872 Encyclopedia of the Solar System
(a)(c)(b)FIGURE 2 Deep Space Network (DSN) stations today are in
(a) California, (b) Spain, and (c) Australia. (Courtesy of NASA).For human spaceflight, the earliest craft were mainly just
capsules capable of sustaining life and returning safely to
Earth. But as space stations in LEO and flight beyond LEO
became program objectives, more functions became the
responsibility of human pilots and other crew members.
TheApolloand space shuttle designs took full advantage
of human capacities, while Soviet missions continued to
make more use of teleoperation and onboard automation,
as shown by the pilotless flight ofBuranand the routine
automated dockings ofSoyuzandProgressservicing craft
with the ISS.
Today, deep space spacecraft design and development is
a mature activity as shown by the success ofSoviet Venus
landers,ApolloMoon missions, the decades-longPioneer
andVoyagermissions to Jupiter and beyond, the missions to
Halley’s Comet in 1986,Galileoto Jupiter,Cassini/Huygens
to Saturn, and the fleet of orbiters, landers, and rovers
now exploring Mars. But in-flight failure, as in seven Mars
attempts since 1992, is an ever-present threat requiring
vigilance and entailing high costs of spacecraft development
and operations.2.4 Operations
In even the earliest lunar and planetary missions, it was nec-
essary to keep track of the spacecraft’s trajectory and issue
commands for onboard functions both engineering and sci-
entific. Gradually a humans-and-machines art developed,
represented today by large rooms full of people and displays
backed by buildings full of computers and data systems. Ini-
tially centered in main theaters, as missions have become
more complex, these facilities have become dispersed, pro-
viding work spaces for the many specialized flight manage-
ment and scientific teams working during a mission. With
the Internet and other modern communications available,