Satellite Tracking Program

Satellites in Low Earth Orbits (LEOs) traverse their orbit over the Earth, whereas satellites in the Geo Stationary Orbits stay in the same position in relation to a point on Earth. Typically LEOs rise and set rapidly, and are within communication range only for a few minutes from a fixed an Earth station. This rapid motion of the LEOs also introduces Doppler effects on their transmitted and received signals. Therefore Earth station antennas have to track actively track these satellites with their antennas and radios. Software programs help in making this task a bit easier.

The role of the tracking software is to compute the exact current location of the tracked object. This is achieved by several means, typically from historical parameters. In the case of satellites, a set standardized Keplerian data values are used to compute their current position in reference to a point on the earth.

There are several free and commercial tracking programs to track Amateur Satellites - SatPC32, HRD Satellite to name a few. The developers of the tracking programs and the developers of tracking units have defined a set of a communication protocols so that the tracking program can effectively communicate with the tracking units. EasyComm II is one such communication protocol, also described on another page.

The main role of the Tracking Program is to track the position of selected satellites, and alert when the satellites are within communication range. The program also adjusts the radio frequency for Doppler correction for the satellite of interest. It can communicate the position of the satellite to an Antenna Rotator to keep it continuously aimed at the moving satellite.

The main screen displays a world map typically centered on the user's position and plots the trajectory of the satellite on the world map. It can display the trajectory of several satellites simultaneously. Companion progams can list the rise and set times of satellites in a list format for saving or printing. This is useful to know when the satellites will pass over the observer's position in the future and plan accordingly.

Usually these programs communicate with the radios and the tracker via serial ports. When serial ports are not available at the PC, USB ports may be used along with USB to Serial Adapters.

For detailed operating instructions of of SatPC32 and HRD Satellite Tracking programs, please refer to the documentation provided by the software program, however, some important aspects are highlighted below. It is assumed that one of these is installed on your PC and is already capable of communicating with the radio(s). Either is capable of controlling the frequency and mode of the radio as well as compute the exact position of the satellite and drive the antenna tracker.

SatPC32

The main screen display the current position of the satellite, its predicted trajectory and the area of illumination of the satellite. The lighted area on the earth is where it is within communication range.

Operational Considerations for SatPC32

Setting Up the Observer

The observer is the station observing the satellite. Configuring this involves simply entering Call Sign and the coordinates as Lat/Lon or Grid Square. Select SETUP -- OBSERVER and proceed to enter the values for your location. Make sure you click STORE when done.

Selecting The Satellites to be Tracked

SatPC32 allows you to setup up to 10 satellites to be continuously tracked by it. This can be configured under the Satellites menu. In the popup window, double clicking the AVAILABLE satellite name adds it to the SELECTED list, and vice-versa :

Setting up the Radio Interface

Among other things, SatPC32 program is capable of controlling the radios as well as this Antenna Positioning System.

Getting the Radio Interfaces configured correctly is usually just a matter of selecting the radio from a list and selecting the parameters of the interface connections. Serial interface is generally used for controlling radios, and in such cases, the selection of the right COM Port and its parameters is necessary.

Most LEOs use 2 frequencies to provide full duplex communication, one for the up-link and one for the down-link. However unlike local repeaters, they use frequencies from two different bands, rather than just an offset. At the earth station this requires a radio capable of full-duplex at these frequencies. Alternately 2 separate radios can be used. In such cases, the SatPC32 program allows the user to select and configure two radios for full duplex operation, as illustrated by the screenshot below.

Setting up the Antenna Rotator Interface

To configure SatPC32 to work with the Antenna Rotator, the following procedure may save some time.

• 1. select Setup menu and Rotor Setup,

  2. then select Rotor "SAEBRTrackBox" and click STORE and click the other STORE and click OK,

  3. then close and restart the program.

  4. now a second small window called ServerEasyComm1 should also start and may become minimized automatically

  5. restore the small window and select the COM port (same as the Arduino programmer) and select BaudRate 4800, and click SAVE

  6. again close SatPC32 and restart it

  7. again open the ServerEasyComm1 to make sure the port number baud rate is correct

This completes the Rotor Setup portion of SatPC32.

Miscellaneous Configuration Options

Finally under Setup -- Options -- Activate at Start -- check mark Rotor, CAT, Auto Select, and Local Time.

Again select STORE and restart the program.

Links to SatPC32:

http://www.dk1tb.de/indexeng.htm

http://store.amsat.org/catalog/product_info.php?products_id=50

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Ham Radio Deluxe (HRD) - Satellite Tracking Program

The Satellite Tracking program is installed as part of the HRD Suite. The suite is capable of controlling radios, tracking satellites, and logging amond other things. HRD Rotator supports many standard tracker protocols. To enable the EasyComm II protocol, simply select it from the dropdown list in HRD Rotator.

Operational Considerations

When the configuration is complete, tracking a satellite is just a few clicks away.

• Start the HRD Satellite Tracker program

• On the PASSES tab select SHOW ALL/SELECTED/ONLY to display the satellite pass you want to track

• Double click on the pass under consideration to open a new tab for the satellite selected

• Click TUNING DIAL to display it

• Check the RX option

• Click on ROTATOR to launch the HRD Rotator program

On the HRD Rotator window:

• Select ROTATOR: EASYCOMM II

• Select PORT: the COM port connecting the Arduino

• Select SPEED:4800

• Click DDE: CONNECT (this will display a bunch of greyed out numbers in the status bar)

• Click DDE: TRACK

If the configuration is correct, the servos should start moving when the satellite is within tracking range. The traffic between the HRD Rotator and the Arduino under the tab LOGFILE should provide more details.

When HRD Rotator starts tracking the satellite, it will work by itself and needs no further attention. Just minimize the HRD Rotator window and focus your attention to the HRD Satellite window where all the action is happening !!

Note: When changing satellite selection, just click make sure the RX option is selected in the HRD Satellite window, there is no need to go back to the HRD Rotator window, it should automatically track the newly selected satellite !!!