A KSP plugin that exposes live telemetry data over HTTP and WebSocket, letting you build external dashboards, flight instruments, and ground control applications for your vessels.

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Features

• HTTP REST + WebSocket API on port 8085 — poll or stream any telemetry value in real time
• Camera streaming — capture in-game camera views as JPEG snapshots over HTTP
• Built-in web UI — flight controls, navigation, orbital data, map, console, SmartASS, and more, accessible from any browser on your network
• Flight control — throttle, staging, SAS modes, RCS, action groups, and fly-by-wire attitude control
• Delta-V readouts — per-stage and total delta-V, TWR, ISP, burn time, and mass breakdown
• Maneuver node management — create, update, and delete maneuver nodes via the API
• Target tracking — set targets, read distance/relative velocity, docking alignment angles
• Landing prediction — impact time, suicide burn countdown, predicted coordinates and slope (WIP — in testing)
• Thermal monitoring — hottest part/engine temperatures, heat shield flux, overheat warnings (WIP — in testing)
• Science & career — experiment data, funds, reputation, science points, game mode (WIP — in testing)
• CommNet telemetry — signal strength, control state, signal delay (WIP — in testing)
• Alarm clock integration — read KSP alarm clock entries
• Antenna parts — three antenna models (Blade, Fustek, Yagi) with configurable up/downlink rates; also runs "partless" if needed
• Resource & sensor monitoring — query any resource or sensor by name
• Plugin API — other mods can register custom telemetry handlers

Mod integrations

Mod	Prefix	Description	Status
MechJeb	mj.*	SmartASS autopilot orientation commands	Released
FAR	far.*	Aerodynamic coefficients, flaps, spoilers, stall detection	Released
RealChute	rc.*	Parachute deployment status, safety, arm/deploy/cut	Released
Astrogator	astg.*	Transfer window planning — delta-V, burn times, maneuver creation	Released
Kerbalism	kerbalism.*	Life support, radiation, habitat, crew health, space weather	Released
Principia	principia.*, o.mean.*	N-body orbit analysis — mean elements, flight plan burns, recurrence	In testing

All mod integrations are soft dependencies via reflection — no mod DLLs are required at build time. Query a.mods at runtime to check which mods are detected, or a.physicsMode to check if Principia's N-body integrator is active ("n_body" vs "patched_conics").

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Installation

1. Download the latest GameData.zip from the Releases page.
2. Extract and merge the GameData/ folder into your KSP installation directory.
3. Launch KSP. The Telemachus server starts automatically when a vessel with a Telemachus antenna is active, or when running in partless mode.
4. Open a browser and navigate to http://localhost:8085/ to access the built-in UI.

The default port is 8085 and binds to 0.0.0.0 (all interfaces). Both can be changed in the plugin configuration file.

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API overview

Endpoints

Endpoint	Protocol	Purpose
/telemachus/datalink	HTTP GET/POST	Poll telemetry values
/datalink	WebSocket	Stream telemetry in real time
/telemachus/cameras	HTTP GET	List available cameras
/telemachus/cameras/<name>	HTTP GET	Capture a camera frame (JPEG)
/telemachus/*	HTTP GET	Built-in web UI (static files)

HTTP polling

Query parameters use key=value format, where the key is an arbitrary label and the value is the API string:

GET /telemachus/datalink?alt=v.altitude&lat=v.lat&lon=v.long

{ "alt": 12345.6, "lat": -0.0974, "lon": 285.4 }

Multiple values in a single request:

GET /telemachus/datalink?alt=v.altitude&pe=o.PeA&ap=o.ApA&throttle=f.throttle

You can also POST a JSON body instead of query parameters:

POST /telemachus/datalink
Content-Type: application/json

{ "alt": "v.altitude", "pe": "o.PeA", "ap": "o.ApA" }

Actions (throttle, staging, SAS, etc.) are invoked the same way — the server executes them on the next game tick:

GET /telemachus/datalink?x=f.setThrottle[0.5]&y=f.stage

WebSocket streaming

Connect to ws://<host>:8085/datalink and send JSON commands:

{ "+": ["v.altitude", "o.PeA", "f.throttle"], "rate": 500 }

The server pushes a JSON object with current values at the requested interval (milliseconds).

Command	Description
"+"	Subscribe to API keys (array)
"-"	Unsubscribe from API keys (array)
"run"	One-shot evaluation — included in the next update only (array)
"rate"	Set update interval in milliseconds (integer, default 500)
"binary"	Subscribe to binary stream — values sent as big-endian float32 (array)

Binary packet format: byte 0 is 0x01 (marker), followed by 4-byte IEEE 754 big-endian floats in subscription order. Sent alongside the JSON text frame each tick.

