NetSim Astra Satellite RF planning, link budget & coverage simulation
NetSim Astra is a web-based studio for satellite constellation visualization, link-budget analysis, and coverage prediction. Built on a 3D globe, it lets you design synthetic constellations, track live satellites from TLEs, and evaluate RF coverage with detailed link budgets, all from your browser.
Watch it in action
Two short walkthroughs: what NetSim Astra does, and how a coverage study is run end to end.
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4:01
NetSim Astra overview: RF planning and coverage for satellite networks
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4:31
Satellite coverage analysis: configure, run, and export RF coverage
What you can do with it
From constellation design to a per-point link budget, on an interactive 3D globe with CSV export.
3D globe visualization
Interactive CesiumJS globe with satellite orbits, ground markers, heatmap overlays, and footprint polygons, with playback for time-series results.
Link budget analysis
Full link budget: EIRP, free space path loss, antenna pattern gain, clutter, polarization, and ITU-R P.618 atmospheric losses.
Coverage prediction
Animated coverage heatmaps over a region at configurable grid resolution. Click any point for a full link-budget breakdown.
Point & footprint
Track received power at a fixed location over time, and map per-satellite coverage footprints from an Rx-power threshold.
Point analysis: satellite tracking and the ground link on the 3D globe.
Constellation sources
Four satellite sources, each compatible with the point, coverage, and footprint analyses.
Walker constellation
Generate Walker Delta or Star constellations with configurable planes, satellites per plane, altitude, and inclination. Scale to 100 planes, 360 satellites per plane, and altitudes up to 36,000 km, from LEO to GEO.
Real satellites (TLE)
Track real satellites three ways. Pick a constellation group, such as Starlink, OneWeb, Iridium or GPS, and pull live TLEs from CelesTrak or N2YO. Paste or upload your own TLE file, up to 500 records. Or look satellites up by NORAD ID or by name. Live runs refresh at a polling interval you set.
Single fixed satellite
Place a stationary satellite at any position for antenna-pattern testing and deterministic, single-timestep coverage analysis.
Geostationary orbits
Analyze GEO and inclined geosynchronous satellites by manual entry, presets (INSAT/GSAT), or live TLEs. GEO adds multibeam CINR.
The configuration form: choose a source, then set orbital and RF parameters.
Multibeam and footprint coverage
Two coverage outputs beyond the received-power heatmap: per-beam interference for GEO payloads, and per-satellite service-area boundaries.
Multibeam CINR
For GEO satellites entered manually, evaluate multi-beam payloads with frequency reuse (FR1–FR4). CINR heatmaps reveal co-channel interference and signal quality across the service area.
Service-area boundaries
Per-satellite coverage polygons show instantaneous service areas from a configurable Rx-power threshold, in both synthetic playback and live modes.
Live footprint: per-satellite coverage polygons on the 3D globe.
Link budget and RF modelling
A full link budget from the satellite EIRP down to received power at the ground terminal, with configurable antennas, bands, and propagation.
Received power
- EIRP, receive gain, and antenna pattern gain at the off-axis angle
- Free space path loss, clutter, polarization, and additional losses
- Click any heatmap point for the full breakdown
RF parameters
- TX power, antenna gain, EIRP, RX gain, system margin
- Bands: L, S, C, X, Ku, K, Ka, Q/V
- Additional losses and polarization loss
Antenna pattern models
- Gaussian: simplified analytical model
- Bessel (3GPP TR 38.811): circular aperture
- ITU-R S.672-4: FSS reference pattern
- Phased array (URA): beam shaping for 5G NTN
- Custom: imported CSV or Ansys HFSS FFD patterns
ITU-R P.618 propagation
- Rain fade and gaseous absorption
- Cloud attenuation and tropospheric scintillation
- Link availability via exceedance conversion
Clutter loss
- Terrain attenuation from ESA WorldCover land classes
- Defaults from 0.5 dB over water to 8 dB in built-up areas
- Per-class values and fallback editable, saved with the project
- Applied per ground point in coverage grids
Off-axis & elevation
- Antenna gain evaluated at the true off-axis angle
- Minimum elevation mask for visibility
- Slant range and geometry from satellite position
Imported patterns
- CSV gain tables over off-boresight and azimuth angles
- Ansys HFSS Far-Field Data (FFD) import
- 2D interpolation for asymmetric beams and measured sidelobes
- Usable in point, coverage, footprint, and multibeam analyses
View Pattern tool
Inspect any antenna pattern before running a simulation: beam shape, sidelobe structure, and pattern quality, for the analytical models and imported patterns alike.
