New Hi Tech Ultimate Infrared Laser Spintronics Wireless Satellite Multimedia Communications System Project.
NEW HI TECHNOLOGY ULTIMATE INFRARED LASER SPINTRONICS WIRELESS SATELLITE MULTIMEDIA COMMUNICATIONS SYSTEM PROJECT.
How It Works: NASA’s Experimental Laser Communication System
NASA recently funded an experimental project to put a laser-based communication system in Earth orbit. Laser communication has the potential to provide much more information than radio-based communication, creating the possibility that astronauts could one day stream HD video across the solar system.
By Adam Hadhazy
September 6, 2011 6:00 PM Text Size: A . A . A
NASA has announced plans to test a laser communication system in space that could make today's radio systems look as outdated as dial-up Internet. Lasers can transmit data at rates 10 to 100 times faster than radio. By encoding information into laser-based communications, future satellites, rovers and astronauts could not only send back postcard snapshots from their destinations, but also stream high-quality video from across the solar system.
"The Neil Armstrong of an asteroid or a Mars landing is going to be able to transmit back to Earth at 3D-HDTV—or whatever it is we have then—and the higher data rate will allow that sort of quality," says David Israel, principal investigator for the Laser Communication Relay Demonstration (LCRD). The LCRD received the greater part of a $175 million NASA award for three tech proposals in August. Israel, who's with the Goddard Space Flight Center in Greenbelt, Md., says the goal is to have the technology ready for use in perhaps a decade.
So what will the demonstration actually look like? The LCRD mission includes three main parts: a payload that will piggyback on a commercial satellite in 2015 to reach Earth orbit, plus two ground stations in Hawaii and California. Mission operators will zap lasers between the satellite package and the ground stations for a few years, experimenting with how to optimize the transmission process. Unlike the laser beams you see in the artist's impression of LCRD, though, the lasers will actually be invisible. The frequency of light used falls in the near-infrared range, just beyond the range our eyes can see.
The infrared light used in LCRD offers great promise for data transmission. Its wavelength is orders of magnitude shorter than radio waves, and a shorter wavelength packs in more waves per unit of time and space, meaning it can carry more bits of information. Moreover, a shorter wavelength also means far better signal strength. Think of a focused flashlight beam as opposed to a radio station that scatters in all directions. "Laser beams diverge much more gradually than radio wave beams, concentrating power into a much narrower spot," says John Moores, LCRD co-investigator and an assistant group leader of optical communications technology at MIT.
The upshot: Lasers communications systems could offer the same data rate as radio communications but use equipment that takes up less space and consumes less energy. Or put another way: With the same space and energy that radio systems use, laser communications could send much more data.
However, the beamlike quality of lasers also requires great precision. A laser's cone of transmission must be aimed at a receiver, so LCRD will be perfecting its tracking technologies to keep the sending and receiving laser terminals in sync. "Once the two terminals see light coming from each other, they know where to point, and it is relatively straightforward to keep both beams cooperatively tracked," Moores says. Those terminals that receive the transmissions would look less like the parabolic dishes that collect radio waves and more like optical telescopes—think of the way the Hubble Space Telescope is shaped to gather light from one particular direction in the sky.
But there's another problem for laser communications that is not as readily solvable: the weather. Radio waves travel right on through clouds, gases and particulates, but those obstacles scatter near-infrared light and would scramble transmissions. "The biggest challenge to an operational [laser] system is the clouds in the atmosphere," Israel says.
Thus, one the main goals of LCRD is to find out just how many ground-receiving stations are needed so that at least one can communicate with an orbiting satellite or deep-space probe at all times. (One option for a future laser communication system would be to place relay stations in orbit that could store the deluge of data beamed from distant spacecraft until the line-of-sight with the ground terminal opens up.) Also, LCRD operators will play with interrupting transmissions midstream to see if they can resume them once the clouds roll away. The experiments will try out two different methods for encoding information in lasers—varying the pulses of light, or the light's phase patterns. Israel's team will also maintain a standard radio frequency link between the satellite and the ground so mission operators can control and monitor the status of the experiment.
