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Telemachus Reborn

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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.

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
  • MechJeb integration — command SmartASS autopilot modes (requires MechJeb)
  • 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

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.

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

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

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.

Building

Dependencies (Unity and KSP DLLs) are pre-committed to references/. No KSP installation is required to build.

With Nix (recommended)

nix develop
msbuild Telemachus.sln /p:Configuration=Release

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

Without Nix

Install Mono (which includes MSBuild), then:

msbuild Telemachus.sln /p:Configuration=Release

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.

License

See LICENSE and Licences/ for third-party licenses.

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Releases 14

v1.9.0 Latest
Mar 9, 2026
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