Error handling

Unknown API keys are returned in an "unknown" array. Exceptions are returned in an "errors" object:

{
  "alt": 12345.6,
  "unknown": ["v.bogus"],
  "errors": { "v.broken": "System.NullReferenceException: ..." }
}

Parameter syntax

Some API keys accept parameters in bracket notation:

r.resource[ElectricCharge]        — resource by name
b.name[3]                         — celestial body by index
o.orbitalSpeedAt[1200.0]          — speed at orbit time
mj.surface[90,45]                 — MechJeb heading + pitch
v.setPitchYawRollXYZ[0,0,0,1,0,0] — FBW attitude + translation

Scaling for embedded controllers

For integer-only boards (Raspberry Pi Pico, MicroBlocks, etc.) that can't handle floating-point JSON, both /api/ and /telemachus/datalink support scaling query parameters.

Input scaling — map an integer range to 0.0–1.0 before the API processes it:

GET /api/f.setThrottle?args=512&scale=0,1023     → throttle set to ~0.5

Output scaling — round to N decimals, optionally shift to integer:

GET /api/v.altitude?precision=2                   → 18345.67
GET /api/v.altitude?precision=2&int=true          → 1834567   (divide by 100 on board)

On the batch endpoint (/telemachus/datalink), use _scale, _precision, and _int as global defaults:

GET /telemachus/datalink?alt=v.altitude&pe=o.PeA&_precision=1&_int=true
→ { "alt": 183457, "pe": 750001 }

Or override per-key with pipe syntax in the value string:

GET /telemachus/datalink?alt=v.altitude|precision:2|int&t=f.setThrottle[512]|scale:0,1023
→ { "alt": 1834567, "t": 1 }

Per-key pipe modifiers take precedence over global _ parameters.

Modifier	Where	Effect
scale=min,max / `	scale:min,max`	Input
precision=N / `	precision:N`	Output
int=true / `	int`	Output

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OpenAPI spec

A machine-readable OpenAPI 3.1 spec is auto-generated from the source code. It covers all endpoints below, including mod-specific ones (tagged with x-requires-mod). (The OpenAPI spec and schema generation pipeline are not yet released — in testing.)

API reference

v.* — Vessel

Position & altitude

Key	Description	Unit
v.altitude	Altitude above sea level	m
v.heightFromTerrain	Height above terrain	m
v.heightFromSurface	Height above surface	m
v.terrainHeight	Terrain altitude	m
v.pqsAltitude	PQS terrain altitude	m
v.lat	Latitude	deg
v.long	Longitude (normalized -180 to 180)	deg

Velocity

Key	Description	Unit
v.surfaceVelocity	Surface velocity magnitude	m/s
v.surfaceVelocityx	Surface velocity X	m/s
v.surfaceVelocityy	Surface velocity Y	m/s
v.surfaceVelocityz	Surface velocity Z	m/s
v.orbitalVelocity	Orbital velocity magnitude	m/s
v.orbitalVelocityx	Orbital velocity X	m/s
v.orbitalVelocityy	Orbital velocity Y	m/s
v.orbitalVelocityz	Orbital velocity Z	m/s
v.surfaceSpeed	Horizontal surface speed	m/s
v.verticalSpeed	Vertical speed	m/s
v.speed	Total speed	m/s
v.srfSpeed	Surface speed (direct)	m/s
v.obtSpeed	Orbital speed (direct)	m/s
v.angularVelocity	Angular velocity magnitude	rad/s
v.angularVelocityx/y/z	Angular velocity components	rad/s

Acceleration & forces

Key	Description	Unit
v.geeForce	G-force (averaged)	G
v.geeForceImmediate	G-force (instantaneous)	G
v.acceleration	Total acceleration magnitude	m/s^2
v.accelerationx/y/z	Acceleration components	m/s^2
v.specificAcceleration	Thrust / mass	m/s^2
v.perturbation	Orbital perturbation magnitude	m/s^2
v.perturbationx/y/z	Perturbation components	m/s^2

Mass & inertia

Key	Description	Unit
v.mass	Total vessel mass	kg
v.angularMomentum	Angular momentum magnitude	—
v.angularMomentumx/y/z	Angular momentum components	—
v.momentOfInertia	Moment of inertia	Vector3d
v.CoM	Center of mass position	Vector3d

