QUOTE (Richard Trigaux @ Mar 23 2006, 01:32 AM)
... for instance diametre of an iron core (if one) and main mantle layers. Eventually if there is a magmatic layer.
Seasonal changes? What could cause seasonal change in gravity field? Swap of ice in polar caps? Or movement of a solid core in a liquid layer, like on Earth?
You're right; the paper says:
QUOTE
3.3.2. Seasonal changes in Mars rotation
The seasonal mass transfer between the Mars polar caps causes small periodic variations in the spin (Yoder and Standish, 1997).
On another matter, I notice that their solutions for the Mars ephemeris do not include any Rover data. I presume that's because:
- They have a better fix on the position of the orbiters in relation to Mars's center of mass.
- The rovers move erratically and their geodetic positions are ill-defined -- pending further study
-- Yep, the paper explains the omission because of "the continual movement of the rovers." It also notes that "the tracking data from MER to Odyssey may significantly reduce the Odyssey orbit errors, and would provide a better measurement of forces normal to the orbit plane,..."
Is that a first: spacecraft tracking from another planet?