interplanetary lasers joss hawthorn, jeremy bailey, andrew mcgrath anglo-australian observatory free...
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Interplanetary LasersInterplanetary Lasers
Joss Hawthorn,Jeremy Bailey,Andrew McGrath
Anglo-Australian Observatory
Free space opticalFree space optical communications communications
This PresentationThis Presentation
Illustrating the current communications problem
Cost advantages of optical solutionReasons for an Australian
involvement
Exploration of MarsExploration of Mars
Highlights the communications problem
Long term and substantial past and continuing international investment
Exploration of MarsExploration 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
Exploration of MarsExploration 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
Planned Mars ExplorationPlanned 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
Interplanetary CommunicationInterplanetary Communication
Radio (microwave) links, spacecraft to Earth
Newer philosophy - communications relay (Mars Odyssey, MGS)
Sensible network topology25-W X-band (Ka-band experimental)
<100 kbps downlink
Communications BottleneckCommunications 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 BottleneckCommunications Bottleneck
Increasing downlink rates critical to continued investment in planetary exploration
Communications BottleneckCommunications Bottleneck
NASA presently upgrading DSNNASA'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 BudgetCommunications Energy Budget
Consider cost of communications reduced to transmitted energy per bit of information received
Communications Energy BudgetCommunications Energy Budget
• 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 / (DT
2DR2)
Assumptions:
Communications Energy BudgetCommunications Energy Budget
Cost proportional to R2 / (DT2DR
2)
X-band transmitter ~ 40 mmLaser transmitter ~ 0.5-1.5 m
Assuming similar aperture sizes and efficiencies, optical wins over microwave by > 3 orders of magnitude
Long-term SolutionLong-term SolutionOptical communications networks
Long-term SolutionLong-term SolutionOptical communications networks
Long-term SolutionLong-term SolutionOptical communications networksAdvantages over radioHigher modulation ratesMore directed energyAnalagous to fibre optics vs. copper
cables
Lasers in SpaceLasers in SpaceLaser transmitter in Martian orbit
with large aperture telescope
Lasers in SpaceLasers in SpaceLaser transmitter in Martian orbit
with large aperture telescope
Lasers in SpaceLasers in SpaceLaser transmitter in Martian orbit with
large aperture telescopeReceiving telescope on or near EarthPreliminary investigations suggest
~100Mbps achievable on 10 to 20 year timescale
Enabling technologies require accelerated development
Key TechnologiesKey TechnologiesSuitable lasersTelescope tracking and guidingOptical detectorsCost-effective large-aperture
telescopesAtmospheric propertiesSpace-borne telescopes
Optical spacecraft commsOptical 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 RoleAn Australian RoleAustralian 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 AdelaideThe University of AdelaideOptics 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 ObservatoryAnglo-Australian ObservatoryTelescope technology Pointing and tracking systems Atmospheric transmission (seeing,
refraction) Cryogenic and low noise detectors Narrowband filter technology
Australian Centre for Space PhotonicsAustralian 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...
http://www.aao.gov.au/lasers
Australian Centre for Space PhotonicsAustralian Centre for Space Photonics
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