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Coverage

Regions and requests over the mission interval

Coverage answers how well your fleet serves a place or a set of requests. Link is one pair at a time. Coverage is the region, the grid, or the population of events.

Add it from the Mission Tree → Analysis → Coverage. Name it, choose type, pick who acquires, Apply Changes, Run Analysis.

Open Web App · walkthrough: LEO optical mission (Continuous)

When to use

Use Coverage when… Prefer something else when…
Percent of a country covered, gaps, heatmaps One satellite–station pass → Link
IoT / imaging requests inside an AOI Time to deliver after the look → Coverage then Latency
Radar-style command then look from a ground station RF margin on one hop → Link with budget
Command that relays over ISL to another imager Time-to-ground of the file → Coverage then Latency / ISL routing

Three types

Pick Coverage type to match the operational question.

Type What it samples Typical story
Continuous A grid over the domain Paint-the-Earth: revisit, percent covered, swath over a country
Discrete Demand events (random or Poisson, in the AOI or born at a facility) Messages, alerts, tasking — not every square kilometre equally
Static A fixed set of points (count + seed) Survey of N representative sites

Finer Continuous grids and larger Discrete N cost more time and may be limited by your plan.

Coverage Properties — type and AOI

Coverage Properties — type, AOI, grid (Continuous).

Coverage — Acquiring assets and method

Coverage — Acquiring assets and computation method.

Who acquires

Check spacecraft, sensors, or constellation rows such as All Satellites / All Sensors. The engine expands a constellation to its members.

  • Sensor — FOV and pointing matter (optical tutorial).
  • Spacecraft only — geometric line-of-sight of the bus (radar-tasking tutorial: no sensor).

Inactive assets and constraints (elevation, eclipse, range) can zero the result without an obvious error.

Where on Earth

AOI type (editor) Meaning
Global Whole Earth
Lat/Lon Region Min/max latitude and longitude box
Custom Area of Interest One or more AOI assets (countries, All Land, polygons)

Computation (method)

Computation mode (Access computation) is how tightly the engine samples geometry over time. Other analyses that need access windows inherit the same idea — this page is the reference.

Picking a preset fills the fields below. Edit any of them and the mode becomes Custom.

Mode Typical use What it actually sets
Fast First look, long scenario, coarse grid 30 s samples, no edge refinement. Short contacts can be missed or discarded.
Balanced Default. Medium accuracy. Included on Trial 10 s samples, edge refinement to 1 s, minimum duration 10 s.
High Accuracy Design decisions. Not on Trial 10 s samples, tighter edges (1 s). Catches short passes; slower.
Custom You own the numbers. Not on Trial Same fields, no preset.
Field (editor) Meaning
Temporal resolution [s] How often geometry is tested. Larger → faster, more likely to skip a short pass.
Find precise event times (sub-sampling) Bisect between samples to pin contact start/end. Off in Fast.
Time tolerance [s] How tightly that bisection may stop. Only with sub-sampling on.
Min access duration [s] Contacts shorter than this are dropped. Fast uses 30 s.
Max iterations Cap on bisection steps. Only with sub-sampling on.

Graphics-only tweaks (colours, translucency) do not recompute. Changing compute settings invalidates a completed run (stale).

Independent contact edges versus GMAT (same engine, including bisection): Independent verification.

Continuous

A spatial grid over the AOI. At each time step the engine marks which cells are acquired, then accumulates statistics. Playback can show dynamic coverage on the globe.

Field (editor) Meaning
Point granularity [deg] Spacing of grid cells. 3° is the finest Trial grid; finer grids resolve narrow gaps and cost more (plan may cap how fine).
Target altitude [km] Height of the sample surface above the ellipsoid (0 = ground). Raise it only if you are covering an elevated layer, not the terrain.

Use it for constellation comparison and sensor swath over a country. Coarse grids hide narrow gaps — tighten granularity before a design decision.

Continuous coverage overlay in 3D

Design — Continuous coverage overlay on the AOI after Run.

