Satellite Navigation Systems

GNSS

stands for Global Navigation Satellite Systems.

1. GPS — United States
2. GLONASS — Russian Federation
3. Galileo — European Union/Europe
4. BeiDou — China
5. QZSS — Japan
6. IRNSS/NavIC — India

GNSS refers to satellite navigation systems involving components from different countries

:satellite datum

is centered on the Earth and uses a Cartesian coordinate framework.

Satellite ephemerides

are information describing the satellite's position and motion as a function of time.

ephemerides

List of coordinates as a function of time

1.2–1.6 GHz;

λ = 19–25 cm

GNSS signals use L-band radio frequencies, approximately: ___ with wavelengths of approximately: ___

Global Positioning System

GPS stands for

GPS

is a satellite-based positioning system developed by the United States Department of Defense (US DoD).

TRANSIT Doppler system

Before GPS, the United States used the

TRANSIT

was a U.S. military navigation system based on the Doppler principle.

1,075 km;

20,200 km altitude

the TRANSIT altitude is approximately: ___ GPS replaced TRANSIT and operates at approximately: ___

United States;

24 satellites;

MEO;

20,200 km;

1970s;

1995

[GPS Key Facts]

Operator: ___ Number in nominal constellation: ___ Orbit: ___ Approximate altitude: ___ Development: ___ FOC: ___

WGS84

The realization of ___ is represented by a catalogue of coordinates of more than 1,500 geodetic stations, and the system is centered on the Earth's center of mass, or geocenter.

a = 6,378,137 m;

f = 1/298.257223563;

ω = 7,292,225 × 10⁻¹¹ rad/sec;

GM = 3,986,005 × 10⁻⁸ m³/sec²

[WGS84 Parameters]

Semi-major axis: ___ Flattening: ___ Earth rotation rate: ___ Geocentric gravitational constant: ___

space-qualified atomic clocks

The satellites use ___ to maintain accurate time.

50 bits per second (50 bps)

location and time information are transmitted at

:onboard frequency synthesizer;

10.23 MHz

GPS navigation signals are coherently derived from an ___ driven by the satellite's active atomic clock.

The nominal frequency is designed around: ___

Coarse/Acquisition code;

L1;

1,575.42 MHz;

Precision code;

L1 and L2;

1,227.6 MHz

[Legacy GPS Signals]

C/A = ___ It is transmitted on: ___ Its carrier frequency is: ___

P = ___ The P code is transmitted on: ___ Its carrier frequency is: ___

Direct Sequence Spread Spectrum (DSSS) modulation

the signals as being generated using

1. RF carrier
2. Data waveform
3. Spreading waveform

A GPS signal is formed by three major components

Pseudo-Random Noise

PRN stands for

PRN Co

It is a contiguous series of rectangular pulses used as a spreading waveform.

Chip

The minimum period between transitions in the spreading waveform is called the

Chip-ping rate, Rc

represents the clock rate of the PRN code

Length-1023 Gold codes;

1.023 MHz;

Unique PRN;

10.23 MHz

[C/A PRN]

The PRN for the C/A code is taken from a family of: ___ generated at: ___ Each GPS satellite has a: ___ The Y-code PRN operates at: ___

50 bps;

300 bits;

6 seconds;

12.5 minutes

[GPS Navigation Data]

The GPS navigation data are transmitted at: ___ Each subframe contains: ___ At 50 bps, one subframe takes: ___ The entire message repeats every: ___

GPS Time

GPS uses its own time scale called

Midnight January 5, 1980 / morning January 6, 1980

The GPS time system begins at

SPS = Standard Positioning Service

This is the civilian GPS service.

PPS = Precise Positioning Service

This is the GPS service for authorized users.

Selective Availability (SA)

was a method used to deliberately degrade positioning accuracy, it degraded accuracy and was ceased on May 12, 2000

Global'naya Navigatsionnaya Sputnikovaya Sistema

GLONASS stands for

GLONASS

It is the satellite navigation system of the Russian Federation

GLONASS

provides dual-frequency L-band navigation signals for both civilian and military navigation.

GLONASS

the second major system after GPS in reaching FOC.

24 satellites

By 2011, GLONASS had

GLONASS

was the second-generation dual-use government GNSS.

Tsyclon/Tsikada

GLONASS predecessor systems

Uragan, meaning Hurricane

The first test satellite of GLONASS was

PZ-90

GLONASS uses the

GLONASS System Time (GLST);

UTC(SU)

[GLONASS Time]

GLONASS uses: ___ Its reference timescale is: ___

National Metrology Institute of the Russian Federation (VNIIFTRI)

UTC(SU) is maintained by the

L1, L2, L3;

5 m horizontal 10 m vertical at 95% (2σ)

[GLONASS Services]

GLONASS has an open service with unencrypted signals in up to three frequency bands: ___

The service is globally available to users without limitations. The performance specification given in the lesson is approximately: ___

1. GLONASS — 1982
2. GLONASS-M — 2003
3. GLONASS-K — 2011

Important GLONASS satellite generations are

Galileo

is the European GNSS.

Galileo

was designed as a self-standing satellite-based positioning system for worldwide service

E1, E6, E5

Galileo navigation signals are provided on three frequencies

:European Space Agency (ESA) and the European Commission

Galileo was developed through collaboration between the

Open Service;

Public Regulated Service;

Commercial Service

[Galileo Services]

The ___ is the publicly accessible positioning service. The ___ is a restricted-access positioning service for Government-authorized users. The ___uses the E6-B/C signal and is intended to provide future added-value services.

Galileo System Time (GST);

UTC;

00:00 UTC on Sunday, August 22, 1999

[Galileo Time]

Galileo uses: ___ GST is linked to: ___ The beginning of GST is: ___

700 kg / 1500 W class spacecraft

Galileo satellites are approximate