Big step toward building a truly-secure global communication network

The National Institute of Information and Communications Technology (NICT, President: Hideyuki Tokuda, Ph.D.) developed the world’s smallest and lightest quantum-communication transmitter (SOTA) onboard the microsatellite SOCRATES. We succeeded in the demonstration of the first quantum-communication experiment from space, receiving information from the satellite in a single-photon regime in an optical ground station in Koganei city. SOTA weighs 6 kg and its size is 17.8 cm length, 11.4 cm width and 26.8 cm height. It transmits a laser signal to the ground at a rate of 10 million bits per second from an altitude of 600 km at a speed of 7 km/s. We succeeded in correctly detecting the communication signal from SOTA moving at this fast speed. This is a major step toward building a global long-haul and truly-secure satellite communication network.

As a result of this research, NICT demonstrated that satellite quantum communication can be implemented with small low-cost satellites, which makes it possible to many research institutions and companies to use this key technology. It is an achievement that opens a new page in the development future global communication networks, being a big boost to the space industry.

Background

The technologies required to launch small satellites at a low cost have progressed immensely during this century, and significant efforts are being made to develop satellite constellations to achieve a global communication network covering the entire Earth. However, there is a need for a technology that can transmit large amounts of information from the space to the ground in short periods of time, and the current RF bands are already congested, setting a bottleneck of communication capacity. By using lasers, satellite optical communication has a readily-available frequency band and can transmit with higher power efficiency and with smaller and lighter terminals. Thus, it is expected to be a key technology to support the future satellite communication networks. Quantum communication, and more specifically, Quantum Key Distribution (QKD) is another key technology to guarantee the information security of the next global communication networks. Current QKD links are limited to several hundreds of km, thus implementing satellite-to-ground QKD is a fundamental step in this endeavor. QKD research is actively conducted in Japan, China, Europe, Canada and the United States. In August of 2016, the University of Science and Technology of China launched a large (635 kg) quantum-communication satellite and performed a quantum-entanglement experiment with two ground stations.

Achieved results

SOTA is the world’s smallest and lightest quantum-communication transmitter (6 kg weight, 17.8 cm length, 11.4 cm width, and 26.8 cm height) embarked on the microsatellite SOCRATES. SOTA transmitted two polarization states, encoding ‘0’s and ‘1’s, to the ground at a rate of 10 million bits per second. The signals from SOTA were received at the NICT optical ground station in Tokyo’s Koganei city, using a 1-m telescope in order to collect the transmitted photons and guide them to the quantum receiver to decode the information using a QKD protocol.

The signal that arrives at the 1-m telescope is extremely weak, with an average of 0.1 photons per received pulse. NICT developed the technology to perform the time synchronization and polarization reference frame matching between the satellite and the ground station directly from the QKD signals, as well as a quantum receiver capable of detecting such a weak signal with low noise. We demonstrated the world’s first quantum communication from a 50-kg microsatellite. This will enable the development of future secure links from space by using quantum cryptography to completely prevent information leakage.

Future prospects

The technology developed in this project demonstrated that satellite quantum communication can be implemented by using low-cost lightweight microsatellites. Therefore, it is expected that many research institutes and companies, which are interested in this technology, will accelerate the practical application of quantum communication from space. In addition, since it was proved that long-distance communication is possible with very-low electric power, this will open up a path to speed up deep-space optical communication with exploration spacecraft.

In the future, there are plans to further increase the transmission speed and improve the precision of the tracking technology, to maximize the secure key delivery from space to ground by using quantum cryptography enabling a truly-secure global communication network, whose confidentiality is currently threatened by the upcoming development of quantum computers.

Summary:

The world’s smallest and lightest quantum-communication transmitter has now been developed, report researchers who have succeeded in the demonstration of the first quantum- communication experiment from space, receiving information from the satellite in a single-photon regime in an optical ground station in Koganei city. This is a major step toward building a global long-haul and truly-secure satellite communication network.

Researchers have been tracking the massive landslide which struck Xinmo Village, Maoxian County, Sichuan Province in China. They are using satellite data to accurately map the movement of the earth before a landslide in a bid to develop a life-saving early warning system.

The team from Newcastle University (UK), Chengdu University of Technology, Tongji University, China Academy of Space Technology and Wuhan University (China) have been tracking the devastating events of last month when a massive landslide struck Xinmo Village, Maoxian County, Sichuan Province in China.

Triggered by heavy rain, the Maoxian landslide swept away homes in Xinmo village, blocking a 2km section of river and burying 1,600 meters of road. The collapsed rubble was estimated to be about eight million cubic meters.

Three days later, a second landslide hit Xinmo Village and almost at the same time, a third landslide occurred in Shidaguan Town, 20km away from Xinmo Village.

Using ESA’s Sentinel-1 satellite radar mission — which comprises a constellation of two polar-orbiting satellites, operating day and night in all-weather conditions — the research team were able to capture before and after images of the landslides.

This provides vital information about the extent of the disaster which can be used to assess the damage and future risk in the area.

Professor Zhenhong Li, Professor of Imaging Geodesy at Newcastle University, explains:

“It is still hard, if not impossible, to detect a landslide using traditional techniques, especially in mountain areas. Using the satellite radar data, we were able to efficiently detect and map the active landslide over a wide region, identifying the source of the landslide and also its boundaries.

“Going forward, we can use this information to set up real-time monitoring systems — such as GPS, Beidou and Galileo — for those sites and whenever we detect abnormal behaviour, the system can send out an early warning message.

“In fact, while we were monitoring the Maoxian landslides we managed to identify over 10 other active landslides in the same region and forwarded this information to the relevant agencies.”

Living with the Constant Threat of a Landslide

Sichuan province is prone to earthquakes, including the devastating Great Wenchuan Earthquake of 2008 when a 7.9 magnitude quake hit the area, killing over 70,000 people.

Professor Li says their data suggests the Maoxian (Shidaguan) landslide had been sliding for at least six months before it failed.

“When you consider this sort of timescale it suggests that a landslide Early Warning System is not only possible but would also be extremely effective,” says Professor Li.

“If we can detect movement at a very early stage then in many cases it is likely we would have time put systems in place to save lives.”

Professor Li and the team have been working on active faults and landslides in Southwest China for over ten years and have identified several active landslides in the area south to Maoxian County but this is the first time they have studied the Maoxian region.

Ultimately, the team hope to use the technology to detect and map active landslides in the whole region of SW China, and then build a landslide database.

The research findings were presented at the Dragon-4 symposium in Copenhagen on 27 June 2017.