MMT Real-Time-Reconstructor

Hardware CPU: Quad-core Xeon 2.66 GHz RAM: 2GB OS: CentOS with RTAI real-time extensions Frame Grabber: EDT PCI-DV Serial link to tip/tilt computer

Requirements NGS – 216 subaperture slopes – R matrix – 216 * 45 – Up to 1kHz LGS – 600 subaperture slopes (averaged by 5 in GLAO) – R matrix – 120 * 55 – Up to 600 Hz

Operation AO system Initialization by separate control computer AO loop turned on but left open (no commands to DM) Loop closed – System gain automatically set to zero User updated gain increased to finite number

Inside RTR during closed loop Read frame from WFS camera A look up table (LUT) maps pixels to subapertures Background subtraction of subapertures Calculation of slopes via center of mass Linearization using LUT – 1024 element vector Read tip/tilt signal from tilt computer Concatenate slopes from WFS and T/T

Inside RTR cont. Matrix multiply slopes by R to get DM delta commands Read in DM position Final commands sent to mirror: Delta command * user gain – 0.1 * modal filter * DM position (modal filter is 1 – control space of R)

‘Old’ RTR layout