Real-world intercontinental quantum communications enabled by the Micius satellite

Private and secure communications are fundamental human needs. In particular, with the exponential growth of Internet use and e-commerce, it is of paramount importance to establish a secure network with global protection of data. Traditional public key cryptography usually relies on the computational intractability of certain mathematical functions. In contrast, quantum key distribution (QKD) uses individual light quanta (single photons) in quantum superposition states to guarantee unconditional security between distant parties. Previously, the quantum communication distance had been limited to a few hundred kilometers, due to the optical channel losses of fibers or terrestrial free space. A promising solution to this problem exploits satellite and space-based link, which can conveniently connect two remote points on the Earth with greatly reduced channel loss because most of the photons' propagation path is in empty space with negligible loss and decoherence. A cross-disciplinary multi-institutional team of scientists from the Chinese Academy of Sciences, led by Professor Jian-Wei Pan, has spent more than ten years developing a sophisticated satellite, Micius, dedicated to quantum science experiments, which was launched on August 2016 and orbits at an altitude of ~500 km. Five ground stations are built in China to cooperate with the Micius satellite, located in Xinglong (near Beijing), Nanshan (near Urumqi), Delingha (37 degrees 22'44.43''N, 97 degrees 43'37.01"E), Lijiang (26 degrees 41'38.15''N, 100 degrees 1'45.55''E), and Ngari in Tibet (32 degrees 19'30.07''N, 80 degrees 1'34.18''E).

Within a year after the launch, three key milestones for a global-scale quantum internet have been achieved: satellite-to-ground decoy-state QKD with kHz rate over a distance of ~1200 km (Liao et al. 2017, Nature 549, 43); satellite-based entanglement distribution to two locations on the Earth separated by ~1200 km and Bell test (Yin et al. 2017, Science 356, 1140), and ground-to-satellite quantum teleportation (Ren et al. 2017, Nature 549, 70). The effective link efficiencies in the satellite-based QKD were measured to be ~20 orders of magnitudes larger than direct transmission through optical fibers at the same length of 1200 km. The three experiments are the first steps towards a global space-based quantum internet.

The satellite-based QKD has now been combined with metropolitan quantum networks, in which fibers are used to efficiently and conveniently connect numerous users inside a city over a distance scale of ~100 km. For example, the Xinglong station has now been connected to the metropolitan multi-node quantum network in Beijing via optical fibers.

Very recently, the largest fiber-based quantum communication backbone has been built in China, also by Professor Pan's team, linking Beijing to Shanghai (going through Jinan and Hefei, and 32 trustful relays) with a fiber length of 2000 km. The backbone is being tested for real-world applications by government, banks, securities and insurance companies.

The Micius satellite can be further exploited as a trustful relay to conveniently connect any two points on Earth for high-security key exchange. To further demonstrate the Micius satellite as a robust platform for quantum key distribution with different ground stations on Earth, QKD from the Micius satellite to Graz ground station near Vienna has also been performed successfully this June in collaboration with Professor Anton Zeilinger of Austrian Academy of Sciences.

The satellite thus establishes a secure key between itself and, say, Xinglong, and another key between itself and, say, Graz. Then, upon request from the ground command stations, Micius acts as a trusted relay.

It performs bitwise exclusive OR operations between the two keys and relays the result to one of the ground stations. That way, a secret key is created between China and Europe at locations separated by 7600 km on Earth. This work points towards an efficient solution for an ultra-long-distance global quantum network.

A picture of Micius (with a size of 5.34 kB) was transmitted from Beijing to Vienna, and a picture of Schrodinger (with a size of 4.9 kB) from Vienna to Beijing, using approximately 80 kbit secure quantum key for one-time-pad encoding.

An intercontinental videoconference was also held between the Chinese Academy of Sciences and the Austria Academy of Sciences, employing the Advanced Encryption Standard (AES)-128 protocol that refreshed the 128-bit seed keys every second. The videoconference lasted for 75 min with a total data transmission of ~2 GB, which included ?560 kbit of the quantum key exchanged between Austria and China.

Rocket Lab successfully sends rocket into orbit

Aerospace company Rocket Lab said Sunday it had successfully fired a rocket into orbit for the first time from its New Zealand launch base. "Electron is orbital. Successful payload deployment," the company tweeted. The Electron rocket, named "Still Testing", took off from Mahia, on the east coast of the North Island, at 2.45pm (0145 GMT) on Sunday and reached orbit eight minutes later. The 17-metre-long (55ft 7in) carbon-fibre rocket is carrying three satellites into space -- one to take images of Earth for United States company Planet Labs, and two to capture weather and ship tracking data for Spire Global. "Speechless. Just like that, @rocketlab reaches orbit and sets a new bar for launch by reaching orbit on just their 2nd test," satellite-powered data company Spire tweeted. Rocket Lab conducted its first launch last May when the firm put a rocket into space, but it did not reach orbit.

