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We present the scientific gain enjoyed by client instruments when NFIRAOS is cooled. If NFIRAOS is cooled to -24◦ C, the background contribution of NFIRAOS will not exceed 15% of the background from sky plus TMT (for a telescope build to current requirements on Mauna Kea). If cooled further to -30◦ C, the K-band inter-OH background-limited exposure times could decrease by more than 7%. We evaluate these gains achieved by cooling NFIRAOS in light of increased technical risks and costs., 1st AO4ELT conference - Adaptive Optics for Extremely Large Telescopes, June 22-26, 2009, Paris, France

Sodium Laser Guide Stars (LGS) induce optical aberrations in adaptive optics (AO) systems.The artificial star is elongated due to the sodium layer thickness, and the variations of thesodium layer altitude and atom density profile induce errors on centroid measurements ofelongated spots. In AO systems, these errors generate spurious optical aberrations, termed LGSaberrations, especially with ELTs for which the spot elongation is greater. According toanalytical models and experimental results obtained with the University of Victoria LGS benchdemonstrator, we characterized the main LGS aberrations and studied two options to mitigatethem: the Radial Thresholding and the temporal filtering., 1st AO4ELT conference - Adaptive Optics for Extremely Large Telescopes, June 22-26, 2009, Paris, France

We outline a concept design for an FPGA based real-time adaptive optics controller that meets the requirements of the Thirty Meter Telescope (TMT) first light Narrow Field Infrared Adaptive Optics system (NFIRAOS). The data and processing rates for NFIRAOS are very demanding. It has pixel input rates of about 5 GB/s and processing requirements of order several hundred GMACs. The hardware proposed is programmable and flexible, and can be used in other AO systems. It is based on a custom FPGA compute blade housed with COTS interface and computer boards in an ATCA chassis. The system accepts data from eight wave front sensors at 10 Gbps each via thirty-two serial front panel data ports (sFPDPs). Nine FPGA blades provide about 2.7 TMAC/s of processing power and are used to perform pixel processing, tomography and deformable mirror fitting. Two general-purpose computer boards are used to perform background processing and control, each with three Intel L7400 dual core processors. The system is also capable of storing 90 TB of telemetry data at rate of 3.5 GB/s., 1st AO4ELT conference - Adaptive Optics for Extremely Large Telescopes, June 22-26, 2009, Paris, France