Orbital Compute Unit

An Orbital Compute Unit (OCU) is a standardized measure of how much useful computation a satellite can deliver per orbit, accounting for power constraints, eclipse fractions, thermal limits, and ground contact availability.

Why OCUs exist — Satellite compute capacity is not a fixed number. It varies with orbit geometry, season, battery age, and thermal state. OCUs normalize this into a single comparable metric so you can plan workloads without modeling the physics yourself.

Bus Profiles

OCU computation starts with a bus profile — a standardized description of the satellite’s compute, power, and thermal capabilities. CAE includes 6 built-in bus classes.

Bus Class	Typical Platform	Compute (GFLOPS)	Solar (W)	Battery (Wh)	Storage (GB)	Memory (MB)
`1U_cubesat`	1U CubeSat	2	2.5	5	8	256
`3U_cubesat`	3U CubeSat	10	7.5	20	32	512
`6U_cubesat`	6U CubeSat	50	25	60	64	1024
`12U_cubesat`	12U CubeSat	150	50	120	128	2048
`microsat`	Microsatellite (50-100kg)	500	150	400	256	4096
`smallsat`	Small Satellite (100-500kg)	2000	500	1500	512	8192

Auto-Detection with inferBusClass

If you don’t specify a bus class, CAE infers it from the satellite’s NORAD ID using orbital parameters and known catalog metadata:

Altitude and inclination narrow the platform category
Radar cross-section (when available) estimates physical size
Catalog metadata matches against known spacecraft databases

The inferred class is returned in the response so you can verify or override it.

OCU Computation

The OCU model combines bus capabilities with orbital geometry to produce a per-orbit capacity estimate.

Sunlit and Eclipse Hours

From the satellite’s current TLE, CAE propagates the orbit and computes:

Metric	Description
`sunlit_hours_per_orbit`	Time in sunlight — full solar power and thermal headroom available
`eclipse_hours_per_orbit`	Time in Earth’s shadow — battery-only, reduced thermal dissipation
`daily_orbits`	Number of complete orbits per 24-hour period
`daily_sunlit_hours`	Total sunlit time per day
`daily_eclipse_hours`	Total eclipse time per day

Confidence Model

OCU values carry a confidence score reflecting the quality of the input data:

Factor	Impact on Confidence
TLE age	Degrades as TLE epoch age increases (stale elements reduce positional accuracy)
Bus class source	Higher for explicit bus class, lower for inferred
Eclipse fraction stability	Higher when eclipse fraction is stable across the prediction horizon
Thermal margin	Higher when peak temperature is well below limits

Confidence is reported as a value between 0 and 1. Values above 0.8 are considered high-confidence.

Cost Model

Each OCU carries an estimated cost based on the bus class and orbital parameters:

Component	Basis
Compute cost	GFLOPS-hours available per orbit, weighted by bus class
Power cost	Watt-hours consumed, factoring solar generation and battery cycling
Storage cost	GB-hours of on-board storage occupied
Transfer cost	Data volume deliverable per orbit given contact window availability

Limiting Resource

The OCU computation identifies which resource constrains capacity:

"limiting_resource": {
  "resource": "power",
  "utilization": 0.92,
  "headroom": 0.08,
  "recommendation": "Reduce eclipse compute load or extend deadline to span more orbits"
}

Common limiting resources: power (eclipse battery budget), thermal (heat dissipation during sunlit compute), storage (on-board buffer for multi-pass transfers), contact (ground pass availability for data delivery).

negotiateOCU Algorithm

The negotiateOCU function runs a 4-phase algorithm to determine achievable OCU for a specific workload:

Phase	Description
1. Resource survey	Compute available GFLOPS-hours, watt-hours, storage, and contact time per orbit
2. Workload mapping	Map workload resource requirements to per-orbit resource availability
3. Constraint resolution	Identify the binding constraint and compute the maximum sustainable throughput
4. OCU normalization	Express the result as a standardized OCU value with confidence and cost breakdown

The negotiation accounts for workload-specific factors like checkpoint overhead, FEC requirements, and quality tier selection.

