Mission Timeline: Entry, Descent, and Landing

Approximately two weeks prior to Mars Science Laboratory's atmospheric entry, the team will send the spacecraft the initialization commands for entry, descent, and landing. As the impending entry approaches, more commands for specific entry, descent, and landing tasks will be sent to prepare the spacecraft for its intense journey to the surface of Mars.

Step One: Communications Prep Begins

The Deep Space Network will provide continuous 34-meter antenna coverage for Mars Science Laboratory beginning 45 days before atmospheric entry. Beginning four days prior to entry, the Deep Space Network will provide continuous 70-meter antenna coverage.

Ten minutes prior to the "turn-to-entry" step, the spacecraft will discontinue communicating through the X-band antenna (via an orbiting spacecraft) and begin using its medium- and low-gain antennas (direct-to-Earth communication).

Step Two: Spacecraft Rotates and Cruise Stage Shuts Down

The aeroshell containing the rover will change its attitude as its final preparation for entering the martian atmosphere. The spacecraft's inertial measurement unit (IMU) - which will serve as a balancing "inner ear"- will be activated. Finally, the cruise stage will be shut down.

Step Three: Transmission of Tones Begins & Relay with Orbiting Spacecraft

The spacecraft will continually be giving its Earth parents updates through tones and through actual telemetry detailing exactly what is happening to it during its journey through the atmosphere. A low-gain antenna on the spacecraft's backshell begins transmitting simple "tones" (sustained radio frequencies coded to report the spacecraft's status) that indicate completion of certain entry, descent, and landing phases.

Mars Science Laboratory engineers are now planning with navigation engineers on orbiter missions to ensure that the rover will be able to communicate with orbiting spacecraft. This communication link will, for the first time during a landed Mars mission, allow earth-bound engineers to get actual telemetry on what it happening to their spacecraft during critical phases.

Step Four: Cruise Stage Separates

As the tones begin, the cruise stage separation commences. This separation is the first stage the rover takes in shedding more than half of the spacecraft in which it has been warmly traveling during its long journey through the frigid temperatures of space.

In only six minutes, the spacecraft will slow down from 35,000 to 0 miles per hour and land on the surface of Mars, ready to rove. This time is particularly nerve-wracking for the mission team back on Earth.

Step Five: Mars Science Laboratory enters the martian atmosphere

The spacecraft should come streaking in through the martian atmosphere, going about 35,000 miles per hour. Given atmospheric friction, the outside surface of the heat shield will be as hot as the surface of the sun (1,447 degrees Celsius, or 2,637 degrees Fahrenheit), but the rover will be protected by the heat shield and will stay at about room temperature inside the lander. The heat shield also aerodynamically acts as the first "brake" for the spacecraft, slowing Mars Science Laboratory down by thousands of miles per hour.

Step Six: Heatshield Separation and Parachute Descent Segment

At about 4 and a half minutes into atmospheric entry, the protective heatshield will be shed. A parachute engineered with the benefit of inherited technology from past landed Mars missions will slow down Mars Science Laboratory from supersonic speeds. The parachute will be deployed approximately 5 minutes after atmospheric entry.

Step Seven: Powered Descent Segment

When the rover is approximately 1500 meters (nearly one mile) above the martian surface, its landing engines will begin to ease it toward the ground. There are eight throttle-able engines mounted on the descent stage that will steer the rover and slow it until only four engines are needed.

Step Eight: Imaging the Descent

Mars Science Laboratory will feature a very capable visual system. MARDI (Mars Descent Imager) will provide a stunning view of the trip to the surface with five frame-per-second video at a high resolution. The images will be "true color," or as the human eye would see.

In addition to stunning video, the data the camera collects will allow scientists and engineers:

• to observe geological processes at a variety of scales;
  
  
• to sample the horizontal wind profile (to prevent potentially damaging sideways movement); and,
  
  
• to create detailed geologic, geomorphic and traverse planning and relief maps of the landing site.
  
  

Step Nine: Bridle and Mobility release

At this point, the spacecraft will be on its intended path, still being controlled by four engines. The rover will then be released from the descent stage and it will begin to descend down its bridle and "umbilical cord." The rover's "legs," or mobility system, will also be released so that it can land in the "ready-to-rove" position. Approximately 8 seconds after rover release, deployment is complete. Eight seconds after that, the rover will touchdown on the surface of Mars.

Step Ten: Bridle is Cut

Once it is determined that the rover is safe, the descent stage computer instructs the rover to cut the bridle and umbilical cord. Mars Science Laboratory is now on its own.

Step Eleven: Fly Away Segment

The descent stage that carefully put Mars Science Laboratory on the surface has done its job and will now fly away and crash land. This process involves a 45-degree pitch away from the rover and firing up the remaining engines for 1 second. Thrust will be applied long enough to ensure that the descent stage crashes far from Mars Science Laboratory (about 150 meters or just under 500 feet), keeping the rover safe from damage.