Minor Planet Center Getting Started: Data Access (2026)

Getting started overview

The Minor Planet Center (MPC) provides comprehensive data on minor planets, comets, and natural satellites. Unlike many modern services that offer RESTful APIs requiring authentication keys, MPC data access is primarily through direct downloads of structured text files or web-based query forms. All data and services are freely available without the need for an account or API keys.

This guide outlines the process for accessing MPC data, focusing on programmatic retrieval methods. Users will learn how to identify relevant datasets, form requests, and interpret the returned data, which typically involves parsing delimited text files. The data supports various astronomical applications, including orbital calculations and observation reporting.

The core of the MPC's offering is its extensive database of observations and orbital elements for small solar system bodies. Researchers and enthusiasts commonly use this data for tasks such as tracking known objects, identifying new discoveries, and performing astrometric analyses. The data formats are standardized to facilitate machine readability, though parsing logic is often required on the client side.

A quick reference for getting started is provided below:

Create an account and get keys

The Minor Planet Center does not require user accounts, API keys, or any form of authentication for accessing its data and services. All resources provided by the MPC are publicly available and can be accessed directly. This open access model simplifies the getting started process by removing the need for registration or credential management.

Users can directly navigate to the MPC data resources page to find links to various datasets, documentation on data formats, and web-based query tools. The absence of an account system means there are no rate limits tied to individual users or API keys. However, users are expected to access data responsibly to avoid overwhelming the MPC servers, especially when programmatically retrieving large datasets. For instance, instead of repeatedly querying for the same data, it is recommended to download full files once and process them locally.

This approach aligns with the MPC's mission to facilitate the widespread dissemination of astronomical information. While other services, such as JPL's Small-Body Database, might offer more interactive API endpoints, the MPC prioritizes direct access to its foundational datasets.

Your first request

To make your first request to the Minor Planet Center, you will typically perform an HTTP GET request to download a specific data file or to query a web interface. We will demonstrate retrieving a commonly used dataset: the orbital elements for numbered minor planets.

Using curl (command line)

The curl command-line tool can be used to download the data file directly. This file, MPCORB.DAT, contains orbital elements for all numbered minor planets. It is a large file, so consider its size before downloading.

curl -O https://www.minorplanetcenter.net/iau/MPCORB/MPCORB.DAT

This command downloads the MPCORB.DAT file to your current directory. The -O flag tells curl to save the file with its original filename.

Using Python

Python's requests library is suitable for programmatically downloading files. After downloading, you would typically parse the content. The MPCORB.DAT file is a fixed-width format, so parsing requires knowledge of its column structure, detailed in the MPC's documentation for orbital elements.

import requests

url = "https://www.minorplanetcenter.net/iau/MPCORB/MPCORB.DAT"
response = requests.get(url, stream=True)

if response.status_code == 200:
    with open("MPCORB.DAT", "wb") as f:
        for chunk in response.iter_content(chunk_size=8192):
            f.write(chunk)
    print("MPCORB.DAT downloaded successfully.")
else:
    print(f"Failed to download MPCORB.DAT. Status code: {response.status_code}")

# Example of how to read the first few lines after download (simplified)
# This is a very basic read, actual parsing requires understanding the fixed-width format.
# For detailed parsing, refer to MPCORB_info.html
with open("MPCORB.DAT", "r") as f:
    for _ in range(5):
        print(f.readline().strip())

This Python script downloads the MPCORB.DAT file and then prints the first five lines. For actual data extraction, you would implement parsing logic based on the file's specified format. For example, the Content-Disposition HTTP header is not typically used by MPC for direct downloads, rather the file name is part of the URL path.

Common next steps

After successfully retrieving your first dataset from the Minor Planet Center, several common next steps can enhance your astronomical research or application development:

1. Data Parsing and Storage: The MPC data files are typically in delimited text formats (e.g., fixed-width, space-delimited). The next crucial step is to write robust parsing routines to extract the relevant information. Consider storing this parsed data in a local database (e.g., SQLite, PostgreSQL) or a structured file format (e.g., CSV, JSON) for easier querying and analysis.
2. Explore Other Datasets: The MPC offers a wide range of data beyond orbital elements. Investigate the full list of available datasets, including:
   • Observation Data: Raw astrometric observations of minor planets and comets.
   • Near-Earth Object (NEO) Data: Specific datasets focused on objects that pose a close approach risk to Earth.
   • Ephemeris Services: Tools to generate predicted positions of objects for specific times and locations (often through web forms).
3. Automate Data Updates: Minor planet data is continuously updated as new observations are made and orbits are refined. Implement a schedule to periodically download updated versions of the datasets you are using. This ensures your applications or research always use the most current information. Be mindful of the MPC's server load when automating downloads.
4. Integrate with Astronomical Software: Many astronomical software packages and libraries can work with MPC data formats. Explore integrating the parsed data into tools like Astropy (Python), SkyMap, or other specialized astrometry software for visualization, further calculations, or simulations.
5. Contribute Observations: If you are an observer, the MPC also provides mechanisms for submitting new observations. This typically involves using standardized formats like the Minor Planet Center's observational data format and submitting them through their designated channels.
6. Reference MPC Documentation: Always refer to the specific documentation for each dataset to understand its format, content, and any specific usage guidelines. This is particularly important for parsing fixed-width files accurately.

Troubleshooting the first call

Troubleshooting issues when accessing Minor Planet Center data typically revolves around network connectivity, file integrity, and data parsing. Since no authentication is involved, credential-related errors are not a concern.

• Network Connectivity Issues:
  • "Failed to connect" or "Connection refused": Verify your internet connection. Ensure there are no firewalls or proxies blocking access to www.minorplanetcenter.net. Try accessing the URL directly in a web browser to confirm it's reachable.
  • DNS Resolution Errors: If you receive errors related to hostname resolution, check your DNS settings.
• HTTP Status Codes:
  • 404 Not Found: Double-check the URL you are trying to access. MPC URLs are case-sensitive. Refer to the MPC data page to confirm the correct link for the dataset.
  • 403 Forbidden: While rare for MPC, this could indicate an IP-based block or an issue with how your request is formed (e.g., an unusual user-agent string). Try a standard curl request first.
  • 5xx Server Error: These indicate an issue on the MPC server. Wait a while and try again. Check the MPC homepage for any announcements about service interruptions.
• Incomplete or Corrupt Downloads:
  • File Size Mismatch: After downloading, compare the size of your local file with the expected size (if available on the MPC website). If they differ, the download may have been incomplete. Implement checksum verification if the MPC provides them.
  • Interrupted Downloads: For very large files, network interruptions can occur. Ensure your download script handles retries or resumes partial downloads if supported by the server (using HTTP Range headers).
• Data Parsing Errors:
  • Incorrect Column Delimiters: MPC files often use fixed-width columns or specific delimiters (e.g., spaces, tabs). Ensure your parsing logic correctly identifies these. Refer to the specific documentation for each file format.
  • Unexpected Data Formats: Occasionally, file formats might see minor updates. If your parser suddenly fails, check the MPC documentation for any recent changes.
  • Encoding Issues: Most MPC files are plain text, likely ASCII or UTF-8. Ensure your parsing software uses the correct character encoding to avoid garbled characters.
• Rate Limiting (Informal): While there are no explicit API keys or formal rate limits, excessive, rapid requests can strain the MPC servers. If you experience slow responses or temporary access issues after many requests, consider implementing delays between requests or downloading larger files less frequently. The HTTP Retry-After header might be returned by some servers to suggest a waiting period, though MPC's direct download model may not explicitly use this.