SatCom New satellite navigation systems – the European Union’s GALILEO, Russia’s GLONASS, Japan’s Quasi-Zenith Satellite System, and China’s Twinstar are going up. Satellite positioning system alliances have formed, and a number of countries are funding new systems. GPS chipsets are increasingly smaller and cheaper, lending themselves to new applications. The market for GPS equipment continues to expand and evolve
A basic snapshot of the various satellite constellation
schemes are listed below. More commercial information is
covered by
Satellite
Today.
- Voice
- Iridium
/ Globalstar
/ Inmarsat /
Super GEOs /
Ellipso
Courier
/ Odyssey
-
-
- Broadband
data
-
Sterling
/
Orblink
/
Pentriad
/
Virtual
Geo/VIRGO
/ Spaceway
/ WildBlue
/
Aster /
SWANsat /
Sky
Station / HALO
/
Platform International
-
-
- Radio
-
Sirius
/XM
Radio / WorldSpace
-
-
- Messaging
- Orbcomm
/
Final Analysis
/
AprizeStar
-
-
- Navigation
- GPS
/
Glonass
-
- Remote
sensing
- RapidEye
/
ERS / EO-1 /
LANDSAT
-
-
- Other
There's search and rescue; some people might consider
Inmarsat's Cospas-Sarsat
to be a constellation, although this is really a service
carried as additional payload on different types of
satellites. The satellites have uncoordinated ground coverage;
wait for a satellite to come overhead and to connect to a
ground station, and there's no positioning information in the
system, which predates GPS use. A GEO constellation has been
proposed.
NASA's Tracking
and Data Relay Satellite System can be thought of as a
private constellation; it's used for communication by the
Space Shuttle and the International Space Station.
To view the Earth as currently seen from a satellite in
Earth orbit, choose the satellite from the list here
or on the figure below. The satellite database is updated
regularly but may not reflect the current position of
satellites.
Also an
excellent resource courtesy of NASA, is
World Wind
-
lets you zoom from satellite altitude into any place on Earth.
Leveraging Landsat satellite imagery and Shuttle Radar
Topography Mission data, World Wind lets you experience
Earth terrain in visually rich 3D, just as if you were really
there.
Link Budget is
a generic term used to describe a series of mathematical
calculations designed to model the performance of a
communications link. In a typical simplex (one-way) satellite
link, there are two link budget calculations: One link from
the transmitting ground station to the satellite, and one link
from the satellite to the receiving ground station.
Link
Budget Calculation
Courtesy Satellite Signals Ltd
Advanced Resources
Corporation
