The CARMA Control System

NCSA/University of IllinoisAbstract. The Combined Array for Research in Millimeter-wave As-tronomy (CARMA) will be the combination of the BIMA, OVRO, andSZA millimeter arrays. With first light scheduled for 2005, CARMA willbe the first heterogeneous millimeter array, combining antennas varyingfrom 3.5 m to 10.4 m in diameter. The controls for CARMA involve cre-ating a uniform interface for all antennas. The antennas are grouped intofive independently-controlled sub-arrays, which will be used for scientificobservations, engineering, or maintenance. The sub-arrays are controlledby two components: the Sub-array Command Processor (SCP) and theSub-array Tracker (SAT). While each sub-array has a dedicated SCP forhandling command processing, a single SAT computes and distributesslowly varying parameters to the necessary sub-arrays. The sub-arrayinterface uses CORBA distributed objects to physically separate the userinterface from the array. This allows for stability in the core enginecontrolling the array while enabling flexibility in the user interface imple-mentation.1. Design ConsiderationsFour major factors were considered when designing the CARMA Control Sys-tem. First, being a multi-institutional collaboration, each developing hardwareand software at their respective locations, it was necessary to have a design thatwould allow institutions to develop independently and in parallel. Second, thearray will consist of eight 3.5 m, nine 6.1 m, and six 10.4 m antennas; to dealwith the heterogeneous nature of the array, the antennas will be treated as dis-tributed objects, each having a uniform interface for the system. Third, having aheterogeneous array means that data collection will differ for different antennas;the system must therefore be able to take such differences into consideration in708