ARTIFICIAL SATELLITE AND NAVIGATION
ABSTRACT
An artificial satellite is a manufactured object that continuously orbits earth or some other body in space. Such a satellite is used to study the universe, help forecast the weather, transfer telephone calls over the oceans, assist in the navigation of ships and aircraft, monitor crops and other resources, and support military activitiesNearly 300 years ago S±r Isaac Newton formulated the laws of celestial mechanics to explain the motion of the earth and planets, and of the earth's natural satellite, the moon. Now after many centuries of watching these laws in operation we will give up our role as passive observers to test these verysame laws on a man-made object, an artificial satellite
INTRODUCTION
An artificial satellite is an object that people have made and launched into orbit using rockets. There are currently over a thousand active satellites orbiting the Earth.Artificial satellites are used to study the Earth, other planets, to help us communicate, and even to observe the distant Universe. Satellites can even have people in them, like the International Space Station and the Space Shuttle.
The first artificial satellite was the Soviet Sputnik 1 mission, launched in 1957. Since then, dozens of countries have launched satellites, with more than 3,000 currently operating spacecraft going around the Earth. There are estimated to be more than 8,000 pieces of space junk; dead satellites or pieces of debris going around the Earth as well.
Satellites are launched into different orbits depending on their mission. One of the most common ones is geosynchronous orbit. This is where a satellite takes 24 hours to orbit the Earth; the same amount of time it takes the Earth to rotate once on its axis. This keeps the satellite in the same spot over the Earth, allowing for communications and television broadcasts.
Satellites are used for many purposes. Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, and space telescopes. Space stations and human spacecraft in orbit are also satellites. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit.
Early satellites were constructed as "one-off" designs. With growth in geosynchronous (GEO) satellite communication, multiple satellites began to be built on single model platformscalled satellite buses. The first standardized satellite bus design was the HS-333 GEO commsat, launched in 1972.
The largest artificial satellite currently orbiting the Earth is the International Space Station.
OBJECTIVE
The main objective of this reserch paper is• To study what is artificial satellite, its working ,application ,how it come into existence ,its future direction and much more about artificial satellite and its navigaton.
• Carrying out research and development in satellite and launch vehicle technology with a goal to achieve total self reliance
• Provide national space infrastructure for telecommunications and broadcasting needs of the country
• Provide satellite services required for weather forecasting, monitoring, etc.
• Provide satellite imagery required for the natural resources survey, management of natural disasters, public good services and monitoring of environment in the country
• Undertake proof of concept demonstration of space applications
• Promote research in space sciences and development of applications programmes as per national needs
• Provide the required satellite transponders and facilities to meet the communications, television broadcasting and security requirements of our country
• Provide adequate earth observation capability in spectral, spatial and temporal domains
• Provide launch services to meet national requirements and commercial need
ARTIFICIAL SATELLITE
An artificial satellite is an object that people have made and launched into orbitusing rockets. There are currently over a thousand active satellites orbiting the Earth. The size, altitude and design of a satellite depend on its purpose.In 1957 the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since then, about 6,600 satellites from more than 40 countries have been launched. According to a 2013 estimate, 3,600 remained in orbit. Of those, about 1,000 were operational; while the rest have lived out their useful lives and became space debris. Approximately 500 operational satellites are in low-Earth orbit, 50 are in medium-Earth orbit (at 20,000 km), and the rest are in geostationary orbit (at 36,000 km)
SIZES AND ALTITUDES OF SATELLITES
Satellites vary in size. Some cube satellites are as small as 10 cm. Some communication satellites are about 7 m long and have solar panels that extend another 50 m. The largest artificial satellite is the International Space Station (ISS). The main part of this is as big as a large five-bedroom house, but including solar panels, it is as large as a rugby field.Altitudes of satellites above the Earth’s surface also vary. These are three common orbits:
• Low Earth orbit (LEO) – from 200 to 2,000 km, for example, the ISS orbits at 400 km with a speed of 28,000 km/hour, and time for one orbit is about 90 minutes.
• Medium Earth orbit (MEO) – most MEO satellites are at an altitude of 20,000 km, and time for one orbit is 12 hours.
• Geostationary orbit (GEO) – 36,000 km above the Earth. Time for one orbit is 24 hours. This is to match the rotation of the Earth so that the satellite appears to stay above the same point above the Earth’s surface. This is used for many communications and weather satellites.