API Usage

Negotiate OCU for a Workload

curl -X POST https://rotastellar-cae.subhadip-mitra.workers.dev/v1/ocu/negotiate \
  -H "Content-Type: application/json" \
  -H "Origin: https://rotastellar.com" \
  -d '{
    "satellite_id": "25544",
    "workload": {
      "compute_gflops": 50,
      "memory_mb": 512,
      "storage_mb": 2048,
      "output_mb": 100
    }
  }'

Response

{
  "satellite_id": "25544",
  "bus_class": "smallsat",
  "bus_class_source": "inferred",
  "ocu": {
    "value": 14.2,
    "unit": "OCU/orbit",
    "daily": 218.7,
    "confidence": 0.87
  },
  "orbital_geometry": {
    "sunlit_hours_per_orbit": 0.96,
    "eclipse_hours_per_orbit": 0.59,
    "daily_orbits": 15.4
  },
  "limiting_resource": {
    "resource": "power",
    "utilization": 0.92,
    "headroom": 0.08,
    "recommendation": "Reduce eclipse compute load or extend deadline to span more orbits"
  },
  "cost": {
    "compute_cost_per_orbit": 0.42,
    "power_cost_per_orbit": 0.18,
    "storage_cost_per_orbit": 0.05,
    "total_cost_per_orbit": 0.65,
    "currency": "OCU-credits"
  }
}

Get Bus Class Summary

Retrieve the reference profile for a bus class without specifying a satellite:

curl https://rotastellar-cae.subhadip-mitra.workers.dev/v1/ocu/summary/6U_cubesat \
  -H "Origin: https://rotastellar.com"

Response

{
  "bus_class": "6U_cubesat",
  "profile": {
    "compute_gflops": 50,
    "solar_w": 25,
    "battery_wh": 60,
    "storage_gb": 64,
    "memory_mb": 1024
  },
  "reference_ocu": {
    "value": 3.8,
    "unit": "OCU/orbit",
    "assumptions": {
      "altitude_km": 550,
      "inclination_deg": 97.5,
      "eclipse_fraction": 0.35
    }
  }
}

Negotiate and Summary Parameters

Parameter	Type	Required	Description
`satellite_id`	string	Yes (negotiate)	NORAD catalog ID
`workload`	object	No	Workload resource requirements for negotiation
`workload.compute_gflops`	number	No	Required compute in GFLOPS
`workload.memory_mb`	number	No	Required memory
`workload.storage_mb`	number	No	Required on-board storage
`workload.output_mb`	number	No	Output data to deliver to ground
`bus_class`	string	No	Override inferred bus class

Console Integration

The Console displays an OCU Capacity card in the sidebar of the asset detail page:

OCU/orbit and OCU/day values with confidence indicator
Bus class label (with “inferred” badge when auto-detected)
Limiting resource bar chart showing utilization per resource
Sunlit/eclipse breakdown as a ring chart
Cost estimate per orbit

OCU values are estimates based on current orbital geometry and bus profiles. Actual capacity may vary due to battery degradation, thermal anomalies, or attitude constraints not captured in the bus model.

Hazard Prediction

Predictive checkpointing around orbital hazards

CAE Overview

Constraint-Aware Execution fundamentals

Getting Started

Planning Tools

Orbital Intelligence

CAE

Operator Agent

Mission Control

Orbital Runtime

Orbital Sim

Distributed Compute

SDKs

Resources

Orbital Compute Unit

Orbital Compute Unit

Bus Profiles

Auto-Detection with inferBusClass

OCU Computation

Sunlit and Eclipse Hours

Confidence Model

Cost Model

Limiting Resource

negotiateOCU Algorithm

API Usage

Negotiate OCU for a Workload

Response

Get Bus Class Summary

Response

Negotiate and Summary Parameters

Console Integration

Hazard Prediction

CAE Overview

​Orbital Compute Unit

​Bus Profiles

​Auto-Detection with inferBusClass

​OCU Computation

​Sunlit and Eclipse Hours

​Confidence Model

​Cost Model

​Limiting Resource

​negotiateOCU Algorithm

​API Usage

​Negotiate OCU for a Workload

​Response

​Get Bus Class Summary

​Response

​Negotiate and Summary Parameters

​Console Integration

Hazard Prediction

CAE Overview

Orbital Compute Unit

Bus Profiles

Auto-Detection with inferBusClass

OCU Computation

Sunlit and Eclipse Hours

Confidence Model

Cost Model

Limiting Resource

negotiateOCU Algorithm

API Usage

Negotiate OCU for a Workload

Response

Get Bus Class Summary

Response

Negotiate and Summary Parameters

Console Integration