GREENBELT, Md. – Neither wind, nor
clouds, nor even atmospheric turbulence
kept NASA’s Lunar Laser Communication
Demonstration (LLCD) from its mission
of providing error-free communications
to ground stations from lunar orbit, NASA
said recently in releasing results of the
30-day experiment.
“Throughout our testing, we did not
see anything that would prevent the
operational use of this technology in the
immediate future,” said Don Cornwell,
LLCD mission manager at NASA’s Goddard Space Flight Center in Greenbelt.
LLCD, which hitched a ride to lunar
orbit aboard the Lunar Atmosphere and
Dust Environment Explorer, known as
LADEE, was designed to confirm laser
communications capabilities from a
distance of almost a quarter of a million
miles. Besides demonstrating record-breaking data download and upload
speeds to the moon at 622 and 20 Mb/s,
respectively, LLCD also showed that it
could operate as well as any NASA radio
system. The sending and receiving of
high-definition video was proved with
a message from NASA administrator
Charlie Bolden, completing the trip to the
moon and back with only a few seconds
of delay.
LLCD demonstrated error-free communications during broad daylight, including
operating when the moon was to within
3° of the sun as seen from Earth, NASA
said. LLCD also demonstrated error-free
communications when the moon was low
on the horizon, less than 4°, as seen from
the ground station, which also demonstrated that wind and atmospheric turbulence did not significantly affect the system. LLCD even communicated through
thin clouds, an unexpected bonus.
LLCD also demonstrated the ability to
download data from the LADEE spacecraft itself. “We were able to download
LADEE’s entire stored science and spacecraft data [1 GB] in less than five minutes,
which was only limited to our 40-Mb/s
connection to that data within LADEE,”
Cornwell said. That feat would have taken
several days to complete using LADEE’s
onboard radio system.
LLCD proved the integrity of laser
technology to send not only error-free
data, but also uncorrupted commands and
telemetry or monitoring messages to and
from the spacecraft over the laser link,
NASA said.
The system also demonstrated the
ability to “hand off” the laser connection
from one ground station to another, just as
a cellphone does a hand-off from one cell
tower to another. An additional achievement was the ability to operate LLCD
without using LADEE’s radio at all.
“We were able to program LADEE to
awaken the LLCD space terminal and
have it automatically point and commu-
nicate to the ground station at a specific
time without radio commands,” Corn-
well said. “This demonstrates that this
technology could serve as the primary
communications system for future NASA
missions.”
NASA’s follow-on mission for laser
communications will be the Laser
Communications Relay Demonstration
(LCRD). Also managed at Goddard,
LCRD will demonstrate continuous laser-
relay communications capabilities at more
than 1 billion bits per second between two
Earth stations using a satellite in geosyn-
chronous orbit. The system also will sup-
port communications with Earth-orbiting
satellites. More importantly, LCRD will
demonstrate this operational capability
for as long as five years.
“We are very encouraged by the results
of LLCD,” said Badri Younes, NASA’s
deputy associate administrator for Space
Communications and Navigation (SCaN)
in Washington, which sponsored the mission. “From where I sit, the future looks
very bright for laser communications.”
TECH pulse • • • • • • • •
Space lasers have bright future in communications
An artist’s impression of the LADEE (Lunar Atmosphere and Dust Environment Explorer) satellite in orbit.
NASA scientists and engineers seeking faster connectivity with their data-gathering spacecraft are moving
away from radio-frequency-based communications and turning to laser communications.
N
A
S
A
‘From where I sit, the future
looks very bright for laser
communications.’
– Badri Younes, NASA
Active cloak is the most broadband to date
AUSTIN, Texas – An active invisibility
cloak – that is, one designed to work
with an external power source – could
significantly broaden the device’s operation bandwidth, moving its applications
beyond camouflage.
A team at the University of Texas at
Austin, led by Andrea Alù, associate professor at Cockrell School of Engineering,
proposed a design for an active cloak that
draws energy from a battery, allowing
objects to become undetectable to radio