Atmosphere & environment

Key	Description	Unit
v.atmosphericDensity	Air density	kg/m^3
v.dynamicPressurekPa	Dynamic pressure	kPa
v.dynamicPressure	Dynamic pressure	Pa
v.staticPressurekPa	Static pressure	kPa
v.staticPressure	Static pressure (FlightGlobals)	kPa
v.atmosphericPressurePa	Atmospheric pressure	Pa
v.atmosphericPressure	Atmospheric pressure	atm
v.atmosphericTemperature	Air temperature	K
v.externalTemperature	External temperature	K
v.mach	Mach number	—
v.speedOfSound	Speed of sound	m/s
v.indicatedAirSpeed	Indicated airspeed	m/s
v.directSunlight	In direct sunlight	bool
v.distanceToSun	Distance to sun	m
v.solarFlux	Solar flux	—

Situation & state

Key	Description	Type
v.name	Vessel name	string
v.body	Celestial body name	string
v.situation	Situation enum	string
v.situationString	Human-readable situation	string
v.vesselType	Vessel type	string
v.landed	Is landed	bool
v.splashed	Is splashed	bool
v.landedOrSplashed	Is landed or splashed	bool
v.landedAt	Biome / location name	string
v.isEVA	Is EVA	bool
v.isActiveVessel	Is active vessel	bool
v.isControllable	Is controllable	bool
v.isCommandable	Is commandable	bool
v.loaded	Vessel is loaded	bool
v.packed	Vessel is on rails	bool
v.currentStage	Current stage number	int
v.missionTime	Mission elapsed time	s
v.missionTimeString	Formatted MET	string
v.launchTime	Launch time (UT)	s
v.crewCount	Number of crew	int
v.crewCapacity	Crew capacity	int
v.crew	List of crew names	string[]
v.angleToPrograde	Angle to orbital prograde	deg

Action group state (read)

Key	Description
v.sasValue	SAS state
v.rcsValue	RCS state
v.lightValue	Lights state
v.brakeValue	Brakes state
v.gearValue	Gear state
v.abortValue	Abort state
v.precisionControlValue	Precision mode state
v.ag1Value … v.ag10Value	Custom action group states

o.* — Orbit

Keplerian elements & apsides

Key	Description	Unit
o.ApA	Apoapsis altitude	m
o.PeA	Periapsis altitude	m
o.ApR	Apoapsis radius	m
o.PeR	Periapsis radius	m
o.timeToAp	Time to apoapsis	s
o.timeToPe	Time to periapsis	s
o.sma	Semi-major axis	m
o.semiMinorAxis	Semi-minor axis	m
o.semiLatusRectum	Semi-latus rectum	m
o.eccentricity	Eccentricity	—
o.inclination	Inclination	deg
o.lan	Longitude of ascending node	deg
o.argumentOfPeriapsis	Argument of periapsis	deg
o.period	Orbital period	s
o.epoch	Epoch	—
o.referenceBody	Reference body name	string

Anomalies

Key	Description	Unit
o.trueAnomaly	True anomaly	deg
o.meanAnomaly	Mean anomaly	deg
o.eccentricAnomaly	Eccentric anomaly	deg
o.maae	Mean anomaly at epoch	—
o.timeOfPeriapsisPassage	Time of periapsis passage (UT)	s
o.orbitPercent	Orbit completion percentage	—

Velocity, position & energy

Key	Description	Unit
o.relativeVelocity	Relative velocity magnitude	m/s
o.orbitalSpeed	Orbital speed	m/s
o.vel	Orbital velocity vector	Vector3d
o.radius	Orbital radius	m
o.pos	Orbital position vector	Vector3d
o.orbitalEnergy	Specific orbital energy	—
o.orbitNormal	Orbit normal vector	Vector3d
o.eccVec	Eccentricity vector	Vector3d
o.anVec	Ascending node vector	Vector3d
o.h	Specific angular momentum	Vector3d

Parameterized queries

Key	Description
o.orbitalSpeedAt[time]	Speed at orbit time (m/s)
o.orbitalSpeedAtDistance[dist]	Speed at distance (m/s)
o.radiusAtTrueAnomaly[deg]	Radius at true anomaly (m)
o.trueAnomalyAtRadius[m]	True anomaly at radius (deg)

