zubair(19457).doc

Balochistan University Of Information Technology, Engineering And Management Sciences, Quetta

Balochistan University Of Information Technology, Engineering and Management Sciences, Quetta

Faculty of ICTDepartment of Telecom Engineering Assignment no.1Class: BS (Electronic) Semester 8th Date: 11.05.2015Course: Satellite Communications

Instructor: Muhammad Bux

Name: Muhammad Zubair

Roll No:19457

Q.1 Describe briefly the main advantages offered by satellite communications. Answer:Cost Effectiveness- Cost of satellite capacity does not increase with the number of users/receive sites, or with the distance between communication points. Whether crossing continents or staying local, satellite connection cost is distance insensitive.

Global Availability- Communications satellites cover all land masses and there is growing capacity to serve maritime and even aeronautical markets. Customers in rural and remote regions around the world who cannot obtain high speed Internet access from a terrestrial provider are increasingly relying on satellite communications.

Superior Reliability- Satellite communications can operate independently from terrestrial infrastructure. When terrestrial outages occur from man-made and natural events, satellite connections remain operational.

Superior Performance- Satellite is unmatched for broadcast applications like television. For two-way IP networks, the speed, uniformity and end-to-end control of today's advanced satellite solutions are resulting in greater use of satellite by corporations, governments and consumers.

Immediacy and Scalability- Additional receive sites, or nodes on a network, can readily be added, sometimes within hours. All it takes is ground-based equipment. Satellite has proven its value as a provider of "instant infrastructure" for commercial, government and emergency relief communications.

Versatility and More- Satellites effectively support on a global basis all forms of communications ranging from simple point-of-sale validation to bandwidth intensive multimedia applications. Satellite solutions are highly flexible and can operate independently or as part of a larger network.

Q.2 Discuss why uplink frequency of satellite is higher than downlink frequency.Answer:I searched a lot but couldnt find any convincing reason for why the uplink is greater then downlink. But still the reasons which I could find are:

As the frequency increases the amount of interference caused by the atmosphere decreases. So as high frequency signal has more signal energy in it so it can penetrate the atmosphere easily.The uplink frequency is kept higher than downlink frequency because as the frequency increases wavelength decreases so it is more practical to keep size of transponder in satellite much less.

Q.3 Describe the history of satellite communications.Answer:A satellite is basically the Secondary body that is rotating/ revolving around the primary body that is the Earth. Satellites nowadays are used for many purposes like the communication, military, broadcasting and weather etc. The journey of the satellites started from Soviet Union who launched the first satellite on the 4th of October 1957 named Sputnik-1 having the life time of 3-months. Soviet launched another satellite named Sputnik-2 having Laika (dog) as the only passenger.Then in 1958 USA launched its first satellite named Explorer-1 under the project Project Vanguard. Then in the same year on 18th December USA launched the first communicational satellite named SCORE (Signal Communication by Orbital RElay) containing the message of peace by the president Eisenhover Peace on earth, Good will toward men, it lasted in space for the period of 12-days.Then in 1960 the first Passive satellite named Echo-1 was launched by USA and in the same year the first ever active satellite was launched named Courier-1B. In 1962, the world's first active communications satellite, Telstar 1, was launched. This satellite was built by Telesat's predecessors at AT&T and Bell Laboratories. During its seven months in operation, Telstar 1 dazzled the world with live images of sports, entertainment and news. It was a simple single-transponder low-earth-orbit (LEO) satellite, but its technology of receiving radio signals from the ground, and then amplifying and retransmitting them over a large portion of the earth's surface, set the standard for all communications satellites that followed. Q.4 Discuss the role of Pakistan in launching satellites in low earth orbit (LEO) and geostationary orbits (GEO) regions.Answer:Pakistan initiated its journey in the field of space technology in the year 1961 when the Space and Upper Atmosphere Research Commission (SUPARCO) was established by the President Field Marshal Ayub Khan on the advice of Prof. Abdus Salam. SUPARCO is an executive and bureaucratic space agency of the Government of Pakistan, responsible for the nation's public and civil space program and for aeronautics and aerospace research. Its mission statement and objective is to conduct peaceful research in space technology and promote the technology for socio-economic uplift of the country. Since its creation in 1961, the SUPARCO has achieved numerous milestones, including the first successful spaceflight of country's first weather expendable launch rocket, Rehbar-I. The country's first satellite, Badr-I, was built by the SUPARCO and launched by the People's Republic of China in 1990 (The satellite successfully completed its designed life and it was termed by the government as "key success "to SUPARCO). SUPARCO launched the second experimental satellite BADR-B on 10 Dec 2001.In August 2006, Peoples Republic of China signed an agreement with Pakistan to conduct joint research in space technology. On 11th August 2011 with the co-operation of China Pakistan launched its first communication satellite PakSat-1R, the satellite was launched from China and is working successfully. According to SUPARCO five GEO satellite and six LEO satellite will be launched in between 2011 till 2040.Q.5 Explain the significant effects which reduces the angular velocity of satellites in low earth orbit (LEO) and geostationary orbits (GEO) regions. Answer:

