The radiotelescope antenna movements can be controlled from a local command pannel on the antenna plateform. However it is more convenient to be able to activate the radiotelescope from remote sites via Internet. This is why we are developping a driver that can activate antenna motors. Control driver is based on the API (acronyme for Application Programming Interface) named Instrument-Neutral-Distributed-Interface control protocol (INDI).
The software driver communicates with an interface card that can read antenna angular positions and activate motors. Driver is writen in C and C++ by Dimension Parabole software team (Patrick F1EBK and Bernard F6BVP). It communicates with INDI server using XTML messages upon receiving target coordinates from an INDI client. Astronomy client softwares such as Stellarium and Cartes du Ciel (Skychart) are compatible with INDI API and connect to INDI server via Internet. Experiments are also being performed with KSTAR application under KDE.
The interface card designed by KK6MK et F1EHN has been assembled by Laurent F6FVY. It is used for remote control of radiotelescope antenna motors. Recently the card has been repared by Patrick F1EBK who added an LCD display card useful for software debuging.
However, although the repared card is able to control the antenna and read its position angles, it is not completely fitted to the radiotelescope for it can only activate four commands. At least three additional commands needs to be added for fast movements in either AD directions and targetting rotation movement. This is why Alain F1CJN (Radio Club de Maison Lafitte) offered to study a new control card based on an ARDUINO micro controller that will be compatible with KK6MK-F1EHN card and will provide more commands possibilities. INDI driver communicates with interface card through a serial link at 9600 bauds.
Interface card prototype is finished and working as can be seen on this vidéo. The LCD screen displays Righ Ascention (AD) changing while antenna is moving. It also displays the commands sent by astronomy client software (PVP means Low Speed +). When the antenna reaches the target coordinates the software sends a command for switching to tracking mode. The antenna rotation is actually simulated by hexadecimal coding wheels connected to the card. A more sophisticated optic coder telescope simulator is to be developped using a Raspberry Pi and a multiport HAT card. It will be used to validate the final driver version.
With its 10 m dimension La Villette radiotelescope antenna was designed for recording of signals from atomic neutral hydrogen on 1420,4 MHz. Our first observations will record galactic hydrogen signals from well known high power radio sources (Cygnus) received using a Software Defined Radio receiver.
The second chapter of our project is to perform moon bounce. This is the term used to describe communications between Earth stations par reflection on the Moon surface using either CW (telegraphy), SSB (phone Single Side Bande) or numerical transmission technics.
All these operations are achieved by capturing radiowaves signals using a Software Defined Radio (SDR) receiver. Receiver is driven by a software driver that is presently under development by INDI developers. Using INDI API for both sky objects targetting and recording will simplify development of both parts of our project, radioastronomy and hamradio communications.
Present SDR market has a few TRX (transmitter and receiver) offers such as LimeSDR. The choice of TRX model for EME (Earth Moon Earth, EME) is not yet fixed. LimeSDR mini seems very interesting and will soon be tested. A driver for LimeSDR is still under beta test in INDI library.
Third chapter of our project is to use the antenna for transmitting toward a radioamateur transponder module abord a geostationary satellite Eshail-2 . The satellite is to be launched at the end of 2018 on a 26° East orbital position. Transponder retransmit radio signals from hamradio stations from 1/3 of the globe.
This publication from Amsat-DL shows the progress of Eshail-2 project :