| name | constellation-design |
| description | Design and analyze satellite constellations and distributed space architectures. Use this skill for Walker constellation patterns, coverage analysis, inter-satellite links, orbital shell design, collision avoidance, spectrum coordination, and deorbit compliance. Trigger for "constellation," "Walker pattern," "coverage analysis," "orbital shell," "inter-satellite link," "ISL," "revisit time," "ground coverage," "mega-constellation," or "distributed architecture." |
Constellation Design Skill
Read CONVENTIONS.md at the repo root before proceeding.
This skill designs and evaluates satellite constellations — multiple spacecraft working together to provide coverage, capacity, or capability that a single satellite cannot. Constellation design is fundamentally different from single-satellite design: the system-level architecture (number of planes, phasing, altitude) drives individual satellite requirements, not the other way around.
Before You Begin
Ask the user (if not already known):
- Mission objective? (Communications, Earth observation, weather, navigation, IoT, SSA, science — each has different coverage metrics)
- Coverage requirement? (Continuous global, regional, specific latitude bands, revisit time, max gap duration)
- Number of satellites (range)? (Budget-driven constraint — can be 3 or 30,000)
- Inter-satellite links? (Yes = mesh network, reduced ground stations. No = simpler satellites, more ground infrastructure)
- What design phase?
Applicable Phases
- Primary: Phase A (constellation architecture trade), Phase B (orbit and phasing design)
- Supporting: Phase C (deployment sequencing), Phase D (on-orbit constellation management)
Core Concepts
1. Walker Constellation Notation
The standard notation for symmetric constellations: T/P/F
- T: Total number of satellites
- P: Number of orbital planes (equally spaced in RAAN)
- F: Phasing parameter (relative spacing between planes, 0 ≤ F < P)
- Example: GPS = 24/6/1 at 55° inclination, 20,200 km altitude
- Example: Iridium = 66/6/1 at 86.4° inclination, 780 km altitude
2. Coverage Geometry
- Half-cone angle (footprint): $\rho = \arccos(R_E / (R_E + h))$ — the angular radius of visibility from one satellite.
- Minimum elevation angle ($\epsilon_{min}$): Typical 5-15°. Higher elevation = smaller footprint but better link quality.
- Effective footprint: $\theta = 90° - \epsilon_{min} - \arcsin((R_E \cdot \cos\epsilon_{min}) / (R_E + h))$
- Street-of-coverage width: For a single plane, the ground swath covered by N satellites evenly spaced.
3. Coverage Metrics
| Metric | Definition | Typical Target |
|---|
| Continuous coverage | 100% of target area has ≥1 satellite visible at all times | GPS, comms constellations |
| Revisit time | Max time between consecutive passes over a point | EO: 1-24 hours |
| Max gap | Longest period with no coverage at any point | Comms: 0 (continuous) |
| Number of folds | Minimum simultaneous visible satellites at any point | Navigation: ≥4 for 3D fix |
| Contact duration | Time a satellite is visible per pass | LEO: 5-15 min per pass |
4. Key Trade Parameters
| Parameter | Lower Value | Higher Value |
|---|
| Altitude | Lower drag, shorter life, smaller footprint, more sats needed | Higher footprint, fewer sats, radiation, higher launch ΔV |
| Inclination | Covers equatorial region well, misses poles | Near-polar covers all latitudes, ground track complexity |
| N satellites | Cheaper, less coverage, longer revisit | Better coverage, higher cost, more complex management |
| N planes | Simpler deployment (all in one plane) | Better longitudinal distribution, needs multiple launches or RAAN drift |
Analysis Workflows
1. Coverage Analysis
- Analytical (Phase A): Use the Walker formula to estimate single-fold or multi-fold coverage for a given T/P/F/i combination.
- Grid-based: Discretize the Earth's surface and compute visibility from each satellite at time steps.
- Higher fidelity: Recommend STK, GMAT, or Orekit propagation for detailed gap analysis.
- Latitude dependency: Coverage is always better near the inclination-matching latitude. Polar coverage requires i > 80°.
2. Inter-Satellite Links (ISL)
- Intra-plane links: Between adjacent satellites in the same plane. Geometry is relatively stable.
- Cross-plane links: Between satellites in adjacent planes. Range and angle vary — most complex for seam planes (where ascending/descending nodes meet).
- RF ISL: Proven (TDRS heritage), lower data rate (1-10 Gbps typical).
- Optical ISL: Higher data rate (10-100+ Gbps), narrower beam, needs precision pointing (Starlink V2 uses optical ISL).
- Latency benefit: ISL routing can be faster than fiber for long distances — signal travels at c in vacuum vs. ~0.67c in fiber.
3. Deployment Strategy
- Shared launch: Multiple satellites per launch to the same plane. Then phase within the plane using differential drag or low-thrust maneuvering.
- RAAN spreading: Either launch to different RAANs directly (expensive) or use J2 precession at different altitudes to naturally drift planes apart.
- Build-up: Deploy in phases — initial operating capability (IOC) with partial constellation, full operating capability (FOC) with all satellites.
4. Constellation Management
- Station-keeping: Drag makeup (LEO), orbit maintenance, RAAN/argument-of-perigee corrections.
- Spare strategy: On-orbit spares (parked at different altitude), ground spares, or rapid launch capability.
- Collision avoidance: Maneuver authority, conjunction assessment cadence, coordination with other operators.
- End-of-life: Deorbit within 5 years of mission end (current guidelines, moving toward 0 years). $\Delta V_{deorbit}$ budget.
5. Spectrum & Regulatory
- ITU coordination: Frequency filing, interference analysis with existing systems.
- Orbital debris compliance: FCC/ITU 25-year rule (legacy), accelerated timelines for large constellations.
- Licensing: National licensing (FCC for US, Ofcom for UK, etc.) before deployment.
Output Format
- Constellation Design Report (
constellation_report.md): Walker notation, orbit parameters, coverage analysis, ISL architecture.
- Coverage Map / Statistics: Revisit time, max gap, number of folds by latitude.
- Deployment Plan: Launch manifest, phasing strategy, IOC/FOC timeline.
- Per-Satellite Requirements: Derived requirements for each satellite (mass, power, propulsion for station-keeping and deorbit).
- 🟢 / 🟡 / 🔴 status: Coverage compliance, regulatory readiness, collision risk.
Interface
- Reads from:
/requirements/, /analysis/mission-analysis-specialist/ (orbital mechanics, ΔV), /analysis/communications-assessment/ (link budgets for ISL and ground), /analysis/cost-modeling/ (per-satellite and total constellation cost)
- Writes to:
/analysis/constellation-design/
- Consumed by:
systems-engineering-assessment (per-satellite requirements flowdown), cost-modeling (constellation economics — per-sat × quantity), trade-study-manager (constellation architecture as a trade option)
