Projects ongoing at la Villette radiotelescope

Three activities are programmed for radiotelescope project.

The first activity will be in agreement with initial project that had been elaborated at the time the instrument was designed thirty years ago : to study Hydrogen-Line of the Galaxy on 1420,4 MHz. By measuring the frequency of spectral line of atomic hydrogen depending on the galactic region will provide dressing a map of frequency shift proportional to radial velocity of targetted regions. Other more discrete radiosources can be studied. Paris Meudon observatory has studied la Villette radiotelescope observations possibilities of galactic hydrogen and various radio sources.

Primary observations will record galactic hydrogen signals from well known high power radio sources (Cygnus) received using a Software Defined Radio receiver. Received signals will be broadcasted via WebSDR.

One major interest of radioastronomy is the study of radiosources from pulsars. Some pulsars transmit signals with audible frequency due to their rotationnal speed. However, pulsar signals are very weak and it is not sure that these objects are within the telescope possibilities. 

The second programmed activity will consist in sending and receiving radio signals in telegraphy or telephony (Single Side Band) or digital signals toward the Moon. CAMRAS WebSDR in diffusing such radio signals sent by radioamateurs and reflected by the Moon. La Villette radiotelescope antenna should be equipped with a source cavity adapted to Earth-Moon-Earth (EME) frequency band around 1296 MHz. We are thinking of using digital transceiver (Transmitter – Receiver) Lime SDR, a device that has been selected by European Space Agency.

Capture d'écran 2018-02-18 02.44.54

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.

Capture d'écran 2018-02-20 20.58.53

The third goal of our project is to use the antenna for transmitting toward radioamateur transponder module P4A abord a geostationary satellite Eshail-2. The satellite has just been launched and will be soon positionned at 26° East above equator. Transponder will be able to retransmit radio signals from hamradio stations from 1/3 of the globe (see footprint on above map).

This publication from Amsat-DL gives news about geostationary satellite.

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