Corner Cube Retroreflector and Smart Dust

Swedishoo from Chemtrail and Company III   Corner Cube Retroreflector and Smart Dust Posted 7-22-2001 00:10 When given 5 reasons proving we went to the moon, the 5th listed was becasue we left reflectors on the surface. Reason #5 -- Things Left Behind on the MoonApollo astronauts left something behind on the Moon that we can see from Earth -- small mirrors called "corner cube retroreflector arrays." The first retroreflector was positioned on the Moon in 1969 by the Apollo 11 astronauts so that it would point toward Earth and be able to reflect pulses of laser light fired from our planet. Because the retroreflectors require no power, they are still operating normally more than 30 years after Neil Armstrong set foot on the Moon. Scientists from around the world regularly bounce laser pulses from these distant reflectors to learn more about tides, the Moon's rotation, Einstein's theory of relativity, and much more. The Soviet Union and France also deposited a retroreflector on the Moon using an unmanned spacecraft, Lunakhod 2. That device was not placed on the lunar surface as carefully as the Apollo astronauts were able to situate their retroreflectors. As a result, the Lunakhod 2 mirror produces a weaker laser echo than the smaller Apollo reflectors -- devices that benefited from the personal attention of humans on the Moon. Now thirty years later, the Corner Cube Retroreflector has made a big come back. At a stationary port like Mars or Venus? No, in a Dust Mote. Not dust as we know it, but a mechanical dust mote with reflectors. It's called Smart Dust. MEMS Corner Cube Retroreflector for Smart Dust Lixia Zhou (Professors Joseph M. Kahn and Kristofer S. J. Pister) (DARPA) DABT63-98-1-0018 The micromachined corner cube retroreflector (CCR) is a key component in the free-space optical communication links used by Smart Dust [1]. An ideal CCR consists of three mutually perpendicular mirrors and, when illuminated, reflects light back in the direction of the source. By misaligning one mirror in the CCR, a Smart Dust mote can transmit a modulated signal back to the interrogating source, without having to emit any energy. This CCR-based passive optical transmission system offers the advantages of small size and low power consumption, and can be fabricated using the same processes used to make MEMS sensors in the dust mote. Our goal is to optimize the performance of MEMS CCRs by improving the mirror flatness and orthogonality, and by increasing the mirror reflectivity. Current CCRs (see figure) have been fabricated using the MCNC MUMPS process. This process yields structural polysilicon layers having significant residual stress, leading to mirror curvature. This process provides a gold layer, which our current CCRs have relied upon to achieve high mirror reflectivity. However, this relatively thick gold layer causes additional mirror curvature. We are considering fabricating future CCRs in the Sandia MEMS process, which should provide much flatter mirrors. We will apply a thin reflective aluminum coating, minimizing coating-induced mirror curvature. We will also attempt to improve mirror orthogonality by modifying the CCR design. Finally, we will characterize the performance of the CCRs, comparing the measured performance to the predictions of detailed numerical simulations that take account of diffraction, mirror curvature, and mirror misalignment [2]. http://buffy.eecs.berkeley.edu/IRO/Summary/00abstracts/lzhou.1.html Christy