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15 Cards in this Set

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  • Back
11) The GPS control segment consists of several government facilities that are responsible for operating the global positioning system. Which of the following procedures would not be executed by the control segment?
a) Continuous tracking of all GPS satellites
b) Creating updated navigation messages
c) Providing precise ephemeris data to the user community
d) Uploading corrected ephemeris data to the satellites.
Answer is C
6) The carriers L1 and L2 are modulated by two PRNs, or pseudo-random noise codes. What are the names given to these codes?
a) Fo code and f1 code
b) P code and C/A code
c) IDOT code and IODE code
Answer is B
13) The Joint Program Office has specified a three dimensional point positioning limit that should normally be available to P code users. Consider also the degradation of two dimensional civilian accuracy with selective availability. What is the maximum degradation allowed in these GPS point positioning accuracies at 2o confidence levels?
a) 16m with full P code access & 100m with C/A code
b) 100m with full P code access & 200m with C/A code.
c) 1m with full P code access & 10m with C/A code
d) 0.01m with full P code access & 1m with C/A code
Answer is A
5) What are the positioning signal frequencies used in GPS?

a) 150 MHz and 400MHz
b) 1832.12 MHz and 3236.92 MHz
c) 420.9 MHz and 1227.60 MHz
d) 1575.42 MHz and 1227.60 MHz
Answer is D
12) What is the meaning of selective availability in GPS?
a) The deliberate degradation of the GPS signal
b) The encryption of the P code transmissions
c) The licensing of all GPS receivers by the federal government
d) The shutdown of selected satellites by the control segment.
Answer is A
8) A navigation message is modulated onto both of the L1 and L2 carrier frequencies. What is the frequency of the navigation message, and what is its significance?

a) The frequency of the navigation message is 100 MHz, and the message contains information on the position of the GPS receiver.
b) It is broadcast at 50 Hz and contains information on the status of both the particular satellite and the system as a whole.
c) The navigation message is broadcast at 1000 MHz, and contains information on the clock corrections needed for the satellite timing systems and the ephemerides for all of the GPS satellites.
d) The frequency of the navigation message is 450 Hz, and the message contains information on the health of all of the GPS space vehicles as well as messages, flags, and ionospheric delay parameters.
Answer is B
15) What is the purpose of a ground plane on a GPS antenna?
a) The ground plane of a GPS antenna provides a convenient reference for its correct polarization
b) The ground plane of a GPS antenna improves its gain and coverage
c) The ground plane of a quadrifilar or volute antenna assists the adjustment of its element phasing.
d) The ground plane of an antenna reduces the interference from reflected signals.
Answer is D
7) The PRN codes repeat themselves over specific intervals of time. What are the periods of those cycles, and what is their significance?

a) The P code has a 38 week period before it repeats itself, but each week of that cycle is assigned to a d different satellite. The C/C code repeats itself every millisecond and each satellite transmits a different C/A code, allowing a receiver to distinguish signals received simultaneously from different satellites.
b) The P code repeats itself every second, during which time it has over 10 million opportunities to switch from a plus 1 to a minus 1. The C/C code repeats itself every second and is, therefore, quite easily acquired.
c) The P code repeats itself every nanosecond. The C/A code repeats itself every week and can be used as a moderately accurate navigation signal as well as a method of rapidly acquiring the P code.
d) All of the above are true at selected intervals determined by the GPS control segment.
Answer is A
14) The remote monitoring stations transfer their data to the Master Control Stations, where computed satellite updates are generated and sent to the upload stations. Where is the Master Control Station located?
a) Hawaii
b) Ascension Island
c) Diego Garcia
d) Colorado Springs, Colorado
Answer is D
4) What is the mask angle in GPS, and what is its significance?

a) Reflected signals received by a GPS antenna are eliminated by a ground plane that defines the mask angle.
b) The mask angle is used in special circumstances to eliminate the reception of signals from satellites with unstable clocks.
c) The mask angle is the zenith at which a particular antenna type ceases to receive signals efficiently and is different for each type.
d) The mask angle is a vertical angle of 10 to 20 degrees from the observers horizon, below which signals from the GPS satellites are considered less reliable.
Answer is D
10) Timeskeeping is critical to the operation of the GPS system. Which of the following statements best describes the devices used to maintain accurate times for positioning with GPS?
a) Each GPS block II satellite is equipped with two high precision oscillators, and GPS receivers do not have on board clocks.
b) Most GPS receivers have quartz crystal oscillators as their internal clock, and each block II GPS satellite has four atomic oscillators.
c) Most GPS receivers employ hydrogen masers as their timekeeping device, and each block II GPS satellite uses quartz crystal oscillators as its frequency standard.
d) Each GPS block II satellite and most GPS receivers employ hydrogen masers as their timekeeping devices.
Answer is B
3) Which of the following orbital parameters best describes the final planned constellation of GPS satellites?
a) Six orbital planes inclined 55d with respect to the celestial equator.
b) Nearly circular orbits at 26,000 km.
c) Nearly circular orbits at 1100 km.
d) Both A and B.
Answer is D
1. The TRANSIT Doppler satellite positioning system was released form commercial use in 19687 and has since been widely used. GPS technology represents an improvement over the earlier TRANSIT system in may respects. Which of the following statements correctly describes some of those improvements?

(a) The orbits of the satellites of the TRANSIT system are much more susceptible to variations in local gravity fields and atmospheric drag than are the satellites of the GPS.
(b) The use of the TRANSIT system requires that line of sight be maintained between the stations of a network, while GPS does not.
(c) The timing technology in GPS is much improved from that which was available when the TRANSIT system was established.
(d) Both A and C are true.
Answer is D
9) The block II GPS satellites are rather large vehicles, 845 kg in final orbit. The satellites are equipped to perform several general functions. Which of the following statements correctly characterizes some of those functions?
a) The satellites receive transmissions from the receivers of GPS users and transmit timing and positioning information to the receivers of GPS users.
b) The satellites store information received from the GPS ground control stations and do some basic data processing on board. The satellites also maintain very accurate time.
c) The satellites are equipped with thrusters to maneuver in orbit and have a life expectancy of 7.5 years.
d) Both B and C are true
Answer is D
2) What is the name given to the GPS satellites?

Answer is C