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Questions tagged [gnss]

Questions about Global Navigation Satellite Systems (GNSS), such as existing Global Positioning System (GPS) and GLObal NAvigation Satellite System (GLONASS), but also future such systems in development, like European Galileo, China's Compass or India's IRNSS (Indian Regional Navigational Satellite System).

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1answer
735 views

How far up have satellites used a GNSS for positioning, and how does the precision degrade with altitude?

GNSS satellites (at least GPS ones) are in Medium Earth Orbit (MEO). LEO satellites can use GNSS for positioning. Is this still possible for satellites in elliptical, such as Molniya, orbits? For ...
36
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3answers
18k views

Why are the GPS constellation satellites in such a high orbit?

Most satellites are in Low Earth Orbit. Some other satellites are in Geostationary Orbit because their function requires it. The GPS (and other GNSS, e.g. GLONASS) satellites are in a much higher ...
15
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2answers
1k views

Do any spacecraft use GNSS for attitude determination?

In principle, by placing a GNSS-receiver on all extremities of a spacecraft (or aircraft, for that matter), one can determine the orientation of the satellite. Google lists some studies, but have ...
9
votes
1answer
376 views

Does the “17” really mean anything with respect to GNSS orbits being rational factions of a sidereal day?

This answer suggests that the orbital periods of the four large GNSSS contstellations are linked to the sidereal rotation period of the earth by rational numbers with 17 or 34 as the denominator in ...
8
votes
1answer
750 views

Radiation pattern and signal strength of navigation satellite antennas

Where can I find the actual radiation pattern and signal strength of transmitting antennas used by GNSS navigation satellites/constellations (GPS, GLONASS, IRNSS, etc)?
1
vote
2answers
612 views

Does GPS spoofing ever come from space? How are spoofings usually detected?

The BBC News article Study maps 'extensive Russian GPS spoofing' says: (GPS spoofing) involves the state using strong radio signals to drown out reliable navigation data, says non-profit C4ADS. ...
10
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1answer
440 views

Why do GPS satellites have increasing eccentricity over time?

When comparing GPS, Beidou, Galileo, GLONASS, and potentially other GNSS, we can see that the eccentricities of GPS spacecraft are increasing with time (i.e. apogees increasing and perigees decreasing)...
11
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1answer
314 views

In LEO, what is the precision of GNSS-based position compared to traditional methods?

GNSS satellites (at least the GPS ones) are in MEO, so LEO spacecraft can use GNSS for their positioning. I've read that it's quite low-cost compared to the alternatives. How does the precision of ...
7
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1answer
279 views

How might excluding the UK from Galileo set the European programme back years and cost the EU billions?

edit 1: More here: Brexit 'will force Airbus work on Galileo out of UK' and now here: Brexit: UK wants £1bn back from EU if it is excluded from Galileo edit 2: And now more here: UK rebuffed over ...