# Halowerk Satellite Pass Predictor

> Halowerk Satellite Pass Predictor is a paid API for AI agents from space.halowerk.com, paid per call via x402, $0.004/call, status unknown (last checked 2026-09-14).

Propagates a circular two-body orbit from orbital elements and samples when a satellite is visible above the horizon from a specified ground station location.

## Facts

- Endpoint: POST https://space.halowerk.com/v1/satellite-pass
- Price: $0.004/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-satellite-pass-predictor-5012aa36
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_vaiBiT_cfI1iSDTyL1MTg

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability halowerk-satellite-pass-predictor-5012aa36 -d '<json body>'
```

Example prompt: Predict satellite pass windows for the next 24 hours (step every 60 seconds) for a circular orbit at 550 km altitude, 53-degree inclination, RAAN 45 degrees, initial phase 0 degrees, over my ground station at 37.4 degrees north latitude and -122.1 degrees longitude, with a minimum elevation of 5 degrees.

## When to prefer this

Choose this endpoint when you need a fast, simplified circular-orbit pass prediction for planning purposes and do not require high-fidelity perturbation modeling, epoch-based Greenwich angle, terrain masking, or ellipsoid Earth corrections. Ideal for early mission design, link budget scheduling, or educational simulations where a two-body Keplerian approximation is sufficient.

## Known failure modes

- altitude_km below 100 or above 100000 returns validation error
- duration_seconds or step_seconds outside allowed bounds returns 400
- ground latitude or longitude out of range returns parameter error
- missing required fields returns schema validation error
- very short step_seconds with long duration may produce large payloads
- result is a planning estimate only — perturbations, eccentricity, terrain, and real ephemeris not modeled

## How this service works

Propagates a circular two-body orbit from altitude, inclination, RAAN, and initial orbital phase; rotates Earth at a fixed sidereal rate; and samples ground-station elevation. It ignores eccentricity, perturbations, epoch-dependent Greenwich angle, refraction, ellipsoid shape, terrain, and antenna masks, so it is a planning estimate rather than operational ephemeris.

## Output

A time-series list of sampled epochs indicating whether the satellite is above the specified minimum elevation angle from the ground station, along with computed elevation values at each step, effectively identifying pass windows (start, peak, end) within the simulation duration.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "raan_deg": {
   "type": "number",
   "maximum": 360,
   "minimum": -360,
   "description": "Right ascension of ascending node relative to Greenwich at t=0."
  },
  "altitude_km": {
   "type": "number",
   "maximum": 100000,
   "minimum": 100,
   "description": "Circular altitude above a spherical Earth."
  },
  "step_seconds": {
   "type": "integer",
   "maximum": 3600,
   "minimum": 10
  },
  "inclination_deg": {
   "type": "number",
   "maximum": 180,
   "minimum": 0
  },
  "duration_seconds": {
   "type": "integer",
   "maximum": 172800,
   "minimum": 10
  },
  "initial_phase_deg": {
   "type": "number",
   "maximum": 360,
   "minimum": -360,
   "description": "Argument of latitude at t=0."
  },
  "ground_latitude_deg": {
   "type": "number",
   "maximum": 90,
   "minimum": -90
  },
  "ground_longitude_deg": {
   "type": "number",
   "maximum": 180,
   "minimum": -180
  },
  "minimum_elevation_deg": {
   "type": "number",
   "maximum": 90,
   "minimum": -5
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-satellite-pass-predictor-5012aa36/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from space.halowerk.com](https://www.zero.xyz/host/space.halowerk.com/llms.txt)