Development of the control system for the 40m radiotelescope of the OAN using the Alma Common Software

The Observatorio Astronómico Nacional (OAN) is building a 40m radiotelescope in its facilities in Yebes (Spain) which will be delivered by Spring 2006. The servosyste m will be controlled by an ACU (Antenna Control Unit), a computer running Windows XP and Twi nCAT, a real time extension developed by Beckhoff and provided by the company contracted for ins talli g the antenna servo system. The ACU may be commanded from a remote computer or from two local panels. The radiotelescope is an instrument composed of antenna, rece ive s, backends, and auxiliary equipment connected through a Local Area Network (LAN). Its control system has to deal with a distributed environment which needs to be remotely controlled and monitored from external heterogenous users (astronomers and engineers). We have chosen the Alma Common Software (ACS) framework because it fulfills the requirements of the control system for the 40m radiotelescope. The control system requires multiple processes simultaneously wor king and being synchronized. ACS provides an implementation of the component/container paradigm v a Common Object Request Broker Architecture (CORBA) and also provides general purpose utili ty l braries, hiding the complexity of CORBA to the developer. ACS supports Python, C++ and J va, which allow the users to manage the radiotelescope using applications which run in diffe rent operative systems. ACS is supported by the European Southern Observatory (ESO) and the Nationa l Radioastronomy Observatory (NRAO) for the Atacama Large Millimeter Arra y (ALMA) with a lifetime similar to our radiotelescope. This is an important guarantee for the OAN wi th a very reduced software team. We present an overview of the software architecture of the r adiotelescope and the current status of the development of the components. We have grouped individual instrume nts with a common relationship in packages. Each instrument is controlled by an ACS component and the whole package is managed by one container. Each container tipically runs on a Li ux computer. We have developed components which use in home developed libraries for using GPIB, serial, and ethernet ports which allow us to manage instruments via different hardware interface s. We have also developed components to compute astronomical ephemeris. All our software is contributed with a LGPL license to the CVS contrib area of ESO.