This paper presents the finite element stress and distortion analysis completed on the receiver telescope lens of the Lunar
Orbiter Laser Altimeter (LOLA). LOLA is one of six instruments on the Lunar Reconnaissance Orbiter (LRO),
scheduled to launch in 2008. LOLA's main objective is to produce a high-resolution global lunar topographic model to
aid in safe landings and enhance surface mobility in future exploration missions. A receiver telescope captures the laser
pulses transmitted through a diffractive optical element (DOE) and reflected off the lunar surface. The largest lens of the
receiver telescope was modeled with solid elements and constrained in a manner consistent with the behavior of the
mounting configuration. Twenty-one temperature load cases were mapped to the nodes based on thermal analysis
completed by LOLA's lead thermal analyst, and loads were applied to simulate the preload applied from the ring flexure.
The thermal environment of the baseline design produces large radial and axial gradients in the lens. These large
gradients create internal stresses that may lead to part failure, as well as significant bending that degrades optical
performance. The high stresses and large distortions shown in the analysis precipitated a design change from BK7 glass
to sapphire.
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