Besides sending pretty pictures of Marscapes back to Earth much faster, laser communications could change the way NASA runs its solar system missions. For instance: Satellites above Earth use hyperspectral cameras to gather data across different wavelengths of light, peering inside hurricanes and tracking wildfires. Because of their proximity to ground-receiving stations, these satellites can transmit loads of data. But over millions of miles of interplanetary space, those signals lose their coherence and strength, and so it would take ages to download such sensitive measurements of, say, storms in Jupiter's atmosphere. Israel says using laser communications could provide the bandwidth for hyperspectral camera data from afar, while also freeing up the energy and payload volume to allow for sending better equipment in the first place. That's just one example. "There are things that we can't even envision yet," Israel said.
NASA will continue to try to squeeze more juice out of traditional microwave and radio frequency communication. But physics will only go so far, Israel said, so the future is optical. "We'll have done every trick we can think of—coding and data compression and fancy modulation—and we'll have built antennas as big as we can make them," Israel says. "If all goes well, we'll prove this [laser] technology and get to the next level of space communications."
Laser Communications Relay Demonstration (LCRD)
"Science and technology multiply around us. To an increasing extent, they dictate the languages in which we speak and think. Either we use those languages, or we remain mute."
-- J.G. Ballard, 20th century British futurist
Radio-based space communications have been the convention since the days of NASA's Mercury and Gemini programs, but even with dramatic improvements to the technology in the last half-century, radio communications are challenged by modern mission needs, which call for significantly higher data rates, or current levels of performance requiring a lot less mass and power -- critical resources on any spacecraft.
Now the Laser Communications Relay Demonstration (LCRD) mission proposes to revolutionize the way we send and receive data, video and other information, using lasers to encode and transmit data at rates 10 to 100 times faster than radio, or at the same data rate as today's fastest RF radios, but using significantly less mass and power. The wavelength of the laser light is orders of magnitude shorter than radio waves, meaning the energy is not spread out as much as it travels through space. For example, a typical Ka-Band signal from Mars spreads out so much that the diameter of the energy when it reaches Earth is larger than the Earth's diameter. A typical optical signal, however, will only spread over the equivalent of a small portion of the United States; thus there is less energy wasted. The shorter wavelength also means there is significantly more bandwidth available for an optical signal, while radio systems have to increasingly fight for a very limited bandwidth.
Such a leap in technology could deliver video and high-resolution measurements from spacecraft over planets across the solar system -- permitting researchers to make detailed studies of conditions on other worlds the way we now track hurricanes and other climate and environmental changes here on Earth. The Laser Communications Relay Demonstration leverages significant work done by MIT Lincoln Laboratory in Lexington, Mass., for NASA's Lunar Laser Communications Demonstration, which in turn built upon the pioneering work done for NASA's Mars Laser Communications Demonstration.
The LCRD team is led by NASA's Goddard Space Flight Center in Greenbelt, Md. Partners include NASA's Jet Propulsion Laboratory in Pasadena, Calif., and MIT Lincoln Laboratory. The team is working to fly and validate a reliable, capable and cost-effective optical communications technology directly applicable to the next generation of NASA's space communications network, serving both near-Earth and deep-space mission requirements. The payload will be flown to orbit on a commercial satellite. Mission operators at ground stations in Hawaii and California will test its invisible, near-infrared lasers, beaming data to and from the satellite as they refine the transmission process, study different encoding techniques and perfect tracking systems. They also will study the effects of clouds and other disruptions on communications, studying mitigating solutions including relay operations in orbit or backup receiving stations on the ground.
The investigation will hold its preliminary design review in 2013 and conduct ground technology validation testing in 2014. It will fly as a commercial satellite payload in 2016.
LCRD: Key Mission Facts
- The Laser Communications Relay Demonstration mission is NASA’s first, long-duration optical communications mission.
- The demonstration will use lasers to encode and transmit data at rates 10-to-100-times faster than radio -- or at the same data rate as today's fastest RF radios, but using significantly less mass and power.
- The project will help mature concepts and deliver technologies applicable to both near-Earth and deep-space communication network missions.
- The investigation will enable a variety of robust future science and exploration missions -- providing a higher data rate, and delivering more accurate navigation capabilities with reduced size, weight and power requirements.
“Spintronics” Places New Twist on Nanotechnology
Nashville Tech Story (9/4/2009)
As technology continues to get smarter, faster and even smaller, it always seems that somewhere in the discussion falls nanotechnology. Researchers are working to reduce the size of computer systems, while making them more reliable and environmentally friendly. If successful, computer systems would be equipped with data storage that would be completely stable and would require the use of less energy. How is this possible?