Orbit patches & transitions

Key	Description
o.orbitPatches	All orbit patches (complex object)
o.timeToTransition1	Time to patch transition 1 (s)
o.timeToTransition2	Time to patch transition 2 (s)
o.patchStartTransition	Patch start transition type
o.patchEndTransition	Patch end transition type
o.StartUT / o.EndUT	Patch start/end UT
o.UTsoi	UT of SOI transition
o.closestEncounterBody	Closest encounter body name
o.closestTgtApprUT	Closest target approach UT
o.trueAnomalyAtUTForOrbitPatch[patch,ut]	True anomaly for patch at UT
o.UTForTrueAnomalyForOrbitPatch[patch,deg]	UT for true anomaly in patch
o.relativePositionAtTrueAnomalyForOrbitPatch[patch,deg]	Position at anomaly
o.relativePositionAtUTForOrbitPatch[patch,ut]	Position at UT

Maneuver nodes

Key	Description
o.maneuverNodes	All maneuver nodes (complex object)
o.maneuverNodes.count	Number of maneuver nodes
o.maneuverNodes.deltaV[id]	Delta-V vector (Vector3d)
o.maneuverNodes.deltaVMagnitude[id]	Delta-V magnitude (m/s)
o.maneuverNodes.UT[id]	Maneuver UT
o.maneuverNodes.timeTo[id]	Time until maneuver (s)
o.maneuverNodes.burnVector[id]	Burn vector in world space (Vector3d)
o.maneuverNodes.orbitPatches[id]	Orbit patches after maneuver
o.addManeuverNode[ut,x,y,z]	Action: add maneuver node
o.updateManeuverNode[id,ut,x,y,z]	Action: update maneuver node
o.removeManeuverNode[id]	Action: remove maneuver node

n.* — Navigation / navball

Key	Description	Unit
n.heading / n.pitch / n.roll	From root part	deg
n.rawheading / n.rawpitch / n.rawroll	Raw from root part	deg
n.heading2 / n.pitch2 / n.roll2	From center of mass	deg
n.rawheading2 / n.rawpitch2 / n.rawroll2	Raw from center of mass	deg

f.* — Flight control

Throttle

Key	Description
f.throttle	Current throttle (0–1)
f.setThrottle[float]	Action: set throttle
f.throttleUp	Action: increase 10%
f.throttleDown	Action: decrease 10%
f.throttleZero	Action: set to 0
f.throttleFull	Action: set to 1

Control inputs (read)

Key	Description	Range
f.pitchInput / f.yawInput / f.rollInput	Rotation axes	-1 to 1
f.xInput / f.yInput / f.zInput	RCS translation axes	-1 to 1
f.pitchTrim / f.yawTrim / f.rollTrim	Trim values	—
f.isNeutral	All controls neutral	bool
f.killRot	SAS kill rotation active	bool

Trim (set)

Key	Description
f.setPitchTrim[float]	Action: set pitch trim
f.setYawTrim[float]	Action: set yaw trim
f.setRollTrim[float]	Action: set roll trim

SAS & autopilot

Key	Description
f.sasEnabled	SAS autopilot enabled
f.sasMode	Current SAS mode (string)
f.setSASMode[mode]	Action: set SAS mode
f.precisionControl	Precision mode enabled

SAS modes: StabilityAssist, Prograde, Retrograde, Normal, Antinormal, RadialIn, RadialOut, Target, AntiTarget, Maneuver

Action groups

Key	Description
f.sas	Action: toggle SAS (optional [bool])
f.rcs	Action: toggle RCS
f.light	Action: toggle lights
f.gear	Action: toggle landing gear
f.brake	Action: toggle brakes
f.abort	Action: trigger abort
f.ag1 … f.ag10	Action: custom action groups
f.stage	Action: activate next stage

Fly-by-wire (FBW)

Key	Description
v.setFbW[1]	Action: enable FBW (0 to disable)
v.setPitch[float]	Action: set pitch (-1 to 1)
v.setYaw[float]	Action: set yaw (-1 to 1)
v.setRoll[float]	Action: set roll (-1 to 1)
v.setAttitude[pitch,yaw,roll]	Action: set rotation
v.setTranslation[x,y,z]	Action: set RCS translation
v.setPitchYawRollXYZ[p,y,r,x,y,z]	Action: set all axes at once

t.* — Time & warp

Key	Description
t.universalTime	Current UT (seconds)
t.deltaTime	Frame delta time
t.currentRate	Current warp rate multiplier
t.currentRateIndex	Current warp rate index
t.warpMode	HIGH or LOW
t.maxPhysicsRate	Max physics warp rate
t.isPaused	Game is paused
t.timeWarp[index]	Action: set time warp rate
t.pause	Action: pause game
t.unpause	Action: unpause game

