The Massachusetts Institute of Technology's Lincoln Laboratory developed a laser communications terminal, ILLUMA-T, which was launched to the International Space Station (ISS) on November 9 via a SpaceX Falcon 9 vehicle. The function of the terminal is to facilitate high-speed data transmission between the ISS and ground stations through NASA's first two-way laser communication relay system. The technology promises to transform how data transfer occurs in space by offering higher rates of transmission and lower mission costs as per Massachusetts Institute of Technology News.
Laser communication systems are potentially capable of replacing traditional radio frequency (RF) systems used in most space missions due to their higher data transmission rates. Data can be transferred 10 to 100 times quicker using infrared laser light compared to RF due to the shorter wavelength of the former. Further, laser systems require less volume, lower weight, and reduced power, leading to decreased mission costs.
ILLUMA-T (Integrated Laser Communications Relay Demonstration LEO User Modem and Amplifier Terminal) has the goal of showing the advantages of laser communications for low Earth orbit (LEO) missions. It aims to transfer data from the ISS to NASA's Laser Communications Relay Demonstration (LCRD) satellite in geosynchronous orbit (GEO) and then back to ground stations on Earth at high speeds. Back in 2013, NASA first tried out two-way space communication using laser light instead of RF in the Lunar Laser Communications Demonstration (LLCD), achieving record download and upload rates over the 239,000 miles between the moon and Earth. The LCRD satellite was launched in 2021 to relay data between ground stations in Hawaii and California for assessing system performance.
Collaborating with the NASA Goddard Space Flight Center, the Lincoln Laboratory team revamped the LLCD terminal design, which had restricted pointing capabilities for use on a LEO satellite. As mentioned by MIT News, they introduced a two-axis gimbal, allowing the terminal to swiftly pivot and track a GEO satellite as it moves through LEO. They further enhanced the terminal's manufacturability by incorporating all the fine-pointing mechanisms into a backend optical assembly, allowing easier alignment and temperature control of the optics.
Install ILLUMA-T on the Japanese Experiment Module—Exposed Facility of the ISS over the next two weeks. Upon successful installation, in-orbit checkouts, and commissioning, the team hopes to achieve "first light" by sending a beam of laser light to LCRD. Subsequent experiments will aim to demonstrate data transfer rates that significantly exceed those provided by current RF systems on the ISS and establish connectivity with ground stations.
"High data rates are beneficial in missions involving astronauts," reports Farzana Khatri, a member of the Laboratory's Optical and Quantum Communication Technology Group as cited by MIT News. Laser systems could potentially enhance streaming internet services, telehealth functionalities, and regular computer updates aboard the ISS.
While ILLUMA-T experiments will last only five months, the terminal design holds potential for future missions such as the Orion Artemis II Optical Communications System (O2O), which is slated for a November 2024 launch. Anticipatedly, the O2O mission is to bring laser communications to the moon, and the Lincoln Laboratory team has already transported the optical terminal for O2O to the Kennedy Space Center.
Apart from O2O, the team is considering integrating MAScOT with a high-rate optical modem to support the Event Horizon Explorer (EHE) mission, which would require data link rates over 200 Gbps. The goal of EHE is to augment the capabilities of the ground-based Event Horizon Telescope (EHT) to capture sharper images of black holes and other celestial bodies.
As Bryan Robinson, associate leader of the Optical and Quantum Communication Technology Group at Lincoln Laboratory, puts it, "Several present and upcoming missions are expected to benefit from this innovative design."
