Overcoming Communication Problems
In November 2011, at Kennedy Space Centre, the rover made its way to the launch pad on the Atlas rocket. For the mission team, the launch is the moment
of no return. While the craft is on the ground, final fixes can always be made. But once it's in the air, a fault could mean the end of the mission.
Brian Portock "There is so much energy involved with launching. All the little piece parts on the spacecraft are designed to survive that vibration
and those forces. Just the fact that it gets into space and we start talking to it for the first time is an incredible achievement. It's the first big
step on the way to Mars."
But any damage caused by the launch to Curiosity's components might not be immediately obvious. So, for the past eight months, the engineers have
needed to stay in careful contact, to check its course and its vital signs. They need to be sure that they receive every message sent back by the
rover… And that every instruction they give will be heard loud and clear.
To communicate with Curiosity, the team have to rely on equipment hidden deep in the Mojave desert. Ann Devereux helped engineer the systems
that allow the team to stay in touch. Now that the spacecraft is nearing the end of its voyage, she feels the distance between her and her rover
more than ever.
Ann Devereux "It's very much akin to having a kid in college. We raised her, we taught her everything she knows, we gave her all the gear
that she needs to investigate her new world, but now she's gone. And, you know, we gave her a calling card. We told her to call often, but we
don't get to talk to her all the time, and, you know, we don't know what she does every day until she's in contact with us."
Curiosity can call home using two ultra-high-frequency radios. But the distance between Mars and Earth, together with the rover's limited
power, makes it difficult to pick up the signal. It's a problem anyone with a car radio knows well.
Radio Transmission Masts
Ann Devereux "We're about a hundred miles outside of Los Angeles. In the car, I've got the radio going, but my favourite radio station is
almost gone. I'm not that far, certainly compared to Mars, and the radio station that I listen to has a 90,000-watt transmitter, and so you'd
wonder why I can't pick up the station here. The problem is my little antenna is just not capable of picking up the signal at this distance,
no matter how powerful it seems the transmitter back at home is."
In space, power is in short supply, and Curiosity will need to use almost all of its energy to drag its near-ton weight across the surface of
Mars. That means the rover's transmitters have to get by with just a fraction of the 90,000 Watts used by a radio station on Earth.
Ann Devereux "She only has a 10-watt transmitter, and she's MUCH further away. We're about 140 km from Los Angeles – Curiosity is going to be 250
million km at Mars. We need something bigger for an antenna."
The DSS14 antenna is the biggest dish in NASA's Deep Space Communications Network. It's their switchboard for every spacecraft in the solar
system. But all this interplanetary chatter means that Ann can't just pick up the phone to Curiosity any time she likes.
Ann Devereux "There's a lot of spacecraft out there, and they all want to talk back home, too, right? They all want to call home. And so, we have
to schedule time at one of these antennas, like here that DSS14, and tell the people that we need to talk to Curiosity and this is how long we want
to talk to her for, and they point the antenna so when to comes over the horizon, this guy is already pointed in that direction and that when
she comes up, then we're talking."
But a queue for the phone is not the only thing that could kill the conversation between the rover and the team back home. Once it arrives At
Mars, the whole mass of the planet will stand in the way.
Ann Devereux "Mars itself rotates as the Earth rotates, and so sometimes, even if we wanted to talk to Curiosity, we couldn't. Because you just
have the whole planet between us and Curiosity."
A Martian day last 24 hours and 40 minutes. For half of that time, the rover will drop behind the red planet's horizon, out of view of Earth's
antennas. When Curiosity arrives, night will be following on Mars. Midway through its perilous landing procedure, the team will lose direct
contact with the spacecraft. But NASA can rely on help from some previous Mars missions.
Ann Devereux "We have an ace in the hole. In fact, we have two. It's called Mars Reconnaissance Orbiter and Mars Odyssey. So, these are two
orbiters that we have around Mars already. They're sitting there, they're waiting for their sister to come."
As the Martian night obscures the rover from Earth's view, Odyssey will attempt to relay its vital messages back to the control room. This is
just one of hundreds of risky procedures that must go right for Curiosity to land safely.