The Solar and Heliospheric Observatory (SOHO) satellite is a joint
project of NASA and the European Space Agency (ESA). Through ONR
and the Naval Research Laboratory, the Navy supported the design
and construction of 3 of SOHO's instruments, which are helping scientists
understand how the Sun works.
Purpose: To study the internal structure of the
Sun, its extensive outer atmosphere and the origin of the solar
wind, the stream of highly ionized gas that blows continuously outward
through the solar system.
Artist's rendering of SOHO (courtesy of ESA & NASA).
Launch vehicle: Atlas IIAS (Atlas/Centaur)
Deployed: SOHO was launched on December 2, 1995
Orbit: Halo orbit around
the L1 Lagrange point. The satellite does
not orbit the Earth, but orbits the Sun while maintaining a distance
of 930,000 miles (1.5 million km) from the Earth, held there by
the gravitational pulls of the Earth and Sun. Just like the Earth,
SOHO takes a full year to orbit the Sun. Its orbit affords SOHO
an uninterrupted view of the Sun, unlike satellites that orbit the
Earth and periodically see the Sun "eclipsed" by the Earth.
Size: 12 by 12 feet (3.65 x 3.65m), 31 feet (9.5m)
with solar panels deployed, approximately two tons.
Program Participants: Naval Research Lab, Stanford
University, NASA, ESA, and several European scientific organizations.
Mission duration: Planned for a minimum of two
years continuous observing with enough fuel for six years, the satellite
surpassed that goal in 2002.
The SOHO satellite is being used to study the solar interior, atmosphere,
and wind. Scientists hope to better understand the mechanisms that
produce the Sun's activity and to predict when this activity will
occur. Storms on the Sun that send powerful disturbances to the
Earth can affect our atmosphere and damage communication and power
systems. With advance warning, we can protect these and other sensitive
systems by temporarily turning them off, as you might protect your
computer by turning it off during an electrical storm.