Satellite Tracking using Gpredict

What is Gpredict

Gpredict is an open-source satellite tracking and prediction application. It is designed to help amateur radio operators, astronomers, and satellite enthusiasts track and predict the movements of artificial satellites, including communication satellites, weather satellites, amateur radio satellites, and more.

Here are some key features and functions of Gpredict:

• Satellite Tracking: Gpredict can provide real-time tracking information for thousands of satellites in Earth's orbit. It displays their current positions in the sky, azimuth and elevation angles, and other relevant data.
• Orbit Prediction: Gpredict can predict the future passes of satellites over a specific location. Users can input their geographic coordinates, and the software will calculate when a satellite will be visible and at what azimuth and elevation angles.
• Doppler Shift Calculation: It calculates and displays the Doppler shift for communication with satellites. This is important for radio communication with satellites, as it helps adjust the frequency to maintain a stable connection.
• Ground Station Control: Gpredict can interface with radio equipment to automatically control antennas and radios to track satellites during passes.
• TLE (Two-Line Element) Data: It supports the use of TLE data, which is a standard format for describing the orbits of satellites. Users can update the TLE data to keep track of the latest satellite positions.
• Visual Pass Predictor: Gpredict includes a visual pass predictor that allows users to see on a map when and where a satellite will be visible in the sky, making it useful for planning observations or radio contacts.
• Customization: The application is highly customizable, allowing users to add their own satellites or ground stations, change display settings, and more.
• Integration with Radio Hardware: Gpredict can be integrated with radio hardware and software-defined radios (SDRs) to facilitate satellite communication.

Gpredict is a valuable tool for satellite enthusiasts, amateur radio operators, and anyone interested in tracking and communicating with satellites. Its open-source nature has led to a supportive community and the development of plugins and extensions to enhance its functionality. It is available for various platforms, including Linux, Windows, and macOS.

Install Gpredict

• On Mac install Brew Brew
• Then install Gpredict Gpredict
• On Mac you may also need to install the XQuartz package XQuartz
• To run Gpredict open the Terminal and enter gpredict

How to use Gpredict

• To track satellites you need to create a new module and add satellites to the module.
• Click File > Â New Module
• A new window will open.
• Name the module. In this case Irridium
• Select Base Station
• Create new Base Station. Choose Melbourne from existing list.

• Add satellites to Module by clicking on right pointing arrow.

• When finalised selected satellites will be visible on map.

Python code to extract satellite data from Gpredict

Accessing satellite data from Gpredict using Python can be achieved through Gpredict's Remote Control Protocol (RCP) API. Gpredict provides a simple way to communicate with the software remotely, allowing you to retrieve satellite tracking information and other data. Here are the steps to access satellite data from Gpredict using Python:

• Install Gpredict: First, make sure you have Gpredict installed on your system. You can download and install it from the official website: https://gpredict.oz9aec.net/

• Enable Remote Control in Gpredict:
• Open Gpredict.
• Go to the "Settings" menu.
• Click on "Preferences."
• In the "General" tab, check the "Enable Remote Control" option.
• Configure the "Port" and "Password" settings as needed.
• Install Required Python Libraries: You will need a Python library to communicate with Gpredict over the RCP API. One commonly used library is xmlrpc.client. You can install it using pip:

pip install xmlrpc.client

Python Code to Access Satellite Data: Here's a sample Python code snippet to access satellite data from Gpredict using the Remote Control Protocol (RCP) API:

import xmlrpc.client

# Gpredict RCP server information
gpredict_host = 'localhost'  # Replace with the actual host where Gpredict is running
gpredict_port = 4532         # Replace with the actual port configured in Gpredict
gpredict_password = 'your_password'  # Replace with the actual password

# Connect to Gpredict's RCP server
server = xmlrpc.client.ServerProxy(f"http://{gpredict_host}:{gpredict_port}/rpc")

# Authenticate with the password (if configured)
server.authenticate(gpredict_password)

# Retrieve satellite tracking data for a specific satellite by name
satellite_name = 'ISS'  # Replace with the name of the satellite you're interested in
tracking_data = server.getSatelliteInfo(satellite_name)

# Print the tracking data
print(tracking_data)

# Close the connection
server.quit()

Make sure to replace gpredict_host, gpredict_port, and gpredict_password with your Gpredict server's information. Run the Python Script: Execute the Python script, and it will connect to Gpredict, retrieve the satellite tracking data for the specified satellite, and print it to the console.

This code allows you to access basic satellite tracking data. You can expand on it to perform more advanced operations or integrate it into your projects as needed.