Discrete

Events are drawn with a seed so the same N is reproducible.

Field (editor) Meaning
Demand mode Where requests are born (table below)
Seed Random draw; same seed + same N → same points
# Events Fixed population (non-Poisson modes). Plan may cap N.
Rate [Hz] Poisson arrival rate instead of a fixed N
Demand mode Where requests are born What you measure
Random N in AOI Inside the AOI Acquisition delay (Generation → Acquisition)
Poisson in AOI Stream inside the AOI Same clock; rate instead of a fixed N
Facility tasking (N) At checked tasking facilities Tasking delay then Look delay; Acquisition delay is the sum
Facility tasking (Poisson) Same chain, Poisson arrivals Same two-leg story

Facility-tasking points still lie in the AOI (the “look”); the facility is the command origin.

Discrete facility tasking with ISL

Direct facility-tasking (above) is same-sat: the imager must see the origin station, then the AOI. Opt in to ISL (CGR earliest delivery) when a neighbour can hear the station and the camera cannot.

That overlay only shortens Tasking delay (T0 → T1). Look delay (T1 → T2) is still first target access after the order is onboard the acquirer. The file dump is Latency, not this page. Planner: ISL routing.

flowchart LR
  subgraph direct [Direct — same satellite]
    F1["Facility T0"] --> A1["Imager hears GS = T1"]
    A1 --> Tgt1["AOI look = T2"]
  end
  subgraph cgr [ISL command]
    F2["Facility T0"] --> R["Receiver sat"]
    R -->|CGR hops| A2["Imager has order = T1"]
    A2 --> Tgt2["AOI look = T2"]
  end

Who hears vs who shoots

sequenceDiagram
  participant F as Facility
  participant R as Command receiver
  participant A as Acquirer
  participant T as AOI target
  F->>R: T0 order generated
  Note over R: First see of the station
  R->>A: ISL command (CGR)
  Note over A: T1 Tasking — order onboard
  A->>T: first see after T1
  Note over A: T2 Acquisition
Field (editor) Meaning
Command routing Same-sat facility contact (default) or ISL (CGR earliest delivery)
Command network Completed Connection Network. Needed for ISL. Must include spacecraft–spacecraft edges if the uplink bus is not the imager, plus spacecraft–facility for the uplink. Those ends may be laser / dump-antenna sensors: access uses their FOV; command ISL collapses them to the parent bus. The nadir camera stays a Coverage acquirer and is not required on the CN. Example: two lasers and a dump dish.
Command receivers Who may hear the station, on Direct and on ISL. Same as acquirers, or Selected spacecraft (the uplink radios). Acquirers still take the picture. A camera uses its parent bus as the radio.
Uplink spacecraft Checklist when receivers are selected. Example: 20 cameras, 1 GS radio.

Without a network, or with Direct routing, Tasking is the first see of the origin facility by a command receiver (usually the same bus as the acquirer).

Practical command cases

1. Full mesh, every imager can hear polar GS

Direct already closes Tasking on the same pass that would have taken the picture. ISL command barely moves Tasking delay. Use Direct.

2. Sparse uplink (one or a few radios)

Only SAT-01 sees the tasking station. SAT-07 has the swath over the AOI.

flowchart LR
  GS["Tasking GS"] -->|uplink| S1["SAT-01 receiver"]
  S1 -->|ISL| S7["SAT-07 acquirer"]
  S7 --> AOI["AOI target"]
  • Direct: yield collapses to “only SAT-01 can take the order and look.”
  • CGR: Tasking delay is until SAT-07 has the order. Look delay is SAT-07’s first see of the AOI after that. Chain outcomes recover.

Set Who hears the GS to the uplink buses on Direct and on ISL; leave Acquirers as the cameras.

3. Command hops ≠ dump hops

Coverage ISL never moves the file. After T2, Latency chooses Direct dump or its own CGR dump. You can command over ISL and still dump Direct (or the other way around).

