juliensimon/deep-space-probes

Deep Space Probes — Merged Hourly Data

Part of the Space Weather Datasets collection on Hugging Face.

Merged hourly magnetic field, solar wind plasma, and energetic particle measurements from humanity's four most distant spacecraft: Voyager 1, Voyager 2, Pioneer 10, and Pioneer 11. Currently 1,192,152 hourly records spanning 1972-01-01 to 2025-12-31, reaching 169.2 AU from the Sun (Voyager 1).

Dataset description

This dataset combines the COHO (COordinated Heliospheric Observations) merged hourly data files from NASA's Space Physics Data Facility (SPDF) for the four deep-space probes that have traveled beyond the outer planets. The data covers the entire mission durations:

• Voyager 1: 429,528 hourly records
• Voyager 2: 368,160 hourly records
• Pioneer 10: 210,384 hourly records
• Pioneer 11: 184,080 hourly records

Each record includes spacecraft position (heliocentric distance, HGI latitude/longitude), interplanetary magnetic field components (RTN coordinates), solar wind plasma parameters (flow speed, proton density, temperature), and energetic particle fluxes at multiple energy channels from the LECP, CRS, and CRT instruments.

Voyager 1 crossed the heliopause (121 AU) in August 2012 and Voyager 2 (119 AU) in November 2018, making this dataset unique in spanning the transition from the heliosphere to interstellar space.

These four spacecraft represent humanity's farthest reach into space and have collectively transformed our understanding of the heliosphere — the vast bubble of solar wind plasma that surrounds the Sun and extends well beyond the orbit of Pluto. Pioneer 10 and 11, launched in 1972-1973, were the first spacecraft to traverse the asteroid belt, encounter Jupiter and Saturn, and measure the outer heliospheric environment. Voyager 1 and 2, launched in 1977, exploited a rare planetary alignment to conduct the "Grand Tour" of the outer planets, returning the first detailed images of Jupiter, Saturn, Uranus, and Neptune along with their ring systems and satellites.

The interplanetary magnetic field (IMF) measurements in this dataset trace the structure of the Parker spiral — the Archimedean spiral pattern of the solar magnetic field carried outward by the solar wind. At increasing heliocentric distances, the radial component of the field falls off approximately as 1/r2, while the tangential component drops as 1/r, causing the field to become increasingly transverse at large distances. Solar wind speed, density, and temperature measurements document how the wind decelerates and heats through interactions with pickup ions (interstellar neutrals ionized by solar UV or charge exchange) in the outer heliosphere. The energetic particle fluxes from LECP, CRS, and CRT instruments record galactic cosmic rays modulated by the 11-year solar cycle, anomalous cosmic rays accelerated at the termination shock, and transient particle events from solar energetic particle events and interplanetary shocks.

The most scientifically profound measurements in this dataset come from the boundary regions of the heliosphere. Voyager 1 crossed the termination shock at approximately 94 AU in December 2004 and the heliopause at roughly 121 AU in August 2012, while Voyager 2 crossed the termination shock at about 84 AU in August 2007 and the heliopause at approximately 119 AU in November 2018. The different crossing distances reflect the asymmetry of the heliosphere compressed by the interstellar medium. In interstellar space, Voyager measurements have revealed a surprisingly strong and steady magnetic field, a denser-than-expected plasma environment, and ongoing cosmic ray anisotropies that continue to challenge theoretical models of the local interstellar medium.

Schema (common columns)

Column	Type	Description
spacecraft	string	Spacecraft identifier (voyager_1, voyager_2, pioneer_10, pioneer_11)
datetime	datetime	Observation timestamp (UTC, hourly cadence)
heliocentric_distance_au	float64	Distance from the Sun (AU)
hgi_latitude_deg	float64	Heliographic Inertial latitude (degrees)
hgi_longitude_deg	float64	Heliographic Inertial longitude (degrees)
b_magnitude_avg_nt	float64	Average magnetic field magnitude 1/N SUM
b_magnitude_nt	float64	Magnetic field magnitude sqrt(Br^2+Bt^2+Bn^2) (nT)
br_rtn_nt	float64	Radial magnetic field component, RTN (nT)
bt_rtn_nt	float64	Tangential magnetic field component, RTN (nT)
bn_rtn_nt	float64	Normal magnetic field component, RTN (nT)
flow_speed_kms	float64	Proton bulk flow speed (km/s)
flow_elevation_deg	float64	Flow velocity elevation angle (degrees)
flow_azimuth_deg	float64	Flow velocity azimuth angle (degrees)
proton_density_cm3	float64	Proton number density (particles/cm^3)
proton_temperature_k	float64	Proton temperature (Kelvin)

