Ground Station Coverage Analysis for Satellites

satellite
Poliastro
Skyfield
Python
Getting satellite coverage for a network of ground stations.
Author

Winfred

Published

February 25, 2025

credit: Photo by Stephan Widua on Unsplash

Code can be found here

Introduction

The visibility of satellites from ground stations impact reliable communications and efficiency of data flow. This project investigates the visibility coverage for a given satellite constellation from several ground stations around the world, particularly the northern and southern polar regions.

Orbit design determines how long and how often the particular satellite will communicate with the ground station. Modeling passes using Two-Line Elements (TLEs) and calculating time each satellite spends over a station would give insight into communication durations and global coverage patterns.

This post describes the method, results, and implications of the analysis that can provide a means for engineers and scientists on optimizing ground station networks for reliable communications and data relay for satellite missions.

Methodology

Step 1: Data Preparation

The ground station data must be loaded from a CSV file that contains this data:

  • Name: This is given as the name for the ground station.
  • Latitude and Longitude: They’re the geographical coordinates of the station.
  • Region: The indicator tells if the station is located in the northern hemisphere or in the southern hemisphere.

Here is a small sample of the dataset:

Name Latitude Longitude Region Notes
Svalbard Satellite Station 78.229 15.408 North Kongsberg Satellite Services
North Pole Station 64.800 -147.650 North Swedish Space Corporation
Awarua -46.530 168.380 South ATLAS Space Operations
Western Australia Space Center -29.010 115.340 South Swedish Space Corporation (SSC)
AU-01 -32.960 138.850 South Leaf Space
Santiago Satellite Station -33.133 -70.667 South Swedish Space Corporation (SSC)
Belo Horizonte -19.861 -44.619 South New
Tahiti, French Polynesia -17.630 -149.600 South ATLAS Space Operations
Capetown -33.951 18.459 South New
Toliara -23.375 43.689 South New

Step 2: Visualising Ground Station Locations

Using matplotlib and geopandas, plot the global distribution of ground stations on a world map. Stations in the northern hemisphere are marked in red, while those in the southern hemisphere are marked in blue. Each station is annotated with its name for clarity.

Global Distribution of Satellite Ground Stations

Summary Statistics:

  • North Region:
    • Number of stations: 2
    • Average latitude: 71.51°
    • Minimum latitude: 64.80°
    • Maximum latitude: 78.23°
  • South Region:
    • Number of stations: 8
    • Average latitude: -29.56°
    • Minimum latitude: -46.53°
    • Maximum latitude: -17.63°

Step 3: Orbit Parameters and Mean Motion

The satellite used in this analysis is in a Sun-Synchronous Orbit (SSO) with the following parameters:

  • Semi-major axis: 6878 km (500 km altitude)
  • Eccentricity: 0.01
  • Inclination: 97.2°
  • Right Ascension of the Ascending Node (RAAN): 90°
  • Argument of Perigee: 0°
  • True Anomaly: 0°

The mean motion of the satellite is calculated as 15.21982 revolutions per day, which determines how frequently the satellite revisits specific regions.

Step 4: Generating TLEs

To simulate satellite passes, generate a Two-Line Element (TLE) set for the satellite. The TLE format is widely used for orbital prediction and includes essential orbital elements such as inclination, RAAN, eccentricity, and mean motion.

Example TLE:

1 99999U 2520250.000000 .00000000 00000-0 00000-0 0 0000
2 99999 97.2000 0.0000 0010000 0.0000 0.0000 15.21982000 00000

Step 5: Visibility Analysis

Using the skyfield library, calculate the visibility of the satellite from each ground station over a 24-hour period. Key metrics include:

  • Rise Time: When the satellite rises above the horizon.
  • Culmination Time: When the satellite reaches its highest point in the sky.
  • Set Time: When the satellite sets below the horizon.
  • Duration: Total time the satellite is visible during a pass.

For example, the Svalbard Satellite Station experienced the following passes:

  • Pass 1:
    • Rise: 2025-01-18T21:08:27Z
    • Culmination: 2025-01-18T21:12:10Z
    • Set: 2025-01-18T21:15:54Z
    • Duration: 7.44 minutes
  • Pass 2:
    • Rise: 2025-01-18T22:43:02Z
    • Culmination: 2025-01-18T22:46:26Z
    • Set: 2025-01-18T22:49:51Z
    • Duration: 6.81 minutes

Step 6: Visualising Satellite Passes

Visualise the satellite passes over all ground stations using a horizontal timeline plot. Each line represents a ground station, with markers indicating rise, culmination, and set times.

Satellite Passes Over Ground Stations

Results

Summary Statistics

The analysis provides detailed statistics for each ground station, including the number of passes, average duration, and minimum/maximum durations. Here are some highlights:

  • Svalbard Satellite Station:
    • Number of passes: 10
    • Average duration: 6.73 minutes
    • Minimum duration: 4.98 minutes
    • Maximum duration: 7.44 minutes
  • Tahiti, French Polynesia:
    • Number of passes: 3
    • Average duration: 5.47 minutes
    • Minimum duration: 3.91 minutes
    • Maximum duration: 7.11 minutes

Observations

  • Ground stations in higher latitudes, such as Svalbard and the North Pole Station, experience more frequent and longer satellite passes due to the near-polar inclination of the orbit.
  • Mid-latitude stations, such as Belo Horizonte and Capetown, provide complementary coverage, ensuring continuous communication opportunities.

Conclusion

The well-placed ground stations support satellite visibility and data-link throughput. Ground stations at high latitudes are very important since they tend to provide frequent communication windows, while stations at mid-latitudes provide further opportunities toward global coverage.

Optimisation of the ground station network based on this knowledge will enhance mission operators’ ability to ensure reliable communications and efficient data relay in support of the operational requirements of satellite missions positioned in a congested orbital environment.