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Interplanetary precision laser could reach to Mars and beyond

Posted on July 15, 2013
Space-time diagram of active laser ranging between the Earth and a planet. In order to achieve long-distance laser ranging, the system uses active transceivers with lasers at both ends, so each end can see a much brighter signal than with passive transceivers. Credit: Chen, et al. ©2013 AIP Publishing LLC

Space-time diagram of active laser ranging between the Earth and a planet. In order to achieve long-distance laser ranging, the system uses active transceivers with lasers at both ends, so each end can see a much brighter signal than with passive transceivers. Credit: Chen, et al. ©2013 AIP Publishing LLC

Currently, precision laser ranging is limited to the Earth-Moon distance. These systems are based on passive laser ranging, so that the signal deteriorates as 1/R4 over distance R. In a new study, physicists have designed a system that has a range thousands of times this distance due to the fact that it is based on active laser ranging, where the signal deteriorates as only 1/R2. The new system also has the potential to achieve sub-millimeter accuracy, yielding an overall performance improvement that is more than three orders of magnitude better than today’s state-of-the-art space ranging systems.

The scientists, Yijiang Chen, Kevin M. Birnbaum, and Hamid Hemmati at the California Institute of Technology’s Jet Propulsion Laboratory in Pasadena, California, have published their paper on the long-range, high-precision laser system in a recent issue of Applied Physics Letters.

“In principle, this approach could be scaled up to any interplanetary distance by increasing the size of the telescopes,” Birnbaum told Phys.org. “We calculated that ranging from Earth to Mars or Jupiter should be achievable with quite modest telescopes of 1 m in diameter on Earth and 15 cm on the spacecraft.”

In the new laser ranging scheme, there is one transceiver at each end of the distance to be measured. Each transceiver transmits and receives laser pulses. The pulses are time tagged when transmitted and when received, and the time it takes the pulses to travel between transceivers is used to measure the distance between the transceivers. As the scientists explain, having these “active transceivers” is key to the long-distance range.

Read more at: Phys.org

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