The altitude chosen for a satellite depends on the job it is designed for.
TYPES OF ARTIFICIAL SATELLITES
Navigation satellites
The GPS (global positioning system) is made up of 24 satellites that orbit at an altitude of 20,000 km above the surface of the Earth. The difference in time for signals received from four satellites is used to calculate the exact location of a GPSreceiver on Earth.Communication satellites
These are used for television, phone or internet transmissions, for example, the Optus D1 satellite is in a geostationary orbit above the equator and has a coverage footprint to provide signals to all of Australia and New Zealand.Weather satellites
These are used to image clouds and measure temperature and rainfall. Both geostationary and low Earth orbits are used depending on the type of weathersatellite.
Earth observation satellites
These are used to photograph and image the Earth. Low Earth orbits are mainly used so that a more detailed image can be produced.Astronomical satellites
These are used to monitor and image space. A satellite such as the Hubble Space Telescope orbits at an altitude of 600 km and provides very sharp images of stars and distant galaxies. Other space telescopes include Spitzer and Chandra.International Space Station (ISS)
This is a habitable space laboratory. At an altitude of 400 km, the ISS travels at a speed of 28,000 km/h and orbits the Earth once every 92 minutes. Scientists inside the ISS are able to perform many valuable experiments in a microgravity environment.
SATELLITE DESIGN
some of the same basic parts satellite :• The bus – This is the frame and structure of the satellite to which all the other parts are attached.
• A power source – Most satellites have solar panels to generate electricity. Batteries store some of this energy for times that the satellite is in the shadow of the Earth.
• Heat control system – Satellites are exposed to extremely high temperatures due to exposure to the Sun. There needs to be a way to reflect and reradiate heat. Electrical components of the satellite can also produce a lot of heat.
• Computer system – Satellites need computers to control how they operate and also to monitor things like altitude, orientation and temperature.
• Communication system – All satellites need to be able to send and receive data to ground stations on Earth or to other satellites. Curved satellite dishes are used as antennae
• Attitude control system – This is the system that keeps a satellite pointed in the right direction. Gyroscopes and rocket thrusters are commonly used to change orientation. Light sensors are commonly used to determine what direction a satellite is pointing.
• A propulsion system – A rocket engine on the satellite may be used to help place the satellite into the correct orbit. Once in orbit, satellites do not need any rockets to keep them moving. However, small rockets called thrusters are used if a satellite needs to change orbit slightly.
WORKING OF SATELLITE
Communications satellites are "space mirrors" that can help us bounce radio, TV, Internet data, and other kinds of information from one side of Earth to the other.
Uplinks and downlinks
If you want to send something like a TV broadcast from one side of Earth to the other, there are three stages involved. First, there's the uplink, where data is beamed up to the satellite from a ground station on Earth. Next, the satellite processes the data using a number of onboard transponders (radio receivers, amplifiers, and transmitters). These boost the incoming signals and change their frequency, so incoming signals don't get confused with outgoing ones. Different transponders in the same satellite are used to handle different TV stations carried on different frequencies. Finally, there's the downlink, where data is sent back down to another ground station elsewhere on Earth. Although there's usually just a single uplink, there may be millions of downlinks, for example, if many people are receiving the same satellite TV signal at once. While a communications satellite might relay a signal between one sender and receiver (fired up into space and back down again, with one uplink and one downlink), satellite broadcasts typically involve one or more uplinks (for one or more TV channels) and multiple downlinks (to ground stations or individual satellite TV subscribers).
Satellites are like any other vehicle inasmuch as they have two main parts: the generic vehicle itself and the specific thing it carries (the payload) to do its unique job. The "vehicle" part of a satellite is called the bus, and it includes the outer case, the solar panels and batteries that provide power, telemetry (a remote-controlled system that sends monitoring data from the satellite to Earth and operational commands back in the other direction), rocket thrusters to keep it in position, and reflective materials or other systems ("heat pipes") to protect it from solar radiation and dissipate heat. The payload might include transponders for a communications satellite, computers and atomic clocks to generate time signals for a navigation satellite, cameras and computers to images back to digital data for a photographic satellite, and so on.