Although New Zealand-founded, Rocket Lab lists itself as an American company with headquarters at a wholly-owned New Zealand subsidiary.

Backers include US companies Khosla Ventures, Bessemer Venture Partners, Lockheed Martin, Promus Ventures and Data Collective.

The company says its mission is to provide "frequent launch opportunities to low Earth orbit" with a range of rocket systems and technologies "for fast and affordable payload deployment".

Rocket Lab launch services with Electron are reported to cost US$4.9 million per flight.

JAXA testing engine for next-generation rocket

Japan's space agency is developing the main engine for its next-generation H-III rocket, which could see service in fiscal 2020. The H-III will be key to Japan expanding its presence in the global satellite launch market, which has been dominated by the U.S., Europe and Russia. This marks the first time in about 20 years that Japan has been developing main rocket engines. The Japan Aerospace Exploration Agency, or JAXA, began the first round of firing tests for the LE-9 engine on the southern island of Tanegashima in late April. A total of 11 ground tests are scheduled through June to check performance and durability. The LE-9 is a liquid cryogenic rocket engine burning liquid hydrogen and liquid oxygen in an expander bleed cycle. After completing another round of firing tests in fiscal 2018 starting next April, developers will construct the actual engine that will be installed in the H-III. The H-III will succeed the country's current H-series rockets, H-IIA and H-IIB. The H-III is designed to use three LE-9 engines when configured without strap-on solid rocket boosters, and two LE-9 engines when configured with them. The rocket is designed to launch with zero, two or four strap-on boosters, allowing it to deliver between two and seven metric tons to geostationary transfer orbit. IHI Aerospace, manufacturer of Japan’s Epsilon small launcher, is MHI’s supplier for the strap-on boosters for the H-2A and future H3. Kawasaki Heavy Industries provides the payload fairings.

 

The rocket will use commercially available components and a fuselage that can be mass produced, lowering launch costs to about half of the current price tag of approximately 10 billion yen ($88.6 million). The new, more powerful engine will allow the H-III to carry a midsize to large satellite weighing up to 6.5 tons -- 60% more than the H-IIA.

JAXA is working with the country's leading heavy machinery makers, such as Mitsubishi Heavy Industries and IHI, on rocket development. The total cost will likely reach about 190 billion yen.

With the powerful engine and lower launch costs, the government and space agency hope that the new rocket will garner more orders for satellite launches. They expect to send an average of about six H-IIIs into space from the Tanegshima Space Center every year.

Meanwhile, other countries are also working to roll out new rockets by around 2020. Russia currently launches on average some 30 rockets every year, while the U.S. sends up about 20 and China approximately a dozen. Japan launches only about three per year.

Unlike its competitors, Japan lacks launch centers. This puts it at a disadvantage as a work delay could affect the entire launch schedule of a satellite project. To compete with other countries, Japan has to improve its launch environment, including the capability for more frequent launches, and expand rocket development.

Japan’s ASNARO-2 launched on third Epsilon flight

Japan’s experimental radar imaging satellite ASNARO-2 was launched Thursday aboard the third flight of the Epsilon rocket. Liftoff – from the Uchinoura Space Centre – occurred at the opening of a twenty-four-minute, two-second window opening at 06:06:11 local time (21:06 UTC on Wednesday). Japan’s first launch of 2018, Wednesday’s mission was originally scheduled towards the end of last year, before an electrical issue with the rocket delayed its liftoff. Epsilon was tasked with deploying the ASNARO-2 satellite into a sun-synchronous low Earth orbit. Advanced Satellite with New System Architecture for Observation 2 – or ASNARO-2 – is the second in a series of experimental Earth imaging satellites operated by Japan Space Systems, formerly the Institute for Unmanned Space Experiment Free Flyer (USEF). A radar imaging mission, it follows the ASNARO-1 optical satellite that launched aboard Russia’s Dnepr rocket in November 2014. The mission is funded by Japan’s Ministry of Economy, Trade and Industry through its New Energy and Industrial Technology Development Organisation (NEDO).

ASNARO-2 was constructed by NEC, and is based on the modular NEXTAR NX-300L platform. It measures 3.9 meters (12.8 feet) in length and 1.5 meters (4.9 feet) in height and width, excluding its solar panels and radar antenna. The satellite has a mass of 570 kilograms (1,257 lb) – including its 220-kilogram (485 lb) payload and 45 kilograms (99 lb) of propellant.

