Use of VSAT to track satellite motion in LEO orbit

[Phummy]

Hi everyone,

Please i need help on the above mentioned topic/idea. Satellites in LEO orbit work in constellation in such a way that they can provide uninterrupted service to a particular location on earth at all time of the day.

I'm looking at a situation where one can have a VSAT (flexible) take will move at thesame time with a particular LEO satellite-1 and receives signal from that satellite-1 until the LEO satellite-1 does not have a footprint on the location of the VSAT anymore. Thereafter, the LEO satellite-1 then handover the connection to LEO satellite-2 which the VSAT will do same to and so on........................................... At the end of the day, i feel the principle/idea should reduce the numbers of LEO satellites required to work in constellation by a particular ratio ............................................................................................... Please, any help on how i can go about this?

Thank you all.

 

[jiripolivka]

Using a VSAT antenna to track a moving satellite overhead is possible, but it is not the only part of a solution.
You will need to install a lower-frequency receiver and primary radiator in the antenna focus, and use a good mount to allow the antenna to scan the sky. Next you will have to build a "monopulse" primary radiator so that the complex receiver could give you a signal usable to drive the antenna to follow the satellite source in the sky.
One of VSAT antenna feature is that it is an offset parabolic dish that has side lobes directed to the sky. As the LEO satellite moves overhead, your receiver can receive its signal by a side lobe instead of the main lobe, and your system could lose the correct pointing.
Most signal-tracking (radar) systems similar to your project therefore use a symmetrical parabolic dish with low side lobes, and the monopulse primary radiator plus a two- or four-channel receiver, to obtain the pointing drive. If you can sit next to your system and follow the satellite by hand-pointing the antenna, you can follow only the LEO signal level to point to the satellite. Only training will show you how not to get confused by the "high" side lobes of an offset VSAT antenna.

LEO satellites like GPS transmit signals that can be received on the visible(from that satellite) part of the globe, with small not too directive antennas. GPS handheld receivers do not need to follow the GPS satellites, so no tracking is needed. I would advise to test the satellite reception with a dipole or low-directivity antenna; it is possible that the complex tracking system is not necessary at all.

 

[Phummy]

@ jiripolivka

Thank you so much for that explanation, i have learnt new things from your solution. Please, i'm actually new to that field/project, hence i will appreciate "reference materials" on the project.

Thank you.

@ Everyone,

Please, more clue will be appreciated.

Thank you.

 

[jiripolivka]

dear Phummy:

As I explained, you can solve the LEO tracking either an easy way, or the difficult way. To assist you more, I would need technical specifications: frequencies and received power of "your" LEO satellite(s), and possibly more. Instead of tracking LEO signals by the complex way I described, you may actually find orbit data of "your" particular LEO satellites, then no tracking is necessary. Like radio amateurs who do track various communication LEO satellites (AMSAT-OSCAR, etc.), you need to calculate pointing of your receive or transmit antenna to such satellite by converting the ephemerides into azimuth and elevation.

I would advise you to contact the radio-amateur group in your country, they will give you the information you need.