Moment of drama ahead for Mars orbiter

One of the most critical parts of today's orbit insertion is a few minutes away, when controllers will pressurize the propulsion system for the thruster firing later this afternoon.

It was at this point in flight, in 1993, that NASA lost the $1 billion Mars Observer spacecraft. At the time the propulsion system pressurized, NASA lost contact with the spacecraft. The investigation that followed found that a ruptured fuel line was to blame. The spacecraft went into a fatal spin and likely blew up.

The pressurization pushes the fuel toward the thrusters to prepare for the burn that will push the spacecraft into Mars orbit. The pressurization is scheduled to take place at 3:50 p.m. Eastern time, about 30 minutes ahead of the thruster firing.