From the Geosynchronous orbit of Inmarsat's communication equipment.
"Telecommunications satellites, as well as other types of satellites, maintain a geosynchronous orbit known as the Clarke orbit. This is essentially a stationary orbit located at an altitude of 22,236 miles (35,786 km) above sea level.
An object in Clarke orbit would appear to maintain the same position above the planet at all times."
" Space Weather, From Physics World, July 2000, by Janet Luhmann ... Space weather describes the conditions that prevail above the stratosphere - that is at altitudes of about 50 km and above - where responses to solar influences are particularly strong.
The regions that are affected include the Earth's upper atmosphere and the ionosphere - the ionized region of the upper atmosphere that extends for a few hundred kilometres into space.
The conditions also change the intensity of the radiation belts in the magnetosphere - the region beyond the ionosphere where electrons and ions are trapped by the Earth's magnetic field (figure 1).
Space weather is caused by the Sun's influence on the region of interplanetary space beyond the reach of the Earth's magnetic field.
This region is filled with a stream of protons and electrons from the outer atmosphere of the Sun together with its magnetic field, which collectively form the solar wind.
Stormy space-weather conditions are usually inferred from deviations in the magnetic fields that are measured by satellites and ground-based instruments.
These disturbances can also be deduced from conditions in the upper atmosphere and ionosphere, where intensified auroras and airglows are found.
At higher altitudes the intensity of both electromagnetic and particle radiation increases, which can pose a hazard for astronauts and possibly even for aircrew travelling on high-altitude routes
- (see "Cosmic rays: an in-flight hazard?" by Denis O'Sullivan Physics World May 2000 p21).
In addition to power and communications failures on the ground, disturbed space weather increases the risk to space-craft on several counts.
During stormy conditions, communication and weather satellites that reside on the outer edges of the radiation belt can suddenly find themselves in an environment that differs from the one for which they were originally designed.
The boost in the intensity of the electromagnetic radiation at extreme ultraviolet wavelengths heats the upper atmosphere and causes it to inflate. The resulting increase in the density of atmospheric gases at satellite altitudes can increase the atmospheric friction or drag on spacecraft, which can affect their orbit.
In the 1970s the Skylab space station re-entered the Earth's atmosphere prematurely following a period of unexpectedly high solar activity.
Indeed, this type of atmospheric drag is an ongoing concern with regard to the Hubble Space Telescope.
Furthermore, since signals to and from satellites are transmitted through the ionosphere, there is a far greater risk that instructions from a command centre will be affected during stormy space weather.
The performance of several expensive satellites, including the Intelstat and GOES-8 satellites in 1995 and Telesat in 1996, suffered briefly during or after a sequence of space-weather events.
More seriously, one of the Telstar satellites was lost in 1997 following such an event. "
So, satellite orbits are not "Stable" and that 40 degree arc isn't so dependable, either.