“Spintronics,” is a new technology that is being researched that exploits magnetic ’spin’ properties of individual molecules or atoms and electronic charges. Combine “spintronics” with nanotechnology and a solution called molecular “nanospintronics” comes to light, which is currently being investigated by researchers.
The initial goal of “spintronic” technology starts out small, with the shrinking of computer systems, but this development has far more potential. Created through a collaboration between London’s Centre for Nanotechnology and two of the top universities in China, Peking University and Tsinghua University, “spintronics” has begun to take a place in the environmental and wireless communications markets.
Scientists "waltz" closer to using spintronics in computing
Spinhelix rendering. Credit: IBM Research - Zurich
(Phys.org) -- Aiming to use electron spins for storing, transporting and processing information, researchers from IBM and scientists at ETH Zurich, a leading European university, today revealed the first-ever direct mapping of the formation of a persistent spin helix in a semiconductor.
Until now, it was unclear whether or not electron spins possessed the capability to preserve the encoded information long enough before rotating. Unveiled in the peer-reviewed journal Nature Physics, scientists from IBM Research and the Solid State Physics Laboratory at ETH Zurich demonstrated that synchronizing electrons extends the spin lifetime of the electron by 30 times to 1.1 nanoseconds -- the same time it takes for an existing 1 GHz processor to cycle.
Today's computing technology encodes and processes data by the electrical charge of electrons. However, this technique is limited as the semiconductor dimensions continue to shrink to the point where the flow of electrons can no longer be controlled. Spintronics could surmount this approaching impasse by harnessing the spin of electrons instead of their charge.
This new understanding in spintronics not only gives scientists unprecedented control over the magnetic movements inside devices but also opens new possibilities for creating more energy efficient electronics.
In this photo, IBM scientists Matthias Walser (left) and Gian Salis who published the finding with C. Reichl and W. Wegscheider from ETH Zurich in the 12 August 2012 online edition of Nature Physics.
The Spintronics Waltz
A previously unknown aspect of physics, the scientists observed how electron spins move tens of micrometers in a semiconductor with their orientations synchronously rotating along the path similar to a couple dancing the waltz, the famous Viennese ballroom dance where couples rotate.
Dr. Gian Salis of the Physics of Nanoscale Systems research group at IBM Research – Zurich explains, "If all couples start with the women facing north, after a while the rotating pairs are oriented in different directions. We can now lock the rotation speed of the dancers to the direction they move. This results in a perfect choreography where all the women in a certain area face the same direction. This control and ability to manipulate and observe the spin is an important step in the development of spin-based transistors that are electrically programmable."
How it Works
IBM scientists used ultra short laser pulses to monitor the evolution of thousands of electron spins that were created simultaneously in a very small spot. Atypically, where such spins would randomly rotate and quickly loose their orientation, for the first time, the scientists could observe how these spins arrange neatly into a regular stripe-like pattern, the so-called persistent spin helix.
The concept of locking the spin rotation was originally proposed in theory back in 2003 and since that time some experiments have even found indications of such locking, but until now it had never been directly observed.
IBM scientists imaged the synchronous 'waltz' of the electron spins by using a time-resolved scanning microscope technique. The synchronization of the electron spin rotation made it possible to observe the spins travel for more than 10 micrometers or one-hundredth of a millimeter, increasing the possibility to use the spin for processing logical operations, both fast and energy-efficiently.
The reason for the synchronous spin motion is a carefully engineered spin-orbit interaction, a physical mechanism that couples the spin with the motion of the electron. The semiconductor material called gallium arsenide (GaAs) was produced by scientists at ETH Zurich who are known as world-experts in growing ultra-clean and atomically precise semiconductor structures. GaAs is a III/V semiconductor commonly used in the manufacture of devices such as integrated circuits, infrared light-emitting diodes and highly efficient solar cells.
Transferring spin electronics from the laboratory to the market still remains a major challenge. Spintronics research takes place at very low temperatures at which electron spins interact minimally with the environment. In the case of this particular research IBM scientists worked at 40 Kelvin (-233 C, -387 F).
This work was financially supported by the Swiss National Science Foundation through National Center of Competence in Research (NCCR) Nanoscale Sciences and NCCR Quantum Science and Technology.
More information: The scientific paper entitled "Direct mapping of the formation of a persistent spin helix" by M.P. Walser, C. Reichl, W. Wegscheider and G. Salis was published online in Nature Physics, DOI 10.1038/NPHYS2383 (12 August 2012).
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