LEO Radar Tasking

Tutorial · Walker Star + facility-born demand

A four-plane Walker Star commanded from five real ground stations, over All Land. This is the radar-CONOPS counterpart of LEO Optical Satellite: instead of painting land in Continuous coverage, a request is born at a facility, the same satellite must see that station first, then a land point. Acquisition is spacecraft line-of-sight — no sensor. The analysis asset is named Radar Tasking Analysis.

Same hypotheses as the blog post. Numbers are sized for a 2-day window (Basic Web or Desktop). Trial is capped at 12 h and is too short for this recipe.

Open Web App · start from Create your first mission

What we will do

1. Set the scenario (RAD-TASK-Demo, 2 days, step 120 s).
2. Create seed spacecraft LEO-RAD-Demo (SSO ~550 km, dawn–dusk) with nadir attitude — no sensor.
3. Grow a Walker Star 4 / 4 / 1 with prefix LEO-RAD-Walker.
4. Add five commanding facilities from the station database.
5. Add an AOI with global layer All Land.
6. Run Coverage Discrete — Facility tasking (N) — named Radar Tasking Analysis.
7. Open Dashboard and read chain outcomes, then the three delay clocks.

Mission card

Field	Tutorial value
Mission name	RAD-TASK-Demo
Scenario	2 days (not the default 12 h Trial window)
Step	120 s (Trial / Basic minimum; do not go finer)
Seed spacecraft	LEO-RAD-Demo
Orbit wizard	SSO, altitude 550 km, MLTAN 6.0 h (dawn–dusk)
Attitude	Nadir
Sensor	None — acquirers are the spacecraft (Earth LoS)
Constellation	Walker Star, N=4, P=4, F=1, prefix LEO-RAD-Walker
Members	LEO-RAD-Walker-SAT-01-01 … SAT-04-01 (one sat per plane)
Facilities	SSC Madrid (partner), KSAT Punta Arenas, KSAT Inuvik, KSAT Troll (TrollSat), ESA New Norcia (Australia)
Facility constraint	Ground elevation min 5°
AOI	AOI-ALL-LAND — global layer All Land (not a country)
Analysis	Coverage Discrete, demand Facility tasking (N), N=200, seed=100, name Radar Tasking Analysis
Acquirer	Constellation All Satellites (the four buses)

Hypotheses (same as the blog)

Radar-style tasking, not paint-the-Earth. Requests are born at a ground station. The same bus must see that facility first, then a point on All Land. Geometry is line-of-sight of the spacecraft — no SAR / optical FOV. Polar stations should show shorter TASKING wait than mid-latitude stations over a 2-day window.

flowchart LR
  SSO["SSO 550 km / 6.0 h"] --> Att["Nadir"]
  Att --> Walker["Walker Star 4/4/1"]
  GS["5 facilities"] --> Cov["Radar Tasking Analysis"]
  Walker --> Cov
  AOI["All Land"] --> Cov
  Cov --> Dash["Chain outcomes + delay clocks"]

Web plan limits

A 2-day scenario fits Basic (up to 4 days) or Desktop. Trial is 12 h only. The full card (4 expanded spacecraft + 5 facilities) needs Pro (or Desktop). Basic can run the Walker (4 satellites) with 4 facilities — drop ESA New Norcia (Australia). Trial is 1 facility and 1 expanded acquirer: you can still learn the two-leg chain on 12 h with KSAT Troll (TrollSat) + seed LEO-RAD-Demo, then grow duration and fleet on a higher plan. Walker Apply itself is Trial-friendly (N=4).

1 — Scenario

1. New mission (or continue the first-mission file). Name it RAD-TASK-Demo.
2. Set the scenario span to 2 days: keep the start, move the end 48 hours later (same clock, next calendar day + remainder).
3. Set Scenario time step to 120 s. Trial and Basic will not accept a finer step — the UI blocks anything below 120 s.
4. Apply Changes on the scenario if the header is dirty.

2 — Seed spacecraft LEO-RAD-Demo

1. Right-click Spacecraft → Add Spacecraft.
2. Name it LEO-RAD-Demo.
3. Open the Orbit tab → Orbit design wizard → type SSO.
4. Set altitude 550 km and MLTAN 6.0 h (dawn–dusk — radar-style CONOPS can look in darkness; arrays stay in sunlight).
5. Click Design orbit (document). Confirm the Keplerian / state fields update to the SSO elements.
6. Attitude → Nadir.
7. Scroll down and click Apply Changes. Confirm the ground track in 3D (coloured marker; right-click to follow).

Do not add a sensor. Coverage will use the bus line-of-sight.

Why not a 10:00 optical SSO?

Morning MLTAN is the Landsat / optical-land pattern. This CONOPS cares about geometry and revisit, not land lighting. Dawn–dusk is the usual radar-style starting point. You can still use LEO Generic at ~550 km and ~98° if you want a non-SSO polar seed; Walker Star will copy whatever you Apply.

3 — Walker Star 4 / 4 / 1

1. From the spacecraft (⋯ or context) → Create Walker Constellation.
2. Seed Satellite = LEO-RAD-Demo.
3. Constellation Type = Walker Star (RAAN spread over 180° — polar-style, not Walker Delta).
4. Total Satellites (N) = 4, Orbital Planes (P) = 4, Walker Phasing (F) = 1.
5. Set Prefix to LEO-RAD-Walker (do not leave the default LEO-RAD-Demo-CONST).
6. Apply. Confirm four members under the constellation:

Plane	Member name
1	LEO-RAD-Walker-SAT-01-01
2	LEO-RAD-Walker-SAT-02-01
3	LEO-RAD-Walker-SAT-03-01
4	LEO-RAD-Walker-SAT-04-01

Each member inherits the seed orbit slot. Refresh the 3D scene — you should see four planes.

