AS 15 - Intro to GPS Flashcards
Review Questions
What are the RADALT basic components?
Receiver/ transmitter
Indicator
Antenna system
Review Questions
What Mode 3 codes are used for hijack, comms failure and emergencies?
7500
7600
7700
What is the basic principle of GPS?
Measures ranges between the receiver and satellites
When a receiver has the position of each satellite stored in its memory, what is this information referred to as?
Ephemeris data
What does a GPS provide?
Highly accurate 3D position
Velocity vector and time
Which type of service is a GPS?
Passive service (receiver)
Why is a GPS somewhat resistant to interference?
It uses a spread spectrum
What kind of coverage and number of users can a GPS accomodate?
Global coverage and unlimited users
What will the GPS Block lll provide in the future?
Distress Alerting Satellite System (DASS) for SAR
Satellite laser reflectors are used for tracking the orbits of the satellites independent of radio signals.
What will the Satellite laser reflectors for the GPS Block lll allow regarding errors?
It will allows satellite clock errors to be disentangled from ephemeris errors
The GPS consists of three distinct segments, what are they?
Space, control and user.
Regarding the Space Segment, the final constellation baseline will provide how many satellites for world wide coverage?
30
Regarding the Space Segment, how many orbital planes of 4-5 satellites are there?
6 orbital planes
Regarding the Space Segment, how many satellites are always in view?
6 to 11 satellites
Regarding the Space Segment, what is the orbit period and altitude of a satellite?
12 hours (approx) and 20 200 km.
Describe the satellite’s orbit.
It is semi-synchronous, meaning it orbits earth twice a day
What does the Control Segment consist of?
5 monitor stations
1 master control station (MCS)
What does MCS mean and what does it do?
Master Control Station
It collates satellite data from the monitoring systems on the satellite’s clock drift and orbital positions.
It uses this data to send corrections to the satellites if necessary and predict satellite behavior for the next few hours.
What do the unmanned stations do?
They passively monitor the satellites in view and collect range and time data transfer.
What does the User Segment consist of?
Antenna
Computer
Signal processing equipment
Oscillator (clock)
Regarding GPS Policy, GPS provides which two navigation services?
Standard Position Service (SPS)
Precise Positioning Service (PPS)
Regarding GPS Policy, SPS is used by who and utilizes which frequencies?
Civil and some military users
C/A on L1 frequency
Interim use of L2 frequency for carrier phase
Regarding GPS Policy, SPS can expect what distance error?
7.8 m error
Regarding GPS Policy, PPS is used by who and uses which frequencies?
Military
C/A on L1 and P/Y on L1 and L2
Regarding GPS Policy, what is PPS’s accuracy?
< or equal to 5.9 m
Regarding GPS Policy, PPS requires what for full access?
Decryption codes
Regarding GPS Policy, DoD and DoT have committed through ICAO:
10+ years of GPS capability to civil aviation
7.8 m accuracy
6 year notification of any service reduction
Regarding GPS Policy, when might civilians use PPS?
Critical national interest
Encryption keys can be adequately protected
If no alternative is available
As GPS phases in, The DoD plans to phase out and retain what?
Phase out: NNSS, TACAN, OMEGA, LORAN and VOR/DME
Retain: INS
Review Questions
The GPS consists of how many segments?
What are they?
Three
Space
Control
User
Review Questions
The User segment consists of what?
Antenna
Signal processing equipment
Computer
Oscillator
