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ET VOL > ET Vol 5 Navigation systems > Flashcards

ET Vol 5 Navigation systems Flashcards

1
Q

Tactical navigation is directly concerned with maneuvering the ship in navigable waters.

A

false

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2
Q

Estimating ship’s position between known navigational points or fixes is known as

A

dead reckoning

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3
Q

Radio navigation consists of which of the following categories?

A
  1. Sub-space systems (SATNAV, TRANSIT, NAVSTAR) 2. Space–based systems (omega, loran)
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4
Q

One of the characteristics of dead reckoning is that the accuracy of the estimated position never exceeds the navigation method used to obtain the last fix. What happens to the accuracy of the estimated position over time?

A

It fluctuates

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5
Q

Referring to landmarks with known positions on earth describes which one of the following navigation methods?

A

piloting

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6
Q

Which of the following actions required to determine position in piloting is/are not required in electronic navigation?

A

Seeing the landmarks

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7
Q

According to the 1992 Federal Radio Navigation Plan, which of the following systems will become the primary reference navigation system for surface ships?

A

NAVSTAR(GPS)

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8
Q

what is LORAN

A

Long Range Aid to NAvigation

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9
Q

What is omega

A

VLF radio NAvigation

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10
Q

LORAN takes advantage of what radio signal characteristic?

A

Constant velocity

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11
Q

OMEGA is a hyperbolic phase— difference measuring system that compares the phase angle of two or more radio signals synchronized to what device or factor?

A

A common time base

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12
Q

Which navigation system continually computes the latitude and longitude of a ship by sensing acceleration?

A

SINS (Ships inertial navigation system)

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13
Q

A ship’s inertial navigation system is dependent on celestial, sight, and radio navigation aids.

A

false

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14
Q

What device measures changes in speed or direction along the axis in which it lies?

A

Accelerometer

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15
Q

What type of system is used to keep a SINS platform stabilized?

A

Gyro

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16
Q

Which of the following is a standalone SINS?

A

AN/WSN-5

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17
Q

Approximately how often can operators using the NNSS obtain fixes?

A

Every 2 hours

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18
Q

NNSS satellites transmit phase modulated data every 2 minutes on how many rf carriers?

A

2

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19
Q

What are the two types of NNSS satellite parameters included in the phase-modulated data?

A

Fixed and variable

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20
Q

The nominal orbit of NNSS satellites is what type of orbital parameter?

A

fixed

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21
Q

NNSS satellite data can be used as an accurate time reference.

A

true

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22
Q

NNSS satellite refined orbits are calculated at which of the following facilities?

A

Tracking station

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23
Q

Which of the following facilities calculates NNSS satellite clock error before satellite message injection?

A

Control center

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24
Q

Approximately how long does it take the injection station to transmit information to an NNSS satellite?

A

15 seconds

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25
Q

If errors are detected during a readback of freshly injected satellite data, how often is NNSS satellite message injection repeated until the transmission is verified as being correct?

A

every 2 minutes

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26
Q

At what point during the satellite pass will expansion effects cause the received frequencies to drop below the generated frequencies?

A

T3- Leaving away from

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27
Q

At what point will the received frequencies exactly match the transmitted frequencies?

A

T2-EVEN

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28
Q

At what point will compression effects cause the received frequencies to be higher than the transmitted frequencies?

A

T1- Approaching Fast

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29
Q

Which of the following factors affects the measurement of Doppler shift?

A

Refraction

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30
Q

Satellites broadcast at what to freqs to fix refraction?

A

150 and 400 MHZ

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31
Q

To solve the problem of Doppler shift accuracy, satellites are designed to transmit on how many frequencies?

A

2

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32
Q

Accurate NNSS position fixes for a moving vessel require what additional computation?

A

vessels speed

33
Q

Which ship’s system will provide the information required to perform the additional computation required by NNSS?

A

SINS

34
Q

Given the orbital parameters of a satellite, the Doppler shift of the signal transmitted from that satellite, and the velocity of a vessel, it is possible to obtain a navigational fix if the satellite is within what distance from the navigation set?

A

LOS Line-of-Sight

35
Q

One of the capabilities of the AN/WRN-5 includes time-ordered alerts for up to how many satellites?

A

8

36
Q

What is the “at sea” accuracy of the AN/SRN-19(V)2?

A

.25 miles

37
Q

What activity may degrade the accuracy of the AN/SRN-19(V)2?

