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.

What is UTC relative to Melbourne time?

Melbourne, Australia, is typically in the Australian Eastern Standard Time (AEST) zone. However, it's important to note that Melbourne observes daylight saving time (DST) during part of the year, which shifts the time zone by one hour. Here's how UTC (Coordinated Universal Time) relates to Melbourne time:

• Standard Time (AEST - Australian Eastern Standard Time): Melbourne is 10 hours ahead of UTC during Australian Eastern Standard Time (AEST). For example, when it's 12:00 PM (noon) UTC, it's 10:00 PM AEST in Melbourne.

• Daylight Saving Time (AEDT - Australian Eastern Daylight Time): Melbourne observes daylight saving time from the first Sunday in October to the first Sunday in April. During daylight saving time, Melbourne is 11 hours ahead of UTC. For example, when it's 12:00 PM (noon) UTC, it's 11:00 PM AEDT in Melbourne. Keep in mind that daylight saving time rules can change, so it's a good practice to check the current time difference when scheduling events or making plans that involve international time zones. Also, not all states and territories in Australia observe daylight saving time, so the time difference can vary within the country.

UTC Time can be changed to Local Time in Gpredict by selecting Edit > Preferences > Number formats

• Select Show local time instead of UTC

Data Next Pass for ISS

Polar representation of Satellite Pass Data

A Polar graphical representation for satellite tracking information is a way to visualize and understand the position of a satellite relative to a specific ground station or observer on the Earth's surface. It is a two-dimensional graph that typically represents the satellite's azimuth (horizontal angle) and elevation (vertical angle) relative to the observer's location. This representation is particularly useful for tracking satellites, especially for satellite dish pointing and communication purposes.

Here's how the Polar graphical representation works:

• Azimuth: The azimuth angle represents the compass direction (in degrees) from which the satellite is visible relative to the observer's location. It starts from 0 degrees (North) and goes clockwise around the horizon to 360 degrees, completing a full circle.

• Elevation: The elevation angle represents how high above the horizon the satellite is at a given moment. It is measured in degrees and ranges from 0 degrees (right on the horizon) to 90 degrees (directly overhead). An elevation of 90 degrees means the satellite is directly above the observer.

• Polar Plot: In a Polar graphical representation, a circle or semicircle typically represents the horizon, with 0 degrees (North) at the top (12 o'clock position). The azimuth angles are marked around the circle, with lines extending outward to indicate the direction of the satellite.

• Satellite's Path: To track the satellite's path, you can plot points on the graph showing the satellite's azimuth and elevation at specific times. By connecting these points, you can visualize the satellite's movement across the sky. The path usually follows a curve from the horizon to its highest point (maximum elevation) and then back down to the horizon.

• Real-Time Tracking: Some tracking software or hardware can provide real-time updates of a satellite's position in this Polar graphical format, making it easier for observers to aim their antennas or telescopes accurately.

• Polar graphs are particularly useful for satellite tracking because they provide a clear representation of when and where a satellite will be visible from a specific location. This information is essential for various applications, including amateur radio communication, satellite TV reception, and tracking satellites for scientific observations.

In summary, a Polar graphical representation for satellite tracking information is a visual representation of a satellite's position in the sky relative to an observer's location, with azimuth and elevation angles used to describe its position and movement. It helps users point antennas or telescopes in the right direction to establish communication or observation.

Az/El Satellite Path representation

In the context of satellite observations and tracking, "Az/El" stands for "Azimuth and Elevation." Azimuth and Elevation are two fundamental parameters used to describe the position of a satellite in the sky relative to an observer's location on the Earth's surface. These parameters are crucial for tracking and communicating with satellites, whether for amateur radio, satellite television, or scientific observations.

Here's what Azimuth and Elevation mean in relation to satellite observations:

• Azimuth (Az): Azimuth is the horizontal angle measured clockwise from the North direction. It indicates the compass direction to which a satellite is located when observed from a specific location on the Earth's surface. Azimuth angles typically range from 0 degrees (North) to 360 degrees, forming a full circle around the observer's location. An azimuth angle of 0 degrees points to the North, 90 degrees to the East, 180 degrees to the South, and 270 degrees to the West.

• Elevation (El): Elevation is the vertical angle measured above the horizon. It tells you how high in the sky a satellite is located when observed from a specific location on the Earth. Elevation angles typically range from 0 degrees (right on the horizon) to 90 degrees (directly overhead). An elevation angle of 90 degrees means the satellite is directly overhead, while 0 degrees means it is on the horizon.

Together, Azimuth and Elevation provide a coordinate system that describes where a satellite is located in the sky at any given moment. Observers use this information to point antennas, telescopes, or other tracking equipment accurately toward the satellite. The combination of these angles changes continuously as the satellite moves across the sky due to its orbital motion.

For satellite tracking purposes, you might receive Az/El data or use tracking software that provides real-time updates of a satellite's Azimuth and Elevation angles. This information is vital for tracking and communicating with satellites effectively, ensuring that the equipment is pointed in the right direction to establish a reliable connection or make observations.

References

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