tar.* — Target

Target info

Key	Description
tar.name	Target name
tar.type	Target type
tar.distance	Distance to target (m)
tar.o.relativeVelocity	Relative velocity (m/s)
tar.o.velocity	Target velocity (m/s)
tar.o.PeA / tar.o.ApA	Target apsides (m)
tar.o.inclination	Target inclination (deg)
tar.o.eccentricity	Target eccentricity
tar.o.period	Target period (s)
tar.o.sma / tar.o.lan	Target SMA / LAN
tar.o.trueAnomaly	Target true anomaly (deg)
tar.o.orbitingBody	Target reference body
tar.o.orbitPatches	Target orbit patches
tar.setTargetBody[index]	Action: set target to body
tar.setTargetVessel[index]	Action: set target to vessel
tar.clearTarget	Action: clear target

dock.* — Docking alignment

Key	Description	Unit
dock.ax	Docking X angle	deg
dock.ay	Docking Y angle / relative pitch	deg
dock.az	Docking Z angle	deg
dock.x	Target X distance	m
dock.y	Target Y distance	m

dv.* — Delta-V

Totals

Key	Description
dv.ready	Calculator is ready
dv.totalDVVac	Total delta-V vacuum (m/s)
dv.totalDVASL	Total delta-V at sea level (m/s)
dv.totalDVActual	Total delta-V current atmosphere (m/s)
dv.totalBurnTime	Total burn time (s)
dv.stageCount	Number of stages
dv.stages	All stages (complex object)

Per-stage (indexed by stage number)

Key	Description
dv.stageDVVac[n]	Stage delta-V vacuum (m/s)
dv.stageDVASL[n]	Stage delta-V ASL (m/s)
dv.stageDVActual[n]	Stage delta-V actual (m/s)
dv.stageTWRVac[n]	Stage TWR vacuum
dv.stageTWRASL[n]	Stage TWR ASL
dv.stageTWRActual[n]	Stage TWR actual
dv.stageISPVac[n]	Stage ISP vacuum (s)
dv.stageISPASL[n]	Stage ISP ASL (s)
dv.stageISPActual[n]	Stage ISP actual (s)
dv.stageThrustVac[n]	Stage thrust vacuum (kN)
dv.stageThrustASL[n]	Stage thrust ASL (kN)
dv.stageThrustActual[n]	Stage thrust actual (kN)
dv.stageBurnTime[n]	Stage burn time (s)
dv.stageMass[n]	Stage total mass (kg)
dv.stageDryMass[n]	Stage dry mass (kg)
dv.stageFuelMass[n]	Stage fuel mass (kg)
dv.stageStartMass[n]	Stage start mass (kg)
dv.stageEndMass[n]	Stage end mass (kg)

b.* — Celestial bodies

All body queries take a body index parameter: b.name[0] (Kerbol), b.name[1] (Kerbin), etc.

Properties

Key	Description
b.number	Total number of bodies
b.name[i]	Body name
b.description[i]	Body description
b.radius[i]	Radius (m)
b.mass[i]	Mass (kg)
b.geeASL[i]	Surface gravity (G)
b.soi[i]	Sphere of influence (m)
b.hillSphere[i]	Hill sphere radius (m)
b.rotationPeriod[i]	Rotation period (s)
b.rotationAngle[i]	Current rotation angle (deg)
b.tidallyLocked[i]	Tidally locked (bool)
b.atmosphere[i]	Has atmosphere (bool)
b.maxAtmosphere[i]	Atmosphere depth (m)
b.atmosphereContainsOxygen[i]	Has oxygen (bool)
b.ocean[i]	Has ocean (bool)
b.referenceBody[i]	Reference body name
b.orbitingBodies[i]	Names of orbiting bodies

Body orbital parameters

Key	Description
b.o.gravParameter[i]	Gravitational parameter
b.o.PeA[i] / b.o.ApA[i]	Apsides (m)
b.o.inclination[i]	Inclination (deg)
b.o.eccentricity[i]	Eccentricity
b.o.period[i]	Orbital period (s)
b.o.sma[i] / b.o.lan[i]	SMA / LAN
b.o.trueAnomaly[i]	True anomaly (deg)
b.o.phaseAngle[i]	Phase angle to vessel (deg)
b.o.truePositionAtUT[i,ut]	Position at UT (Vector3d)

r.* — Resources

Key	Description
r.resource[name]	Resource amount across all parts
r.resourceMax[name]	Resource max capacity
r.resourceCurrent[name]	Resource amount in current stage
r.resourceCurrentMax[name]	Resource max in current stage
r.resourceNameList	List of all resource names

