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Design and performance data on two laser transmitters for spaceborne laser ranging are presented. The first laser uses a master oscillator/power amplifier configuration consisting of a diode pumped Nd:YAG slab ring and a multipass diode pumped slab amplifier which can operate at 40 Hz for 109 shots. The other laser is a diode pumped Nd:YAG slab standing wave oscillator which operates at 10 Hz for 0.6 X 109 shots. For submillimeter laser ranging, one laser operates in a mode-locked cavity-dumped mode to produce 180 mJ, 40 psec pulses at 1.064 micrometers . For altimetry, the same laser operates in a Q-switched mode to produce 700 mJ, 3.5 nsec pulses at 1.064 micrometers . Second and third harmonic generators generate 0.532 micrometers and 0.355 micrometers for ranging at 2 wavelengths to terrestrial targets with inherent atmospheric correction. The oscillator utilizes a ring resonator configuration with active mode locking, active Q-switching, active pre-lase stabilization, and active cavity dumping. The mode-locked output pulsewidth is 40 psec. A second oscillator mode, remotely selectable, produces 3.5 nsec pulses. Stabilization and alignment is done with real-time feedback during the mission. The amplifier is a multipass slab. Parasitic (ASE) oscillations are suppressed despite very high stored energy in the amplifier medium. The second laser transmitter is a linearly polarized Q-switched Nd:YAG slab laser cavity. The Nd:YAG is pumped by a 44-bar array of AlGaAs laser diodes. It produces 45 mJ, 10 nsec, pulses at 1064 nm and will operate at 10 Hz for the two-earth-year on-orbit lifetime. The expected operation will produce 6 X 108 shots during the mission. The laser transmitter will consume 15 watts, which represents a 3 wall plug efficiency. The laser transmitter has a beam divergence of 0.25 mrad and will maintain boresight to the receiver within 100 (mu) rad. The lasers have been specifically developed for ultra-high reliability for use in space exploration of the earth and nearby planets. Applications include planetary altimetry of Mars (MOLA) and earth (GLRS), as well as space geodesy, navigation, and tracking.
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