Satellite Sun Eclipse

Updated 23 March 2012

More calculators at http://www.satellite-calculations.com

 

Earth Caused Eclipse

There are two types of Sun eclipse that causes a
geostationary satellite to be in the shadow. The most common one is caused by
the earth blocking the sunlight and happens near equinoxes.
Earth caused eclipses can continue for up to 45 days around equinox
with the satellite being in the shadow for up to 70 minutes each day.

A satellite will have the eclipse duration symmetric around the time
t=Satellite Longitude/15 + 12 hours.
A satellite at Greenwich longitude 0 will have the eclipse duration
symmetric around 0/15 UTC +12hours = 00:00 UTC. The eclipse will
happen at night(local time) but for satellites in the east it will
happen late evening local time. For satellites in the west eclipse will
happen in the early morning hours local time.

An earth caused eclipse will normally not happen during peak viewing hours
if the satellite is located near the longitude of the coverage area.
Modern satellites is well equipped with batteries for operation
during eclipse.

An Earth caused eclipse is regular and will always happen around equinoxes.

The Earth caused eclipses can be calculated at http://www.satellite-calculations.com/Satellite/satellite_eclipse.htm

Note 1: This calculator assumes that the Sun does not move during the eclipse. The error is most likely less than 1 second
The duration can be calculated by the equation:
Ts=(24/pi)*[Acos(Sqrt(1-R*R)/Sin(Beta))
where,
R=r_eq/r_sat
r_eq=6378.14km (Earth radius)
r_sat=42164.57km (distance between earth center and the satellite)
Beta= Sun declination angle
Sun declination should be calculated for the time, t=Satellite Longitude/15 + 12 hours.

Sun declination can be calculated after the method on http://www.stjarnhimlen.se/comp/tutorial.html

Earth caused eclipse is regular and will always happen around equinoxes.

Eclipse is calculated afther the method found at http://www.cdeagle.com

Moon Caused Eclipse

A Moon caused eclipse is irregular and is much harder to predict.
Moon caused eclipse will always happen when the Moon is on the day
side of the earth, i.e. when the Moon is located somewhere between
the Earth and the Sun. When the Moon is located on the dark side of the earth
there will never be Moon caused eclipses

A moon caused eclipse may happen during peak viewing hours
Modern satellites is well equipped with batteries for operation
during eclipse.


2006 Jens T. Satre