Key Topic 95: Low Earth Orbit Systems

Question 1

3-95P1: What is the orbiting altitude of the Iridium satellite communications system?

A. 22,184 miles.
B. 11,492 miles.
C. 4,686 miles.
D. 485 miles.

Answer 1

D. 485 miles.

Question 2

3-95P2: What frequency band is used by the Iridium system for telephone and messaging?

A. 965 - 985 MHz.
B. 1616 - 1626 MHz.
C. 1855 - 1895 MHz.
D. 2415 - 2435 MHz.

Answer 2

B. 1616 - 1626 MHz.

Question 3

3-95P3: What services are provided by the Iridium system?

A. Analog voice and Data at 4.8 kbps.
B. Digital voice and Data at 9.6 kbps.
C. Digital voice and Data at 2.4 kbps.
D. Analog voice and Data at 9.6 kbps.

Answer 3

C. Digital voice and Data at 2.4 kbps.

Question 4

3-95P4: Which of the following statements about the Iridium system is true?

A. There are 48 spot beams per satellite with a footprint of 30 miles in diameter.
B. There are 48 satellites in orbit in 4 orbital planes.
C. The inclination of the orbital planes is 55 degrees
D. The orbital period is approximately 85 minutes.

Answer 4

A. There are 48 spot beams per satellite with a footprint of 30 miles in diameter.

Question 5

3-95P5: What is the main function of the COSPAS-SARSAT satellite system?

A. Monitor 121.5 MHz for voice distress calls.
B. Monitor 406 MHz for distress calls from EPIRBs.
C. Monitor 1635 MHz for coded distress calls.
D. Monitor 2197.5 kHz for hexadecimal coded DSC distress messages.

Answer 5

B. Monitor 406 MHz for distress calls from EPIRBs.

Question 6

3-95P6: How does the COSPAS-SARSAT satellite system determine the position of a ship in distress?

A. By measuring the Doppler shift of the 406 MHz signal taken at several different points in its orbit.
B. The EPIRB always transmits its position which is relayed by the satellite to the Local User Terminal.
C. It takes two different satellites to establish an accurate position.
D. None of the above.

Answer 6

A. By measuring the Doppler shift of the 406 MHz signal taken at several different points in its orbit.