It was nail-biting time about 1:15 a.m. Monday morning, as engineers in NASA's Jet Propulsion Laboratory control room gathered to monitor the Mars Science Laboratory (aka "Mars Curiosity") on its final descent and landing.
As a veteran space nut, I was right there with them, tuned in to NASA TV and holding my breath as Allen Chen announced telemetry reports: the parachute had deployed, the heat shield separated, the rocket pack was powering its descent, its speed was slowing, the sky crane was lowering the rover on its tether, the wheels were -- on the ground! The room erupted with such joy that you'd think every person there had won the lottery.
In some ways, they had, because the landing was a scary and chancy business: putting a car-sized rover on Mars had never been done before, and the complex landing system was a new design. Oh -- and the entire $2.5 billion program depended on everything working correctly so the landing could come off as planned. The engineers referred to the landing as "Seven Minutes of Terror."
Compounding the problem was the time delay in communicating with the spacecraft. It took the rover 8 1/2 months to reach Mars, and even at the speed of light, it takes 14 minutes for a communication signal to reach the MSL -- or return to earth.
That means the craft had to be programmed with all the information needed to make the landing, then left on autopilot to do what needed to be done. That will continue: as Curiosity goes about its business of exploring the Gale Crater and its central mountain, it will also be given a daily mission, but will have to guide itself as it drives from place to place and initiates operations.
It's like a Baptist on Mars: given lots of instructions and a clear mission, but free (and required) to do some of its own thinking as it maneuvers the obstacles and opportunities before it.
Good luck, Curiosity.