juliensimon/huygens-titan-atmosphere

---
license: cc-by-4.0
pretty_name: "Huygens Probe — Titan Atmospheric Profile"
language:
- en
description: "Titan atmospheric profile from the Huygens Probe descent (Jan 14, 2005) — temperature, pressure, and density from 1,400 km altitude to the surface."
task_categories:
- tabular-regression
tags:
- space
- titan
- huygens
- cassini
- atmosphere
- esa
- planetary-science
- probe
- descent
- saturn
- open-data
- tabular-data
- parquet
size_categories:
- 1K<n<10K
configs:
- config_name: default
data_files:
- split: train
path: data/huygens_titan_atmosphere.parquet
default: true
---

# Huygens Probe — Titan Atmospheric Profile

*Part of the [Space Probe and Mission Datasets](https://huggingface.co/collections/juliensimon/space-probe-and-mission-datasets-69c3fe82d410a42b1e313167) collection on Hugging Face.*

Titan atmospheric profile measured by the Huygens Atmospheric Structure Instrument (HASI)
during descent on **January 14, 2005** (09:05:28--11:38:10 UTC). Currently **2,727** measurements
spanning **0.0** to **1380.2 km** altitude — the only in-situ atmospheric profile
ever taken of Titan.

## Dataset description

On January 14, 2005, the ESA Huygens probe separated from the Cassini orbiter and descended
through Titan's atmosphere for approximately 153 minutes, from atmospheric entry
at ~1,400 km altitude to touchdown on the surface. The Huygens Atmospheric Structure
Instrument (HASI) measured pressure, temperature, and density throughout the descent.

The dataset combines two mission phases:

- **Entry phase** (911 measurements): Upper atmosphere (1380 km down to ~157 km), where
pressure and temperature were derived from accelerometer deceleration data. Density was not
directly measured during this phase.
- **Descent phase** (1,816 measurements): Lower atmosphere (~147 km to the surface at 0.0 km),
where direct pressure/temperature sensors provided measurements after parachute deployment.
Density was computed from pressure and temperature.

Vertical velocity from the trajectory reconstruction is merged for each measurement point.

Surface conditions at landing: **1466.5 hPa** pressure, **93.5 K** temperature.

## Schema

| Column | Type | Description |
|--------|------|-------------|
| `utc_time` | datetime | Measurement timestamp (UTC) |
| `mission_elapsed_time_s` | float64 | Seconds since atmospheric entry (T0 = 09:05:28 UTC) |
| `phase` | string | Mission phase: "entry" (upper atmosphere) or "descent" (parachute phase) |
| `altitude_m` | float64 | Altitude above surface (meters) |
| `altitude_km` | float64 | Altitude above surface (kilometers) |
| `pressure_pa` | float64 | Atmospheric pressure (Pascals) |
| `pressure_hpa` | float64 | Atmospheric pressure (hectopascals / millibars) |
| `temperature_k` | float64 | Atmospheric temperature (Kelvin) |
| `density_kg_m3` | float64 | Atmospheric density (kg/m^3) — null during entry phase |
| `velocity_m_s` | float64 | Probe vertical velocity (m/s) |

## Quick stats

- **2,727** atmospheric measurements (911 entry + 1,816 descent)
- Altitude range: **0.0** to **1380.2 km**
- Temperature range: **70.3** to **207.2 K**
- Surface conditions: **1466.5 hPa**, **93.5 K**
- Duration: **153 minutes** of atmospheric profiling

## Usage

```python
from datasets import load_dataset

ds = load_dataset("juliensimon/huygens-titan-atmosphere", split="train")
df = ds.to_pandas()

# Temperature profile
import matplotlib.pyplot as plt
plt.plot(df["temperature_k"], df["altitude_km"])
plt.xlabel("Temperature (K)")
plt.ylabel("Altitude (km)")
plt.title("Titan Atmospheric Temperature Profile")
plt.show()

# Entry vs descent phase
entry = df[df["phase"] == "entry"]
descent = df[df["phase"] == "descent"]
print(f"Entry: {len(entry)} pts, {entry['altitude_km'].min():.0f}-{entry['altitude_km'].max():.0f} km")
print(f"Descent: {len(descent)} pts, {descent['altitude_km'].min():.0f}-{descent['altitude_km'].max():.0f} km")

# Pressure-temperature diagram
plt.semilogy(df["temperature_k"], df["pressure_hpa"])
plt.xlabel("Temperature (K)")
plt.ylabel("Pressure (hPa)")
plt.gca().invert_yaxis()
plt.title("Titan P-T Profile")
plt.show()
```

## Data source

[NASA PDS Atmospheres Node — Huygens HASI Archive](https://pds-atmospheres.nmsu.edu/data_and_services/atmospheres_data/Huygens/HASI.html)
(Volume `hphasi_0001`, Level 4 calibrated profiles).

Original instrument paper: Fulchignoni, M. et al., "In situ measurements of the physical
characteristics of Titan's environment," *Nature*, 438, 785--791 (2005).

## Related datasets

- [cassini-saturn-observations](https://huggingface.co/datasets/juliensimon/cassini-saturn-observations) — Cassini orbiter observation log
- [deep-space-probes](https://huggingface.co/datasets/juliensimon/deep-space-probes) — Voyager & Pioneer merged hourly data
- [mars-perseverance-weather](https://huggingface.co/datasets/juliensimon/mars-perseverance-weather) — Mars atmospheric measurements

## Pipeline

Source code: [juliensimon/space-datasets](https://github.com/juliensimon/space-datasets)

## Support

If you find this dataset useful, please give it a ❤️ on the [dataset page](https://huggingface.co/datasets/juliensimon/huygens-titan-atmosphere) and share feedback in the Community tab! Also consider giving a ⭐️ to the [space-datasets](https://github.com/juliensimon/space-datasets) repo.

## Citation

```bibtex
@dataset{huygens_titan_atmosphere,
author = {Simon, Julien},
title = {Huygens Probe — Titan Atmospheric Profile},
year = {2026},
publisher = {Hugging Face},
url = {https://huggingface.co/datasets/juliensimon/huygens-titan-atmosphere},
note = {Based on ESA/NASA Huygens HASI Level 4 calibrated atmospheric profiles from the PDS Atmospheres Node}
}
```

## License

[CC-BY-4.0](https://creativecommons.org/licenses/by/4.0/)