Example: r.resource[ElectricCharge], r.resource[LiquidFuel], r.resource[Oxidizer]

s.* — Sensors

Key	Description
s.sensor[type]	Sensor data by type
s.sensor.temp	Temperature sensors
s.sensor.pres	Pressure sensors
s.sensor.grav	Gravity sensors
s.sensor.acc	Acceleration sensors

alarm.* — Alarm clock

Key	Description
alarm.count	Number of active alarms
alarm.list	All alarms (complex object)
alarm.nextAlarm	Next alarm to trigger
alarm.timeToNext	Time until next alarm (s)

m.* — Map view

Key	Description
m.mapIsEnabled	Map view is active
m.toggleMapView	Action: toggle map view
m.enterMapView	Action: enter map view
m.exitMapView	Action: exit map view

mj.* — MechJeb (requires MechJeb)

Key	Description
mj.smartassoff	Action: disable SmartASS
mj.node	Action: point to maneuver node
mj.prograde / mj.retrograde	Action: orbital prograde/retrograde
mj.normalplus / mj.normalminus	Action: normal/anti-normal
mj.radialplus / mj.radialminus	Action: radial in/out
mj.targetplus / mj.targetminus	Action: toward/away from target
mj.relativeplus / mj.relativeminus	Action: along/against relative velocity
mj.parallelplus / mj.parallelminus	Action: parallel/anti-parallel to target
mj.surface[heading,pitch]	Action: surface orientation
mj.surface2[heading,pitch,roll]	Action: surface with roll
mj.stagingInfo	Staging simulation data

p.* — Pause state

Key	Value	Meaning
p.paused	0	Flight scene OK
	1	Paused
	2	No power
	3	Off
	4	Antenna not found
	5	Not in flight scene

a.* — API meta

Key	Description
a.version	Telemachus version string
a.ip	Server IP addresses
a.api	Full API listing
a.apiSubSet[key1,key2,...]	Subset of API listing
a.mods	Detected mod integrations (object)
a.physicsMode	"patched_conics" or "n_body" (Principia)
a.schema	Full API schema as JSON

Camera API

GET /telemachus/cameras

Returns a JSON array of available cameras:

[
  { "name": "FlightCamera", "type": "Flight", "url": "/telemachus/cameras/FlightCamera" }
]

Fetch a JPEG snapshot:

GET /telemachus/cameras/FlightCamera

Returns image/jpeg. Returns 503 if the camera hasn't rendered yet, 404 if the camera name is unknown.

far.* — FAR aerodynamics (requires FAR)

Aerodynamic data & controls

Key	Description	Unit
far.available	FAR is installed	bool
far.liftCoeff	Lift coefficient (Cl)	—
far.dragCoeff	Drag coefficient (Cd)	—
far.refArea	Reference area	m^2
far.ballisticCoeff	Ballistic coefficient	—
far.dynPres	Dynamic pressure (FAR)	kPa
far.termVel	Terminal velocity	m/s
far.tsfc	Thrust specific fuel consumption	—
far.aoa	Angle of attack	deg
far.sideslip	Sideslip angle	deg
far.stallFrac	Stall fraction (0–1)	—
far.flapSetting	Flap deflection level (0–3, -1 if none)	—
far.spoiler	Spoilers active	bool
far.voxelized	Vessel has valid voxelization	bool
far.increaseFlaps	Action: increase flap deflection
far.decreaseFlaps	Action: decrease flap deflection
far.setSpoilers[bool]	Action: set spoilers

rc.* — RealChute (requires RealChute)

Key	Description
rc.available	RealChute is installed
rc.count	Number of RealChute parts
rc.anyDeployed	Any chutes deployed
rc.safeState	Deployment safety (SAFE / RISKY / DANGEROUS)
rc.chutes	All chute status (object)
rc.deploy	Action: deploy all chutes
rc.cut	Action: cut all chutes
rc.arm	Action: arm all chutes
rc.disarm	Action: disarm all chutes

astg.* — Astrogator (requires Astrogator)

