Building 12, N036
8800 Greenbelt Road
Greenbelt, Maryland 20771
The LLCD ground segment consists of three ground terminals that will perform high-rate communication with the LLST aboard LADEE.
Lunar Lasercomm Ground Terminal (LLGT)
NASA's White Sands Complex, White Sands, New Mexico
The Lunar Lasercom Ground Terminal (LLGT), developed by MIT Lincoln Laboratory, will be the primary ground terminal for data transmission to and from the LLST aboard the LADEE spacecraft. LLGT consists of an array of 8 total transceiver and receiver telescopes and a control room. In total the LLGT and its enclosure stands about 15ft high and has a total mass of 7 tons, which is near 75% smaller than current RF-antennas in use today. Each telescope is connected to the control room where the optical transmitters and receivers reside. The telescopes are housed in a fiberglass environmental enclosure, which maintains a suitable environment for their operation. The telescope arrays are used to demonstrate a scalable and cost-effective approach for providing large-aperture transmitters and receivers.
Within the LLGT enclosure there are four 15 cm transmitting (uplink) and four 40 cm receiving (downlink) telescopes, mounted on a single gimbal. The four 15 cm transceiver telescopes are used to send both an uplink beacon and data to the Lunar Lasercomm Space Terminal (LLST) aboard the LADEE spacecraft. These telescopes will use a highly-reliable infrared laser to send data in the form of hundred of short pulses of light every second to the LLST. While undergoing operations the transmitting telescopes will be able to uplink data to the LLST at a rate of 20 Mbps. Also within the enclosure are the four 40 cm receive telescopes that will collect and focus the faint downlink signals from the LLST via optical fibers to detectors in the control room.
The control room houses the downlink receiver, the low-power parts of the uplink transmitter, high-speed data handling electronics, and various computers and monitors for controlling and monitoring the entire terminal and facility. The downlink receiver is based on a high-efficiency architecture that uses superconducting nanowire detector arrays (SNDAs) which provide high-speed photon-counting measurements of the downlink. Each fiber from a downlink telescope terminates in a focusing lens that illuminates an intertwined 4-array of detectors housed in a cryo-cooler. In another rack is the set of high-speed electronics that converts the analog signals into synchronized data signals, and then performs demodulating and decoding. The electronics also performs a comparison of the timing of the downlinks with the uplinks, thus deducing the high-precision round-trip time.
The LLGT was designed to be transportable. After initial assembly and deployment at MIT Lincoln Laboratory in Lexington, MA, the LLGT was transported to the White Sands Complex in New Mexico, during May of 2013.
Lunar Lasercom OCTL Terminal (LLOT)
NASA/JPL's Table Mountain Facility, Wrightwood, California
The Lunar Lasercom OCTL Terminal (LLOT) is located at the Optical Communications Telescope Laboratory (OCTL) situated at JPL's Table Mountain Facility near Wrightwood, CA. OCTL is based on a 1-meter diameter gimbaled telescope housed in a permanent domed structure. Its single feed to the telescope will see a duplex combination of downlink plus six uplink beamlets.
Optical Ground Station (OGS)
ESA's La Teide Observatory, Tenerife, Spain
The Lunar Lasercom Optical Ground System (LLOGS) is located at the Optical Ground Station (OGS) of ESA situated at the La Teide Observatory on Tenerife in Spain's Canary Islands. The OGS is based on a 1-m diameter gimbaled telescope housed in a permanent domed structure. Two 4-cm transmit telescopes are configured as outriggers on the large telescope, each transmitting a 20-W beacon signal.
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