|Mission Timeline: Communications Relay
The relay phase starts when the primary science phase ends and
lasts about two years, ending December 21, 2010. (However, the orbiter
is designed to carry enough propellant to remain operational for 5 additional
years in Mars orbit if it is needed to support future missions.)
During this phase, the orbiter will support the Mars Exploration
Program by providing approach- navigation and relay-communications
support to future Mars missions. The relay orbit will be similar to that of
the primary science orbit. In general, this orbit allows for relay access to
any point on Mars. Most locations on Mars will have contact opportunities
once or twice per day.
Relay activities and other activities in support of newly arrived
missions have highest priority during the relay phase. Electra, the
navigation and telecommunications relay payload, can provide UHF
coverage to Mars landers and rovers on the surface using its
nadir-pointed (pointed straight down at the surface) antenna.
Mars Reconnaissance Orbiter provides three kinds of service to future spacecraft:
Navigation services support arriving spacecraft and provides
precise locations of landers and rovers on the surface of Mars.
When spacecraft are still a month or so away from arrival,
Mars Reconnaissance Orbiter will point its high-gain antenna toward
the incoming spacecraft and send its normal Deep Space Network
If the arriving spacecraft has an Electra
communications payload, it can receive these signals and
determine its distance and speed in relation to Mars. This
communication allows much more precise navigation . When landers
and rovers have landed safely on Mars, Mars Reconnaissance Orbiter's
Electra payload can provide precise Doppler data
which, when combined with Mars Reconnaissance Orbiter's position
information, can accurately determine the location of the lander or
rover on the surface of Mars.
|Forward and return link relay services
With these services, commands from Earth are forwarded to the lander
or its data is returned to Earth. It's a bit like providing Mars landers
and rovers with a broad-band internet connection and letting them use
it for 5 minutes twice a day. These services allow landers and rovers
to have more opportunities to communicate with Earth, especially
when they are on the opposite side of Mars from the Earth or need
to get more data back to Earth. Some landers might not even have
direct communications with the Earth (to save power and mass by
not having the radio equipment) and might therefore rely on Mars
Reconnaissance Orbiter to provide all of their communications.
These services provide landers and rovers with signals that let
them know the time very precisely.