The determination of the precession rate of Mars from Phobos and Deimos observations

An examination is made of the accuracy with which it is possible to determine the precession rate of Mars from all the available positional observations of Phobos and Deimos made from the Earth and from the Mariner 9, Viking I and II, and Phobos II spacecraft. It is concluded that this quantity can only be marginally determined, and at best could be constrained within the limits of about -7 to -13 ″/yr, which is not sufficient to give useful geophysical information. The data give a value for the right ascension of the pole of Mars which is about 0.03° different from the currently accepted value, and give a slight suggestion that there may be a small problem with the Phobos II declination observations