The following chart shows the sequence of critical steps monitored by members of the Mars Reconnaissance Orbiter team during Mars Orbit Insertion. Times are based on the arrival of signals from the orbiter on Earth. All times PST.
Step One: Pressurize
Valves between helium tank and main fuel tank opened. Two small pyrotechnic charges electrically ignited, opening valves in tubing about the diameter of a pencil. Each charge broke open a seal and created a clear line to allow the pressurant -- helium gas -- to flow into the fuel tank.
Step Two: Switch to Low-gain Antenna
Telecommunications channels switched from the spacecraft's high-gain antenna to the low-gain antenna for receipt of commands. The low-gain antenna was less powerful but could receive and send signals without having to face Earth. The high-gain antenna had to be pointed toward Earth to be able to communicate with Deep Space Network antennas in Goldstone, California and Madrid, Spain. The low-gain antenna sent telemetry data at 160 bits per second from this point until about an hour later.
Step Three: Turn spacecraft
Pre-programmed commands turned the spacecraft to position it for the burn that captured the spacecraft in orbit around Mars.
Step Four: Commence Firing for Orbit Insertion
A valve electrically opened to allow fuel to flow into the six main engines. The fuel flowed over high-temperature catalyst beds that caused it to "explode" and exit the rocket nozzles at very high speed. The rockets fired for nearly 27 minutes, decreasing MRO's speed by 2,200 miles (3,541 kilometers) per hour.
Flexible extensions on the spacecraft -- for example, on the solar panels -- vibrated lightly in response to the initial engine firing. The small reaction-control thrusters strategically mounted on various parts of the spacecraft fired to correct oscillations in the spacecraft's orientation, keeping the main engine pointed in the right direction for orbit insertion.
Step Five: Bye For Now, MRO!
The firing continued as the spacecraft passed behind Mars, and the Deep Space Network temporarily lost the spacecraft signal as planned. This time was perhaps the most excruciating period for flight controllers. They endured the silence and hoped that all was going as planned.
Step Six: Burn Ends
While hidden behind the red planet, Mars Reconnaissance Orbiter's main engines ceased firing. The duration of the planned burn put the spacecraft in the optimal position to be captured by Mars' gravity.
The Mars Reconnaissance Orbiter team waited for their spacecraft to break the long silence and report on its condition. On the spacecraft itself, the reaction wheels turned the orbiter to point its high-gain antenna toward Earth in preparation for resumed communications.
Step Seven: Hello Again, MRO!
At last, from Earth's point of view, the orbiter emerged from behind Mars and Deep Space Network antennas locked onto the spacecraft's carrier signal. The spacecraft continued transmitting data at 160 bits per second; the Deep Space Network took several minutes to lock on to the low-rate data stream.
The Mars Reconnaissance Orbiter was captured into an initial, elliptical orbit that took the spacecraft about 35 hours to complete.
Step Eight: Check Health and Status
By this time, spacecraft controllers had begun receiving limited data informing them of the state of the spacecraft and the result of its orbital insertion burn.