Sun outages explained

3 min. read

They happen twice a year, but what exactly are sun outages?

We inform our customers twice a year about sun outage season, but what exactly are sun outages and how can they affect transmissions? Our Network Management Supervisor Claudio Fanciullacci explains.

What exactly is a sun outage?

Sun outage (also known as sun interference or sun fade) is interference caused by the sun and it occurs when the receiving earth station, the satellite and the sun are aligned. This situation is called conjunction of the sun and the satellite.

How does a sun outage affect a satellite signal?

Any receiving antenna is characterised by its figure of merit, the G/T, where G is the antenna gain at the receive frequency, and T is the equivalent noise temperature of the receiving system. The higher the G/T value, the better the performance of the link.

During conjunction, since the sun is a giant source of radiation, the antenna noise temperature increases, decreasing the overall G/T and the link performance. Depending on the receive antenna size, its efficiency and the frequency band used, this interference can cause degradation of the satellite signal and a service outage.

How long can a sun outage last?

Sun interference occurs for several minutes. The actual timing, the duration of the interference and the level of service degradation varies depending the location of the receiving earth station, the size of the antenna, the received frequency and the link margin.

Why do they happen twice a year?

Sun outages for earth stations receiving from geostationary earth orbit (GEO) satellites happen during the equinox seasons (February-March and September-October) for a period of around two weeks, when the sun passes through the equatorial plane, that is used by the GEO satellites. During these periods, the sun crosses the equatorial plane and in specific time intervals is directly behind the satellite as seen as from the receiving earth station.

Is it possible to predict exactly when a sun outage will occur in my location?

Yes, you can find several free tools on the Internet that will allow you to calculate times for expected outages at your location. Usually the satellite operators provide calculators on their webpage that allow the user to determine interference times in advance.

How can I find out whether a sun outage might have an impact on my transmission?

If you intend to receive a service from Eurovision Services, you will see a note in the Eurovision Services synopsis informing that we are entering sun outage season. It is then recommended that you check via the online calculators when the outage for that specific satellite is expected for your antenna and location; if the estimated sun outage time overlaps with the service transmission time, then it is recommended to use an alternative receiving antenna at a different location.

What can I do to mitigate against the impact of a sun outage?

Eurovision Services guarantee that the signal is always on the satellite at nominal power level during a transmission but, unfortunately, the sun outage is beyond our control and the receiving earth stations will be impacted during those specific times. A possible mitigation is to use a receiving back-up antenna at a different geographical location, since the sun outage will not affect two geographically distant locations at the same time.

How does Eurovision Services secure its teleports against sun outages?

The Eurovision Global network is based on multiple teleports and we can overcome sun interferences thanks to the geographical redundancy: we check sun outage times well in advance and we plan our reception according to the calculations.