FIGURE 7 Constraints on the shape of near-Earth asteroid 1620 Geographos from Goldstone 3.5-cm
radar echoes. (a) Spectra obtained at phases of bandwidth extrema. OC (solid curve) and SC (dotted
curve) echo power is plotted versus Doppler frequency. (b) Comparison of an estimate of the hull (H)
on the asteroid’s pole-on silhouette (S) with an estimate ofSitself. The white curve is the cw estimate of
Hand the X marks the projected position of the asteroid’s center of mass (COM) with respect toH.
That curve and the X are superposed on an estimate ofSfrom delay–Doppler images; the bright pixel is
the projection of the COM determined from analysis of those images. The absolute scales and relative
rotational orientations of the two figures are known: Border ticks are 1 km apart. The offset between the
X and the bright pixel is a measure of the uncertainty in our knowledge of the COM’s delay–Doppler
trajectory during the experiment. In the diagram at right, the arrows point to the observer at phases of
lightcurve maxima (M1,M2) and minima (m1,m2). (From S. J. Ostro et al., 1996,Icarus 121 , 46–66.)
747