A

sunspots

38
Q

You are initializing the AN/SRN– 19(V)2. In addition to programing the set’s position, what other parameter must you enter?

A

antenna length

39
Q

What navigational system will replace the NNSS?

A

NAVSTAR GPS

40
Q

Which of the following terms describe GPS satellite positioning data?

A

Almanac (data for ground satellites) and ephemeris (position data for single satellite)

41
Q

How often is the GPS satellite navigation data message updated?

A

every 24 hours

42
Q

What facility transmits the data required to update the GPS satellite navigation data message?

A

Manned Control Center

43
Q

There are how many (a) active spare and (b) active operational GPS satellites?

A

(a) 21 (b) 3

44
Q

How many earth orbits will each GPS satellite complete in a 24–hour period

A

2

45
Q

What communications technique is used for GPS satellite broadcasts?

A

Spread–spectrum

46
Q

What are the to Spread-Spectrum Rf Freqs?

A

1575.42 MHz (L1-RF) 1227.60 MHz (L2-RF)

47
Q

GPS satellites are positioned so a minimum of how many satellites are observable to a user anywhere on earth?

A

4

48
Q

Which of the two codes (C/A and P) transmitted by GPS satellites is NOT available to civilian users?

A

Precise code (only Military)

49
Q

Which of the following data is NOT included in the GPS NAV–msg?

A

Spectral

50
Q

GPS navigation is based on what principle?

A

Satellite ranging (measure time from Satellite to NAVSET divide travel time by speed of light

51
Q

Within how many feet can GPS determine position fixes?

A

50ft

52
Q

To obtain the above accuracy, how many satellite inputs are required

A

4

53
Q

How is the time difference between satellite transmission and when the navigation set receives this signal related to the distance between the satellite and the receiver?

A

Directly proportional

54
Q

GPS satellites use atomic clocks; the receivers do not. What type of error must be computed based on this fact?

A

Clock

55
Q

Tropospheric delay is predicted and included in what satellite data?

A

Almanac

56
Q

Ionospheric delay is greatest when a signal is received from directly overhead.

A

false (near the horizon)

57
Q

Of the frequencies listed below, which one will ionospheric delay phase–shift the most?

A

1227.60 MHz L2

58
Q

Satellite signals reflecting off one or more objects before reaching the navigation set produce what type of reception?

A

Multipath-reached it different times

59
Q

What data do operators enter into the AN/WRN-6(V) to speed up satellite acquisition?

A

Time and date Current position

60
Q

Which of the following is the normal operating mode of the AN/WRN-6(V)?

A

Navigation

61
Q

Which of the following is a portable GPS receiver?

A

AN/PSN–8

62
Q

TACAN is based on what type of radio air-navigation system?

A

Polar-coordinate

63
Q

Instead of depending on radio-wave reflection, beacon-transponders generate what type of replies?

A

Artificial

64
Q

What type of decoders do TACAN transponders use?

A

Twin–pulse

65
Q

Which of the following receiver controls provides noise–generated output?

A

Squitter

66
Q

If more interrogating aircraft come into the TACAN’S range, the number of noise–generated pulses will

A

decrease

67
Q

What signal does the TACAN ground station transmit to identify itself?

A

Identification pulse group

68
Q

What characteristic of the transmitted TACAN pulses supplies the distance information to aircraft?

A

Timing

69
Q

What type of modulation is used to convey TACAN bearing information?

A

bearing

70
Q

What type of radiation pattern is transmitted by the TACAN ground station antenna?

A

cardioid

71
Q

What is the common name of the 135–Hz reference burst?

A

Auxiliary reference burst

72
Q

How often is the identification code broadcast?

A

Every 37.5 minutes

73
Q

What is the designation of latest TACAN equipment in the fleet?

A

URN-25

74
Q

In the AS–3240 electronically– scanned antenna, the old singlephase rotating parasitic element has been replaced by how many electronically–switched inner parasitic elements?

A

12

75
Q

What is one big advantage the electronically–scanned antenna has over the old mechanically–rotated antenna?

A

It eliminates bandwidth limitations

76
Q

The AN/URN-20 uses the same electronically-scanned antenna as the AN/URN-25.

A

true

77
Q

What is the total number of TACAN channels available using both X and Y modes?

A

252 (126 for X) (126 for Y)

78
Q

The TACAN receiver frequency is always displaced how many MHz from the transmitter frequency?

A

63

79
Q

How many aircraft can be provided distance data simultaneously?

A

100

ET VOL (7 decks)

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