For many decades, NASA has used radio frequency (RF) communications to transmit voice and data back and forth between the space shuttle, as well as to transmit data to and from remote spacecraft on the moon, on Mars, and in deep space.
Now that a greater number of critical space missions require even more data transmission bandwidth, NASA is exploring cutting edge laser communications technologies to improve not only bandwidth, but also transmission speed as well.
On September 6th, 2013, NASA launched the LADEE/LLCD mission to the moon. The Space Agency launched its Lunar Atmosphere and Dust Environment Explorer (LADEE) probe, which also carried the LLCD laser communications equipment, which will demonstrate laser-based communications to and from the Earth for the first time.
The experiment will transmit hundreds of millions of bits of data per second through space along a photon-based communications channel that will not experience the sort of interference that RF signals were susceptible to, and laser communications are far less likely to be jammed. Communications will be picked up at the NASA White Sands Complex in New Mexico, with the NASA Jet Propulsion Lab in California serving as a back-up station. Both sites are capable of receiving the laser communications from space. (1)
Laser-based communications through space offer NASA the ability to send communications to places like the orbiting space station or to spacecraft on Mars at transmission rates 10 to 100 times faster than RF transmission signals. (2)
Higher transmission rates are accomplished due to the fact that laser light has a shorter wavelength than radio waves, so the spread of energy as the transmission travels through space is much smaller. The shorter wavelength also provides NASA with a wider bandwidth to work with, since the limited bandwidth of radio-based systems would no longer be an issue.
A larger bandwidth means NASA could more easily transmit high-resolution images and data through space in much less time. NASA scientists have plans to use “bandwidth-hungry” instruments such as hyperspectral imagers and synthetic aperture radar. (3)
The Lunar Mission
The LADEE mission to test the laser-based communication for the first time actually has a fascinating primary mission to begin with. NASA is sending the Lunar Atmosphere and Dust Environment Explorer probe to explore a mystery identified by Apollo astronauts through the years.
During the mid-to-late 1960’s, NASA Apollo astronauts noticed an odd glow on the horizon of the lunar surface. NASA Surveyor landers also recorded the glow hovering just 1-2 meters above the lunar surface. Orbiting astronauts reported back that they observed “streamers of light” hundreds of miles over the surface of the moon.
The top explanation for the glow among NASA scientists is that it’s caused by light from the Sun reflecting off of dust suspended in the atmosphere. The goal of the LADEE mission is to fully investigate the glow and hopefully ascertain its actual cause. While past missions to the moon have explored its surface, mineral resources and its weather, this is the first mission to study the atmosphere of the moon.
The hope is that the LLCD experiment, being conducted at the same time as LADEE’s primary mission, will prove out the concept of transmitting data through space with laser, reaching higher data transmission rates than ever before accomplished in space.