Link quality and dynamics
Beyond received power, assess whether a link will close, what error rate it will deliver, and how it moves with the satellite.
Carrier-to-noise
Carrier-to-noise density ratio (C/N₀, dB-Hz) and carrier-to-noise ratio (C/N, dB) from the receiver system noise temperature and channel bandwidth, to judge whether a link will close, not just its signal strength.
Figure of merit
Receiver figure of merit (G/T, dB/K) from receive gain and system noise temperature, to compare receiver and antenna configurations. A default 290 K is used when no temperature is specified.
Frequency shift
Doppler shift from the radial velocity between satellite and ground station. Positive when approaching, negative when receding; a 550 km LEO satellite reaches roughly ±280 kHz at Ku-band (12 GHz), scaling to about ±37 kHz at L-band.
Digital link BER
Bit error rate for BPSK, QPSK, OQPSK, 8PSK, 16QAM, and 64QAM from Eb/N₀ and the configured bit rate, with a code-rate based coded-BER estimate and symbol rate, in point, coverage, and multibeam analyses.
Power flux density and regulatory limits
Report the incident power density at the ground, and check it against a regulatory limit mask with a per-point margin.
Flux density outputs
- Free-space PFD (dBW/m²) from effective EIRP and slant range
- PFD after atmospheric attenuation, when the ITU-R P.618 model is enabled
- Spectral PFD normalized to a selectable reference bandwidth
- Reported per point, per grid cell, and per beam in multibeam runs
Limit masks and margin
- Built-in ITU Article 21 style masks for the satellite downlink bands, from S-band through C, X, Ku and Ka up to Q/V
- Limits follow the elevation angle, with separate masks for geostationary and non-geostationary systems where the rules differ
- Astra picks the mask from the frequency and the orbit, or takes a custom limit and reference bandwidth
- PFD margin on every sample, positive when the point is below the limit
Astra screens a design against the mask you select and reports the margin. It does not replace a coordination or regulatory submission.
Under the hood
The geometry and orbital mechanics behind every position, angle, and loss.
Coordinate reference frames
Positions and angles are computed across Earth-Centered Earth-Fixed (ECEF), East-North-Up (ENU), and Local-Vertical-Local-Horizontal (LVLH) antenna frames.
SGP4 orbit propagation
Live satellites are propagated from their TLEs using the SGP4 model, then transformed to ground-relative geometry for elevation, slant range, and off-axis angle.
Time-stepped analysis
Synthetic scenarios step through a configurable simulation window; live scenarios poll in real time. Each step yields a full link budget per ground point.
Projects and reproducibility
Save a study, share it, and reproduce it exactly, even when live TLEs have moved on.
Save and load projects
Store a complete configuration, constellation, RF parameters, and analysis settings, as a JSON project, then reload it with every field repopulated.
TLE storage
Save live TLEs with their capture time and source alongside the project. Reload with the saved TLEs for identical positions, or fetch fresh ones for the current sky.
Record and replay
Record a live session and replay it later exactly as captured, with the same playback and scrubbing controls as synthetic runs.
Access reports
STK-style visibility statistics for every point analysis, generated from the same per-satellite time series.
STK-aligned figures of merit
Coverage %, total accesses, max simultaneous satellites, access-duration and gap statistics, Time Average Gap, and mean and maximum response time, following Ansys STK Figure of Merit definitions.
Visibility charts
A per-satellite visibility Gantt chart and a simultaneous-satellites step chart, with system-level gaps highlighted across both. Hover any bar for the satellite, time range, and duration.
Interval downloads
Collapsible access-interval and gap-interval tables with CSV downloads:
access_intervals.csv (one row per satellite pass) and
gap_intervals.csv (one row per system gap).
Access report: KPI cards and summary statistics behind each pass.
Outputs and results
Interactive on the globe, and exportable for offline analysis.
