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Maintenance occuring at

La Villette radiotelescope

A number of maintenance operations have been achieved in 2018 and some are still to be achieved on the radiotelescope motors :

Unfortunately at the present time the radiotelescope cannot move for the declinaison motor reductor is broken and has been removed in order to be repaired ! (see below)

Meanwhile a three phase 380 Volts power cable and an Ethernet cable have been routed underground from nearby red building Folie N4 to the radiotelescope. These cables are providing power supply to the antenna motors and remote communication link to electronic devices.

After thirty years the coaxial cable needed to be replaced by a new low loss cable !

We inserted a preamplifier and a pass-band filter into coaxial pathway located in the radio rack on antenna plateform.

A second preamplifier had been previously inserted for additional amplification. However it was then removed when we discovered that an amplifier was already present on the top of the reception chain, close to the dipole antenna. This amplifier had been designed 33 years ago and is still working as soon as a power supply is providing 12 V DC through the coaxial cable using a Bias-Tee (picture below).

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Some important work must be performed on the antenna motorisation for it has been damaged by accumulation of rust on the gears.

When motor reductor are repaired the radiotelescope will be remotely driven by astronomy client software in order to aim it at a target from which we want to record radio signal. Two applications are generally used  : Stellarium and Cartes du Ciel (Skychart). The last one is available under both Windows and Linux and provides more informations while the radiotelescope is instructed to move. We have developed a telescope driver that connects client application and drives interface board controling the antenna motors. It is using INDI (Application Programming Interface, API), Instrument-Neutral-Distributed-Interface control protocol (INDI).

A former interface had been designed long time ago by KK6MK and F1EHN. However it was not well adapted to drive our radiotelescope with only four commands available. This is why Patrick F1EBK and Alain F1CJN have designed a new interface board using an Arduino micro controler and with much more commands capabilities.

Prototype board and Arduino firmware are working. A PCB version has been manufactured and is being tested. New interface is fully compatible with former KK6MK-F1EHN interface board both for connector and software remote control. However it has more output control lines suitable for complete radiotelescope remote commands.

Until motors are fully repaired, we designed a telescope simulator version 2.1 with a nano PC RaspBerry Pi equipped with a 32 bits serial to parallel HAT. A software is simulating parabol movements by setting both 12 bits opto coders values. Written in C language it is using curses library for color text display.

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Interface board protype is being tested in remote control rack