SATELLITE NAVIGATION
The main principle behind a satellite navigation system is the creation of a trilateration from any point on the earth’s surface to the satellites in view. The distance to the satellites is measured by the time the radio signal needs to reach the receiver. Because a radio signal travels with the speed of light, highly precise clocks are used. The satellites contain atomic clocks, and the receivers advanced quartz clocks. The distance to the satellite can be calculated by multiplying the travel time by the speed of light (approximately 300 000 km/s). The exact location of the satellite in space is a prerequisite for this procedure. This is possible because the orbits are very stable and predictable. The satellites are observed and controlled by ground stations, which put the spatial information into the signal. These are the so-called ‘‘ephemeris data’’ (orbit of one satellite) and ‘‘almanac data’’ (relation between all of the satellites). Additionally, information on the satellite clocks is transmitted.In principle, three satellites must be available to determine a three-dimensional position. All points, which have the same distance to one satellite, form a spherical surface with the satellite in the centre. Three spherical surfaces intersect in two points. One point can be disregarded, because its position is located too far from the earth. A fourth signal is necessary to eliminate the time difference between the satellite’s atomic clocks and the receivers’ quartz clocks. After all, four satellites are necessary to determine a three-dimensional position. Another satellite is needed for integrity monitoring (quality control and identification of satellite malfunction). One more additional satellite is needed to identify the deficient satellite. The probability of receiving four or more GPS satellites with good geometry, quantified by a position dilution of precision (PDOP) of less than six and an elevation higher than 5° is about 99%. This is, however, a 24-h global average, and not a guarantee for the availability at a special place and time on Earth.
The main influences on accuracy are:
➢ the geometric position of the satellites (PDOP);
➢ clock errors of the satellites;
➢ ephemeris errors;
➢ tropospheric and ionospheric conditions;
➢ multipath effects;
➢ inaccuracies of the receiver;
INTERNATIONAL AND NATIONAL STATUS OF ARTIFICIAL SATELLITE
ADITYA Mission ;-The Aditya mission of ISSRO to the Sun is being proposed as an Indian solar observatory. Aditya-L1 mission is expected to be placed in a halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system. The scientific objectives are to study the solar dynamics in the chromosphere and corona with a suite of instruments including a coronagraph and a UV imager. The orbit around L1 is favorable as it provides continuous solar observations without any eclipse/ occultation and is an excellent outpost outside Earth’s magnetic field to make in-situ measurements of incoming charge particles.
The selected payloads and their scientific objectives are provided below:• Visible Emission Line Coronagraph (VELC) will study the diagnostic parameters of solar corona and dynamics and origin of Coronal Mass Ejections (CMEs). It can measure the magnetic field of solar corona down to tens of Gauss.
• Solar Ultraviolet Imaging Telescope (SUIT) will image the spatially resolved Solar Photosphere and Chromosphere in near Ultraviolet (200-400 nm) region and measure solar irradiance variations.
• The Solar Low Energy X-ray Spectrometer (SoLEXS) payload is aimed at monitoring the X-ray flares (1 – 30 keV) for studying the heating mechanism of the solar corona.
• High Energy L1 Orbiting X-ray Spectrometer (HEL1OS) is designed to study hard X-ray emission from 10 keV to 150 keV during the impulsive phase of solar flares.
• Aditya Solar wind Particle EXperiment (ASPEX) will study the variation of solar wind properties as well as its distribution and spectral characteristics.
• Plasma Analyser Package for Aditya (PAPA) payload is aimed at understanding the composition of solar wind and its energy distribution.
The Baseline Design Review (BDR) for the payloads is completed and the payloads are under development. The project proposal will be submitted for further approvals shortly.
