NASA's Deep Space Network (DSN) has been in partnership
with Voyager 1 and Voyager 2 since 1977, providing daily
communications support to the two very distant spacecraft.
The excellent partnership continues as the Voyager twin
spacecraft explore the regions of our universe near the
area where the solar wind meets the interstellar winds – areas
never before explored by human-made objects.
Voyager 1 reached a historic milestone in 2004 when it
crossed the termination shock where the solar wind slows
abruptly from a speed that ranges from 700,000 to 1.5 million
mph. Another important milestone was reached on August
15, 2006 when Voyager 1 became 100 AU (Astronomical Unit)
from the Sun! One AU is the average distance from Earth
to the Sun, 150 million km, or 93 million miles.
In 2007, Voyager 2 crossed the termination shock multiple
times at about 84 AU in the southern Solar System, analogous
to surfing across an ocean wave that moved in and out.
Since Voyager 1 crossed the termination shock at about
94 AU in the northern part of the Solar System, the crossings
of the twin Voyager spacecraft showed the asymmetry of
the heliosphere, which may be due to an interstellar magnetic
field pushing inwards more in the south than the north
as described by Voyager Project Scientist and former JPL
Director Dr. Ed Stone who leads the team of Principal Investigators.
The excellent Project team effort is led by Project Manager
Ed Massey, and many have contributed significantly to the
outstanding project, as described by a sample of team members’ quotes:
http://voyager.jpl.nasa.gov/news/quotes.html
As of September 1, 2008, at the speed of light, it took
about 14 hours and 52 minutes for a signal from Voyager
1, which was about 107 AU away from the Sun, to reach one
of the giant antennas of the DSN, and about 11 hours and
58 minutes for Voyager 2, which was nearly 87 AU away from
the Sun
The above diagram, which depicts the termination shock,
heliosphere, heliosheath, heliopause and bow shock, shows
Voyager 1 having crossed the termination shock and Voyager
2 before crossing the termination shock. The source of
the diagram and information is the Voyager Project. The
solar wind is a stream of electrically charged ions ejected
from the Sun's atmosphere, which sweeps past all the planets
at supersonic speeds. It creates a bubble around the Sun,
called the heliosphere, which extends far beyond the orbits
of the planets. Inside the heliosphere is a boundary called
the termination shock where the speed of the supersonic
solar wind is suddenly reduced. The outer boundary of the
heliosphere, where the expanding solar wind is balanced
by the inward pressure of interstellar matter is called
the heliopause. The heliosheath is the region between the
termination shock and the heliopause. A bow shock forms
as the Sun progresses through the ionized interstellar
gas.
Because of the enormous distances and the resultant weak
signals from the spacecraft, the large antennas and the
very sensitive receivers of the DSN are required to provide
the necessary communications capabilities. The DSN is the
world's largest and most sensitive spacecraft communications
network. It consists of three deep space communications
complexes located approximately 120 degrees of longitude
apart around the world: at Goldstone, California; near
Madrid, Spain; and near Canberra, Australia. This placement
permits continuous communication with a spacecraft.
Each deep space communications complex provides capabilities
required to perform telemetry data processing, including
signal reception and amplification, signal demodulation
and decoding, and data extraction. It also provides a capability
to send commands generated by the project to the Voyager
spacecraft. All DSN complexes are linked to JPL via a world-wide
communications network.
The Deep Space Network, the premier network for deep space
communications, allows the Voyager spacecraft to continue
to send new and unique data from the far reaches of space.
Voyager 1 is the farthest spacecraft from the Sun, even
beyond the recently discovered Sedna, and Voyager 2 is
the second farthest operating spacecraft. As these distances
continue to increase, the DSN has implemented new techniques,
such as arraying of antenna and combining of weak signals,
that will allow continuing excellent support of the Voyager
spacecraft.
The thrilling discoveries during Voyager's many years of
exploration, including the grand tour of the outer planets,
would not have been possible without the sustained exemplary
support of the Deep Space Network. The excellent Voyager-DSN
partnership continues during the Voyager Interstellar Mission
as Voyager 1 and 2 explore the transition region between
the heliosphere and interstellar space and are poised to
become humanity's first interstellar probes