For LEO orbit the satellites does not appear stationary to earth stations. The LEO orbit can also be used to cover a polar region which GEO cant accomplish. Objects in LEO encounter atmospheric drag in the form of gases in the thermosphere or exosphere depending on the orbit height due to which angular velocity of a satellite in low earth orbit reduces. GEO orbit satellites are placed in orbit such that they remain stationary relative to a fixed spot on earth. If a satellite is placed at 35900 km above the earth its angular velocity is equal to that of the earth but due to the gravitational pull of the sun and moons its angular velocity is reduced. Q.6 Example 2.2, Example 2.5, Example 2.6.EXAMPLE 2.2: Calculate the semi major axis for the satellite parameters given in Table 2.1

Solution:The mean motion is given in table 2.1 is:

n = 14.22296917.1 /day

Converting to Rad/Sec as:

no :=n.2.pi

no=14.22296917.1

no=89.32024639/86400

no=1.033799148*10-3no2=1.068740678*10-6And

= 3.986005.10 14 .m3 .sec-2According to Keplers 3rd Law

a :=(/no2)1/3a=((3.986005/1.068740678)*1020)1/3Semi major axis=a=7197.29km

EXAMPLE 2.5: Determine the rate of regression of the nodes and the rate of rotation of the line of apsides for the satellite parameters specified in table 2.1.the value for a from example2.2 can be used.

Solution:

Inclination=i=98.6328 deg

Eccentricity=e=.0011501

Semi major axis=a=7197.29km

Mean motion=n=14.23304826/day

Known constant: K1: = 66063.1704 km2 no = 2.pi .nno=89.38354307 rad/day

K = n. K1/a2. (1-e2)2After putting the values in the above formula we will get

K= 6.544 . deg/day Now

= -K .cos(i)= -6.544*-0.1501

= 0.9822 deg/day

= K. (2-2.5sin (i)2)=6.544(2-2.5(0.98867)2)=6.544(-0.44)=-2.903 deg/day

EXAMPLE 2.6: Calculate for the satellite in example 2.5 the new values for and one period after epoch.

Solution:= 0.9822 deg/day

=-2.903 deg/dayFrom the table 2.1 we know the values of

Mean motion=n=14.23304826/dayo= Argument of perigee=113.5534 dego=Right ascension of the ascending node=251.5324 degPeriod=PA=1/n

So

PA=1/14.23304826PA=0.070259018

= o+ . PA

=251.5324+0.9822(0.070259018)

=251.601 deg

= o+ . PA =113.5534+ (-2.903(0.070259018))

=113.349 degQ.7 List the various applications and services of satellite.

Answer:

Few of the major services and applications that the satellites are used for are as under:

Navigation: Navigation satellite is an artificial satellite stationed in space for the purposes of navigation. The GPS system is the first core element of the satellite navigation system widely available to civilian users.Communication: A communication satellite is a satellite stationed in space for the purposes of telecommunications. Like telephony, Television and Radio and Satellite Broadband.

Weather: Satellites can also be used for the purpose of weather forecasting.

Earth Observation: from the satellite we can also observe the following aspects of Earth:

Agriculture

Forestry

Geology

Environment

Few of the other application and services involve:Military, broadcasting satellite service, fixed satellite services, mobile satellite services etc.Q.8 Why is there a need for satellite communication?