Additional spacecraft-specific flux columns (energetic particle differential flux in 1/(cm^2 s sr MeV)) are included with names like flux_h_lecp_*_mev, flux_h_crs_*_mev, and flux_h_crt_*_mev.

Quick stats

• 1,192,152 hourly records (1972-01-01 to 2025-12-31)
• 4 spacecraft: Voyager 1 & 2, Pioneer 10 & 11
• Maximum heliocentric distance: 169.2 AU (Voyager 1)
• Covers heliosphere, heliosheath, and interstellar space

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/deep-space-probes", split="train")
df = ds.to_pandas()

# Voyager 1 in interstellar space (beyond heliopause at ~121 AU)
v1_interstellar = df[
    (df["spacecraft"] == "voyager_1") &
    (df["heliocentric_distance_au"] > 121)
]

# Compare solar wind speed across all probes
for sc in df["spacecraft"].unique():
    sub = df[df["spacecraft"] == sc].dropna(subset=["flow_speed_kms"])
    print(f"{sc}: mean flow speed = {sub['flow_speed_kms'].mean():.0f} km/s")

# Magnetic field decay with distance
import matplotlib.pyplot as plt
v1 = df[df["spacecraft"] == "voyager_1"].dropna(subset=["b_magnitude_nt"])
plt.scatter(v1["heliocentric_distance_au"], v1["b_magnitude_nt"], s=0.1, alpha=0.3)
plt.xlabel("Distance (AU)")
plt.ylabel("|B| (nT)")
plt.yscale("log")
plt.title("Voyager 1: Magnetic Field vs Distance")
plt.show()

# Pioneer 10 complete mission timeline
p10 = df[df["spacecraft"] == "pioneer_10"]
print(f"Pioneer 10: {p10['datetime'].min()} to {p10['datetime'].max()}")
print(f"  Distance range: {p10['heliocentric_distance_au'].min():.1f} - {p10['heliocentric_distance_au'].max():.1f} AU")

Data source

NASA Space Physics Data Facility (SPDF) — COordinated Heliospheric Observations (COHO) merged hourly data files:

• Voyager 1: spdf.gsfc.nasa.gov/pub/data/voyager/voyager1/merged/
• Voyager 2: spdf.gsfc.nasa.gov/pub/data/voyager/voyager2/merged/
• Pioneer 10: spdf.gsfc.nasa.gov/pub/data/pioneer/pioneer10/merged/coho1hr_magplasma_ascii/
• Pioneer 11: spdf.gsfc.nasa.gov/pub/data/pioneer/pioneer11/merged/coho1hr_magplasma_ascii/

Update schedule

Monthly (1st at 07:00 UTC) via GitHub Actions. Voyager data is still being collected; Pioneer missions ended in the 1990s.

Related datasets

• solar-wind-plasma — Near-Earth solar wind from DSCOVR/ACE
• dst-index — Geomagnetic Dst index
• kp-index — Geomagnetic Kp index

Pipeline

Source code: juliensimon/space-datasets

Support

If you find this dataset useful, please give it a ❤️ on the dataset page and share feedback in the Community tab! Also consider giving a ⭐️ to the space-datasets repo.

Citation

@dataset{deep_space_probes,
  author = {Simon, Julien},
  title = {Deep Space Probes — Merged Hourly Data},
  year = {2026},
  publisher = {Hugging Face},
  url = {https://huggingface.co/datasets/juliensimon/deep-space-probes},
  note = {Based on NASA/SPDF COHO merged hourly data for Voyager 1, Voyager 2, Pioneer 10, and Pioneer 11}
}

License

CC-BY-4.0