Running Title: Laser and T/R optics

Keywords: SLR, Laser, Eye-safe

Lasers are one of major components in the KSP SLR system for generating a high power and ultra-short pulse. Transmission/Receiving(T/R) optics also plays an important roll the interface between the telescope and the photon detector. The laser and T/R optical system includes a diode pumped Nd:YAG laser, a regenerative amplifier, a double stage amplifier, T/R switch optics, beam expanders, filters and mirrors. All these temperature and dust-sensitive devices are located in the optical compartment of a trailer housing unit.

In the history of SLR systems, the first generation laser developed in 1960’s-70’s was a ruby laser. It was powerful but had a low pulse repetition rate and did not produce a short pulse width, resulting in inaccuracies of ranging measurements⁽¹⁾. It was generally regarded as unable to endure continuous and high efficient operation. Highly reliable laser operations and stable optics are two of the keys for a long-life, high performance SLR system. The systems which widely used in SLR and referred as the third generation system developed in 1980’s –1990’s uses a flash lamp pumping Nd:YAG laser that has a repetition rate of 5 to 10 Hz.

Regular maintenance of laser is a problem for un-manned SLR system, especially in human task such as alignment, adjustment of dye concentration and cleaning of the optical components that are necessary weekly or more often. A diode pumped laser uses a solid state pumping source to excite the laser medium efficiently and has come to commercially available as a very compact and rugged device. The KSP SLR uses diode pumped Nd:YAG laser for oscillator and regenerative amplifier that operates at small energy.

A Laser with higher repetition rates has the benefit of increasing full-rate data and of minimizing the time to form normal points (the means of sub-sets of the measurements about their overall mean of full-rate data) when the system is tracking the satellite.