System Architecture¶

ORION is a two-segment system: a flight segment running on a Raspberry Pi 5 in orbit, and a ground segment at the EPFL Ecublens ground station in Switzerland.

graph LR
    SimSat["SimSat<br/>(Orbital Propagator<br/>+ Mapbox API)"]
    NT["NavTelemetry"]
    EA["EventAction"]
    CM["CameraManager"]
    VLM["VlmInferenceEngine"]
    TR["TriageRouter"]
    GCD["GroundCommsDriver"]
    BM["BufferManager"]
    RX["receiver.py<br/>(Ground Station)"]
    GDS["F-Prime GDS<br/>(Commands/Telemetry)"]

    SimSat -->|"HTTP position"| NT
    SimSat -->|"HTTP Mapbox tile"| CM
    NT -->|"NavState (sync)"| CM
    NT -->|"NavState (sync)"| EA
    EA -->|"ModeChangePort"| CM
    EA -->|"ModeChangePort"| VLM
    EA -->|"ModeChangePort"| TR
    EA -->|"ModeChangePort"| GCD
    BM -->|"Fw::Buffer"| CM
    CM -->|"InferenceRequestPort"| VLM
    VLM -->|"TriageDecisionPort"| TR
    TR -->|"FileDownlinkPort<br/>(HIGH)"| GCD
    TR -->|"disk write<br/>(MEDIUM)"| TR
    GCD -->|"TCP :50050<br/>(ORIO frames)"| RX
    GDS <-->|"TCP :50000<br/>(F-Prime link)"| EA

    CM -->|"buffer return"| BM
    VLM -->|"buffer return"| BM
    TR -->|"buffer return"| BM
    GCD -->|"buffer return"| BM

Flight Segment¶

The flight segment is an F-Prime deployment (Orion) composed of six custom active/passive components plus the standard F-Prime infrastructure (CdhCore, ComCcsds, FileHandling, DataProducts subtopologies).

Component Inventory¶

Component	Real Satellite Equivalent	Type	Priority	Role
EventAction	On-Board Computer (OBC) mode manager	Active	38	Mission mode state machine owner. Evaluates mode transitions at 1 Hz, broadcasts mode changes to all pipeline components.
NavTelemetry	GNSS receiver payload	Active	35	Polls SimSat for orbital position every 5 seconds. Computes Haversine distance to ground station and determines comm window state.
CameraManager	Earth observation camera payload	Active	30	Acquires imagery from SimSat's Mapbox API. Fuses GPS telemetry and dispatches to the VLM queue. Auto-capture at 65s intervals in MEASURE mode.
VlmInferenceEngine	On-board AI co-processor	Active	10	Runs the LFM2.5-VL-1.6B model via llama.cpp. 120-second per-frame timeout with KV cache reset on abort.
TriageRouter	On-board data handling unit	Active	25	Executes triage doctrine: HIGH to downlink, MEDIUM to storage, LOW discarded. Drops all frames in SAFE mode.
GroundCommsDriver	X-band radio transmitter	Active	20	Manages the simulated X-band link. Transmits HIGH frames over TCP. Queues to disk outside comm window.
BufferManager	On-board mass memory	Passive	:	Static pool of 20 x 786,432-byte (512x512 RGB) image buffers.
comDriver (F-Prime)	UHF radio transceiver	Passive	:	F-Prime TcpClient on port 50000. Always-on command/telemetry link to GDS.

Rate Groups¶

All ORION components are driven by a 1 Hz Linux timer through three rate groups:

Rate Group	Frequency	Members
RG1	1 Hz	Telemetry send, FileDownlink, SystemResources, ComQueue, CmdDisp, NavTelemetry, CameraManager, GroundCommsDriver, EventAction
RG2	0.5 Hz	CmdSequencer
RG3	0.25 Hz	Health watchdog, BufferManagers (Comms, DataProducts, ORION), DataProducts writer/manager

Ground Segment¶

The ground segment consists of three software elements:

receiver.py: Image Downlink Receiver¶

A standalone Python TCP server listening on port 50050. Accepts incoming ORIO-framed image data from GroundCommsDriver, validates the 8-byte header (magic ORIO + payload length), and writes each 512x512 RGB frame to disk as a .raw file.

F-Prime GDS: Command and Telemetry¶

The standard F-Prime Ground Data System connects to the flight segment over TCP port 50000 via Drv.TcpClient. Provides:

Uplink: Command dispatch (SET_ECLIPSE, ENTER_SAFE_MODE, LOAD_MODEL, TRIGGER_CAPTURE, etc.)
Downlink: Telemetry channels (position, mode, inference time, triage counts), event logs, and file transfers

SimSat: Orbital Simulator (External)¶

An external service (default port 9005) that provides:

Orbital propagator: Returns current latitude, longitude, and altitude via HTTP
Mapbox satellite tiles: Returns 512x512 RGB imagery for the satellite's current ground track position