Antenna

Dual-band Arrow antenna

• 146/437-10 Solid boom without duplexer.
• Use two radios with this antenna

What is a Duplexer

A duplexer, when used with an antenna, is a device that allows a single antenna to be shared by both the transmit and receive functions of a radio system. It is commonly used in applications where a single antenna needs to serve both the transmitter and receiver while preventing interference between them. Duplexers are often used in two-way radio systems, such as those used by amateur radio operators, public safety agencies, and mobile communication networks.

Here's how a duplexer works and why it's necessary in certain situations:

• Transmit and Receive Frequencies: In a two-way radio system, there are separate transmit and receive frequencies. When you transmit, the radio transmits signals on one frequency, and when you receive, it listens for signals on another frequency.
• Shared Antenna: In many situations, it is impractical or cost-prohibitive to use separate antennas for transmitting and receiving. Using a single shared antenna is more space-efficient and can simplify the installation.
• Isolation: The challenge with using a shared antenna is that transmitting and receiving signals can interfere with each other. When you transmit, the powerful transmit signal can bleed into the receiver, potentially overwhelming it and causing communication problems.
• Duplexer Function: A duplexer serves as a filter that allows only the transmit frequency to pass from the transmitter to the antenna and only the receive frequency to pass from the antenna to the receiver. It achieves this by using a combination of filters and resonant cavities that selectively pass or block certain frequencies.
• Isolation and Filtering: The key function of the duplexer is to provide high isolation between the transmit and receive paths, ensuring that the transmit signal doesn't interfere with the receiver's sensitivity. This is achieved by attenuating the transmit frequency in the receive path and vice versa.
• Frequency Separation: Effective duplexing depends on having sufficient frequency separation between the transmit and receive frequencies. The duplexer is designed based on the specific frequency separation requirements of the radio system.
• Applications: Duplexers are commonly used in applications like repeater stations, where a station receives signals on one frequency and retransmits them on another. They are also used in mobile and base station setups for various radio communication systems.

In summary, a duplexer is a critical component in radio systems that allows a single antenna to be shared between transmit and receive functions while ensuring isolation between them. It does so by using filters and cavities to separate and filter the transmit and receive frequencies, preventing interference and ensuring reliable communication.

Tracker

LSM303DLHC e-Compass 3 axis Accelerometer and 3 axis Magnetometer Module

How to use Gpredict to find out when the ISS will pass over Melbourne

To use Gpredict to work out when the International Space Station (ISS) will pass over Melbourne, you can follow these steps:

• Install and Open Gpredict: First, make sure you have Gpredict installed on your computer. If you haven't installed it yet, you can download it from the official website: https://gpredict.oz9aec.net/. Once installed, open Gpredict.

• Update TLE Data: Gpredict relies on Two-Line Element (TLE) data to track satellites like the ISS. TLE data contains information about the satellite's orbital elements. To ensure you have the latest TLE data for the ISS:
  • Go to the "Satellites" menu.
  • Click on "Update TLE data."
  • Select "ISS" from the list of satellites and update the TLE data.

• Set Your Location: Gpredict needs to know your specific location to predict satellite passes accurately. To set your location:

• • Go to the "Ground Stations" menu.
  • Click on "Add."
  • Enter your geographic coordinates (latitude and longitude) for Melbourne. You can find these coordinates online or use a GPS device to determine them accurately.

• Select the ISS:
  • Go to the "Satellites" menu.
  • Search for "ISS" in the search bar or scroll down to find it in the list of satellites.

• Track the ISS Pass:
  • Select the ISS from the list.
  • Click on "Passes" in the toolbar or right-click on the ISS and select "Predict Passes."
  • A window will open with a list of upcoming passes of the ISS for your location (Melbourne). It will display the date and time (in UTC) when the ISS will be visible, its maximum elevation above the horizon, and the duration of the pass.

• Convert UTC Time to Local Time:
  • Note that the times provided in Gpredict are in Coordinated Universal Time (UTC). You may want to convert these times to your local time zone (e.g., Australian Eastern Standard Time - AEST for Melbourne) for your convenience.

• Plan Your Observation:

Once you have the pass information, you can plan your observation accordingly. Pay attention to the maximum elevation, as this indicates how high the ISS will be in the sky during the pass. Higher elevations generally provide better visibility.

• Observe the Pass:

On the scheduled date and time, set up your equipment (binoculars or a telescope, if available) and go to a location with a clear view of the sky in the direction of the pass. Be ready to spot the ISS as it crosses the sky.

Remember that the ISS orbits the Earth approximately every 90 minutes, so there are multiple passes each day. Use Gpredict to find the most suitable passes for your observation based on your location and preferences.

References

• Making ham radio satellite contacts via ISS with the Icom ID-52 and IC-705 radios