Page 45 - Satellite Communications, Fourth Edition

Overview of Satellite Systems 25

1.8 Problems

1.1. Describe briefly the main advantages offered by satellite communications.
Explain what is meant by a distance-insensitive communications system.

1.2. Comparisons are sometimes made between satellite and optical fiber
communications systems. State briefly the areas of application for which you
feel each system is best suited.

1.3. Describe briefly the development of INTELSAT starting from the 1960s
through the present. Information can be found at Web site
http://www.intelsat.com/.

1.4. From the Web site http://www.intelsat.com/, find the positions of the
INTELSAT 901 and the INTELSAT 10-02 satellites, as well as the number of
C-band and Ku-band transponders on each.

1.5. From Table 1.3, and by accessing the Intelsat web site, determine which
satellites provide service to each of the regions AOR, IOR, and POR.
1.6. Referring to Table 1.4, determine the power levels, in watts, for each of
the three categories listed.
1.7. From Table 1.5, determine typical orbital spacing in degrees for (a) the 6/4-
GHz band and (b) the 14/12-GHz band.
1.8. Give reasons why the Ku band is used for the DBS service.

1.9. An earth station is situated at longitude 91°W and latitude 45°N.
Determine the range to the Galaxy VII satellite. A spherical earth of uniform
mass and mean radius 6371 km may be assumed.

1.10. Given that the earth’s equatorial radius is 6378 km and the height of the
geostationary orbit is 36,000 km, determine the intersatellite distance between
the VisionStar Inc. satellite and the NetSat 28 Company L.L.C. satellite,
operating in the Ka band.

1.11. Explain what is meant by a polar orbiting satellite. ANOAApolar orbiting
satellite completes one revolution around the earth in 102 min. The satellite
makes a north to south equatorial crossing at longitude 90°W. Assuming that
the orbit is circular and crosses exactly over the poles, estimate the position of
the subsatellite point at the following times after the equatorial crossing: (a) 0 h,
10 min; (b) 1 h, 42 min; (c) 2 h, 0 min. A spherical earth of uniform mass may
be assumed.

1.12. By accessing the NOAA Web page at http://www.noaa.gov/, find out how
the GOES take part in weather forecasting. Give details of the GOES-12
characteristics.