Control of the Subaru telescope instrument exchanger system

Cassegrain Instrument Automatic eXchanger (CIAX) system for the Subaru Telescope exchanges instruments between the Cassegrain flange and stand-by flanges using a transport cart on the observation floor. CIAX-3 is a sub-system that swaps three smaller instruments on the telescope flange. To maximize operation efficiency, the CIAX system communicates with the telescope control computers. The system consists of (1) CIAX control system: The software of the CIAX control system runs on a UNIX workstation (CIAX-WS) which communicates with two PCs running by Windows NT (CNTs) for the transport cart and the stand-by flanges by file sharing. Interlocks between the flanges and the cart are provided locally by CNTs located in each of the two stand-by rooms. The control software can be operated through telnet or from another software. (2) Transport cart: The cart travels along the routes defined by magnetic tapes and 12 magnetic tags. The tags at preset positions control three actions: slowing the speed, checking for runaway and interlocking. The cart has a wireless LAN. (3) Stand-by flanges: Stand-by flanges are controlled by Programmable Logic Controllers (PLCs) and by CNTs through RS-232C. (4) CIAX-3: CIAX-3 is also controlled by a PLC linked through RS-232C to the CIAX-WS. Its power supply is controlled by another PLC and is shut down during observations. (5) Control of other equipment: Automatic doors of the stand-by rooms, lighting, and pou er supply to instruments are controlled through I/O relays by a PC with LINUX (CLX), which also checks the proximity of the top of an instrument to the telescope or stand-by flange with potentiometers. This paper describes software of CLAX systems. Details of the CIAX system hardware are described elsewhere(1).