Transfer planning

Key	Description
astg.available	Astrogator is installed
astg.active	Instance is active
astg.errorCondition	Transfer calculation error
astg.retrogradeOrbit	Retrograde orbit detected
astg.hyperbolicOrbit	Hyperbolic orbit detected
astg.transferCount	Number of available transfers
astg.transfers	All transfer opportunities (object)
astg.transfer[index]	Transfer by index (object)
astg.activeTransfer	Transfer with active maneuver node
astg.nextDeltaV	Next transfer total delta-V (m/s)
astg.nextDestination	Next transfer destination name
astg.nextBurnTime	Next transfer burn time (UT)
astg.nextBurnCountdown	Seconds until next transfer burn
astg.createManeuver[index]	Action: create maneuver for transfer
astg.warpToBurn[index]	Action: warp to transfer burn

kerbalism.* — Kerbalism life support & radiation (requires Kerbalism)

Availability & features

Key	Description	Type
kerbalism.available	Kerbalism is installed	bool
kerbalism.features	Enabled feature flags (radiation, habitat, etc.)	object

Radiation

Key	Description	Type
kerbalism.radiationEnabled	Radiation system enabled	bool
kerbalism.radiation	Environment radiation	rad/h
kerbalism.habitatRadiation	Habitat radiation	rad/h
kerbalism.magnetosphere	Inside magnetosphere	bool
kerbalism.innerBelt	Inside inner radiation belt	bool
kerbalism.outerBelt	Inside outer radiation belt	bool
kerbalism.stellarActivity	Stellar activity level (0–1)	double

Habitat & life support

Key	Description	Type
kerbalism.habitatVolume	Habitat volume	m³
kerbalism.habitatSurface	Habitat surface area	m²
kerbalism.habitatPressure	Habitat pressure (0–1)	double
kerbalism.co2Level	CO₂ poisoning level	double
kerbalism.radiationShielding	Radiation shielding (0–1)	double
kerbalism.habitatLivingSpace	Living space comfort factor	double
kerbalism.habitatComfort	Overall habitat comfort	double

Environment

Key	Description	Type
kerbalism.envTemperature	Environment temperature	K
kerbalism.envTempDiff	Temp difference from survival	double
kerbalism.envStormRadiation	Storm radiation dose	double
kerbalism.breathable	Atmosphere breathable	bool
kerbalism.inAtmosphere	Inside atmosphere	bool
kerbalism.solarExposure	Solar panel average exposure (0–1)	double

Comms & data

Key	Description	Type
kerbalism.connectionLinked	Signal connected	bool
kerbalism.connectionRate	Data rate	MB/s
kerbalism.connectionTransmitting	Files transmitting	int
kerbalism.connection	Full connection info	object
kerbalism.drivesFreeSpace	Drive free space	MB
kerbalism.drivesCapacity	Drive total capacity	MB

Space weather & crew

Key	Description	Type
kerbalism.stellarStormState	Storm state (0=none, 1=incoming, 2=active)	int
kerbalism.stellarStormIncoming	Storm incoming	bool
kerbalism.stellarStormInProgress	Storm in progress	bool
kerbalism.stellarStormDuration	Storm duration	s
kerbalism.stellarStormStartTime	Storm start time (UT)	s
kerbalism.malfunction	Part malfunction active	bool
kerbalism.critical	Critical failure active	bool
kerbalism.crew	Crew health summary (per-kerbal)	object
kerbalism.experimentRunning[id]	Experiment is running	bool

principia.* / o.mean.* — Principia N-body physics (requires Principia) (WIP — in testing)

When Principia is installed, KSP's patched-conic orbit propagator is replaced with an N-body integrator. Stock o.* values become osculating (instantaneous Keplerian) snapshots. Principia's orbit analyser computes mean elements averaged over many orbits — these are available under o.mean.*.

All data is read via reflection from Principia's runtime state. No Principia DLLs are needed at build time, and Principia's (removed) external API is not used.

Detection & status

Key	Description
principia.available	Principia is installed
principia.version	Principia assembly version
principia.active	Principia plugin is running
principia.analysisProgress	Orbit analysis progress (0–1)
principia.missionDuration	Analysis mission duration (s)

Mean orbital elements

These mirror the stock o.* keys but report mean (time-averaged) values from Principia's orbit analyser. Angles are in degrees, distances are altitudes (body radius subtracted).

Key	Description	Unit
o.mean.sma	Mean semi-major axis	m
o.mean.eccentricity	Mean eccentricity	—
o.mean.inclination	Mean inclination	deg
o.mean.lan	Mean longitude of ascending node	deg
o.mean.argumentOfPeriapsis	Mean argument of periapsis	deg
o.mean.PeA	Mean periapsis altitude	m
o.mean.ApA	Mean apoapsis altitude	m

Element ranges (min/max from N-body integration)

Each returns { "min": number, "max": number }.

