The satellite is constantly revolving around the Earth in its ORBIT. The
motion of the satellite has significant effects on its
performance.
These includes
These includes
- Doppler shift
- Effect due to variation in the orbital distance
- Effect of solar eclipse
- Sun's transit outage
Doppler Shift:
The geostationary satellites appear stationary with respect to an Earth station terminal, whereas in the case of LEO satellites, the satellite is in relative motion with respect to the terminal.In the case of geostationary satellites also there are some variations between the satellite and the Earth station terminal. As a result of this (since the satellite is moving with respect to the Earth station
terminal) the frequency of the satellite transmitter varies with
respect to the receiver on the Earth station terminal.
If the frequency transmitted by the satellite is fT, then the received
frequency fR is given by
Variation in the Orbital Distance:
Variation in the orbital distance results in variation in the range between the satellite and the Earth station terminal. If a time division multiple access (TDMA) scheme is employed by the satellite, the timing of the frames within the TDMA bursts should be carefully worked out so that the user terminals receive the correct data at the correct time.Range variations are more predominant in LEO and MEO satellites as compared to the geostationary satellites.
Solar Eclipse
During solar eclipse the satellites does not receive radiations from the sun and therefore they have to rely on on board batteries.The design of the battery is so as to provide continuous power during the period of the eclipse. Ground control Stations perform battery conditioning routines prior to the occurrence of an eclipse to ensure best performance during the eclipse.These include discharging the batteries close to their maximum depth of discharge and then fully recharging them just before the eclipse occurs.
Also, the rapidity with which the satellite enters and exits the shadow of the celestial body creates sudden temperature stress situations. The satellite is designed in such a manner so as to cope with these kind of thermal stresses.
Sun Transit Outage
A Sun outage, Sun transit, or Sun fade is an interruption in or distortion of geostationary satellite signals caused by interference (background noise) of the sun when it falls directly behind a satellite which an earth station is trying to receive data from or transmit data to.
Sun outages occur before the March equinox (in February and March) and after the September equinox (in September and October) for the Northern Hemisphere, and occur after the March equinox and before the September equinox for the Southern Hemisphere.
There are times when the satellite passes directly between the sun and the Earth.
The Earth station antenna will receive signals from the satellite as well as the microwave radiation emitted by the sun.
This might cause temporary outrage if the magnitude of the solar radiation exceeds the fade margin of the receiver.
The traffic of the satellite may be shifted to other satellites during such periods
Read About: Orbital Perturbations
Six vital orbital parameters
Variation in the Orbital Distance:
Variation in the orbital distance results in variation in the range between the satellite and the Earth station terminal. If a time division multiple access (TDMA) scheme is employed by the satellite, the timing of the frames within the TDMA bursts should be carefully worked out so that the user terminals receive the correct data at the correct time.Range variations are more predominant in LEO and MEO satellites as compared to the geostationary satellites.
Solar Eclipse
During solar eclipse the satellites does not receive radiations from the sun and therefore they have to rely on on board batteries.The design of the battery is so as to provide continuous power during the period of the eclipse. Ground control Stations perform battery conditioning routines prior to the occurrence of an eclipse to ensure best performance during the eclipse.These include discharging the batteries close to their maximum depth of discharge and then fully recharging them just before the eclipse occurs.
Also, the rapidity with which the satellite enters and exits the shadow of the celestial body creates sudden temperature stress situations. The satellite is designed in such a manner so as to cope with these kind of thermal stresses.
Sun Transit Outage
A Sun outage, Sun transit, or Sun fade is an interruption in or distortion of geostationary satellite signals caused by interference (background noise) of the sun when it falls directly behind a satellite which an earth station is trying to receive data from or transmit data to.
There are times when the satellite passes directly between the sun and the Earth.
The Earth station antenna will receive signals from the satellite as well as the microwave radiation emitted by the sun.
This might cause temporary outrage if the magnitude of the solar radiation exceeds the fade margin of the receiver.
The traffic of the satellite may be shifted to other satellites during such periods
Read About: Orbital Perturbations
Six vital orbital parameters
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