Two deployable solar arrays will generate electrical power for the satellite. At the end of the spacecraft’s five-year design life, these are still expected to be generating at least 1,300 watts of power.

ASNARO-2 will be operated in a near-circular sun-synchronous orbit, at an altitude of 505 kilometers (314 miles, 273 nautical miles) and an inclination of 97.4 degrees. It will orbit the Earth about once every 95 minutes.

The spacecraft carries XSAR, a synthetic aperture radar (SAR) payload operating in the X band. This can be operated in three different observation modes: spotlight, strip mapping and scanning.

The spotlight mode, where the instrument focusses on a small area of the Earth’s surface, offers the highest resolution – one meter (3 feet) or better – with a swath width of 10 kilometers (6.2 miles, 5.4 nautical miles). In strip mapping mode, the satellite can image a longer strip of the Earth’s surface in the direction of travel.

This offers a resolution of better than 2 meters (7 feet) over a swath width of 12 kilometers (7.5 miles, 6.5 nautical miles). Scanning mode allows the satellite to image a wider area – with a swath width of at least 50 kilometers (31 miles, 27 nautical miles) – at a resolution of at least 16 meters (52 feet).

Japan’s Epsilon rocket will undertake the ASNARO-2 launch. Epsilon, which made its debut in September 2013 with the Hisaki – formerly SPRINT-A – satellite. In its standard configuration, Epsilon is a three-stage all-solid rocket, however it can also fly with an optional liquid-fuelled fourth stage. Thursday’s launch – designated Epsilon-3 – will use this four-stage configuration.

JAXA developed Epsilon to provide Japan a rocket capable of placing small satellites into orbit. It draws heavily on pre-existing components, with its first stage based on the SRB-A3 boosters used by the larger H-IIA rocket, and its upper stages derived from the older M-V vehicle. M-V, which Epsilon replaced, was retired in 2006 as its high cost-to-payload ratio made it uneconomical to operate.

During the gap between the M-V’s retirement and Epsilon’s introduction, JAXA relied on foreign rockets such as Dnepr to launch its small satellites.

The Epsilon launches from the same launch complex at the Uchinoura Space Centre that was used by the M-V – and earlier members of the Mu family of rockets. The Uchinoura Space Centre is one of Japan’s two operational orbital launch sites. The facility was originally used by Japan’s Institute for Space and Astronautical Science, or ISAS, one of three Japanese space agencies that merged in 2003 to form JAXA.

Before the merger, ISAS operated Japan’s smaller rockets – Mu, Lambda and the country’s sounding rockets – while the National Space Development Agency (NASDA) flew larger liquid-fuelled rockets from the Tanegashima Space Centre. While operated by ISAS, what is now Uchinoura was named the Kagoshima Space Centre.

The Mu rockets were rail-launched, so Uchinoura’s Mu Centre launch complex was originally designed as a rail launcher. Now that the complex is used by the vertically-launched Epsilon, it has been modified and the former launch rail now serves as an umbilical tower.

Although it is Epsilon’s third flight, Thursday’s launch was the first to combine both the operational version of the rocket and the CLPS upper stage. The operational form of Epsilon, described by JAXA as “Enhanced Epsilon” at the time of its last launch – although this name seems to have been dropped – incorporates enhanced second and third stages over the original design that flew the vehicle’s maiden flight. The second Epsilon used this “Enhanced” configuration, which is now the standard for all launches, while the CLPS was used on the first Epsilon launch.

Thursday’s launch began with ignition of Epsilon’s SRB-A3 first stage at the zero mark in the countdown. Epsilon lifted off and climbed quickly away from Uchinoura. The SRB-A3 burned for 108 seconds, propelling the rocket to a speed of 2.3 kilometers per second (1.4 miles per second). Following first stage burnout, the mission entered a brief coast phase as the vehicle continues to ascend.

Two minutes and 31 seconds into the flight, Epsilon was in space at an altitude of about 123 kilometers (76 miles, 66 nautical miles). The payload fairing, which will have protected ASNARO-2 during its ascent through the atmosphere, was no longer be needed and was jettisoned to save weight. Ten seconds later, the spent first stage separated.

Epsilon’s second stage, M-35, ignited four seconds after first stage separation. Producing 445 kilonewtons (100,000 pounds) of thrust, the stage burned for two minutes and nine seconds. The second stage separated 96 seconds after ending its burn and the KM-V2c third stage ignited four seconds later.

The third stage burn lasted 88 seconds. Separation occurred one minute and 52 seconds after burnout, with the fourth stage – the Compact Liquid Propulsion System (CLPS) – igniting after another four minutes and 37 seconds. CLPS uses hydrazine propellant. It made two burns during Thursday’s launch, with the first lasting five minutes and 16 seconds.

