Info

Once the spacecraft is on station, the payload pointing requirements usually dominate. These may require Garth-relative or inertial attitudes, and fixed or spinning fields of view. In addition, we must define the need for and frequency of attitude slew maneuvers. Such maneuvers may be necessary to:

TABLE 11-2. Typical Attitude Control Modes. Performance requirements are frequently tailored to these different control operating modes.

Mode

Description

Orbit Insertion

Period during and after boost while spacecraft Is brought to final orbit Options include no spacecraft control, simple spin stabilization of solid rocket motor, and full spacecraft control using liquid propulsion system.

Acquisition

Initial determination of attitude and stabilization of vehicle. Also may be used to recover from power upsets or emergencies.

Normal, On-Station

Used for the vast majority of the mission. Requirements for this mode should drive system design.

Slew

Reorienting the vehicle when required.

Contingency or Sate

Used in emergencies if regular mode fails or Is disabled. May use less power or sacrifice normal operation to meet power or thermal constraints.

Special

Requirements may be different for special targets or time periods, such as eclipses.

TABLE 11-3. Typical Attitude Determination and Control Performance Requirements.

Requirements need to be specified for each mode. The following lists the areas of performance frequently specified.

TABLE 11-3. Typical Attitude Determination and Control Performance Requirements.

Requirements need to be specified for each mode. The following lists the areas of performance frequently specified.

Area

Definition*

Examples/Comments

0 0

Post a comment