Link¶
Pairwise contacts, optional RF budget
Link computes when two named assets can see each other over the scenario (or a custom window). Optionally, if the primary is a Transmitter and the secondary is a Receiver, it can close a first-order RF budget (margins vs required Eb/N₀), including polarisation and atmosphere from Scenario → Environment → RF.
Add from Mission Tree → Analysis → Link.
When to use¶
| Use Link when… | Prefer something else when… |
|---|---|
| Contact intervals between two assets | Area statistics → Coverage |
| One space–ground RF hop | Multi-hop mesh → Connection network + Routing |
| Sanity-check after changing an orbit | Time from acquire to gateway → Latency |
Geometry only vs budget¶
Budget off — “when do we have contact?” Spacecraft, facilities, targets, vehicles, sensors. Several secondaries are allowed when the pair types match. The first shot is that case (primary Athens, secondary a facility).
Budget on — primary must be a Transmitter, exactly one secondary a Receiver. The Link Budget block appears only then. Configure Simple or Complex RF (and a linked antenna on Complex) before you trust margins.
Link Properties — geometry (platform / target / facility).
Link Properties — Transmitter + Receiver, Compute link budget on.
| Field (editor) | Meaning |
|---|---|
| Compute link budget | Closes a first-order RF budget on that Tx→Rx hop. Disabled until the primary is a Transmitter (plan may hide it). |
| Required Eb/N₀ [dB] | Threshold the margin is measured against. 0 is a first look, not a coding/modulation spec. |
| Extra path loss [dB] | Implementation / pointing / cable margin you add by hand. |
| Include polarization loss | Polarisation mismatch between the Tx and Rx assets. |
| Include atmospheric loss | Rain / gases / cloud from Scenario → Environment → RF. Plan-gated independently of budget. |
With budget enabled, the secondary list is forced to one Receiver.
Who can pair with whom¶
| Primary | Allowed secondaries |
|---|---|
| Transmitter | Receivers only |
| Receiver | Transmitters only |
| Spacecraft, sensor, facility, target, vehicle | Other platforms in that family |
With budget enabled, the secondary list becomes a single Receiver (see the second figure above).
What to set¶
- Name, Active.
- Primary and compatible secondaries.
- Interval: scenario (usual) or custom UTC.
- Budget (optional, Tx + Rx): Compute link budget and the fields in the table above.
- Line colour / width for the 3D contact lines.
Facilities often need a ground elevation constraint. Sensors need FOV and pointing if they are a participant.
After Run¶
Design shows contact lines while the geometry is true. Dashboard: sky plot (azimuth / zenith of each pass), range, elevation; RF series only if budget was on.
Design — geometric contact lines during a pass.
Dashboard — sky plot (azimuth and zenith angle per pass).
Dashboard — RF margin vs required Eb/N₀ when budget is on.
No contacts — horizon, elevation, eclipse, inactive assets, short interval.
Contacts but failed budget — EIRP or power, G/T or noise figure, antenna pointing, required Eb/N₀, atmosphere.