'Houston, we have a modem': Scientists reveal laser communication could be used to give astronauts broadband on the MOON
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Scientists have proved that the sky is certainly not the limit for the internet, by showing it could be possible to get broadband on the moon.
A team of researchers from the Massachusetts Institute of Technology's (MIT) Lincoln Laboratory demonstrated for the first time that a the technology exists to provide space dwellers with the connectivity we all enjoy here on Earth.
It could allow large data transfers and even high-definition video streaming.
Scientists at MIT say they have devised a way to transfer large amounts of data quickly and easily across the vast expanse of space. This could provide future astronauts with a 'broadband network' on the moon. This is a computer-aided design drawing of the optical module on the satellite showing the telescope and gimbal (pivoted support)
The team has been conducting tests transferring data from the earth to the moon, with specialist laser-based communication equipment.
HOW 'SPACE BROADBAND' WORKS
A ground terminal at White Sands, New Mexico, uses four separate telescopes to send the uplink signal to the moon.
Each telescope is about six inches (15 centimetres) in diameter and fed by a laser transmitter that sends information coded as pulses of invisible infrared light.
The reason for the four telescopes is that each one transmits light through a different column of air that experiences different bending effects from the atmosphere, Stevens said.
This increases the chance that at least one of the laser beams will interact with the receiver, which is mounted on a satellite orbiting the moon.
This receiver uses a slightly narrower telescope to collect the light, which is then focused into an optical fibre similar to those used in terrestrial fibreoptic networks.
From there, the signal is amplified about 30,000 times. A photodetector converts the pulses of light into electrical pulses that are in turn converted into data bit patterns that carry the transmitted message.
At the Conference on Lasers and Electro-Optics (Cleo) 2014, held between 8 and 13 June in San Jose, California the team will present new details and the first comprehensive overview of the 'on-orbit performance' of their record-shattering laser-based communication uplink between the moon and Earth, which beat the previous record transmission speed by a factor of 4,800.
Earlier reports have stated what the team accomplished, but have not provided the details of the implementation.
Mark Stevens of MIT Lincoln Laboratory said: 'This will be the first time that we present both the implementation overview and how well it actually worked.
'The on-orbit performance was excellent and close to what we'd predicted, giving us confidence that we have a good understanding of the underlying physics.'
The team made history last year when their Lunar Laser Communication Demonstration (LLCD) transmitted data over the 239,000 miles (385,000) kilometers between the moon and Earth at a download rate of 622 megabits per second, faster than any radio frequency (RF) system.
They also transmitted data from Earth to the moon at 19.44 megabits per second, a factor of 4,800 times faster than the best RF uplink ever used.
Nasa's Lunar Laser Communication Demonstration (LLCD) involved two-way laser communication between the Ladee spacecraft and Earth. It showed that such a method could transmit huge amounts of data. This means, for example, HD video could be transmitted to and from deep space
Mr Stevens added: 'Communicating at high data rates from Earth to the moon with laser beams is challenging because of the 400,000-kilometer distance spreading out the light beam.
'It's doubly difficult going through the atmosphere, because turbulence can bend light-causing rapid fading or dropouts of the signal at the receiver.
'We demonstrated tolerance to medium-size cloud attenuations, as well as large atmospheric-turbulence-induced signal power variations, or fading, allowing error-free performance even with very small signal margins.'
While the LLCD design is directly relevant for near-Earth missions, the team predicts that it's also extendable to deep-space missions to Mars and the outer planets.
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