Spacecraft¶

Spacecraft represents a vehicle with mass properties, instruments, engines, fuel tanks, and either a propagated or kernel-backed ephemeris.

Standard Constructor¶

Creates a spacecraft for numerical propagation.

var spacecraft = new Spacecraft(
    naifId: -1001, name: "MySat",
    mass: 500.0, maximumOperatingMass: 2000.0,
    clock: new Clock("OnboardClk", 256),
    initialOrbitalParameters: orbit,
    sectionalArea: 10.0, dragCoeff: 2.2,
    cosparId: "2024-001A", solarRadiationCoeff: 1.5);

Kernel-Backed Constructor¶

Creates a spacecraft whose ephemeris comes from loaded SPK/CK kernels. Use for archived missions (LRO, Cassini, JWST) or when using a spacecraft as an observer without propagation.

var lro = new Spacecraft(naifId: -85, name: "LRO",
    epoch: new Time(2024, 6, 1, 12, 0, 0), mass: 1018.0, sectionalArea: 12.0);

Parameter	Default	Description
`epoch`	`Time.J2000TDB`	Epoch for initial state lookup
`mass`	`0.0`	Dry mass (kg)
`maximumOperatingMass`	`double.MaxValue`	Maximum operating mass (kg)
`clock`	Auto-created	A new `Clock` named `"{name}_CLK"`
`sectionalArea`	`1.0`	Mean sectional area (m2)
`dragCoeff`	`2.2`	Drag coefficient
`solarRadiationCoeff`	`1.0`	Solar radiation pressure coefficient

Kernel-backed spacecraft: IsSpiceBacked returns true. Calling Propagate() throws InvalidOperationException.

Properties¶

Property	Description
`NaifId`	NAIF ID (negative)
`DryOperatingMass`	Mass without fuel (kg)
`MaximumOperatingMass`	Maximum operating mass (kg)
`SectionalArea`	Cross-sectional area for drag and SRP (m2)
`DragCoefficient`	Cd (default 2.2)
`SolarRadiationCoeff`	Cr (default 1.0)
`CosparId`	COSPAR international designator
`HardBodyRadius`	Hard-body radius for conjunction assessment (m)
`BodyFront` / `BodyRight` / `BodyUp`	Instance body axes (override static defaults)
`Instruments`	Read-only collection of instruments
`Engines`	Read-only collection of engines
`FuelTanks`	Read-only collection of fuel tanks
`Payloads`	Read-only collection of payloads
`IsSpiceBacked`	Whether ephemeris comes from SPICE kernels
`Frame`	Spacecraft body-fixed reference frame

Static Body Axes¶

Default body-frame directions used by all attitude maneuvers when no instance override is set.

Field	Direction	Vector
`Spacecraft.Front`	Forward	+Y
`Spacecraft.Back`	Aft	-Y
`Spacecraft.Right`	Starboard	+X
`Spacecraft.Left`	Port	-X
`Spacecraft.Up`	Zenith-facing	+Z
`Spacecraft.Down`	Nadir-facing	-Z

Instance-level overrides can be set via constructor parameters (bodyFront, bodyRight, bodyUp). Custom axes must be orthogonal and right-handed.

Methods¶

Method	Description
`AddCircularInstrument(...)`	Add circular FOV instrument
`AddRectangularInstrument(...)`	Add rectangular FOV instrument
`AddEngine(Engine)`	Add propulsion engine
`AddFuelTank(FuelTank)`	Add fuel tank
`AddPayload(Payload)`	Add payload
`GetTotalMass()`	Total mass including fuel
`SetStandbyManeuver(Maneuver, Time?)`	Set maneuver to execute
`Propagate(Window, IEnumerable, bool, bool, TimeSpan)`	Propagate orbit
`GetEphemeris(Time, ILocalizable, Frame, Aberration)`	Get state relative to observer
`WriteEphemeris(FileInfo)`	Write ephemeris to SPK file
`ToOpm(...)`	Export to CCSDS OPM

Components¶

Engine¶

Property	Description
`Name`	Engine name
`Model`	Engine model identifier
`SerialNumber`	Serial number
`ISP`	Specific impulse (s)
`FuelFlow`	Fuel mass flow rate (kg/s)
`Thrust`	Computed thrust (N)
`FuelTank`	Associated fuel tank

var engine = new Engine("MainEngine", "RS-25", "SN001",
    isp: 366.0, fuelFlow: 0.5, fuelTank: tank);

FuelTank¶

Property	Description
`Name`	Tank name
`Model`	Tank model identifier
`SerialNumber`	Serial number
`Capacity`	Maximum capacity (kg)
`InitialQuantity`	Initial fuel quantity (kg)
`Quantity`	Current fuel quantity (kg)

var tank = new FuelTank("MainTank", "FT-100", "SN001",
    capacity: 1000.0, initialQuantity: 800.0);

Instrument¶

Property	Description
`NaifId`	NAIF instrument ID
`Name`	Instrument name
`Model`	Instrument model identifier
`FieldOfView`	Field of view angle (rad)
`Shape`	`InstrumentShape` (Circular, Rectangular, Elliptical)
`Boresight`	Boresight direction in instrument frame
`RefVector`	Reference vector in instrument frame
`Orientation`	Instrument orientation relative to spacecraft

Method	Description
`IsInFOV(Time, ILocalizable, Aberration)`	Check if target is in field of view
`FindWindowsInFieldOfViewConstraint(...)`	Find visibility windows
`GetBoresightInSpacecraftFrame()`	Transform boresight to spacecraft body frame
`GetRefVectorInSpacecraftFrame()`	Transform reference vector to spacecraft body frame

Payload¶

var payload = new Payload("Camera", 25.0, "SN-42");