Zhang Tong
An image of Doha, the capital of Qatar, transmitted by China’s Jilin-1 MF02A04 satellite, part of a 108-strong constellation. Photo: Aerospace Information Research Institute, Chinese Academy of Sciences
China has successfully deployed laser-based high-speed communication technology on commercial satellites, increasing space-to-ground data transfer speed tenfold to 10 gigabytes per second (Gbps).
“Using a ground-based 500mm (19.7 inches) aperture, researchers received laser signals emitted from a transmitter on the Jilin-1 MF02A04 satellite,” the official Science and Technology Daily reported earlier this week.
The 108-strong Jilin-1 constellation in lower Earth orbit is the world’s largest imaging satellite network, and sends back commercial remote sensing data for sectors including land resource survey, urban planning and disaster monitoring. The latest breakthrough is forecast to significantly enhance ground communication with the satellites.
Traditionally, satellite-to-ground links have primarily relied on microwave technology. However, as the range of microwave frequencies is restricted, so is the speed of data transfer.
Lasers, by contrast, have a much wider spectrum. Therefore, using lasers as data carriers can help pack more data into each transmission, with the bandwidth potentially reaching several hundred gigahertz.
A team from the Aerospace Information Research Institute (AIR), under the country’s premier research institute – the Chinese Academy of Sciences – set up a satellite-to-ground link using lasers, for what is formally known as “optical communication”.
Their system, sent into orbit with the Jilin-1 MF02A04 in December, was successfully tested on Wednesday, opening the doors to more efficient data exchange.
Li Yalin, the leader of the ground system at AIR, compared the technology to city roads.
“Using the common microwave at 375 MHz is like driving on a single lane, and the emerging [technology of a] higher 1.5 GHz microwave would be a four-lane road,” he said. “Lasers, meanwhile, can accommodate hundreds or even thousands of lanes.”
“With [such] optical communication, it is possible to transmit a high-definition movie in one second, which is 10 to 1,000 times faster than the current microwave communication method.”
The first batch of data sent back to Earth by the Jilin-1 transmitter included a picture of Doha, the capital of Qatar.
“It is the first ultra-high-speed [10 Gbps] satellite-to-ground optical communication test for business applications in China, and the single communication lasted for more than 100 seconds,” chief designer Chen Shanbo at Chang Guang Satellite Technology, the commercial company that launched the Jilin-1 MF02A04 satellite, said.
The highly concentrated energy of lasers also means the size, weight, and power consumption of satellite-borne laser transmitters are markedly less than those powered by microwave.
Lasers also have strong anti-electromagnetic interference capabilities, which can significantly improve the security of ground-to-satellite communication.
Notably, Nasa has speeded up similar research, and teamed up with the Massachusetts Institute of Technology (MIT) researchers to achieve a downlink speed of 100 Gbps last June.
The feat was achieved by the MIT-developed TeraByte InfraRed Delivery (TBIRD) system, which was taken into orbit by Nasa’s Pathfinder Technology Demonstrator 3 (PTD-3) satellite. The system is named after the terabyte, a unit of digital data that equals 1,000 gigabytes or about 500 hours of high-definition video.
PTD-3 is about the size of two stacked cereal boxes, and the TBIRD payload it carries is no larger than the average tissue box, according to Nasa.
This year, the US laser link doubled that data rate, reaching a record-breaking transmission speed of 200 Gbps.
“With optical communications, we’re blowing that out of the water as far as the amount of data we can bring back. It is truly a game-changing capability,” TBIRD project manager Beth Keer said.
The Nasa record, however, was achieved on a demonstration satellite, which are usually more powerful than the commercial type.
The Jilin-1 MF02A04 is a commercial satellite designed for practical use and a longer lifespan. It weighs less than 40kg (88 pounds) but the weight of its transmitter is not known.
Faster data transmission could drive development in many areas. Missions to collect important data on Earth’s climate and resources, as well as astrophysical discoveries and military detection could all be boosted by this technology.
“Laser communications is the missing link that will enable the science discoveries of the future,” Keer was reported as saying in May.
However, when it comes to the technology’s commercial application, China might have an edge. The Jilin-1 constellation is set to have 138 satellites in orbit this year and complete the second phase of construction by 2025, by which time it will have 300 satellites.
The system’s powerful remote sensing image capability will generate a large amount of data every day by then, feeding the growing demand for data transmission from satellite to ground and between satellites.
Another Jilin-1 series satellite coded “02A” was successfully launched by Chang Guang Satellite Technology on June 15. It carries a new generation of optical communication payload to validate high-speed inter-satellite, and satellite-to-ground and back to satellite communication technologies, and aims to form a network with the others in orbit.
According to the company website: “As the next step, Chang Guang Satellite Technology will carry out the normalisation and commercial trial operation of ground-to-satellite laser communication, providing a technical foundation for the subsequent large-scale application of 40 Gbps satellite-to-ground laser communication payloads.”
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