Voyagers in Interstellar Space and Cassini at Saturn
The Voyager 1 and 2 spacecraft were launched in 1977. Both carry charged particle
instruments built by the University of Maryland Space Physics Group. Voyager 1 has
(probably) entered interstellar space, crossing the heliopause on Aug. 25, 2012 at a
distance of 122 AU from the Sun. Voyager 2, traveling 3.3 AU/year and currently at 109
AU, has not yet reached the heliopause. Both Voyagers explored the magnetospheres of
Jupiter and Saturn (also Uranus and Neptune for Voyager 2) during flybys on their way
out of the solar system. Another of the many space instruments built by the Space
Physics Group was carried on the Cassini spacecraft, which was launched in 1997 and
went into orbit about Saturn in 2004. That mission is scheduled to end on Sept. 15, 2017,
with a dive into Saturn’s atmosphere after a “Grand Finale” during which Cassini will zip
between Saturn and its innermost ring 22 times. I will discuss some of the Voyager and
Cassini discoveries at Saturn and in the outer heliosphere and what might be expected
during the final years of these missions (possibly another 10 years for the Voyagers).