|Communications with Earth
NASA's Deep Space Network,
operated and managed by the Jet Propulsion Laboratory, will:
augment a new European Space Agency tracking station located
outside Perth, Australia near a locale known as New Norcia.
This European-sponsored tracking station will provide all of the coverage
of the martian southern hemisphere, while the Deep Space Network
stations at Goldstone, California and Madrid, Spain will complete
coverage in the northern hemisphere of Mars.
provide support during launch and the early operations phase
of the European Space Agency's Mars Express mission.
provide support for navigation tracking up through Mars orbit insertion.
provide support for the Radio Science Experiment
on Mars Express, which uses a ground station as an instrument for
collecting information on the transmission of radio signals to receiving
stations on Earth from the spacecraft as it passes through the thin
Tracking support through the Deep Space Network will be provided by
a subnet of antennas known as the Beam Waveguide Subnet. These
state-of-the-art antennas are 34 meters (112 feet) in diameter. The unique
feature of these antennas is that none of the electronics is located on the
antenna structure itself, as occurs in older antennas. On these antennas,
large diameter beam waveguides and reflectors focus all of the radio-frequency
energy to a room in the basement of the antenna where it is directed to
transmitting and receiving equipment. This technological approach saves
weight on the antenna structure, and provides for greater flexibility for
the electronics subsystems.
A unique feature of the support provided to Mars Express is a relatively
new implementation of data standards, which allows a very simple interface
between the Deep Space Network stations and the European Space
Operations Center in Darmstadt, Germany. Interoperability between all
United States and international spacecraft radio systems is the key, but
until recently, NASA telecommunications standards have not been the same
as those of the European Space Agency. Researchers from around the
world agreed to use a set of protocols for Mars missions for mutually
compatible data formation and radio signals. With a standard called
"Space Link Extension," commands and data can be
transmitted between the European and U.S. ground stations and
operations centers with ease. Mars Express is the first international
mission to use this system.
The Mars Express mission operates on two frequency bands, S-band
at around 2.3 GigaHertz and X-band at around 8.4 GigaHertz. The
predominant role of the S-band transmission is to provide access to the
spacecraft during mission phases in which the high-gain, X-band system
is not physically practical, such as immediately after launch, or in a