Satellite Latency Viewer

This tool generates relationship information between satellites for the latency project by creating a satellite_relationships.json file.

Prerequisites

• Python 3.9 or higher
• Apache web server with CGI enabled
• Proper file permissions

Installation

1. Ensure Python 3.9+ is installed on your system
2. Make sure all Python scripts have proper execution permissions:

   chmod +x generate_relationship.py
   chmod +x satellites.py
   chmod +x sat_db_functions.py
   chmod +x data.py

3. Verify that the shebang line in all Python scripts points to the correct Python interpreter:

   #!/home/oper/py39env/bin/python

4. Make sure install Max's sat_latency python library using this and install the requirements.txt

   pip install -r requirements.txt
   pip install sds-sat-latency --index-url https://gitlab.ssec.wisc.edu/api/v4/projects/2693/packages/pypi/simple
   

Usage

Generating Satellite Relationships

To generate the satellite_relationships.json file, run:

python3 generate_relationship.py

This will create or update the satellite_relationships.json file with the latest relationship data between satellites.

Common Issues and Troubleshooting

Satellite ID Mapping

Both satellites.py and sat_db_functions.py contain a hardcoded mapping dictionary to normalize satellite IDs:

SATELLITE_ID_MAPPINGS = {
    # Format: 'variant': 'canonical'
    'G16': 'G16',
    'g16': 'G16',
    'G18': 'G18',
    'g18': 'G18',
    'G19': 'G19',
    'g19': 'G19',
    'DMSP-17': 'DMSP-17',
    'dmsp17': 'DMSP-17',
    'DMSP-18': 'DMSP-18',
    'dmsp18': 'DMSP-18',
    'DMSP-16': 'DMSP-16',
    'dmsp16': 'DMSP-16',
    'NOAA-19': 'NOAA-19',
    'n19': 'NOAA-19',
    'NOAA-20': 'NOAA-20',
    'n20': 'NOAA-20',
    'NOAA-21': 'NOAA-21',
    'n21': 'NOAA-21'
}

This mapping is used to normalize different satellite ID formats to their canonical forms.

Web Server Configuration

Make sure your Apache configuration allows CGI script execution. The included .htaccess file contains the necessary settings:

Options +ExecCGI -Indexes
AddHandler cgi-script .py

"Internal Server Error" Troubleshooting

If you're getting "Internal Server Error" in the web interface:

1. Check file permissions:

   chmod 755 data.py sat_db_functions.py

2. Check the latency viewer log file permissions:

   chmod 644 latency_viewer.log

   Make sure the directory it's in is writable by the web server.

3. Verify the Python path in the shebang line of all scripts:

   #!/home/oper/py39env/bin/python

File Structure

• generate_relationship.py - Main script to generate satellite relationships
• satellites.py - Contains satellite configuration and helper functions
• sat_db_functions.py - Database functions for satellite data
• data.py - Data processing utilities
• satellite_relationships.json - Output file containing relationship information

Notes

• The system requires Python 3.9 or higher due to specific feature dependencies
• All satellite IDs are normalized using the SATELLITE_ID_MAPPINGS dictionary
• Web access is configured through Apache CGI with proper CORS headers for API access