4. Lasers on the Connection Network

Same as case 2, but the sat–sat edges are sensor rows (+V-01 → +V-07, and the −V pair if you have one). Command ISL still routes SAT-01 → SAT-07. Access uses each laser cone; Max. Concurrent ISL Links is per laser. Leave the camera on Coverage. Two lasers and a dump dish.

Dashboard: chain outcomes still never-tasked / tasked-no-image / acquired. ISL shows up as Tasking delay CDFs that recover when Direct yield collapsed (single uplink). Empty Look is a pointing / FOV problem, not a missing ISL — the camera never saw the AOI after T1.

Delay clocks (Discrete)

Geometry only. Coverage stops at Acquisition. Dump to ground is Latency Delivery delay. Names: Coverage and latency clocks.

Name Interval When it exists
Tasking delay Generation → Tasking (satellite takes the order) Facility-tasking only
Look delay Tasking → Acquisition (satellite has the information) Facility-tasking only
Acquisition delay Generation → Acquisition Every Discrete mode

Without a facility, only Acquisition delay exists. Best-acquirer plots are statistics of Acquisition delay.

Delay CDFs only include successful sees. Misses are chain outcomes (never tasked / tasked-no-image / acquired). Dashboard catalogue IDs may still say TOTAL or ACQUISITION-LEG — the plot title is the name above.

Discrete facility-tasking in 3D

Design — Discrete events after a facility-tasking run.

Static

Static draws a frozen sample of sites inside the AOI and then treats those points like a sparse Continuous grid: they stay put for the whole interval. It is a survey of N places, not a live demand process.

That is the contrast with Discrete: Discrete events are generated (random N or Poisson, optionally at a facility) and the clock is Acquisition delay. Static sites have no Generation, so Coverage has no Tasking delay / Look delay / Acquisition delay / Delivery delay.

These four names are Coverage KPIs (same family as Continuous, only at N points). They are not Latency clocks:

Name What it is What it is not
Reachability Site seen at least once in the interval, or never Not Acquisition delay. A never-seen site is a miss, not an infinite wait.
Access duration How long the site is in view (min / mean / max / total) Not Delivery delay. No bytes move.
Availability Fraction of the interval the site is in view Not session Unattended. Unattended is Latency: in view but not served.
Revisit / blind gap Time between successive passes (min / mean / max) Not Unattended, not packet wait. A gap is “nobody geometrically there.”
Field (editor) Default Meaning
# Targets 500 How many sites to draw in the AOI. Plan may cap N.
Seed 100 Random draw. Same seed + same N + same AOI → same sites. Change the seed to get another survey of the same region.

AOI is the same Global / Lat/Lon Region / Custom Area of Interest as the other types — points are rejected until they land inside that domain.

Use Static when… Prefer Discrete when… Prefer Continuous when…
You want revisit / access stats on a representative set of clients or towns Requests arrive over time (alerts, tasking, one-shot events) You need a field / heatmap over every cell
You will later attach Latency Fixed packet (IoT) or Continuous session on these sites Latency Discrete payload per event Percent area covered, swath paint

Latency linked to this Coverage uses the same N sites as clients. Coverage still only answers who is in view, for how long, how often. Latency then emits packets (Acquisition delay + Delivery delay) or runs a session (Served / Unattended / No coverage). Names: Coverage and latency clocks.

On the globe, Static shows the sample points. Show filled area is Continuous-only (disabled here).

Static coverage points in 3D

Design — frozen sample points after a Static run.

After Run

  1. Status completed.
  2. Design: grid, filled area, discrete events, or static sample points, depending on type.
  3. Dashboard: select this Coverage analysis — Continuous heatmaps; Discrete CDFs / chain outcomes; Static reachability / access / availability / revisit at the sample sites. Latency plots are a different analysis.

Empty result: FOV, pointing, ground track vs AOI, constraints, who is checked as acquirer, or Min access duration longer than the pass — Troubleshooting.