Solar outages to be expected on MSG-1 next weeks


a_van_belle
 

Solar outages to be expected on MSG-1 in Spring and Autumn:

Twice a year, in the spring and the fall the sun passes across the equator
directly behind each geo-stationary satellite in the Clark belt. When the
main beam of our Hotbird dish is in direct line of sight with the sun, a
sun outage occurs. The LNB is bombarded by the sun's RF radiation focussed
by the dish. This causes a drastic deterioration of the receive C/N
(carrier to noise ratio). Basically, the satellite signal is overwhelmed by
the unwanted signal from the sun; the signal from the sun is what we call
noise. This phenomenon is also known as Sun transit or Solar Interference.
Solar outages only affect downlinks (receivers), not uplinks
(transmitters). They also occur in cloudy weather, as the RF radiated by
the sun is only dampened slightly by clouds.
A solar outage will effectively cause about 10 minutes loss of signal from
that satellite. On the days before and after when the sun is directly
aligned with that satellite there will be less outage. The actual days and
times depend on your latitude and longitude, longitudinal position of the
satellite, diameter of the dish and the received frequency. The larger the
dish diameter and higher the frequency, the shorter time and the fewer days
sun outages last.

Can it damage my system?
Modern LNB's can handle the high levels of RF noise (using moderate sized
dishes). But during a solar outage all visible sunrays will be focused on
your LNB. Normally a LNB can cope with this, but in exceptional cases (a
wet, shiny dish surface and bright, sunny weather), the plastic cap
covering your LNB can burst!

Can I prevent this?
You cannot block the RF noise from the sun without blocking the signal from
Hotbird, so everyone will experience loss of signal during a solar outage.
But you can block the visible sunrays by putting a non-transparent plastic
bag over the LNB or dish without blocking Hotbird's signal. Alternatively
you could swing the dish out of position during a sun outage to prevent
damage to the LNB.

When will I be affected?
To calculate the date and time of solar outages you need to know your
latitude and longitude, the longitudinal position of the satellite, the
receive frequency and the diameter of your dish.
David Taylor has extended WXtrack to calculate solar outages (registration
required). Use version 3.4.0.705 or newer and go to View, Solar outage...
Check the default values already entered, and then go to the "Outage List"
tab.

For my location in the Netherlands, solar outages in Fall 2003 for Hotbird
6 are predicted for October 7 to 15, between 10:41 and 10:55 UTC with a
peak outage on October 11.
Receive systems for Meteosat 5/6/7, GOES, GMS (1691 MHz band) will be
affected too.

For a full explanation look at: http://www.geo-orbit.org/sizepgs/Noise.html
and http://www.david-taylor.myby.co.uk/wxsat/atovs/solar-outages.htm

Arne van Belle
Co-ordinator Radio Observers
Werkgroep Kunstmanen
N51.774 E4.612

Thanks to David Taylor for extending his WXtrack and editorial work on this
article.

Join MSG-1@groups.io to automatically receive all group messages.