Technical Concept of a European Laser Altimeter for Plane- Tary Exploration

In the past year, our team has developed an alternative concept for a high-performance Laser Altimeter for Planetary Exploration (LAPE) for a Mercury mission with parameters similar to the BepiColombo Mercury Planetary Orbiter mission. The instrument must be capable to operate in a harsh thermal environment. Its mass is required to be less than 10kg and the power consumption less than 20W. In order to avoid excessive thermal loading and to keep the weight down we have chosen to study the applicability of a small receiver telescope with 15cm aperture. The key features of this alternative altimeter concept are a high repetition rate microlaser and single photon detection by gated "Geigermode" APDs. The cw-operation of the pump laser diodes of the microlaser avoids power switching and also makes bulky capacitor banks unnecessary. These features lower the operation risk and mass requirements substantially. However, due to the high shot repetition rate the data processing becomes more complex and requires special provisions for binning and averaging of the data. The basic performance of our concept has been evaluated by simulation. This paper outlines critical aspects of the altimeter design and discusses some of the simulation results.