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Interplanetary Lasers

Interplanetary Lasers. Free space optical communications. Joss Hawthorn, Jeremy Bailey, Andrew McGrath Anglo-Australian Observatory. This Presentation. Illustrating the current communications problem Cost advantages of optical solution Reasons for an Australian involvement.

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Interplanetary Lasers

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  1. Interplanetary Lasers Free space optical communications Joss Hawthorn,Jeremy Bailey,Andrew McGrath Anglo-Australian Observatory

  2. This Presentation • Illustrating the current communications problem • Cost advantages of optical solution • Reasons for an Australian involvement

  3. Exploration of Mars • Highlights the communications problem • Long term and substantial past and continuing international investment

  4. Exploration of Mars • 1960 Two Soviet flyby attempts • 1962 Two more Soviet flyby attempts,Mars 1 • 1964 Mariner 3, Zond 2 • 1965 Mariner 4 (first flyby images) • 1969 Mariners 6 and 7 • 1971 Mariners 8 and 9 • 1971 Kosmos 419, Mars 2 & 3 • 1973 Mars 4, 5, 6 & 7 (first landers) • 1975 Viking 1, 1976 Viking 2

  5. Exploration of Mars • 1988 Phobos 1 and 2 • 1992 Mars Observer • 1996 Mars 96 • 1997 Mars Pathfinder, Mars Global Surveyor • 1998 Nozomi • 1999 Climate Orbiter, Polar Lander and Deep Space 2 • 2001 Mars Odyssey

  6. Planned Mars Exploration • 2003 Mars Express • 2004 Mars Exploration Rovers • 2005 Mars Reconnaissance Orbiter • 2007+ Scout Missions 2007 • 2009 Smart Lander, Long Range Rover • 2014 Sample Return

  7. Interplanetary Communication • Radio (microwave) links, spacecraft to Earth • Newer philosophy - communications relay (Mars Odyssey, MGS) • Sensible network topology • 25-W X-band (Ka-band experimental)<100 kbps downlink

  8. Communications Bottleneck • Current missions capable of collecting much more data than downlink capabilities (2000%!) • Currently planned missions make the problem 10x worse • Future missions likely to collect ever-greater volumes of data

  9. Communications Bottleneck • Increasing downlink rates critical to continued investment in planetary exploration

  10. Communications Bottleneck • NASA presently upgrading DSN • NASA's perception of the problem is such that they are considering an array of 3600 twelve-metre dishes to accommodate currently foreseen communications needs for Mars alone

  11. Communications Energy Budget • Consider cost of communications reduced to transmitted energy per bit of information received

  12. Communications Energy Budget • Assumptions: • information proportional to number of photons (say, 10 photons per bit) • diffraction-limited transmission so energy density at receiver proportional to (R/DT)-2 • received power proportional to DR2 • photon energy hc /  • So:Cost proportional to R2/ (DT2DR2)

  13. Communications Energy Budget Cost proportional to R2/ (DT2DR2) X-band transmitter  ~ 40 mm Laser transmitter  ~ 0.5-1.5 m Assuming similar aperture sizes and efficiencies, optical wins over microwave by > 3 orders of magnitude

  14. Long-term Solution • Optical communications networks

  15. Long-term Solution • Optical communications networks

  16. Long-term Solution • Optical communications networks • Advantages over radio • Higher modulation rates • More directed energy • Analagous to fibre optics vs. copper cables

  17. Lasers in Space • Laser transmitter in Martian orbit with large aperture telescope

  18. Lasers in Space • Laser transmitter in Martian orbit with large aperture telescope

  19. Lasers in Space • Laser transmitter in Martian orbit with large aperture telescope • Receiving telescope on or near Earth • Preliminary investigations suggest ~100Mbps achievable on 10 to 20 year timescale • Enabling technologies require accelerated development

  20. Key Technologies • Suitable lasers • Telescope tracking and guiding • Optical detectors • Cost-effective large-aperture telescopes • Atmospheric properties • Space-borne telescopes

  21. Optical spacecraft comms • ESA have already run intersatellite test • NASA/JPL and Japan presently researching the concept and expect space-ground communications tests in the near future

  22. An Australian Role • Australian organisations have unique capabilities in the key technologies required for deep space optical communications links • Existing DSN involvement • High-power, high beam quality lasers • Holographic correction of large telescopes • Telescope-based instrumentation • Telescope tracking and guiding

  23. The University of Adelaide • Optics Group, Department of Physics and Mathematical Physics • High power, high beam quality, scalable laser transmitter technology • Holographic mirror correction • Presently developing high power lasers and techniques for high optical power interferometry for the US Advanced LIGO detectors

  24. Anglo-Australian Observatory • Telescope technology • Pointing and tracking systems • Atmospheric transmission (seeing, refraction) • Cryogenic and low noise detectors • Narrowband filter technology

  25. Australian Centre for Space Photonics • Manage a portfolio of research projects in the key technologies for an interplanetary optical communications link • Work in close collaboration with overseas organizations such as NASA and JPL

  26. Australian Centre for Space Photonics • Take advantage of unique Australian capabilities • Australian technology critical to deep space missions • Continued important role in space FOR MORE INFO... http://www.aao.gov.au/lasers

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