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Re: Mares express doppler



A friend of mine on the beagle 2 team explains the manoevres as folows:


"The initial MEX orbit was highly eccentric, with apogeum considerably
larger than the value your correspondent refers to. MEX is now being driven
out to this high apogeum value. Then there will be a burn, whilst at
apogeum, to change the tilt of the orbit, and then finally a perigee burn
(I believe) to place MEX in its final orbit-near polar with the final
eccentricity.

I don't have the details of these orbit burns but ESA should have them on
their web-site. They were discussed at yesterday's press conference in
London. I can't comment on the effect of these manoevres on the doppler
shift measurements. Hope this limited information may be of some use."


esa website  added:


"27 December 2003
 
The Mars Express orbiter, mothership of Europe’s first mission to the Red
Planet, is in a stable and precise orbit around Mars.
 
The essential Mars Orbit Insertion (MOI) manoeuvre had been completed on 25
December at 3:47 CET. This brought the spacecraft as close as 400
kilometres to the surface of Mars. 
Afterwards, the spacecraft went into a highly elliptical orbit, going as
far as 188 000 kilometres away from the planet. The most essential part of
the Mars Express mission is performing very well and we are expecting
exciting science from January 2004 onwards.

Today, 27 December, the mission control team at ESOC prepared the next
steps to turn Mars Express from a near-equatorial orbit into a polar orbit.
Michael McKay, Mars Express Flight Director explained, “Our flight dynamics
and flight operations teams thoroughly discuss, evaluate and prepare the
commands to perform a series of manoeuvres starting with a major move on 30
December – where we will fire the main engine again for three minutes. 

“These key manoeuvres will allow us to get even closer to Mars. They will
not only allow us more frequent ‘overflights’ of the Beagle 2 landing area,
but also ensure the beginning of the orbiter’s science mission. As Mars
Express is the planned main communication partner of the Beagle 2, the
chances of obtaining a signal strongly increase with these manoeuvres after
4 January 2004.”"





hope this helps

Mit freundliche Gruessen


andy G0SFJ

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