ephessos 1.0.2

Ephemeris for Solar System Objects with JPL/Horizons

EPHESSOS

Ephemeris for Solar System Objects with JPL/Horizons

EPHESSOS is a Python library for querying ephemeris data of solar system objects from NASA's JPL Horizons system. It provides an easy interface to retrieve positional and observational data for asteroids, comets, and planets.

Features

• Query JPL Horizons using orbital elements or object designations
• Parse MPC NEA (Near-Earth Asteroid) data files
• Retrieve comprehensive ephemeris data including RA, Dec, distance, and more
• Support for custom time ranges and step sizes
• Integration with Astropy for astronomical calculations

Installation

Install EPHESSOS using pip:

pip install ephessos

Or from source:

git clone https://github.com/Borlaff/EPHESSOS.git
cd EPHESSOS
pip install .

Quick Start

Here's a simple example showing how to query the ephemeris of asteroid (433) Eros:

import ephessos as ep
from astropy.time import Time

# Define time range
mjd_start = Time('2024-01-01T00:00:00', format='isot', scale='utc').mjd
mjd_end = Time('2024-01-15T00:00:00', format='isot', scale='utc').mjd

# Query Horizons for Eros (designation: 00433)
eros_data = ep.core.sso_query_to_horizons(
    designation="00433",
    mjd_start=mjd_start,
    mjd_end=mjd_end,
    step_size="1d",
    verbose=True
)

print(eros_data.head())

This will return a pandas DataFrame containing ephemeris data including:

• Right Ascension (RA) and Declination (Dec) in degrees
• Distance from observer
• Magnitude and other observational quantities
• Modified Julian Date (MJD)

Advanced Usage

Reading MPC Data Files

EPHESSOS can parse MPC-formatted NEA files:

# Read MPC NEA data
nea_table = ep.core.read_mpc_nea_file("path/to/nea.txt")

# Query ephemeris for the first object
first_object = nea_table.iloc[0]
data = ep.core.sso_query_to_horizons(
    designation=first_object["Designation"],
    epoch=first_object["Epoch"],
    eccentricity=first_object["Eccentricity"],
    node=first_object["Node"],
    arg_perihelion=first_object["Arg_Perihelion"],
    inclination=first_object["Inclination"],
    mean_anomaly=first_object["Mean_Anomaly"],
    semimajor_axis=first_object["Semimajor_Axis"],
    mean_motion=first_object["Mean_Motion"],
    mjd_start=mjd_start,
    mjd_end=mjd_end,
    step_size="1d"
)

Command Line Interface

EPHESSOS also provides a command-line interface through the ephessos executable, which allows you to query ephemeris data directly from the terminal without writing Python code.

Basic Usage

After installation, you can use the ephessos command to generate ephemeris data. You must provide the orbital elements and time range:

 ephessos --designation=433 --epoch=2461000.5 --eccentricity=0.222836 --node=304.27008 --arg_perihelion=178.92978 --inclination=10.82847 --mean_anomaly=310.55432 --semimajor_axis=1.458121 --mean_motion=0.55977529 --mjdstart=58849.0 --mjdend=61042.0 --step_size=1d --output="eros_ephem.csv"

Required Parameters

• --designation: Object designation (e.g., "00433" for Eros)
• --epoch: Julian Date of the osculating elements
• --eccentricity: Orbital eccentricity
• --node: Longitude of the ascending node (degrees)
• --arg_perihelion: Argument of perihelion (degrees)
• --inclination: Orbital inclination (degrees)
• --mean_anomaly: Mean anomaly (degrees)
• --semimajor_axis: Semi-major axis (AU)
• --mean_motion: Mean motion (degrees/day)
• --mjdstart: Start time as Modified Julian Date
• --mjdend: End time as Modified Julian Date

Optional Parameters

• --step_size: Time step for ephemeris (default: "1d" for 1 day)
  • Examples: "1d", "12h", "6h", "1h", "30m"
• --output: Output CSV filename (default: "horizons_ephemeris.csv")
• --verbose: Enable verbose output

The output will be a CSV file containing columns for:

• Date/time information
• Right Ascension and Declination (ICRF)
• Apparent magnitude
• Distance from observer and Sun
• And other ephemeris quantities

Converting Dates to MJD

To convert calendar dates to Modified Julian Dates for use with --mjdstart and --mjdend, you can use online converters or Python:

from astropy.time import Time
t = Time('2024-01-01T00:00:00', format='isot', scale='utc')
print(f"MJD: {t.mjd}")

Contributing

Contributions are welcome! Please see our contributing guidelines for details.

License

EPHESSOS is licensed under the BSD 3-Clause License. See LICENSE for details.

Citation

If you use EPHESSOS in your research, please cite:

Borlaff, A. S., & Dotson, J. (2026). EPHESSOS: Ephemeris for Solar System Objects with JPL/Horizons.

Contact

• Authors: Alejandro S. Borlaff, Jessie Dotson
• Email: [e-mail], [e-mail]
• Repository: https://github.com/Borlaff/EPHESSOS