GNSS simulator · Space receivers · Hardware-in-the-loop

Put your GNSS receiver in orbit, on the bench.

Stellar GNSS generates the signals of a GNSS constellation as your receiver would see them, and tells you how well it did. Scenarios are code, the simulator is driven in real time through an API, and every run leaves truth data to judge each fix. Built for space receivers rather than cars.

Join the early access See the status
drift-detection · GPS L1 C/A 12 channels
LOAD RUN INJECT REPORT
t+0.000 s load ephemeris brdc2740.26n · 11 SV RINEX 3
t+0.001 s commit channels 1–11 · PRN 2 … 31 tick 1 ms
t+42.0 s fix receiver position 3D · 11 SV
t+60.0 s inject position offset 0.5 m/s · cap 300 m ramp
t+180 s patch power cn0_offset −6 dB applied
t+600 s compare --against injected --min-pull passed
Satellites 11 / 12
Mean C/N₀ 43.5 dB-Hz
Pull 300 m
Who it is for

For the teams who fly GNSS receivers

Space receiver manufacturers

Qualify your receiver against repeatable scenarios, and hand your customers the scenarios and reports with it.

GNC and AOCS engineers

Feed the navigation chain of your flatsat with the fixes it will get in orbit, outages and weak signals included.

AIT and IVV teams

Run the same GNSS scenario on every campaign, and keep the truth data next to the verdict.

Integrity and security teams

Drift the position or the clock on purpose, and measure whether and when the receiver notices.

Why another simulator

Built for orbit, not for the road

Record-and-replay boxes are made to bring a drive test back to the lab. A receiver in orbit needs something else: a sky that moves at 7.8 km/s, scenarios that can be versioned and reviewed, and a simulator that the test procedure can steer.

Record and replay

  • Replays what an antenna once received, on the ground
  • A scenario is a recording: hard to review, hard to change
  • Operated by hand next to the test
  • The verdict is left to the operator

Stellar GNSS

  • Computes the sky for the trajectory you declare, orbits included Roadmap
  • A scenario is a reviewed file: ephemeris, trajectory, power, events
  • Steered in real time through its API, by a script or a procedure
  • Truth data and a pass or fail report for every run
Capabilities and status

What it does today, and what comes next

Stellar GNSS is in development. Implemented features run end to end in continuous integration, from the real control software through a bit-exact model of the FPGA to a reference receiver. The RF output on hardware is in bring-up.

ImplementedIn bring-upRoadmap

Signals and scenarios

  • GPS L1 C/A, 12 channels Implemented

    PRN 1 to 32, full LNAV navigation message (subframes 1 to 5), each channel with its own carrier, code and gain.

  • Ephemeris from the real sky Implemented

    Broadcast ephemeris from RINEX 2 and 3 navigation files, a YUMA almanac, or a synthetic 24-satellite constellation.

  • Scenarios as code Implemented

    A versioned JSON scenario: start time, ephemeris, trajectory, power and a timeline of events, edited in the dashboard or in Git.

  • Power and noise Implemented

    C/N₀ per satellite with elevation fade and mask, calibrated noise, timed fades and satellites switched off and on.

Space dynamics

  • LEO, MEO and GEO orbits Roadmap

    Receiver trajectories propagated from TLEs or orbit states, from low Earth orbit to geostationary.

  • Orbital Doppler and dynamics Roadmap

    Receiver velocities of 7.8 km/s and the Doppler and code-rate ranges they imply, validated end to end.

  • Space service volume Roadmap

    Signals received from above the constellation: weak side lobes, few satellites, long outages.

  • Ground and air trajectories Implemented

    Static, constant velocity, waypoints and splines, speed-planned paths, GPX, KML, NMEA and CSV import.

Test and control

  • Real-time control API Implemented

    REST and WebSocket API: load, start and stop scenarios, steer the receiver live, change power and noise on the fly, on a 1 ms tick.

  • Injected offsets Implemented

    Position and clock offsets ramped smoothly into the signal, to test how a receiver and its integrity checks react to a spoofing-like drift.

  • Double truth Implemented

    Every run records the true trajectory and the injected one, so a report can tell how far the receiver was pulled.

  • Closed loop with Stellar Control Roadmap

    GNSS scenarios started, steered and checked by Stellar Control procedures, in step with the flatsat.

Evidence and hardware

  • Truth data and reports Implemented

    RINEX 3.05 observations, trajectory CSV and NMEA truth, compared against the receiver output with pass and fail thresholds.

  • Reference receiver in CI Implemented

    A software receiver tracks the generated signal and computes a fix in continuous integration, against a bit-exact model of the FPGA.

  • RF output at 1575.42 MHz In bring-up

    Direct RF synthesis on an AMD RFSoC: 12 channels summed in the FPGA and converted straight to L1, no external upconverter.

  • Stellar Control evidence Roadmap

    Scenario, truth and verdicts attached to the AIT and IVV reports of the run that used them.

With Stellar Control · Roadmap

The GNSS sky as a step of the procedure

Stellar GNSS is designed to join the Stellar Control chain: the procedure that tests the flatsat also sets the sky its receiver sees, and the verdict carries the GNSS truth with it.

  1. Declare

    The orbit and the GNSS scenario live in the configuration repository, reviewed like the rest of the mission.

  2. Start

    A Stellar Control procedure starts the scenario at the epoch of the test, in step with the flatsat.

  3. Steer

    Steps change power, inject an offset or cut satellites, through the real-time API.

  4. Check

    Telemetry of the on-board receiver is compared with the GNSS truth, within tolerances.

  5. Report

    Scenario, truth and verdict end up in the AIT and IVV evidence of the run.

Current specification

Under the hood

Signal GPS L1 C/A, LNAV navigation message
Channels 12 simultaneous satellites
Generation FPGA, 16-bit I/Q at 122.88 MS/s, direct RF synthesis to 1575.42 MHz (in bring-up)
Hardware AMD Zynq UltraScale+ RFSoC
Ephemeris RINEX 2 and 3 navigation, YUMA almanac, synthetic constellation
Trajectories Static, constant velocity, waypoints and splines, speed-planned paths, GPX, KML, NMEA, CSV; orbits on the roadmap
Control REST and WebSocket API, live steering, power and noise changes, Prometheus metrics, web dashboard
Truth outputs RINEX 3.05 observations, trajectory CSV, NMEA, comparison reports
Early access

Bring your receiver. Shape the roadmap.

We are looking for space receiver manufacturers and integrators to test Stellar GNSS with us, and to tell us which orbits and signals come first.

Join the early access
  1. Tell us about your receiver, its orbit and its interfaces.
  2. Run your first scenarios on GPS L1 C/A.
  3. Compare its fixes with the truth data, report by report.
  4. Move to orbital scenarios as they land.