[Illustration: _Voyager 1 approached within 124,000 kilometers
(77,000 miles) of Saturn’s cloudtops. Six of the satellites that
were photographed are shown in their approximate positions at
closest approach by the spacecraft._]
TITAN
DIONE
TETHYS
MIMAS
ENCELADUS
RHEA
Voyager 1’s Saturn encounter period began on August 22, 1980, at a range
of 109 million kilometers (68 million miles) from the planet. Even at
this great distance, Voyager’s images were better than any from
Earth-based telescopes. During the long encounter period, which extended
through December 19, 1980, continuous observations of Saturn’s realm
were carried out by Voyager’s instruments. Voyager 1’s flight path
through the Saturn system demanded navigation of the highest precision
to meet three critical targets: (1) a close 4000-kilometer (2300-mile)
flyby and occultation at Titan, (2) a precise, three-minute time period
when the spacecraft was emerging from occultation at the same time Earth
was in a position to receive the spacecraft signals passing through the
gap between Saturn and its rings, and (3) a flight path through the
E-Ring at Dione’s orbit to assure safe passage through a zone clear of
potentially dangerous material. To assure these targets were achieved,
small trajectory trim maneuvers were executed on October 11, 1980, and
again on November 6, 1980, as Voyager 1 sped toward Saturn.
[Illustration: _Voyager spacecraft and scientific instruments._]
HIGH-GAIN ANTENNA (3.7-meter diameter)
LOW-ENERGY CHARGED PARTICLE
COSMIC RAY
PLASMA
IMAGING
ULTRAVIOLET SPECTROMETER
INFRARED INTERFEROMETER SPECTROMETER
PHOTOPOLARIMETER
OPTICAL CALIBRATION TARGET
PLANETARY RADIO ASTRONOMY AND PLASMA WAVE ANTENNA (2)
RADIOISOTOPE THERMOELECTRIC GENERATOR (3)
MAGNETOMETER BOOM
By October 24, 1980, when Voyager 1 was about 30 million kilometers (19
million miles) from Saturn, the spacecraft’s narrow-angle camera could
no longer capture the planet in a single picture. Thus, a period of
multiple images or mosaics began. By November 2, 1980, even four-picture
mosaics could no longer cover the rapidly growing scene. Voyager 1’s
pace of operations reached an exciting peak during the near-encounter
phase from November 11 through November 13, 1980. While still about 1.6
million kilometers (1 million miles) from closest approach to Saturn,
Voyager 1 encountered Titan on November 11, 1980, and then dipped below
the ring plane as it accelerated rapidly toward Saturn. On November 12,
1980, Voyager 1 came within 124,000 kilometers (77,000 miles) of the
cloudtops of Saturn’s southern hemisphere, where Saturn’s gravity
altered the spacecraft’s course, hurtling the spacecraft upward past the
ring plane. Close observation of Saturn’s other major satellites and its
rings were made during this passage.
From Earth to Saturn, Voyager 1 has traveled in the ecliptic plane, the
plane in which the major planets orbit. Now, having completed its final
planetary flyby, Voyager 1 is rising above this plane on a trajectory
that will eventually carry it above and out of the solar system,
probably before the end of this century. As it proceeds, the spacecraft
will return information about the solar wind and magnetic fields in the
far, unexplored reaches of our solar system and will observe cosmic rays
emitted from the distant stars among which Voyager will ultimately
cruise.