NIR camera and spectrograph SWIMS for TAO 6.5m telescope: array control system and its performance

SWIMS (Simultaneous-color Wide-field Infrared Multi-object Spectrograph) is a near-infrared imager and multi object spectrograph as one of the first generation instruments for the University of Tokyo Atacama Observatory (TAO) 6.5m telescope. In this paper, we describe an array control system of SWIMS and results of detector noise performance evaluation. SWIMS incorporates four (and eight in future) HAWAII-2RG focal plane arrays for detectors, each driven by readout electronics components: a SIDECAR ASIC and a JADE2 Card. The readout components are controlled by a HAWAII-2RG Testing Software running on a virtual Windows machine on a Linux PC called array control PC. All of those array control PCs are then supervised by a SWIMS control PC. We have developed an "array control software system", which runs on the array control PC to control the HAWAII-2RG Testing Software, and consists of a socket client and a dedicated server called device manager. The client runs on the SWIMS control PC, and the device manager runs on the array control PC. An exposure command, issued by the client on the SWIMS control PC, is sent to the multiple device managers on the array control PCs, and then multiple HAWAII-2RGs are driven simultaneously. Using this system, we evaluate readout noise performances of the detectors, both in a test dewar and in a SWIMS main dewar. In the test dewar, we confirm the readout noise to be 4.3 e(-) r.m.s. by 32 times multiple sampling when we operate only a single HAWAII-2RG, whereas in the case of simultaneous driving of two HAWAII-2RGs, we still obtain sufficiently low readout noise of similar to 10 e(-) r.m.s.. In the SWIMS main dewar, although there are some differences between the detectors, the readout noise is measured to be 4.1-4.6 e(-) r.m.s. with simultaneous driving by 64 times multiple sampling, which meets the requirement for background-limited observations in J band of similar to 14 e(-) r.m.s..