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LGS AO photon return simulations and laser requirements for the Gemini LGS AO program C. d'Orgeville, F. Rigaut and B. L. Ellerbroek Gemini Observatory, 670 N. A'Ohoku Place, Hilo, HI 96720...

Gemini Preprint #55...

LGS AO photon return simulations and laser requirements for the Gemini LGS AO program...

C line d'Orgeville , Fran ois Rigaut, and Brent L. Ellerbroek Gemini Observatory, 670 N. A'Ohoku Place, Hilo, HI 96720...

Laser Guide Star Adaptive Optics system operation at an 8-m class telescope like Gemini North and Gemini South require minimum laser output power in the 10 W range. Since each additional Watt of laser power increases the laser purchase and operational costs, it is highly desirable to understand how laser parameters can be optimized in order to decrease the total laser power requirement. This paper provides some tools to calculate the output power requirement of a candidate laser system and its optimized parameters in the case of continuous wave lasers and high repetition rate pulsed lasers. Laser power requirements for Gemini North and Gemini South are given as examples of this calculation. Keywords Laser Guide Star Adaptive Optics, photon return, sodium/laser interaction efficiency, laser power requirements...

1. INTRODUCTION...

Gemini North and Gemini South, two IR-optimized 8-m telescopes respectively located at the summit of Mauna Kea, Hawaii, and Cerro Pachon, Chile, will soon be equipped with both Natural Guide Star (NGS) and Laser Guide Star Adaptive Optics (LGS AO) systems. The Gemini 8-m Telescopes Project LGS AO program includes three generations of laser systems to be implemented on one or the other sites. Providing funding is secured a 3 W continuous wave (CW) commercial dye laser will be the first laser system to come on line in mid-2001. Teamed with a curvature-LGS AO system 1, this laser system will enable LGS AO operation at Gemini South. The second, 10 W-class laser system will be associated with ALTAIR 2, the altitude conjugated- NGS AO system at Gemini North. The laser system will complete ALTAIR's upgrade to a LGS AO facility instrument in 2003. Last but not least, the third-generation, 5 x 10 W-class laser system will equip the proposed five-LGSs Multi-Conjugated Adaptive Optics (MCAO) system 3, 4, 5, 6, 7, the Gemini South facility AO module scheduled to come on line in 2004 pending definitive approval. All three LGS systems rely on the excitation of mesospheric sodium atoms to create the artificial wavefront referen...

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