Constellation DAG

Single-satellite planning assigns steps to orbital windows on one spacecraft. Constellation DAG planning distributes a workload across multiple satellites, routing intermediate data through inter-satellite links (ISL) and ground relays to minimize end-to-end latency.

When to use this — Any workload that benefits from parallelism across satellites, or where a single satellite lacks the resources (compute, power, storage, contact time) to complete the job within the deadline.

Architecture

Constellation planning is built on two core components:

ContactGraph

The ContactGraph builds a time-expanded graph of all communication opportunities across the fleet within the planning horizon.

Capability	Details
ISL detection	Line-of-sight between satellite pairs, accounting for Earth obstruction
Ground pass detection	Visibility windows to all 12 ground stations per satellite
Routing algorithm	Time-expanded Dijkstra — finds shortest-latency path through ISL and ground hops
Fleet construction	`buildContactGraph` generates the full fleet graph from TLE data

The graph edges are weighted by link capacity (data rate x duration) and propagation delay. Dijkstra finds the minimum-latency path for transferring data from any satellite to any other satellite or ground station.

ConstellationPlacer

The placer runs a 5-phase algorithm to assign steps to satellites:

Phase	Description
1. Preparation	Propagate orbits, build contact graph, compute per-satellite resource envelopes
2. Greedy placement	Score each satellite for each step (resource fit, data locality, contact opportunity) and assign greedily by priority
3. Replication	For critical steps, place redundant copies on backup satellites for fault tolerance
4. Schedule assembly	Build the final timeline with ISL transfer segments between cross-satellite dependencies
5. Metrics	Compute critical path, reliability estimate, and resource utilization

Scoring considers four factors: available compute capacity, proximity to upstream data, upcoming contact windows, and current battery state-of-charge.

For fleets of 10 or more satellites, the placer uses a k-d tree spatial index to accelerate nearest-neighbor queries during ISL detection. This keeps planning time sub-linear with fleet size.

ISL Transfer Segments

When two dependent steps are placed on different satellites, the planner inserts ISL transfer segments. These are scheduled during mutual visibility windows and include FEC overhead.

{
  "type": "isl_transfer",
  "from_satellite": "25544",
  "to_satellite": "48274",
  "data_mb": 36.75,
  "fec_overhead_mb": 1.84,
  "link_budget": {
    "distance_km": 1240,
    "data_rate_mbps": 10,
    "duration_s": 31
  },
  "window": {
    "start": "2026-03-10T08:12:00Z",
    "end": "2026-03-10T08:18:30Z"
  }
}

If no direct ISL path exists, the contact graph routes through intermediate satellites or ground relay (satellite A downlinks to a ground station, which uplinks to satellite B during a later pass).

API Usage

Create Constellation Plan

curl -X POST https://rotastellar-cae.subhadip-mitra.workers.dev/v1/constellation/plan \
  -H "Content-Type: application/json" \
  -H "Origin: https://rotastellar.com" \
  -d '{
    "satellite_ids": ["25544", "48274", "55909"],
    "custom_job": {
      "name": "Distributed EO Pipeline",
      "steps": [
        {
          "id": "capture_1",
          "name": "Capture Region A",
          "location": "onboard",
          "compute_s": 60,
          "output_mb": 2000,
          "depends_on": []
        },
        {
          "id": "capture_2",
          "name": "Capture Region B",
          "location": "onboard",
          "compute_s": 60,
          "output_mb": 2000,
          "depends_on": []
        },
        {
          "id": "merge",
          "name": "Merge and Mosaic",
          "location": "onboard",
          "compute_s": 180,
          "input_mb": 4000,
          "output_mb": 500,
          "depends_on": ["capture_1", "capture_2"]
        },
        {
          "id": "downlink",
          "name": "Deliver Results",
          "location": "ground",
          "depends_on": ["merge"]
        }
      ],
      "policy": { "objective": "min_latency", "deadline_orbits": 6 }
    }
  }'

Request Parameters

Parameter	Type	Required	Description
`satellite_ids`	string[]	Yes	NORAD catalog IDs of satellites in the constellation
`preset_id`	string	No	Use a preset workload (mutually exclusive with `custom_job`)
`custom_job`	object	No	Custom DAG definition
`policy.objective`	string	No	`min_latency`, `balanced`, `max_reliability`
`policy.deadline_orbits`	number	No	Maximum orbits to complete the workflow
`replication_factor`	number	No	Number of redundant copies for critical steps (default: 1)

Response Structure

The response extends the standard plan format with constellation-specific fields:

{
  "id": "const-7b2e4f...",
  "constellation": {
    "satellites_used": 3,
    "satellites_available": 3,
    "isl_transfers": 2,
    "ground_relays": 0
  },
  "critical_path": {
    "steps": ["capture_1", "isl_transfer_1", "merge", "downlink"],
    "duration_s": 4320,
    "bottleneck": "isl_transfer_1"
  },
  "metrics": {
    "total_compute_s": 300,
    "total_transfer_s": 186,
    "isl_data_mb": 2038.5,
    "ground_data_mb": 525,
    "reliability": 0.964,
    "satellites_used": 3
  },
  "placements": [
    { "step_id": "capture_1", "satellite_id": "25544", "reason": "best_resource_fit" },
    { "step_id": "capture_2", "satellite_id": "48274", "reason": "best_resource_fit" },
    { "step_id": "merge", "satellite_id": "55909", "reason": "data_locality" }
  ],
  "plan": { ... },
  "events": [ ... ]
}

Metrics

Metric	Description
`critical_path.duration_s`	Longest sequential chain through the DAG including transfers
`critical_path.bottleneck`	The step or transfer that dominates the critical path
`satellites_used`	Number of satellites with at least one assigned step
`isl_transfers`	Number of inter-satellite link transfers in the plan
`reliability`	Combined delivery confidence across all paths

Console Integration

The Console displays constellation plans in a DAG tab powered by React Flow:

Each satellite is a swim lane
Steps are nodes, colored by satellite assignment
ISL transfers appear as animated edges between lanes
The critical path is highlighted
Clicking a node shows step detail, resource usage, and the scoring breakdown from the placement phase

Constellation planning requires valid TLE data for all satellites in the request. If any satellite ID is not found in the CelesTrak catalog, the request returns a 400 error with the missing IDs listed.

Pareto Planning

Multi-objective optimization for constellation plans

Agent Protocol

Agent constellation mode for multi-satellite execution

Getting Started

Planning Tools

Orbital Intelligence

CAE

Operator Agent

Mission Control

Orbital Runtime

Orbital Sim

Distributed Compute

SDKs

Resources

Constellation DAG

Constellation DAG

Architecture

ContactGraph

ConstellationPlacer

ISL Transfer Segments

API Usage

Create Constellation Plan

Request Parameters

Response Structure

Metrics

Console Integration

Pareto Planning

Agent Protocol

​Constellation DAG

​Architecture

​ContactGraph

​ConstellationPlacer

​ISL Transfer Segments

​API Usage

​Create Constellation Plan

​Request Parameters

​Response Structure

​Metrics

​Console Integration

Pareto Planning

Agent Protocol

Constellation DAG

Architecture

ContactGraph

ConstellationPlacer

ISL Transfer Segments

API Usage

Create Constellation Plan

Request Parameters

Response Structure

Metrics

Console Integration