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1 NASA to demonstrate communications via laser beam on Mon Oct 31, 2011 7:48 am

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It
currently takes 90 minutes to transmit high-resolution images from
Mars, but NASA would like to dramatically reduce that time to just
minutes. A new optical communications system that NASA plans to
demonstrate in 2016 will lead the way and even allow the streaming of
high-definition video from distances beyond the Moon. This dramatically
enhanced transmission speed will be demonstrated by the Laser
Communications Relay Demonstration (LCRD), one of three projects
selected by NASA's Office of the Chief Technologist (OCT) for a trial
run. To be developed by a team led by engineers at the NASA Goddard
Space Flight Center in Greenbelt, Md., LCRD is expected to fly as a
hosted payload on a commercial communications satellite developed by
Space Systems/Loral, of Palo Alto, Calif.

"We want to take NASA's communications capabilities to the next
level," said LCRD Principal Investigator Dave Israel, who is leading a
multi-organizational team that includes NASA's Jet Propulsion
Laboratory, Pasadena, Calif. and Lincoln Laboratory at the
Massachusetts Institute of Technology, Cambridge, Mass. Although NASA
has developed higher data-rate radio frequency systems,
data-compression, and other techniques to boost the amount of data that
its current systems can handle, the Agency's capabilities will not keep
pace with the projected data needs of advanced instruments and future
human exploration, Israel added.

"Just as the home Internet user hit the wall with dial-up, NASA is
approaching the limit of what its existing communications network can
handle," he said.

The solution is to augment NASA's legacy radio-based network, which
includes a fleet of tracking and data relay satellites and a network of
ground stations, with optical systems, which could increase data rates
by anywhere from 10 to 100 times. "This transition will take several
years to complete, but the eventual payback will be very large
increases in the amount of data we can transmit, both downlink and
uplink, especially to distant destinations in the solar system and
beyond," said James Reuther, director of OCT's Crosscutting Technology
Demonstrations Division.

First Step

The LCRD is the next step in that direction, Israel said, likening
the emerging capability to land-based fiber-optic systems, such as
Verizon's FiOS network. "In a sense, we're moving FiOS to space."

To demonstrate the new capability, the Goddard team will encode
digital data and transmit the information via laser light from
specially equipped ground stations to an experimental payload hosted on
the commercial communications satellite.

The payload will include telescopes, lasers, mirrors, detectors, a
pointing and tracking system, control electronics, and two different
types of modems. One modem is ideal for communicating with deep space
missions or tiny, low-power smallsats operating in low-Earth orbit. The
other can handle much higher data rates, particularly from
Earth-orbiting spacecraft, including the International Space Station.
"With the higher-speed modem type, future systems could support data
rates of tens of gigabits per second," Israel said.

Once the payload receives the data, it would then relay it back to
ground stations now scheduled to operate in Hawaii and Southern
California.

The multiple ground stations are important to demonstrating a fully
operational system, Israel said. Cloud cover and turbulent atmospheric
conditions impede laser communications, requiring a clear line of sight
between the transmitter and receiver. If bad weather prevents a signal
from being sent or received at one location, the network could hand
over the responsibility to one of the other ground stations or store it
for later retransmission.

The demonstration is expected to run two to three years.

Follow-On to LADEE Experiment

The project isn't NASA's first foray into laser communications.
Goddard engineers are now developing a laser communications payload for
NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE), which
the Agency plans to launch in 2013 to characterize the Moon's wisp-thin
atmosphere and dust environment. The main goal of the LADEE experiment
is proving fundamental concepts of laser-based communications and
transferring up to 622 megabits per second, which is about five times
the current state-of-the-art from lunar distances.

However, the LADEE payload, called the Lunar Laser Communications
Demonstration (LLCD), is equipped with only one modem, the lower-speed
model best suited for deep space communications. In addition, LADEE is
a short-duration mission. LLCD is expected to operate for only 16 days
of the LADEE mission, not enough time to demonstrate a fully
operational laser-communications network, Israel said.

"What we're trying to do is get ahead of the curve," Israel said.
"We want to get to the point where communications is no longer a
constraint on scientists who want to gather more data, but are worried
about getting their data back from space."]

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