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RE: mars express orbit



Hello Joe,

The current Mars ephemeris gives +13.9 km/s for 
the gross motion of Mars, which provides -390kHz
Doppler for Mars Express' 8420.4321MHz signal.
This will change a lot in a couple of months
and need correction.
>http://sunearth.gsfc.nasa.gov/eclipse/TYPE/mars2.html

The Earth's diurnal motion is about 0.5 km/s on
the equator and provides +/-13kHz.

The orbit of the Mars Express seems highly eccentric
(e=0.4).
>http://sci.esa.int/science-e/www/area/index.cfm?fareaid=9
The max velocity is 3.3 km/s at pericentre, which
provides +/-93kHz Doppler.

Those numbers are the worst case. The actual Doppler
should be much smaller.

Hope this helps,

Yuri


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