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LEO Optical Satellite

Tutorial · Sun-synchronous imager

A sun-synchronous optical spacecraft in LEO — the same kind of mission as Landsat 8/9 (NASA / USGS): morning SSO, nadir imager, land-facing ground track. This is not a Landsat digital twin. Numbers are simplified for a 12 h Trial window. Real Landsat uses a ~185 km swath (~15° full FOV) and a 16-day repeat.

Open Web App · start from Create your first mission

What we will do

  1. Set the scenario (SSO-OPT-Demo, keep the 12 h Trial window).
  2. Create an SSO spacecraft (~705 km, MLTAN 10.2 h) with nadir attitude.
  3. Mount an optical sensor and see the swath in 3D.
  4. Add an area of interest.
  5. Run a first Continuous coverage over that AOI (we will add other studies to this same mission later).
  6. Open Dashboard and generate plots / reports.

Mission card

Field Tutorial value Landsat 8/9 (reference)
Mission name SSO-OPT-Demo —
Scenario Keep the default 12 h Trial window Multi-day / 16-day repeat
Step 120 s (Trial minimum; do not go finer) Finer sampling on higher plans
Spacecraft LANDSAT-CLASS-1 Landsat 8 or 9
Orbit wizard SSO, altitude 705 km, MLTAN 10.2 h ~705 km, ~10:12 descending, inc ~98.2°
Attitude Nadir Nadir imaging
Sensor OLI-CLASS-1 — conical FOV, half-angle 20° OLI ~15° full FOV (~7.5° half-angle, 185 km swath)
AOI Country preset United States of America Land / coastal Long-Term Acquisition Plan
Analysis Coverage Continuous, Balanced, granularity 4° first Grid / WRS-2 scene planning

The 20° half-angle is wider than Landsat on purpose: in 12 h a 185 km strip can still miss CONUS depending on RAAN. Widen the FOV so Continuous coverage has something to show; tighten it later when you lengthen the scenario.

flowchart LR
  SSO["SSO 705 km / 10.2 h"] --> Att["Nadir"]
  Att --> Sens["Optical sensor"]
  AOI["Area of interest"] --> Cov["Coverage Continuous"]
  Sens --> Cov
  Cov --> Dash["Dashboard KPIs"]

1 — Scenario

  1. New mission (or continue the first-mission file). Name it SSO-OPT-Demo.
  2. Leave start and end as they are (12 h, Trial).
  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 — SSO spacecraft

  1. Right-click Spacecraft → Add Spacecraft.
  2. Name it LANDSAT-CLASS-1.
  3. Open the Orbit tab → Orbit design wizard → type SSO.
  4. Set altitude 705 km and MLTAN 10.2 h (10:12 local time — Landsat-like morning descending).
  5. Click Design orbit (document). That writes the designed orbit into the spacecraft state fields (SMA, eccentricity, inclination, RAAN, …). Look at the initial state — it should update to the SSO elements before you touch the 3D view.
  6. Attitude → Nadir.
  7. Scroll down and click Apply Changes. Confirm the ground track in 3D (coloured marker; right-click to follow).

Explore the SSO wizard

Change MLTAN (try 10.5 h vs 13.5 h), click Design orbit (document) again, and watch the Keplerian / state fields update. Then Apply Changes to see the new ground track and terminator. Morning SSO is the Landsat / optical-land pattern; afternoon SSO is a different lighting story.

3 — Optical sensor

  1. Right-click the spacecraft → Add Sensor. Name it OLI-CLASS-1.
  2. Type optical (or the optical fallback).
  3. FOV Conical, half-angle 20° for this 12 h demo.
  4. Pointing Body-Fixed (the bus is already nadir).
  5. Enable Show sensor swath.
  6. Apply Changes. In 3D you should see the satellite and the sensor swath on the Earth.

To mimic Landsat more closely later: half-angle ~7.5° (or rectangular ~7.5° × 7.5°) and a scenario of several days.

SSO spacecraft with optical sensor swath

3D scene — spacecraft and optical sensor swath after Apply.

4 — Area of interest

  1. Right-click the Area of interest category → Add.
  2. Name it AOI-USA.
  3. In Countries, select United States of America.
  4. Apply Changes.

5 — Continuous coverage

Landsat-class missions acquire continuously along the sunlit ground track (land / coast), not as one-shot events. In ASTROLAB that is Coverage type Continuous.

Trial is for exploring the tool

The Trial exists so you can try ASTROLAB end-to-end — tree, orbit wizard, sensors, coverage, Dashboard — and see what the product can do. With a 12 h window and a 4° grid, results are intentionally coarse: they are not decision-grade coverage products. When you move to a higher plan you can lengthen the scenario, refine the mesh, and run analyses that actually deliver detailed engineering value.

  1. Right-click Coverage Analysis → Add. Name it COV-SSO-1.
  2. Type Continuous.
  3. AOI type = Area of Interest; select AOI-USA.
  4. Acquirers = OLI-CLASS-1 (the sensor, not only the bus).
  5. Granularity 4°, computation Balanced.
  6. Run Analysis. Wait until it finishes.

If percent covered is still ~0, this 12 h phasing missed CONUS: widen the FOV a few degrees. A real Landsat swath needs 16 days to tile the continent.

Continuous coverage — dynamic coverage overlay over the United States

Continuous coverage — dynamic coverage overlay (red) over the USA AOI.

6 — Dashboard

  1. Top bar: Design → Dashboard.
  2. Asset = COV-SSO-1 (coverage templates live on the analysis, not only on the spacecraft).
  3. Open Plots and pick a Continuous metric — for example Total Access as a heatmap.
  4. Click Generate Plot. You can also switch to Reports for tabular summaries.

Dashboard — Total Access heatmap for Continuous coverage

Dashboard — Total Access heatmap over the USA AOI.

Checkpoint

  • SSO at ~705 km, morning MLTAN, nadir attitude.
  • Optical sensor swath visible in 3D.
  • Coverage Continuous completed with the sensor as acquirer.
  • At least one Dashboard plot for COV-SSO-1 (e.g. Total Access heatmap).

Optional next (same mission)

If you want… Then…
Landsat-like swath Half-angle ~7.5° and a longer scenario (beyond Trial 12 h)
Daylight-only collects Constraint Target illuminated (or eclipse rules) on the sensor / coverage
Finer map Granularity 2° + High Accuracy (plan permitting)
Lifetime of the bus Separate Lifetime run with drag properties set