Answer:

The satellite communication has totally changed the world of communication. Broadcasting on the other hand depends to a very high degree on satellites. New services such as HDTV and 3D television require more and more of the finite natural resource of the electromagnetic spectrum (Bandwidth). Internet access by satellite, considered as an efficient way to support under-developed regions.In military sector providing robust and sophisticated secure communication network.

Traditional telecommunication links used direct "cables "linking different areas. As a result of the cost of installation and maintenance of these cables, satellites were seen as ideal alternative. They provided a high bandwidth and were able to operate for many years and are considered cheap.Satellite communication allows us to learn more about our surroundings than ever before.

Q.9 What are the primary factors needed for defining an orbit of a satellite?

Answer:

There are 8 elements to define an orbit. These elements are also called Keplerian Elements after the German astronomer Johannes Kepler .Kepler discovered that planets moved in elliptical orbits rather than circular orbits. The following are Keplerian Elements:

(1)Inclination

(2)Elevation

(3)Semi major axis

(4)Eccentricity

(5)Mean anomaly

(6)Argument of perigee

(7)Inclination

(8)Right ascension of ascending modeQ.10 List the names of SUPARCO space centers located in the Pakistan. Explain the history, functions and the development of SUPARCO?Answer:

1) Space application & research center Karachi

2) Remote Sensing Applications Directorate Karachi

3) Space and Atmospheric Sciences Directorate Karachi

Space Application Div

Space Science Div

4) National Center for Remote Sensing and Geo informatics (NCRG) Karachi

5) Satellite Research & Development Center for Remote Sensing Satellite Lahore.

6) Satellite Research & Development Center for Communication Satellite Lahore

7) Telemetry, Tracking and Command (TT&C) Facility Lahore

8) Space Application & Research Cell Lahore 9) Satellite Ground Station Islamabad

10) Ionospheric Research Station Islamabad

11) Geomagnetic Observatory Islamabad

12) Space & Atmospheric Research Station Multan

13) Space Application & Research Center Peshawar

FUNCTIONs OF SUPARCO:

Undertake research and conduct pilot studies based on the applications of Satellite Remote Sensing data and Geographic Information System technology to natural resources surveying, mapping and environmental monitoring

Undertake research studies in space and atmospheric sciences including satellite meteorology, satellite radiance, troposphere/stratosphere studies, atmospheric pollution, satellite geodesy and astronomy

Undertake research studies relating to the ionosphere and associated radio wave propagation and geomagnetism

Development, design, fabrication, assembly, and launching of:

[SIZE=-2].[/SIZE]

Communication satellites for voice, video, Direct-to-home TV broadcast services and digital data transfers

Earth observation satellites for various scientific/technological applications

Sounding rockets for upper and middle atmospheric research

Establishment and operation of ground receiving stations for

Acquisition of SRS data for earth resources surveying, mapping and environmental

Monitoring studies

Acquisition of data for atmospheric/meteorological studies

Transmitting and receiving signals from communication satellites

Reception of signals from ships, boats and vehicles in distress under the satellite-aided search and rescue COSPAS-SARSAT programme

Establishment and operation of facilities for tracking satellites/rockets to determine their Orbital parameters, trajectories,

Development for various scientific & technological experiments

Development of software for different functionsDEVELOPMENT OF SUPARCO

Towards late 1990s, SUPARCO planned an Earth Observation Satellite System (EOSS), which by 2006/7 was reconfigured and renamed as Remote Sensing Satellite System (RSSS), comprising of two remote sensing satellites, one carrying an electro-optical payload and the other a Synthetic Aperture Radar (SAR).

The PRSS-1 project is currently under the process of approval from the Government of Pakistan. The planned satellite will carry a high-resolution electro-optical payload with designed service life of 05 years. The satellite is envisaged to be designed, developed and launched in a low Earth orbit by 2015/16, through cooperation/ collaboration with reputed international satellite manufacturers. Pakistans first communication satellite was launched on 12 Aug 2011. The satellite was developed and launched by the China Great Wall Industry Corporation (CGWIC). The satellite is located at the 38 degrees East orbital slot. The service life of the satellite is 15 years. The commercial services of the satellite were inaugurated by the Prime Minister of Pakistan on 05 Nov 2011 from the satellite ground station located near Lahore. The satellite is providing satisfactory services to a broad spectrum of national and international customers.