Re: GRACE-inspired question

From: Sebastian Stabroth (
Date: Wed Jun 05 2002 - 13:53:29 EDT


> could the same data be acquired by very closely monitoring the
> orbit(s) of satellite(s) at many ground stations around the world
> (perhaps you could also measure the Doppler shifts of its radio signals)
> ?

everything is possible, why not? :-) But, this would be very expensive since you
need a tracking network which provides continuous orbital measurements. That
means a lot of sensor stations on Earth. The efficient way is to measure the
gravitational attractions itself by two satellites.

> But I suppose there is also the question of an unknown atmospheric
> density to the required degree of precision; the GRACE satellites will
> both be affected by the atmosphere essentially equally.  Drag could
> conceivably be confused with a gravimetric gradient.

The GRACE satellites have on-board accelerometers to measure non-gravitational
effects such as atmospheric drag.


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