4 — Five commanding facilities

Add five Facility assets. For each one: pick the Facility database preset (name + lat/lon/alt fill in), then add constraint Ground elevation with min 5°, then Apply Changes.

Order	Database preset	Why it is in the set
1	SSC Madrid (partner)	Mid-latitude Europe (~40°N)
2	KSAT Punta Arenas	Southern Cone (~53°S)
3	KSAT Inuvik	High Arctic (~68°N)
4	KSAT Troll (TrollSat)	Antarctic polar (~72°S)
5	ESA New Norcia (Australia)	Mid-latitude Western Australia (~31°S)

Polar sites (Inuvik, Troll) see a high-inclination LEO far more often than Madrid or New Norcia. That contrast is the experiment: TASKING wait should be shorter at the poles.

Trial / Basic subset

Trial: only KSAT Troll (TrollSat). Basic: the first four rows (drop New Norcia). Pro / Desktop: all five.

3D scene — Walker Star 4/4/1, five commanding facilities, spacecraft line-of-sight (no sensor).

5 — Area of interest · All Land

1. Right-click the Area of interest category → Add.
2. Name it AOI-ALL-LAND.
3. Under Global Layers, check All Land. Do not pick a country.
4. Apply Changes.

All Land is the Natural Earth land mask — continents, not ocean. Facility-tasking demand points are then born toward land, which matches a radar look at the surface rather than a single country box.

6 — Radar Tasking Analysis

Facility-tasking Discrete is not “paint the continents”. Each demand event is born at a checked facility. The payload to acquire is a point inside All Land. The same acquirer must see that origin facility first (TASKING), then the land target (ACQUISITION-LEG). TOTAL is birth → target (the sum of the two legs in this CONOPS). Acquisition here is geometric LoS of the spacecraft, not a sensor footprint.

1. Right-click Coverage Analysis → Add. Name it Radar Tasking Analysis.
2. Type Discrete.
3. Demand mode Facility tasking (N). The Tasking facilities checklist appears — check every station you added.
4. Demand N events 200 (about 40 per facility across the five stations), demand seed 100.
5. AOI type = Area of Interest; select AOI-ALL-LAND.
6. Acquirers = constellation All Satellites (the four Walker members — not the seed only, and not sensors). On Trial, select LEO-RAD-Demo instead.
7. Computation Balanced.
8. Run Analysis. Wait until it finishes.

This recipe is 2 days

Two days and 200 events (~40 per origin facility) are enough to see polar vs mid-latitude tasking. They are not decision-grade response-time products. Lengthen the scenario and raise N on Pro / Desktop when the workflow is clear. Trial caps Discrete at 100 events — this N=200 recipe needs Basic or above.

Delay CDFs only include successful contacts. Misses are not plotted as infinite delay. Read Chain Outcomes for never-tasked / tasked-no-image / acquired.

7 — Dashboard

1. Top bar: Design → Dashboard.
2. Asset = Radar Tasking Analysis.
3. Generate these plots in this order:

Plot template	What you are looking at
Discrete Chain Outcomes by Facility	Failure modes per origin station (plot title: Radar tasking chain by origin facility). Never tasked / tasked-no-image / acquired. Start here.
Discrete Delay CDF by Facility	Conditional wait by origin station. Polar curves should rise sooner on the TASKING clock.
Discrete Facility Tasking Delay Legs	TASKING vs ACQUISITION-LEG vs TOTAL on one bar chart.
Discrete Acquirer Delay Range	Min / P50 / mean / P95 / P99 / max of TOTAL wait (birth → target) per spacecraft. Not ACQUISITION-LEG.

1. Click Generate Plot for each. You can also switch to Reports for tabular summaries.

Clock naming

Templates called “Acquisition Delay by Acquirer” still plot TOTAL (birth → AOI target), not ACQUISITION-LEG. The three clocks are defined in the ReportGraph glossary: TASKING = birth → origin facility; ACQUISITION-LEG = facility → target; TOTAL = birth → target.

Chain outcomes by origin facility — never tasked / tasked-no-image / acquired.

Delay CDF by origin facility — polar commanding typically rises sooner than mid-latitude stations.

Facility tasking delay legs — TASKING vs ACQUISITION-LEG vs TOTAL.

Discrete acquirer delay range — min / P50 / mean / P95 / P99 / max TOTAL wait (birth → target) per spacecraft.

Checkpoint

• SSO dawn–dusk seed LEO-RAD-Demo, nadir, no sensor.
• Walker Star members LEO-RAD-Walker-SAT-01-01 … SAT-04-01.
• Commanding facilities from the database (full set or the plan subset).
• AOI AOI-ALL-LAND with global layer All Land.
• Coverage Discrete Facility tasking (N) completed as Radar Tasking Analysis, acquirers = All Satellites.
• Dashboard: chain outcomes and at least one delay-clock plot (CDF by facility or delay legs).

Optional next (same mission)

If you want…	Then…
A flight-like footprint	Mount a sensor later and switch acquirers to All Sensors
Stronger polar vs equatorial contrast	Keep Troll + Inuvik; drop Madrid or New Norcia and re-run
Imaging-only Discrete (no uplink)	Demand random N in AOI — requests are born on the land point, not at a GS
Delivery after the look	Connection Network + Latency pointed at this Discrete coverage (Latency still uses TOTAL as pickup)
Paint-the-Earth products	Separate Continuous coverage on the same Walker

Related

• Constellation · Spacecraft · Facility · Area of interest
• Coverage · Reporting · Plans and entitlements
• Blog: Radar Tasking Analysis