation methods in
antenna is tailored for Chandrayaan-1 conformance with SFCG (space frequency
mission, the 32-m antenna can also support coordination group) and CCSDS
other planetary missions. The established
Recommendations.
IDSN is a state-of-the-art system, with its
base band system adhering to CCSDS Data Relaying:Some missions
(Consultative Committee for Space Data may propose dropping probes, landers, or
Systems) Standards, thus facilitating cross-
support among other TTC agencies. The even rovers to explore the surface of a
supporting network stations will ensure the planet/body. Others may insert orbiters

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around the same body. The result can be a problems where they are out of
multiplicity of spacecraft on or around a service for months at a time.
planet/body. While Mars has been the recent Furthermore, they are reaching the
focus, it is foreseeable that other planets or end of their lives. At some point they
objects in space could be of equal interest in will need to be replaced. The leading
the future. candidate is an array of smaller
dishes.
• By 2020, the DSN will be required to
support twice the number of
missions it was supporting in 2005.
CONCLUSION: Since all these
spacecraft are controlled by the DSN.
By 2015 NASA is planning for a
There are a number of limitations to
the current DSN, and a number of second Moon mission and by end of 2030 a
challenges going forward.
manned mission to Mars. These all require a
• There is only one DSN site in the powerful Earth communication Network.
Southern Hemisphere, Canberra.
There are no DSN network dishes in REFERENCE:
South America or Southern Africa, [1] How Spacecraft Will Communicate “on
so the DSN coverage of the Southern the Fly”, NASA CICT Program Office
Ames Research Center.
Hemisphere is limited.
www.cict.nasa.gov/infusion
• The need to support "legacy" [2] "NASA Tests First Deep-Space Internet."
missions that have remained PHYSorg.com. 18 Nov 2008.
www.physorg.com/news146245446.html
operational beyond their original
lifetimes but are still returning [3] http://deepspace.jpl.nasa.gov/dsn/
scientific data. Programs such as
[4] http://www.space.com/searchforlife/
Voyager have been operating long
past their original mission [5]http://www.spacetoday.org/SolSys/DeepS
termination date. They also need paceNetwork/DeepSpaceNetwork.

some of the largest antennas.

• The DSN's deferred maintenance of
its 70m antennas. This causes

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