Assignments

Basic Questions:

1. Explain the purposes of the United Nations’ Committee on the Peaceful Uses of Outer Space.
2. Describe Newton’s first, second, and third laws of motion.
3. Explain the goal of the ITU/WARC of 1985 and 1988 and the conclusion they arrived at.
4. Who was Arthur C. Clarke and what was his main contribution to the space science and technology?
5. Describe the layers of the Earth’s atmosphere and their unique characteristics.
6. Explain the essence of the International Agreement on a Code of Conduct for Outer Space Activities.
7. Name the nine indications of the Space Security Index.
8. Explain the two categories of the launching vehicles.
9. Describe the different types of rocket engines used in satellite communications.
10. Given the way we the humans have behaved on our own planet, regarding the use or misuse of Earth’s natural resources, preserving the environment, or lack of, for future generations, a logical question is whether or not we should be encouraging private space exploration. Write an essay expressing your opinion answering this question.

More Advanced Questions:

1. Define TT&C and explain the function of each element on the ground and on the spacecraft.
2. Define VSAT, its topologies and briefly explain some of its applications.
3. Name the three types of Low Earth Orbit satellite systems used in satellite communications and explain the followings for each orbit:
   • The frequency bands that they operate at.
   • Services that they provide.
   • Example of a satellite system designed or operating in each case.
4. Draw the Center-Feed antenna and Offset-Feed antenna and explain which one is preferable and what are the limiting factor for using the Offset-Feed antenna.
5. What are the different kinds of power amplifiers used in satellite communication? Name them, explain each one in terms of power capabilities, and back-off factor.
6. Show and explain the effect of wide-beam and narrow-beam Earth station antennas on GEO arc utilization.
7. Name the sub-systems onboard of a communication satellite and briefly describe the function of each of the sub-systems.
8. Explain different methods of making more efficient use of the GEO.
9. Explain the three Kepler’s laws.
10. Name the different orbits used in satellite communications and briefly explain the characteristics of each orbit.
11. What are the three remote sensing platforms used to collect information from ground-based targets and compare them in terms of coverage area and resolution.
12. Describe the active and passive remote sensing and give examples for each one.
13. Within the electromagnetic spectrum, what are the two bands that most of the scientific research in remote sensing are carried out? Explain each band’s characteristics.
14. Explain Synthetic Aperture Radar (SAR) and its significance in satellite remote sensing.
15. Name the ground surface characteristics affecting the EM signal reflection.
16. Explain the EIRP relationship with the antenna size on the ground and define spot, zonal, regional, hemispheric and global beam coverages and their corresponding EIRP.
17. Explain what Steerable phased-array antenna is and what its main applications are.
18. Why uplink frequency is higher than downlink frequency?
19. Define Transponder and explain its function.
20. For which satellite communications link, the frequency of 40-60 GHz is used?
21. Explain the types of satellite stabilization.
22. Name the three main building blocks of any satellite communication system.
23. What are the main shortfalls of geostationary satellite communication systems and explain if there are any possible solutions to overcome these shortfalls.
24. The frequency bands most commonly used in satellite communication are C-band, Ku-band, and Ka-:. Compare these frequency bands in terms of attenuation, bandwidth, interference with terrestrial systems, and earth station antenna size.
25. Draw the diagram for different modes of interference between a terrestrial station and two satellite systems (composed of the earth station and space segment) and explain the possible inference modes.

Problems:

1. A C-band earth station has an antenna with a transmit gain of 56 dB. The transmitter output power is set to 110 W at a frequency of 6.00 GHz. The signal is received by a satellite at a distance of 36,500 km by an antenna with a gain of 25 dB. The signal is then routed to a transponder with a noise temperature of 480 K, a bandwidth of 36 MHz, and a gain of 105 dB.

• Calculate the path loss at 6.0 GHz. Wavelength is 0.05 m.
• Calculate the power at the output port of the satellite antenna, in dBW.
• Calculate the noise power at the transponder input, in dBW, in a bandwidth of 36 MHz.
• Calculate the /N ratio, in dB, in the transponder.
• Calculate the carrier power, in dBW and in watts, at ttransponder output.

2. A 4 GHz earth station receiving system has an antenna with a noise temperature of 40 K, a LNA with a noise temperature of 80 K and a gain of 38 dB, and a mixer with a noise temperature of 900 K. Find the system noise temperature.

3. A satellite in GEO orbit is a distance of 36,000 km from an earth station. The required flux density at the satellite to saturate one transponder at a frequency of 14.1 GHz is -88.0 dBW/m2. The earth station has a transmitting antenna with a gain of 50 dB at 14.1 GHz. Find:

• The EIRP of the earth station
• The output power of the earth station transmitter.

4. Geostationary satellites use C, Ku and Ka bands. The path length from an earth station to the GEO satellite is 36,000 km. For this range, calculate the path loss in decibels for the following frequencies:

• 6.1 GHz, 4.2 GHz
• 14.2, GHz, 12.1GHz
• 30 GHz, 20 GHz

5. A satellite is in a 800 km high circular orbit. Determine:

• The orbital angular velocity in radians per second
• The orbital period in minutes; and
• The orbital velocity in meters per second.