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Cruise [ Archive page ]

What is Cruise?

Mars Express
Image courtesy of ESA.

The cruise phase is the voyage between Earth and Mars. It begins after the spacecraft completes the launch phase and ends slightly before the spacecraft slows down to be captured into Mars' orbit during Mars Orbit Insertion.

What Happens During Cruise?

During the cruise phase, the main task is navigation. Tracking data will determine where the spacecraft is in the solar system, and engineers will use this data to execute any trajectory correction maneuvers to make sure the spacecraft gets to Mars. To adjust the spacecraft's path, engineers will rely on on-board propulsion for trajectory correction maneuvers. Corrections will be achieved by firing two or more of the eight 10-Newton* thrusters that are attached to each corner of the spacecraft and are fuelled by the same bi-propellant mixture as the main engine.

The main engine is pretty powerful, and is used to decelerate the spacecraft to go into orbit around Mars. By the time Mars Express gets to its final orbit, most of the propellant will be used up. The main engine, attached to the underside of the spacecraft bus, is capable of delivering a force of 400 Newtons.* It uses a mixture of two propellants that are contained in two tanks, each with 267 liter (71 gallon) capacity. Fuel is fed into the engine using pressurized helium from a 35-liter (9-gallon) tank.

(*A Newton is a unit of force required to accelerate a mass of one kilogram one meter per second squared).

NASA Participation During Cruise

While the main responsibility for navigation belongs to the European Space Operations Center (ESOC) located in Darmstadt, Germany, engineers at NASA's Jet Propulsion Laboratory with many years of experience in navigating missions to Mars will work collaboratively with their European colleagues. Together, they must validate software that determines spacecraft trajectories and compare solutions using real data from other flying spacecraft.

The JPL team will start regular navigation operations during the approach to Mars. Solutions will be compared against those computed by the ESOC navigation team on a regular basis for accuracy. JPL's involvement in the navigation of Mars Express will formally end once the spacecraft has reached a safe orbit around Mars.

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