(_Range to Jupiter, 3.6 million kilometers_). Early in the morning, a twelvefold increase in solar wind pressure caused another contraction of the magnetosphere, which was behaving like a spring, compressing in response to outside forces. As the magnetopause boundary moved rapidly inward, it crossed the spacecraft at 59 R_J from the planet. An hour later the bow shock also flashed past, and Voyager was once more in the interplanetary medium. By noon reinflation of the magnetosphere began again; Voyager crossed the bow shock for the fifth and final time at 55 R_J, followed by three more magnetopause crossings, as the magnetospheric boundary flopped in and out between 45 R_J and 50 R_J. [Illustration: A few days before encounter, the Voyager images of the larger Galilean satellites, Callisto and Ganymede, were beginning to show distinctive surfaces with many bright spots. These two pictures were taken on March 5 at a range of 8 million kilometers; the resolution is about 100 kilometers. Although extremely tantalizing, these images were uninterpretable, because the spots could not be associated with any recognizable geological features, such as mountains or craters. Like a naked-eye view of the Moon, these pictures seemed to reveal more than was actually meaningful. [P-21188C and P-21150C]] [Illustration: Ganymede] Some Project officials began to worry about the contracted state of the magnetosphere. The radiation “hardening” of Voyager was carried out to protect against the energetic particle fluxes observed by Pioneers 10 and 11. Under the new conditions, would the particles in the inner magnetosphere be more concentrated and perhaps increase the radiation levels beyond the design limits? Scientists asked how long the compression might last and speculated about how much energy might be pumped into the Jovian radiation belts, but only time could provide the answers. VOYAGER 1 BOW SHOCK (S) AND MAGNETOPAUSE (M) CROSSINGS Boundary Day Distance (R_J) _Inbound_ S 2/28 86 S 2/28 82 S 3/01 72 M 3/01 67 M 3/02 59 S 3/02 58 S 3/02 56 M 3/03 47 _Outbound_