美国国家公共电台 NPR Waiting For Opportunity To Get In Touch（在线收听）

MARY LOUISE KELLY, HOST:

NASA's plucky rover known as Opportunity has been on Mars nearly 15 years - a tad longer than the 90 days it was designed for. It has taken thousands of images. It has helped scientists better understand the red planet. But NASA hasn't heard from Opportunity since June. NPR's Joe Palca recently visited the rover's control room at the Jet Propulsion Laboratory in Pasadena. Engineers there are still hoping to make contact with the rover.

JOE PALCA, BYLINE: In a building near the cafeteria, there's a large, dimly lit room filled with computer consoles. On the walls, large flat panel displays show readouts from various spacecraft.

ASHTON VAUGHS: This is the console where we send our commands to the Opportunity rover.

PALCA: That's Ashton Vaughs.

VAUGHS: I'm one of the Aces.

PALCA: The Aces are the ones who actually hit the button to send a command to the rover.

VAUGHS: What we have been sending for the last several weeks are commands to ask the rover to send us a tone, let us know it's there.

PALCA: Pinging the rover is a new tactic. NASA lost contact with the rover in June when a dust storm prevented the rover's solar panels from generating power. In such a circumstance, the rover would have put itself to sleep. The dust storm is long over so it should wake up and send a message back to Earth, but it hasn't. Engineers think it may be waking up and then going back to sleep before it can transmit. So Vaughs says they're sending it commands hoping to catch it before it nods off. It takes about six minutes for a radio signal to travel to Mars then another six minutes to come back.

VAUGHS: Around 12 minutes from the time we've sent the command is when we would expect to hear back from the rover.

PALCA: Let's say it wakes up tonight. Are you going to be the first person to know that?

VAUGHS: Yes.

BILL NELSON: He would be the first person in the world to know that we've heard from Opportunity.

PALCA: Bill Nelson is engineering manager for the rover.

NELSON: We trust that he would share that information rapidly.

PALCA: Nelson has been with the rover team since before the rover landed on Mars.

NELSON: I have to admit I'm beginning to be a little bit worried. I thought, you know, about now is when I would've expected to hear from the vehicle.

PALCA: Nelson says even though the skies are clear, the solar arrays may be covered with too much dust from the storm to work properly. He says this is a time of year when the winds kick up on Mars so he's hoping they'll blow the dust away. That's happened before. But not hearing anything is unsettling. Abigail Fraeman is deputy project scientist.

ABIGAIL FRAEMAN: Right now we're kind of in this state of limbo - OK, what's going to happen next? And we don't know.

PALCA: Like Nelson, Fraeman has a long history with the rover. In 2004, when she was 16, she was in a JPL control room when Opportunity landed. She was there as part of an outreach program, called, Red Rover Goes to Mars, run by the Planetary Society. She says even if the rover is never heard from again, it's important to remember it was only expected to last 90 days.

FRAEMAN: It's accomplished so much more than we even could've imagined. I mean, the fact that I was able to be in the room when it landed when I was in high school, and now I'm - I got my Ph.D., I'm at JPL and I'm the deputy project scientist, just tells you how long this has been running and how much has happened. And so it's sad, but it's not terribly sad. It's terribly happy how wonderful the mission has been.

PALCA: The team working on Opportunity is treating the rover's silence as an opportunity. Ashley Stroupe is a rover driver. I met her in what was historically known as the Mars sandbox, a hangar-like room where there are replicas of the rover that can be used for testing. Stroupe says she's been trying out new software for the rover here.

ASHLEY STROUPE: We're at least taking advantage of the downtime to try to finish all that up so that when - we'll will say when - Opportunity talks to us again, we'll be ready to go.

PALCA: I guess we can call that Opportunity optimism. Joe Palca, NPR News, Pasadena.