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scientists can now reside at their home institutions and par-
ticipate in missions in real time.
The latest trend is toward increasing onboard auton-
omy, which holds the promise of reducing the large staffing
needed round the clock to control missions. Some degree of
autonomy is needed anyway in deep space, simply because
of the round-trip signal times to distant spacecraft, tens of
minutes for Mars and Venus, and many hours in the outer
solar system.
Operations have become more and more dependent on
software whose design and verification now constitute one
of the main cost items in each new mission’s budget. With
the maturing of the operations art have come numerous
stories of remarkable rescues when a distant robot (or, as
inApollo 13, a human crew) got into trouble, but there are
also instances where a mistake on Earth sent a mission to
oblivion.
2.5 Reliability and Quality Assurance
A vital part of the deep space exploration art is the creation
of systems having but a small chance of disabling failures,
plus an ability to work around failures when they do oc-
cur. One reason for the high cost of lunar and planetary
missions is the need for multiple levels of checking, test-
ing, reviewing, and documentation at every stage from the
manufacturing of thousands of tiny components, through
assembly into subsystems and systems for both ground and
flight, organization of human teams capable of imagining
and analyzing failure scenarios and designing around them,
and finally launching and controlling a mission during its
years or decades of activity.
These costs are aggravated by the nature of deep space
exploration as a work of building very complicated things
(hardware, software and human-machine complexes) in
ones and twos, as distinct from the repetitive manufacture
of highly reliable items such as cars or computers whose
teething troubles can be eliminated in early prototype test-
ing. In a sense, every lunar or planetary mission is a first
effort.
2.6 Management
In the 20th century, as cold and hot warfare became more
and more technological, a suite of skills, traditions, and
managerial methods grew and created the capability of
planning and executing large complicated projects. Many
disciplines were involved, ranging from what became
known as systems engineering all the way to new ways of or-
ganizing academic institutions, industries, and government
agencies. The sometimes maligned worldwide military-
industrial complex is a product of those developments, and
it was the seedbed of the world’s deep space programs.
The great lunar contest of the mid-20th century high-
lighted some stark differences between American and
Soviet management methods and organizations. At the out-
set, both used existing military hardware and existing mili-
tary ways of working, but over time the programs evolved
along different paths. With their head start the Soviets
garnered all the early prizes in robotic lunar exploration,
but when planning began for human lunar exploration the
Soviet system faltered.
Despite a huge and highly capable engineering and in-
dustrial base of talented and motivated people, the Soviet
human flight lunar enterprise proved unable to solve prob-
lems of interagency rivalry and timely decision making, with
the result that Apollo won the day. The USSR cut its losses
and canceled its program, andApollosoon followed be-
cause of pressure on the US federal budget and the lack of
the political stimulus of Soviet competition. Decades then
passed before lunar robotic exploration resumed, and more
decades will pass before humans again bestride the Moon.3. Sun and Heliosphere
The emphasis in this chapter is on missions to the Moon and
planets. However, now that star-planet aggregates are at last
being observed as a class of known objects in the cosmos,
it is essential for us to include at least a part of the story
of missions devoted to our own star as host of a planetary
system.
Our tale begins with the International Geophysical Year
(IGY). Centuries of ground-based investigations of sunspots
and solar and terrestrial magnetism, plus decades of iono-
spheric and auroral research, had led by the mid-20th
century to a drive by scientists for a worldwide campaign
of coordinated measurements resembling previous efforts
such as international polar years. The new element now
was the knowledge that rockets could take instruments be-
yond Earth’s atmosphere and even into orbit. In both the
USSR and the US, satellite experiments were planned and
announced in support of this goal, and in 1957 and 1958 it
was achieved.
Explorer Ifound an excess of radiation saturating its de-
tector.Explorer IVshowed that this radiation is due to en-
ergetic particles trapped in Earth’s magnetic field, the Van
Allen belts. Then, in 1962, an instrument aboardMariner
II, en route to Venus, confirmed predictions of a fast out-
ward flow of plasma from the Sun—the solar wind, now
known to bathe the entire solar system out to the boundary
of the heliosphere, where it meets the oncoming, tenuous
interstellar medium.Voyager 1and 2 are now entering that
interaction region, more than 90 AU from the Sun. Over the
next 5 to 10 years, they are expected to continue to yield
information on phenomena at the outer limits of the Sun’s
domain.
Meanwhile, over the past five decades, many space-
craft have journeyed into interplanetary space, investigat-
ing the particles and fields environment of the solar system