Key	Description
o.mean.smaRange	SMA range
o.mean.eccentricityRange	Eccentricity range
o.mean.inclinationRange	Inclination range (deg)
o.mean.PeARange	Periapsis altitude range (m)
o.mean.ApARange	Apoapsis altitude range (m)

Periods, precession & recurrence

Key	Description	Unit
o.mean.siderealPeriod	Sidereal period	s
o.mean.nodalPeriod	Nodal period	s
o.mean.anomalisticPeriod	Anomalistic period	s
o.mean.nodalPrecession	Nodal precession rate	rad/s
o.mean.recurrence	Orbit recurrence info (object)	—

Flight plan

Key	Description
principia.plan.count	Number of planned burns
principia.plan.guidance	Navball guidance active
principia.plan.burns	All planned burns (array of objects)
principia.plan.burn[index]	Single burn by index
principia.analysis	Complete orbit analysis dump (object)

Each burn object contains { tangent, normal, binormal, initial_time, duration } in m/s and seconds.

land.* — Landing prediction (WIP — in testing)

Key	Description	Unit
land.timeToImpact	Estimated seconds to impact	s
land.speedAtImpact	Predicted speed at impact (current thrust)	m/s
land.bestSpeedAtImpact	Predicted speed at impact (max thrust)	m/s
land.suicideBurnCountdown	Seconds until suicide burn start	s
land.predictedLat	Predicted landing latitude	deg
land.predictedLon	Predicted landing longitude	deg
land.predictedAlt	Predicted landing terrain altitude	m
land.slopeAngle	Terrain slope angle under vessel	deg

therm.* — Thermal monitoring (WIP — in testing)

Key	Description	Unit
therm.hottestPartTemp	Hottest part temperature	C
therm.hottestPartTempKelvin	Hottest part temperature	K
therm.hottestPartMaxTemp	Hottest part max temperature	K
therm.hottestPartTempRatio	Hottest part temp ratio (0–1)	—
therm.hottestPartName	Hottest part name	string
therm.hottestEngineTemp	Hottest engine temperature	K
therm.hottestEngineMaxTemp	Hottest engine max temperature	K
therm.hottestEngineTempRatio	Hottest engine temp ratio (0–1)	—
therm.anyEnginesOverheating	Any engine near overheat (>90%)	bool
therm.heatShieldTemp	Heat shield temperature	K
therm.heatShieldTempCelsius	Heat shield temperature	C
therm.heatShieldFlux	Heat shield thermal flux	kW

sci.* / career.* / comm.* — Science, career & comms (WIP — in testing)

Key	Description
sci.count	Number of science experiments aboard
sci.dataAmount	Total science data aboard
sci.experiments	Experiments with data (object)
career.funds	Available funds
career.reputation	Current reputation
career.science	Available science points
career.mode	Game mode (CAREER / SCIENCE / SANDBOX)
comm.connected	CommNet is connected
comm.signalStrength	CommNet signal strength (0–1)
comm.controlState	CommNet control state (0=none, 1=partial, 2=full)
comm.controlStateName	CommNet control state name
comm.signalDelay	CommNet signal delay (s)

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Building

The project targets .NET Framework 4.7.2 via an SDK-style csproj and builds with the .NET SDK. Unity and KSP reference DLLs are pre-committed to references/ — no KSP installation is required to build.

With Nix (recommended)

nix develop
dotnet build Telemachus/Telemachus.csproj

Without Nix

Install the .NET SDK 8+ (or Mono), then:

dotnet build Telemachus/Telemachus.csproj

The post-build script stages the output to publish/GameData/ and downloads the Houston and mkon companion apps automatically.

OpenAPI spec

A source generator extracts all [TelemetryAPI] attributes at build time into publish/api-schema.json. To regenerate the OpenAPI spec and docs:

bun tools/generate-openapi.ts

This merges the auto-generated schema with tools/manual-apis.json (for constructor-registered APIs) and writes docs/openapi.yaml.

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Contributing

Contributions are welcome — see CONTRIBUTORS.md for the full list of people who have helped build this.

• Bug reports and feature requests: open an issue
• Chat: Discord server
• Pull requests: please follow the conventional commits format (feat:, fix:, docs:, etc.). A commit-msg hook is installed automatically when you enter the Nix dev shell.

Please follow the Code of Conduct.

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License

See LICENSE and Licences/ for third-party licenses.