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 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.

OutgassingEvent OutgassingEvent1;

OutgassingEvent1.AttitudeSystem = 1; // VNB

OutgassingEvent1.BurnDirection = {4e-7, 0, 0}; // km/s2

OutgassingEvent1.TimeConstant = 100; // seconds

OutgassingEvent1.MinimumMagnitude = 0.1; // percent

Report OutgassingEvent1.EventDuration.ToMinutes();

Maneuver Spacecraft1 using OutgassingEvent1;

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

Coordinate System	Attitude System	X-Component	Y-Component	Z-Component
International Celestial Reference System (ICRF)	0	GCI X	GCI Y	GCI Z
Velocity-Normal-Binormal (VNB)	1	Velocity	Orbit Normal	Binormal
Local Vertical Local Horizontal (LVLH)	2	Co-Velocity	Negative Orbit Normal	Nadir
Spacecraft Body Fixed	3	Body coordinate X-directed component of maneuver	Body coordinate Y-directed component of maneuver	Body coordinate Z-directed component of maneuver
Geodetic	4	Geodetic X	Negative Orbit Normal	Normal to Earth's surface
UVW	5	U (Position)	V (Along Velocity Direction)	W (Orbit Normal)
RIC	6	R (Position)	I (Along Velocity Direction/"In-Track")	C (Orbit Normal/"Cross-Track")

Outgassing Events

Coordinate Systems

See Also