During certain times of the year for several minutes every day, energy from the sun can overpower a satellite's signal. This is called a sun fade, sun transit or sun outage. Use the sun outage calculator below to estimate the times that your signal may be potentially degraded.
To read more about solar outages click here or scroll below.
Solar Interference Calculator
Commercial communications satellites are geostationary and therefore have orbits that lie in the equatorial plane. During the spring and fall equinoxes, the sun also passes through this plane. As seen from the ground, the sun seems to pass behind the satellites once per day. During the time when both the satellite and the sun are in the ground station's field of view, the energy from the sun can overpower the signal from the satellite. It is this loss or degradation of communications traffic from the satellite that is referred to as sun fade, sun transit or sun outage. The duration of the sun outage depends on several things: the beam width of the field of view of the receiving ground antenna, the apparent radius of the sun as seen from the Earth (about 0.25°), the RF energy given off by the sun, the transmitter power of the satellite, the gain and S/N performance of the ground station receive equipment, and other factors. All this can be used to determine the outage angle of the receive antenna. Outage angle is defined as the separation angle (measured from the ground station antenna) between the satellite and sun at the time when sun outage or signal degradation begins or ends (see diagram).
The exact point at which sun outage begins and ends is difficult to determine as it is a gradual transition. Also, due to the many differences in ground station equipment, some stations may experience a complete loss of signal while others may only experience a tolerable degradation of signal. This makes the determination of antenna outage angles difficult without complete information about the ground station equipment. For this reason, the following approximations were used to generate the antenna outage angles attached later:
OutageAngle = 11 (Freq)(Diam) + 0.25° where: Freq = Downlink Frequency in GHz (11.95 for Ku) Diam = Dish diameter of ground station receive antenna in meters.
Sun outages affect a geostationary satellite
Geostationary satellites are fantastic means of communication except for one little problem called SUN OUTAGES. These sun outages happen during March and September when the sun passes the equator. Here is a quote from the book Satellite Technology:
"The elevated temperature of the sun causes it to transmit a high-level electrical noise signal to receiving systems whenever it passes behind the satellite and comes within the beams of the receiver antennas. The increase in noise is so severe that a signal outage usually results. The length and number of the outages depends on the latitude of the earth station and the diameter of the antenna. At an average latitude of 40° in the continental United States, and a 10-meter antenna, the outages occur over 6 days with a maximum duration of 8 minutes each day. With a less directional 3-meter antenna, the outages occur over 15 days, with a maximum duration of 24 minutes."(Satellite Technology, p. 13).
Two times each year the sun passes the equator as it makes it north-south spiral. On that time, the sun lies on the celestial equator. The word equinox refers to the fact that, on this day, the night is equal to the day: each is twelve hours long. The sun is directly above the equator, so its rays fall vertically down.
The sun moves across the equator twice a year giving us the vernal (spring) and fall (autumnal) equinoxes.
Unfortunately the stationary satellites eclipses the sun and that causes electrical noise or interference to the broadcasting signals.
Obviously the Jesuits forget to change the definition of the word EQUINOX in the English dictionary because it still gives the true scientific definition of the word with the sun MOVING across the equator 2 times each year:
"Either of the two times during a year when the sun crosses the celestial equator and when the length of day and night are approximately equal; the vernal equinox or the autumnal equinox."(Webster's Third New International Dictionary).
Description of sun outages
Many commercial communications satellites are geostationary, and therefore have orbits that lie near the equatorial plane. During the spring and fall equinoxes, the sun also passes close to this plane. As seen from the ground, the sun seems to pass behind the satellites once per day. During the time when both the satellite and the sun are in the ground station's field of view, the RF noise energy from the sun can overpower the signal from the satellite. It is this loss or degradation of communications traffic from the satellite that is referred to as sun fade, sun transit or sun outage (see diagram).
The duration of the sun outage depends on several things such as: the beam width or field of view of the receiving ground antenna, the apparent radius of the sun as seen from the Earth (about 0.25°), the RF energy given off by the sun, the transmitter power of the satellite, the gain and S/N performance of the ground station receive equipment, along with other factors. All this can affect whether a ground station will experience a complete loss of signal or only a tolerable degradation in signal quality. The exact point at which sun outage begins and ends is difficult to determine since it is a gradual transition. The gain of an antenna falls off sharply outside the 3dB beam width, but it does not immediately go to zero. Therefore, if the sun is just outside the antenna's beam width, it can still contribute noise and degrade system performance. This makes it difficult to define exactly what conditions constitute a sun outage.