Masubi (P₈) is faintly visible in the crescent (above and below).
Loki (P₂) rises 250 kilometers above the surface, catching the morning sunlight on the east edge of Io.
Tuesday, July 10.
(Range to Jupiter, 1.4 million kilometers). The Io watch continued through the night. As time passed, the satellite rotated in the same direction as the motion of the spacecraft, keeping nearly the same side in view. Because of this, a few volcanoes could be closely watched, but most would be missed entirely. During the sequence, the illuminated crescent steadily shrank, until at the end, volcanic plumes could be seen on both edges, one illuminated by the setting Sun, the other shining in the dawn light.
At the 11 a.m. press conference, Esker Davis announced that engineers had lost contact with the spacecraft radio receiver Monday evening (probably due to Jupiter’s radiation) and had to “chase it around most of the night,” sending commands at various frequencies until they locked on to the frequency the spacecraft would accept. The major trajectory correction maneuver, begun at about the same time contact with the receiver was lost, was successful. The 76-minute thruster firing, done at periapsis instead of two weeks after encounter, enabled the spacecraft to get a bigger “boost” from Jupiter than was originally planned, amounting to a fuel saving of about 10 kilograms of hydrazine, enough to preserve the option of going on from Saturn to Uranus.
Andrew Ingersoll discussed some results of the analysis of the Jovian atmosphere. “At first, Voyager seemed to do nothing but emphasize the chaos, not the order.” But, with the help of ground-based observations, Reta Beebe found that there is a “regular alternation of eastward and westward jets” underlying the seemingly chaotic visible features. “The turbulence we see in the visible clouds seems to be a minor side show, or a process without much energy or mass compared to the very great energy and mass that might be moving around in the deep atmosphere.”