SPONSORED RESEARCH
RESPOND (Research Sponsored) programme started in the 1970s, aims at encouraging academia to participate and contribute in various space related activities. Under RESPOND, projects are taken up by universities/academic institutions in the areas of relevance to Space Programme. Apart from this, ISRO has also set up Space Technology Cells (STC) at premiere institutions like Indian Institute of Technologies (IITs) - Bombay, Kanpur, Kharagpur and Madras; Indian Institute of Science (IISc), Bengaluru and Joint Research Programme (JRP) with University of Pune (UoP) to carry out research activities in the areas of space technology and applications.Projects at STC:
During the year, RESPOND has supported 60 new projects and 115 ongoing projects of five Space Technology Cells and Joint Research Programme at UoP and further 28 projects have been completed. Details are given in the table below:
The projects are reviewed by domain experts in ISRO and later by Joint Policy Committees consisting of experts from ISRO and the academia. In addition to the R&D Projects, ISRO under RESPOND programme has established research Chairs to guide advanced research in niche areas of space at Indian Institute of Science (IISc) Bengaluru, National Institute of
Advanced Studies (NIAS) Bengaluru, IIT Kharagpur, University of Pune (UoP) and Bangalore University
Highlights of few Major RESPOND Projects
➢ Design and development of 32-bit RISC (Reduced Instruction Set) processor based IP core for space application➢ Morpho-Tectonic evaluation of the Kosi river basin, Bihar using Remote Sensing Data
➢ Study of ionospheric behavior during Total Solar Eclipse of July 2009 using the characteristics of Very Low Frequency (VLF) signals:
➢ Development of advanced nano ZnO sensors for atmospheric and environmental monitoring
➢ Radio frequency (RF) Local Area Network (LAN) for satellites
➢ Preparation of Carbon Nitrides for Space Applications
Launch-Capable Countries
This list includes countries with an independent capability to place satellites in orbit, including production of the necessary launch vehicle. Note: many more countries have the capability to design and build satellites but are unable to launch them, instead relying on foreign launch services. This list does not consider those numerous countries, but only lists those capable of launching satellites indigenously, and the date this capability was first demonstrated.
Global Positioning System:
The United States Department of Defense (DoD) has developed the Navstar GPS, which is anall-weather, space based navigation system to meet the needs of the USA military forces and
accurately determine their position, velocity, and time in a common reference system, any where
on or near the Earth on a continuous basis (Wooden, 1985).
GPS has made a considerable impact on almost all positioning, navigation, timing and
monitoring applications. It provides particularly coded satellite signals that can be processed in a
GPS receiver, allowing the receiver to estimate position, velocity and time (Hofmann-Wellenhof
et al., 2001). There are four GPS satellite signals that are used to compute positions in three
dimensions and the time offset in the receiver clock.
APPLICATIONS OF ARTIFICIAL SATELLITES
Artificial satellites revolve around the earth because of the gravitational force of attraction between the earth and satellites. Unlike the natural satellites (moon), artificial satellites are used in various applications. The various applications of artificial satellites1. Weather forecasting
Weather forecasting is the prediction of the future of weather. The satellites that are used to predict the future of weather are called weather satellites. Weather satellites continuously monitor the climate and weather conditions of earth. They use sensors called radiometers for measuring the heat energy released from the earth surface.2. Navigation
Generally, navigation refers to determining the geographical location of an object. The satellites that are used to determine the geographic location of aircrafts, ships, cars, trains, or any other object are called navigation satellites. GPS (Global Positioning System) is an example of navigation system.3. Astronomy
Astronomy is the study of celestial objects such as stars, planets, galaxies, natural satellites, comets, etc. The satellites that are used to study or observe the distant stars, galaxies, planets, etc. are called astronomical satellites. They are mainly used to find the new stars, planets, and galaxies.4. Satellite phone
Satellite phone is a type of mobile phone that uses satellites instead of cell towers for transmitting the signal or information over long distances. Mobile phones that use cell towers will work only within the coverage area of a cell tower.5. Satellite television
Satellite television or satellite TV is a wireless system that uses communication satellites to deliver the television programs or television signals to the users or viewers.TV or television mostly uses geostationary satellites because they look stationary from the earth. Hence, the signal is easily transmitted.
Observation
Our study provides a balanced assessment of the state of satellite servicing and charts a path toward a future where the benefits of satellite servicing will be realized and become routine. The resulting paradigm changes could result in new space architectures to enable otherwise impossible applications.It is perhaps not generally realized how restricted out earth-bound view of the universe really is. We see astronomical objects only in the visible part ofthe optical spectrum. Thanks to developments in the science of radio we can now
also observe the objects in our galaxy and beyond, which emit radio waves„ We have thus learned to extend the limited sensitivity of the human eye; the main obstacle now becomes our own atmosphere which absorbs most of the incident radiations and hides much of the universe from our view.
It is therefore not difficult to appreciate how even a small satellite will
revolutionize observational astronomy and geophysics ; much more so when larger
and more elaborate satellites capable of carrying television cameras and tele
scopes become technically feasible.
We do not need to belabor this great scientific importance of artificial
satellites further
CONCLUSION
our nation can continue to claim remarkable achievement in science ,engineering,technology,robotics and human exploration in space.As we deliberate the something are very clear .For any meanigful future endeavor in space ,success is more assured with architectures that include satellite servicing .For our national security ,a domestic satellite servicing capability is paramount .
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