xhelio-spice

Spacecraft ephemeris made easy — auto-managed SPICE kernels for heliophysics missions.

xhelio-spice wraps SpiceyPy with automatic kernel download, caching, and loading. Ask for a spacecraft position and xhelio-spice handles the rest: downloading the right NAIF kernels, loading them in the correct order, and returning results as Python dicts or pandas DataFrames.

Installation

bash

pip install xhelio-spice

For MCP server support (Claude Desktop, Claude Code, Cursor, etc.):

bash

pip install xhelio-spice[mcp]

Quick Start

python

from xhelio_spice import get_position, get_trajectory

# Where is Parker Solar Probe right now?
pos = get_position("PSP", observer="SUN", time="2024-01-15", frame="ECLIPJ2000")
print(f"PSP is {pos['r_au']:.3f} AU from the Sun")

# Get a month of trajectory data as a DataFrame
df = get_trajectory(
    "PSP", observer="SUN",
    time_start="2024-01-01", time_end="2024-01-31",
    step="1h", frame="ECLIPJ2000",
)
print(df[["r_au"]].describe())

Kernels are automatically downloaded from NAIF on first use and cached in ~/.xhelio_spice/kernels/.

Supported Missions

With SPICE Kernels (auto-downloaded)

PSP (Parker Solar Probe) — 2018-2030
Solar Orbiter (SOLO) — 2020-2030
STEREO-A — 2017-2031
Juno — 2011-present (updated regularly)
Voyager 1/2 — 1981-2100 / 1989-2100
New Horizons — 2019-2030

NAIF IDs Only (no auto-download yet)

ACE, Wind, DSCOVR, MMS (1-4) — no public SPK kernels exist
Cassini, MAVEN — require multi-segment kernel loading (planned)
Galileo, Pioneer 10/11, Ulysses, MESSENGER, STEREO-B

Natural Bodies

Sun, Earth, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto

API Reference

Position & Trajectory

python

from xhelio_spice import get_position, get_trajectory, get_state

# Single position
pos = get_position("ACE", observer="EARTH", time="2024-06-01", frame="GSE")

# Full state (position + velocity)
state = get_state("PSP", observer="SUN", time="2024-01-15", frame="ECLIPJ2000")

# Trajectory timeseries (returns pandas DataFrame)
df = get_trajectory(
    "Cassini", observer="SATURN",
    time_start="2010-01-01", time_end="2010-12-31",
    step="6h", frame="ECLIPJ2000",
    include_velocity=True,
)

Coordinate Transforms

python

from xhelio_spice import transform_vector, list_available_frames

# J2000 to Ecliptic
v_ecl = transform_vector([1.0, 0.0, 0.0], "2024-01-15", "J2000", "ECLIPJ2000")

# RTN transform (requires spacecraft)
v_rtn = transform_vector(
    [5.0, -3.0, 1.0], "2024-01-15",
    from_frame="ECLIPJ2000", to_frame="RTN",
    spacecraft="PSP",
)

# List all frames
print(list_available_frames())

Mission Registry

python

from xhelio_spice import resolve_mission, list_supported_missions

# Resolve name aliases
naif_id, key = resolve_mission("Parker Solar Probe")  # -> (-96, "PSP")

# List all spacecraft
missions = list_supported_missions()

Kernel Management

python

from xhelio_spice import get_kernel_manager

km = get_kernel_manager()
km.ensure_mission_kernels("PSP")  # Download + load
print(km.get_cache_info())        # Cache stats
km.unload_all()                    # Free memory

Configuration

Method	Description
`XHELIO_SPICE_KERNEL_DIR` env var	Override kernel cache directory
`KernelManager(kernel_dir=...)`	Per-instance override
Default	`~/.xhelio_spice/kernels/`

MCP Server

xhelio-spice includes an MCP server for LLM tool use:

bash

# Run directly
xhelio-spice-mcp

# Or via Python
python -m xhelio_spice.server

Claude Desktop Configuration

Add to claude_desktop_config.json:

json

{
  "mcpServers": {
    "xhelio-spice": {
      "command": "xhelio-spice-mcp"
    }
  }
}

Available MCP Tools

Tool	Description
`get_ephemeris`	Position/velocity — single time (inline) or timeseries (CSV)
`compute_distance`	Distance between two bodies
`transform_coordinates`	Coordinate frame transform
`list_spice_missions`	Supported missions
`list_coordinate_frames`	Available frames with descriptions
`manage_kernels`	Kernel cache management

MCP smoke test

For a CI-safe MCP check that does not request kernel downloads, run:

bash

uv run --extra mcp python scripts/smoke_mcp_list_tools.py --json

The smoke starts the stdio server with an isolated temporary kernel cache, runs MCP initialize + list_tools, and verifies the advertised tool names.