applied within Earth’s orbit as well.
The European Space Agency (ESA) and
Airbus recently put lasers to work as a
broadband data transfer technology, the
European Data Relay System (EDRS).
Normally, a satellite flying in low
Earth orbit transmits data only when it
is within view of a ground station. As a
result, it may take 90 minutes for the
ground station to receive data after it
has been collected.
In the EDRS system, lasers are used
both to send more data and to accelerate its transfer. A geostationary satellite locks onto the low-orbiting satellite via laser the moment it passes over
the horizon, then remains connected
as the craft soars over the hemisphere
below. The observing satellite begins
transmitting data via laser once the
link is established. The satellite can
transfer far more data this way, but
it also gets that data to the ground
faster. Instead of waiting for the observing satellite to fly within view of
the ground station, the laser transfer
begins once the craft establishes line
of sight with the geostationary craft,
which then transmits data to the
IN MARCH, THE U.S. National Aero- nautics and Space Administra- tion (NASA) announced that its planned Orion spacecraft, which could one day carry astronauts to the Moon and Mars, will
include a new kind of communication system. Typically, manned and
unmanned vehicles and probes use
radio waves to send and receive information. For decades, though, scientists have been pushing toward using
laser-based communications in space.
Lasers are no faster, but they can deliver far more information than radio
waves in the same amount of time.
NASA’s Apollo missions to the Moon
were capable of transmitting 51kb
worth of data per second, for example,
but Orion’s planned Laser-Enhanced
Mission and Navigation Operational
Services (LEMNOS) system could send
back more than 80 megabytes each second from the lunar surface.
That stream could be packed with
rich scientific data, or it could include ultra-high-resolution video of
distant worlds. Scaled-up versions of
this system could dispatch movies of
dust devils, storms, or even astronauts
walking on the surface of Mars. During the six-month-long trip to the Red
Planet, space travelers could potentially trade videos with family members back on Earth, and mitigate the
psychological toll of the long journey.
The LEMNOS project is just one of
many planned or existing laser-based
communications systems in orbit and
These recent and anticipated advances cannot be attributed to a single,
revolutionary breakthrough, according
to experts. Instead, this new age of laser-based broadband in space has resulted
from steady improvements in detectors,
actuators, control systems, and more.
Broadband in Orbit
The idea of laser communications in
space has been around nearly since
the invention of the laser itself, notes
Abi Biswas, supervisor of the Optical
Communications Systems group at
NASA’s Jet Propulsion Laboratory in
Pasadena, CA. From a basic physics
standpoint, Biswas says the advan-
tage is clear: lasers occupy the higher-
frequency end of the electromagnetic
spectrum, relative to radio waves. That
means the beam itself is much nar-
rower. If you were to aim a beam of ra-
dio waves back at Earth from Mars, the
beam would spread out so much that
the footprint would be much larger
than the size of our planet. “If you did
the same thing with a laser,” Biswas
says, “the beam footprint would be
about the size of California.”
When those beams are sent with
the same amount of power, the laser
ends up concentrating more power
on that receiver. “You can send many
more bits of information for the same
amount of power,” Biswas explains.
Relative to radio, laser or optical com-
munications can transmit anywhere
from 10 to 100 times as much data.
The advantages are not limited to
solar system exploration; they can be
Broadband to Mars
Scientists are demonstrating that lasers
could be the future of space communication.
Technology | DOI: 10.1145/3121442 Gregory Mone
Artist’s conception of how a NASA spacecraft would use lasers to communicate with Earth.