In two year’s time, the planet Mars will receive a Christmas present
from planet Earth — a flotilla of spacecraft. Gifts from different
nations, the spacecraft will share communications channels to solve a
problem which will intensify as Mars exploration gathers pace: how to
relay the data gathered by so many missions back to Earth.

First to arrive, just before Christmas 2003, will be the European Space
Agency’s Mars Express and its lander, Beagle 2, with the Japanese ISAS’s
Nozomi and NASA’s two Rovers arriving in the New Year. They will join
NASA’s Mars Odyssey, which arrived at the Red Planet last October and
will still be operating.

By early 2004, Mars will therefore have six visitors (three landers and
three orbiters). Just as on Earth, these festive season guests could
strain the available resources. Each of the spacecraft will need to
send a steady stream of data back to Earth via limited communications

Data can be relayed only when a spacecraft’s antenna has an
uninterrupted view of the receiving antenna on Earth. Because of the
rotations of Mars and Earth and the movement of the orbiters around
Mars, this condition is met intermittently for each spacecraft.

By sharing compatible communications technologies and algorithms,
however, the spacecraft will be able to provide an open communications
channel for most of the time. The availability of more than one
communications channel also provides valuable insurance against the
technical failure of one.

Thus, Mars Express will be able to forward data and messages between
Earth and NASA’s Rovers, if needed, and Beagle 2 can do the same via
Mars Odyssey as well as Mars Express. Only Nozomi, which was launched
too early to be included in the communications scheme, will look after
its own data relay requirements alone.

Future missions are expected to follow a communications standard
compatible with that now adopted by ESA and NASA, thus giving Mars
Express and Mars Odyssey the potential of maintaining a useful role as
communications relays long after their scientific missions have ended.

The spacecraft due to arrive at Mars around Christmas 2003 will thus
do so in a spirit of cooperation entirely fitting for the season.


* More about Mars Express

* Why 2003?

* Missions to Mars


ESA’s Mars Express orbiter and its lander, Beagle 2, will arrive at the
Red Planet just before Christmas 2003.