Mesospheric Metals for Guide Star Generation

Abstract

Elemental Na has been the tracer of choice for the generation of high altitude (mesospheric) guide stars because of its relatively large natural abundance and large absorption cross section. Dye based systems using Na are currently under development for several large aperture telescopes. However, robust solid state laser technology to generate high power narrow linewidth light at 589 nm has progressed slowly. Here we consider both the tracer and the transmitter technology and show that using either the K D1 line at 769 nm or the 372 nm line of Fe (a 5D-z 5F°) for the tracer may provide robust solutions until solid state Na transmitter technology can be more fully developed. The comparable performance is primarily due to the fact that both lines can be generated with existing solid state materials (Alexandrite, Ti:Sapphire).