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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.

Alan Sewards <alan.sewards@...>
 

As usual, Arne has given a detailed and factual account of what happens
during a solar transit. However, there are millions of TV dishes out there
which suffer these insults on an annual basis, and I have never seen or
heard of any problems, so I suspect that the gloomy prognostications of
possible damage are rather pessimistic. Yes, you will lose some signal (as
you will on your Sky service or any other satellite TV) for a few minutes,
but I very much doubt that any damage will be suffered by the LNB. You are
far more likely to injure yourself, cause damage or lose signal by messing
around with the dish trying to avoid the problem!

If it ain't broke, don't fix it!

Best regards - Alan

----- Original Message -----
From: "Arne van Belle" <a.van.belle@...>
To: <MSG-1@...>
Sent: Saturday, September 27, 2003 1:20 PM
Subject: [MSG-1] Solar outages to be expected on MSG-1 next weeks


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.




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a_van_belle
 

Hello Alan,

You're partly right Alan, TV dishes do suffer from the same effects.
But there won't be many TV viewers watching around 11:00 UTC. And
before they know what is happening, the solar outage will be over.
But MSG "viewers" might miss multiple images and unnecessarily start
checking their equipment or blaming Eumetsat!

About damage to LNB's: As I said, only in exceptional cases damage
could occur because modern dishes have a rough, structured surface to
prevent reflecting too much sun and LNB's have a sturdy cap. But this
won't be of any help if your dish is covered by ice. What are the
chances of rain, followed by a frosty night and a sunny morning in
early October ?
Let's hope we don't have these conditions!

Most TVsat installers will confirm that a burst cap due to solar
outage is a common problem around this time of year!

Greetings,
Arne van Belle

James Brown <james@...>
 


Most TVsat installers will confirm that a burst cap due to solar
outage is a common problem around this time of year!

Greetings,
Arne van Belle
Arne, I have seen these split caps and have wondered what caused them. Thanks for the warnings, I can always throw some cover over the LNB. More likely than not, the sun just won't shine!!

Cheers,
James
--
James Brown

johnrigsec@...
 

Arne,

You beat me to it!

In fact there will be two losses of data due to sun, satellite co-liniarity.
The first 'outage' will be when the sun and users Hot Bird 6 receiving dish
are
co-aligned.

The second outage will be when the sun, MSG-1 and EUMETSAT's ground
station are co-aligned.

Regards,
John Tellick.