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Martian Diaries

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The Pre-landing Frenzy
By Jeffrey Marlow

Landing minus 3 days
We are landing on Mars in 3 days!

The pre-landing frenzy is in full force down on the JPL mall, where countdown clocks tick away and a fountain provides dramatic percussion, like a constant Mission Impossible soundtrack. News outlets from around the world are setting up tripods, running sound checks, and marking their territory with masking tape on the concrete plaza. (Don't mess with those TV crews; they seem to be guarding their spots like the next iPad's about to go on sale.)

With all of the building tension, it's easy to forget that Mars Science Laboratory is still very much an active mission, zooming toward Mars at thousands of kilometers per hour. The Entry, Descent, and Landing team needs no reminder, and they've gathered this morning in the War Room to discuss potential course corrections for their precious spacecraft.

The room fills up quickly with the men and women who will soon have their tense faces splashed across TVs the world over as they endure the "seven minutes of terror." Laptops are unsheathed, the projector is fired up, and weak jokes get an unwarranted amount of laughter, betraying the team's frayed nerves.

We've gathered for the "Practice Playcall" meeting, a precursor for a potential Trajectory Correction Maneuver. There have been four trajectory correction maneuvers since launch last November, each one nudging the spacecraft toward its ideal trajectory. With the next opportunity to correct course quickly approaching, the plan is to go over the latest data and determine if the team needs to start the process of coding up a correction to the spacecraft's path.

It's essentially the practice session for the preparatory meeting for the plan-making conference to possibly send commands to the spacecraft, which would happen tomorrow afternoon. At this stage in the mission, you don't take any chances.

There are two reasons you'd want to fire up the thrusters and change course: either to avoid lurking hazards or to get closer to the optimal landing site.

We start with the hazards, as Mars weatherman, Ashwin Vasavada - more formally known as Mars Science Laboratory Deputy Project Scientist, if you must know - gives an update on a dust storm that had been escalating throughout the week. "As of yesterday, this storm had three options," he says with the typical comprehensiveness of a scientist. "It could have spread, it could have moved, or it could have dissipated. Fortunately, it took the third option." Vasavada takes his seat, recommending no changes on account of the martian weather.

But dust storms streaking across the surface aren't the only weather patterns that could cause problems. Martin Ratliff, a member of the Mission Environments Group at JPL, has been watching the Sun for signs of imminent solar flares, whose beams of radiation could fry the spacecraft. He speaks up from the corner of the room, cautioning that assessing radiation risks from flares is as much an art as a science. But, in conclusion, "we're doing well; everything is very quiet other than a few small flares." No trajectory correction maneuver needed from the solar weather team.

The Navigation Team is last. They've been monitoring the spacecraft's trajectory, and the nudge from Trajectory Correction Maneuver-4 seems to have been good enough to obviate further course corrections. If anything, a 3-milimeter shift might be useful. But, it's a fine line between enhancing the chances of success and doing no harm: there is a certain margin of error associated with any thruster burn, and when the magnitude of the correction you're attempting is close to that margin, you risk pushing the spacecraft further off course.

Deputy Entry, Descent and Landing Operations Lead Devin Kipp breaks it down for me after the meeting disperses, helping me wade through the meeting's EUOA (excessive use of acronyms).

"Right now, it looks like Trajectory Correction Maneuver-5 won't be necessary," he says, "but that official decision will be made tomorrow with the latest trajectory and weather information."

The War Room breathes a sigh of relief, and the engineers hurry to work up commands for a minor thruster burn, just in case

Update: As suspected, Friday's Trajectory Correction Maneuver-5 wasn't necessary, and Curiosity continues on-course toward Mars at a speed of 3576 meters per second.