Abstract. From the perturbing effects of the asteroid (16) Psyche on the motion of the asteroid (13206) 1997GC22 the mass of (16) Psyche is determined. A close approach between these two asteroids at 0.00376 AU, and at a relative velocity of 0.74 km s −1 , occured in July 1974. The value of (3.38 ± 0.28) 10 −11 M has been found for the mass of (16) Psyche, which yields a density of (6.98 ± 0.58) g cm −3 . These values are very different from those obtained by other authors, but the mass is much closer to the value based on the IRAS estimation of (16) Psyche diameter and its M-type taxonomical classification.

In this paper, we present a recalculated value of the mass of (4) Vesta, derived from its largest gravitational perturbations on selected asteroids during their mutual close encounters. This was done by using a new method for mass determination, which is based on the linking of pre-encounter observations to the orbit determined from post-encounter ones. The estimated weighted mean of the mass of (4) Vesta is (1.300 ± 0.001) × 10 −10 M .

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