Recently, a small satellite developed by MIT engineers created a new record of data transmission between satellites and the earth.
It is reported that the TeraByte infrared transmission (TBIRD) system of MIT has transmitted terabit (TB/Terabyte) level massive data from satellites to the earth at a record breaking speed of 100 gigabits per second (100Gbps), which is expected to change a series of scientific tasks in the future.
Specifically, this data transmission rate is more than 1000 times higher than the radio frequency link traditionally used for satellite communication, and it is also the highest rate of laser link from space to the ground up to now.
How fast is 100Gbps? You should know that the downlink speed of Starlink satellite Internet plan, which SpaceX spent a lot of money to build, is 500Mbps (1Gbps=1000Mbps), and even the data transmission of the International Space Station can only reach about 600Mbps. This means that TBIRD systems are 200 times faster than them.
In addition to this amazing speed, TBIRD system also greatly breaks through the previous limitations in preventing data corruption, and can overcome a series of engineering challenges. Through small and low-cost space and ground terminals, TBIRD system allows scientists from all over the world to make full use of laser communication to link down the massive data they once hoped to transmit.
In the past, space communication based on laser always has some engineering challenges. First, unlike radio waves, the laser beam is usually very narrow. In order to achieve smooth data transmission successfully, this narrow beam requires more accurate alignment between the sender and receiver on the ground. Although the laser can travel a long distance in space, due to the influence of atmospheric and weather conditions, the laser beam will be distorted, resulting in data loss.
TBIRD missions and technologies were developed by the MIT Lincoln Laboratory in cooperation with NASA's Goddard Space Flight Center. TBIRD satellite communication system integrates three key commercial off the shelf components: a high-speed optical modem, a large high-speed storage driver and an optical signal amplifier, all of which are packaged in a communication payload the size of a tissue box. To deal with data loss, the team developed a new version of Automatic Repeat Request (ARQ). ARQ is a protocol used to control data transmission errors on the communication link. It enables receivers on the earth to remind the sender to retransmit any data block that is lost or damaged through low-speed uplink signals.
"If the signal is interrupted, the data can be retransmitted; but if it is inefficient, it means that you spend all your time sending duplicate data instead of new data, and you may lose a lot of data throughput in this process," explained Curt Schieler, a TBIRD system engineer and technician, "By using our ARQ protocol, the receiver will tell the payload which frames it has correctly received, so the payload knows which frames to resend."
In addition, the TBIRD system no longer requires a gimbal pointing to a narrow laser beam. On the contrary, it relies on the error signal system developed by the laboratory to accurately point to the body of the spacecraft. The system precisely points to the receiver by adjusting the entire satellite itself. The team said that without universal joints, its payload could even be further miniaturized.
At present, for satellites, high-speed Internet based on laser communication has not been really built. Compared with radio waves, infrared light used for laser communication now has a higher frequency (or shorter wavelength), which allows more data to be included in each transmission. From Earth observation to space exploration, a series of scientific missions will benefit from high-speed data transmission. With the development of instrument capability, scientists can capture more high-resolution data.
Jade Wang, research director of the team, said: "We intend to demonstrate a low-cost technology that can quickly connect a large amount of data down from low Earth orbit to the Earth to support scientific missions. In just a few weeks of operation, we have achieved this goal, achieving an unprecedented transmission rate of up to 100 gigabits per second. Next, we plan to use other functions of the TBIRD system, including increasing the rate to 200 gigabits per second, so that the downlink exceeds Data passing 2Tb (equivalent to 1000 high-definition movies) will pass through the ground station in 5 minutes.
Source: OFweek Laser Network
