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

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

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

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

Exploration of Mars 1988 Phobos 1 and Mars Observer 1996 Mars Mars Pathfinder, Mars Global Surveyor 1998 Nozomi 1999 Climate Orbiter, Polar Lander and Deep Space Mars Odyssey

Planned Mars Exploration 2003 Mars Express 2004 Mars Exploration Rovers 2005 Mars Reconnaissance Orbiter Scout Missions Smart Lander, Long Range Rover 2014 Sample Return

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

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

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

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

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

Communications Energy Budget information proportional to number of photons (say, 10 photons per bit) diffraction-limited transmission so energy density at receiver proportional to ( R/D T ) -2 received power proportional to D R 2 photon energy hc / So: Cost proportional to R 2 / (D T 2 D R 2 ) Assumptions:

Communications Energy Budget Cost proportional to R 2 / (D T 2 D R 2 ) X-band transmitter ~ 40 mm Laser transmitter ~  m Assuming similar aperture sizes and efficiencies, optical wins over microwave by > 3 orders of magnitude

Long-term Solution Optical communications networks

Long-term Solution Optical communications networks

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

Lasers in Space Laser transmitter in Martian orbit with large aperture telescope

Lasers in Space Laser transmitter in Martian orbit with large aperture telescope

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

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

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

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

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

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

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

Take advantage of unique Australian capabilities Australian technology critical to deep space missions Continued important role in space FOR MORE INFO... Australian Centre for Space Photonics