Each year, NASA spends millions of dollars operating its communications network, which consists of ground- and space-based assets located around the globe. In an era of burgeoning U.S. budget deficits, reducing those costs and achieving even more capability have become a top Agency priority.
To realize its ambitions, the Agency has tapped the Goddard Space Flight Center to lead and demonstrate the Lunar Laser Communications Demonstration (LLCD), an experiment to provide the proof-of-concept for laser-based communications from lunar orbit. During the experiment, Goddard plans to transmit more than 600 megabits of data per second using a Lincoln Laboratory-built 4-inch telescope and a half-watt laser installed on the $80-million Lunar Atmosphere and Dust Environment Explorer (LADEE), which NASA plans to launch in 2012 to characterize the Moon’s wisp-thin atmosphere and dust environment.
“This is the first step in augmenting or replacing some of our current communications infrastructure — which is made up entirely of radio frequency (RF) communication systems — with an optical system that offers more tool flexibility. In other words, we can use the right communications tool for the right job. This will unburden the Agency’s existing infrastructure,” said Julie Crooke, who oversees astrophysics and communications programs for the Center’s New Opportunities Office. “This likely will result in overall cost savings on the ground and in space, while providing more capability. It is a huge step for the Agency in becoming more efficient with its limited resources.”
Currently, NASA’s communications network consists of three main elements: the Space Network, the Near-Earth Network, and the Deep Space Network. Goddard leads and operates the Space and Near-Earth Networks and the Jet Propulsion Laboratory operates the Deep Space Network. These networks provide communications and tracking in the RF bands to all NASA assets, everything from the International Space Station to spacecraft orbiting Earth and traveling out to the very edge of the solar system.
However, operating these networks has become increasingly more expensive, which has motivated NASA to investigate potentially more cost-effective solutions.
This image shows the three-dimensional mass model of the optical module that will comprise the optical interface of the optical communications experiment flying on the Lunar Atmosphere and Dust Environment Explorer.
Optical Communications a Possible Solution
Optical communications is one possible solution. It transmits data using the visible and near-infrared wavelength bands, which the Federal Communications Commission and the International Telecommunications Union do not regulate. However, they do regulate the radio bands to prevent interference among users, said Harry Shaw, who is managing the LLCD project for Goddard. Due to the lack of interference, future missions would be able to transmit very high data-rate communications, provided the system provided enough power to the receiver, he said.
In addition, optical-communications systems consume less mass, volume, and power, especially compared with similar RF systems, Shaw added. As the technology evolves, the transition to these types of communications systems will ultimately reduce mission costs and provide opportunities for new science payloads, he said.
To demonstrate the concept, Goddard plans to transmit more than 600 megabits of data per second from the LLCD on LADEE to a small array of four 16-inch ground telescopes, also built by Lincoln Laboratory. The optical ground terminal, which is 10 times more efficient at these data rates than any optical receiver ever demonstrated in a spaceflight application, will operate at White Sands, New Mexico, as a first step toward supplementing Goddard’s longstanding RF ground network capability. LLCD on LADEE is the first of three planned demonstrations.
Natural Fit for Goddard
“The LLCD experiment is a natural fit for Goddard,” Crooke added. “Since NASA’s inception, we’ve operated communications networks for spacecraft operating in low- and near-Earth orbits. We also have a tremendous amount of experience building laser-based instruments. This demonstration combines both areas of expertise. It also leverages the R&D investments we’ve made to build our optical-communications expertise,” Crooke said.
First Lunar Mission to Launch from Wallops
“To say this is exciting is an understatement,” said Mike Krainak, a Goddard technologist and expert in laser applications, adding that Goddard succeeded in securing a flight opportunity for the technology by proposing a low-cost mission. Not only is LADEE the first to include an optical-communications demonstration, he said, it’s also the first lunar mission to launch from the Wallops Flight Facility onboard a Minotaur-5 launch vehicle. “When it launches, it will get a tremendous amount of publicity,” he said.
Goddard technologists win new work, secure follow-on funding to mature new technologies, formulate concepts, and validate new instrument concepts in flight demonstrations — successes that benefit Goddard and the scientific community as a whole.