Integrated LCRD Low-Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T)

NASA's Integrated LCRD Low Earth Orbit User Modem and Amplifier Terminal (ILLUMA-T) is a payload on the exterior of International Space Station demonstrating the benefits laser communications can have for science and exploration missions.

ILLUMA-T launched on November 9, 2023, as part of the Commercial Resupply 29 (CRS-29), which brought science experiments, technology demonstration, and crew cargo to the space station.

Now, ILLUMA-T is communicating with NASA's first laser relay - the Laser Communications Relay Demonstration (LCRD), located in geosynchronous orbit. LCRD, launched in 2021, has been conducting experiments to refine laser communications technologies. ILLUMA-T is LCRD's first in-space user - or experiment. Together, LCRD and ILLUMA-T complete NASA's first two-way, end-to-end laser relay system, and demonstrating how a spacecraft in low Earth orbit can benefit from a laser communications relay.

ILLUMA-T and LCRD are one of many laser communications demonstrations, which are showcasing the benefits infrared light can have for missions transmitting terabytes of important science data.

ILLUMA-T sends data from the space station to LCRD at 1.2 gigabits per second (Gbps), then LCRD relays the data down to optical ground stations in California or Hawaii. Once the data reaches these ground stations, it is sent to the LCRD Mission Operations Center located at NASA's White Sands Complex in Las Cruces, New Mexico.

After this, the data is sent to the ILLUMA-T ground operations teams at the agency's Goddard Space Flight Center in Greenbelt, Maryland. There, engineers will determine if the data sent through this end-to-end relay process is accurate and of high-quality.

The LCRD project is still accepting experiments. Learn more: /projects/LCRD?tab=opportunities%20for%20experimenters

ILLUMA-T was built by engineers at NASA's Goddard Space Flight Center and the Massachusetts Institute of Technology – Lincoln Laboratory, a federally funded research and development center.

ILLUMA-T utilizes multiple laser sources housed within the modem module to create the specific wavelengths required to initialize the communication and then perform the high-speed data transfer. The modem module is based upon heritage from both the LCRD design and the laser terminal developed for the 2013 Lunar Laser Communications Demonstration, which displayed laser communications capabilities from an orbit around the Moon.

ILLUMA-T utilizes existing communication paths between the laser terminal and the International Space Station. The space station upgraded the internal network to create gigabit connections that will allow for full utilization of the laser link. This provides a direct path from the space station's network to the ground via a laser communications link, which will increase both the uplink and downlink data rates over the current radio frequency capabilities.

There are five key subsystems in ILLUMA-T, and the details of the ILLUMA-T payload are shown in the picture below. It shows the relative positioning of the optical module with respect to the Payload Interface Unit (PIU), which is the interface between the terminal and the space station, as well as the H-fixture and grapple fixture, which are used for robotic transfer of the payload. The picture below also displays the various parts and subsystems of the ILLUMA-T payload:

1. Optical Module: is responsible for both transmitting and receiving the laser signals carrying the information. On the transmitting side, it receives the amplified optical signal from the modem and directs it toward LCRD, while on the receiving side it collects the light signal, couples it to a fiber that will take it to the modem.
2. Modem Subsystem: The subsystem where information received from the space station in the form of electrical signals and is modulated on laser signals, amplified, and then directed through fiber to the optical module. For the other direction, it receives the signal from the optical module, converts it to electrical signal, and sends it to the space station.
3. Media Converter: This component is used as an interface between the space station and ILLUMA-T, and uses the existing fiber connection between the JEM-EF, where ILUMA-T will be mounted, and inside the pressurized section of the space station to enable high-speed data connections.
4. Controller Electronics: This is responsible for controlling the optical terminal, accepts commands, gathers operational parameters and provide information to operators.
5. Power Converter Unit: A unique subsystem responsible for converting the supplied power from the space station of 120V to 28V, which is common on unmanned spacecraft platforms. All other ILLUMA-T electronic boxes use a 28V power input which allows future unmanned missions to use the ILLUMA-T hardware without having to redesign the power interfaces.

Together, these systems ensure the data transmission between the terminal and the space station run smoothly. With ILLUMA-T leveraging laser communications, more data can be transmitted to Earth in single downlink.