Outgassing Events

The OutgassingEvent object, when used with the Maneuver command or WhileManeuvering command, models the effect of accelerations due to a leaking thruster on a Spacecraft. The accelerations are modeled using an analytic exponential decay model. The OutgassingEvent object specifies the time constant and the minimum magnitude of the burn as a percentage of the initial value, which determine the total duration of the event. The effective magnitude of the force generated by the event is added to the Force Model of the Spacecraft for the duration of the event. OutgassingEvent maneuvers do not deplete mass from the Spacecraft.

The acceleration model for the Outgassing Events is as follows:

where,

  is the initial acceleration magnitude of the outgassing

is the initial epoch of the Outgassing Event

   is the time-constant for the exponential decay

Like Finite and Impulsive Burns, Outgassing Events also contain the three estimable parameters: the acceleration offset corrections and , and the acceleration scale factor . For Outgassing Events, there is an additional estimable parameter, the time-constant for the exponential decay .

The sample script below provides an example of modeling an OutgassingEvent in FreeFlyer. The acceleration in this particular case is in the velocity direction of the orbit.

Note: When maneuvering with an OutgassingEvent, FreeFlyer takes into account the length of the event in the spacecraft propagation. For example, if the OutgassingEvent.TimeConstant property is equal to 100 seconds and the OutgassingEvent.MinimumMagnitude is 0.01% of the initial value, the spacecraft epoch will advance about 460 seconds during the maneuver event.

Coordinate Systems

The direction of the maneuver can be specified in any of the following attitude reference frames.

See Also