Interactive 3D globe
- Heatmaps, footprint polygons, satellite markers, and ground links
- Click any heatmap point for satellite ID, Rx power, elevation, distance, gain, and losses
- Playback for synthetic modes: play/pause, restart, speed 1x–50x, timeline scrubbing
- Recording controls for live modes with elapsed and total time
CSV export
point_analysis.csv– received power time seriescoverage_grid.csv– per-point coverage resultssatellite_footprint.csv– footprint boundariesmultibeam_cinr.csv– CINR per beamaccess_intervals.csv/gap_intervals.csv– from the access report
Inside the log file
A coverage run writes coverage_grid.csv: 39 columns per grid
point per time step, carrying every term of the link budget so results can be re-derived offline.
| Time & identity | Position | Geometry | Losses | Atmospheric | Losses | Rx power | Link quality | Digital link | Power flux density | |||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| timestamp | sat_id | grid_lat | grid_lon | sat_lat | sat_lon | sat_alt_km | distance_km | elevation_deg | azimuth_deg | off_axis_deg | fspl_db | pattern_db | clutter_db | clutter_class | atm_total_db | atm_rain_db | atm_gas_db | atm_cloud_db | atm_scint_db | additional_losses_db | polarization_loss_db | received_power_dbm | cn0_db_hz | cn_db | g_over_t_db_per_k | doppler_hz | modulation | eb_n0_db | ber | ber_coded | symbol_rate_baud | pfd_limit_band | pfd_ref_bw_hz | serving_sat_pfd_dbw_m2 | pfd_atm_dbw_m2 | pfd_ref_dbw_m2 | pfd_limit_dbw_m2 | pfd_margin_db |
| 2026-03-14T09:00:00Z | 44713 | 12.9716 | 77.5946 | 14.204 | 79.311 | 547.62 | 712.44 | 48.31 | 112.60 | 21.07 | 163.42 | 1.86 | 0.90 | urban | 0.71 | 0.12 | 0.34 | 0.14 | 0.11 | 1.50 | 0.30 | -92.14 | 78.36 | 12.42 | 13.05 | -24310.70 | QPSK | 9.412 | 1.204e-05 | 3.100e-09 | 20000000.000 | ITU 21.8-2 | 4000.000 | -138.42 | -139.13 | -146.15 | -140.00 | -6.15 |
| 2026-03-14T09:00:30Z | 44714 | 12.9716 | 77.5946 | 13.051 | 78.442 | 549.10 | 661.02 | 55.90 | 104.18 | 17.44 | 162.77 | 0.94 | 0.90 | urban | 0.64 | 0.10 | 0.31 | 0.13 | 0.10 | 1.50 | 0.30 | -90.55 | 79.95 | 14.01 | 13.05 | -18920.30 | QPSK | 11.002 | 2.115e-07 | 4.000e-12 | 20000000.000 | ITU 21.8-2 | 4000.000 | -136.83 | -137.47 | -144.56 | -140.00 | -4.56 |
- Time & identity (2)
- Position (5)
- Geometry (4)
- Losses (6)
- Atmospheric (5)
- Received power (1)
- Link quality (4)
- Digital link (5)
- Power flux density (7)
The five atm_* columns are always in the header; they carry 0 when
atmospheric loss is turned off. Point analysis, footprint, and multibeam runs write their own files
with the same naming convention.
Related product
Protocol and traffic simulation
Where NetSim Astra plans the constellation, link budget, and RF coverage, NetSim NTN simulates the protocol stack and traffic end-to-end. Use the two together to move from coverage design to measured throughput, latency, and error performance.
- Standards-based 5G NTN protocol simulation
- End-to-end, packet-level traffic and performance
- Throughput, latency, and error metrics per beam
Frequently asked questions
Short answers, with links to the detailed Astra Q&A.
What is NetSim Astra?
NetSim Astra is a web-based satellite RF planning tool. It visualizes constellations on a CesiumJS 3D globe and computes link budgets, coverage prediction, BER, power flux density and access reports, all from the browser.
Which constellations can NetSim Astra model?
Synthetic constellations, including Walker patterns, designed in the tool, and live satellites tracked from TLEs. LEO, MEO and GEO orbits are supported, with 5G NTN beam layouts.
How does NetSim Astra compare with Ansys STK and MATLAB?
Astra reports STK-aligned figures of merit and covers the RF planning workflow of coverage, link budget and access analysis in a browser, without desktop installation or scripting. For the detailed workflow comparison, see the Astra Q&A.
Can I go from coverage planning to network simulation?
Yes. Plan the constellation and coverage in Astra, then simulate the same scenario end to end, with the full 5G protocol stack and application traffic, in NetSim's NTN library.
Related and useful links
From coverage planning to packet-level simulation and enterprise network design.