Two uplinks a day are anticipated. The orbiter flight system consists of the orbiter, aeroshell, and cruise stage. The orbiter is mounted inside the aeroshell from launch until the conclusion of the aerocapture phase. The cruise stage is attached to the heatshield of the aeroshell during the cruise phase of the mission. The launch configuration of this flight system inside the Delta 9.5 foot payload fairing is shown in Figure 2.2.a.
Launch occurs with the orbiter science deck oriented up.
The aeroshell is a derivative of the Pathfinder aeroshell with approximately the same 2.65m diameter. Following injection, the cruise stage solar array is deployed and the flight system cruises to Mars in a three-axis stabilized configuration, as shown in Figure 2.2.b. Attitude is controlled throughout cruise by the orbiter reaction wheels, which periodically reorient the flight system as relative Sun and Earth geometry changes, so that the cruise stage can provide power and telecommunications services. The flight system blowdown hydrazine propulsion subsystem is integrated into the orbiter equipment module, and functions during all mission phases. The cruise stage is jettisoned prior to the aerocapture phase and the aeroshell is reoriented so that the aeroshell protects the enclosed orbiter during the high drag and aeroheating phase.