Once the upper stage’s first burn has concluded, the vehicle coasted for 23 minutes and 17 seconds before the second burn began. This was a seven-minute, seven-second firing of the CLPS to place ASNARO-2 close to its operational orbit.

Spacecraft separation occurred two minutes and 24 seconds after the end of the second burn, at 52 minutes, 35 seconds mission elapsed time. At separation, Epsilon was at an altitude of 513 kilometers (319 miles, 277 nautical miles).

Thursday’s launch was Japan’s first of 2018. In 2017 the country made seven orbital launches – the most it has achieved in a calendar year. Japan’s next scheduled launch is expected to be a reflight of last January’s attempt to place a CubeSat into orbit using a modified SS-520 sounding rocket. This launch was delayed from December, and is awaiting confirmation of a new launch date once Epsilon lifts off.

After the SS-520 launch, Japan’s next mission will then be an H-IIA flight at the end of February, which is expected to deploy an IGS optical reconnaissance satellite. Thursday’s launch will be Epsilon’s only flight in 2018 – its next launch is currently scheduled for the first quarter of 2019 with the Innovative Technology Demonstration Satellite.

Steep Slopes on Mars Reveal Structure of Buried Ice

Researchers using NASA's Mars Reconnaissance Orbiter (MRO) have found eight sites where thick deposits of ice beneath Mars' surface are exposed in faces of eroding slopes.These eight scarps, with slopes as steep as 55 degrees, reveal new information about the internal layered structure of previously detected underground ice sheets in Mars' middle latitudes.The ice was likely deposited as snow long ago. The deposits are exposed in cross section as relatively pure water ice, capped by a layer one to two yards (or meters) thick of ice-cemented rock and dust. They hold clues about Mars' climate history. They also may make frozen water more accessible than previously thought to future robotic or human exploration missions. Researchers who located and studied the scarp sites with the High Resolution Imaging Science Experiment (HiRISE) camera on MRO reported the findings today in the journal Science. The sites are in both northern and southern hemispheres of Mars, at latitudes from about 55 to 58 degrees, equivalent on Earth to Scotland or the tip of South America.

"There is shallow ground ice under roughly a third of the Martian surface, which records the recent history of Mars," said the study's lead author, Colin Dundas of the U.S. Geological Survey's Astrogeology Science Center in Flagstaff, Arizona. "What we've seen here are cross-sections through the ice that give us a 3-D view with more detail than ever before."

Windows into underground ice
The scarps directly expose bright glimpses into vast underground ice previously detected with spectrometers on NASA's Mars Odyssey (MRO) orbiter, with ground-penetrating radar instruments on MRO and on the European Space Agency's Mars Express orbiter, and with observations of fresh impact craters that uncover subsurface ice.

NASA sent the Phoenix lander to Mars in response to the Odyssey findings; in 2008, the Phoenix mission confirmed and analyzed the buried water ice at 68 degrees north latitude, about one-third of the way to the pole from the northernmost of the eight scarp sites.

The discovery reported today gives us surprising windows where we can see right into these thick underground sheets of ice," said Shane Byrne of the University of Arizona Lunar and Planetary Laboratory, Tucson, a co-author on today's report. "It's like having one of those ant farms where you can see through the glass on the side to learn about what's usually hidden beneath the ground."

Scientists have not determined how these particular scarps initially form. However, once the buried ice becomes exposed to Mars' atmosphere, a scarp likely grows wider and taller as it "retreats," due to sublimation of the ice directly from solid form into water vapor.

At some of them, the exposed deposit of water ice is more than 100 yards, or meter, thick. Examination of some of the scarps with MRO's Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) confirmed that the bright material is frozen water. A check of the surface temperature using Odyssey's Thermal Emission Imaging System (THEMIS) camera helped researchers determine they're not seeing just thin frost covering the ground.

Researchers previously used MRO's Shallow Radar (SHARAD) to map extensive underground water-ice sheets in middle latitudes of Mars and estimate that the top of the ice is less than about 10 yards beneath the ground surface. How much less? The radar method did not have sufficient resolution to say. The new ice-scarp studies confirm indications from fresh-crater and neutron-spectrometer observations that a layer rich in water ice begins within just one or two yards of the surface in some areas.


Astronauts' access to Martian water

The new study not only suggests that underground water ice lies under a thin covering over wide areas, it also identifies eight sites where ice is directly accessible, at latitudes with less hostile conditions than at Mars' polar ice caps. "Astronauts could essentially just go there with a bucket and a shovel and get all the water they need," Byrne said.

The exposed ice has scientific value apart from its potential resource value because it preserves evidence about long-term patterns in Mars' climate. The tilt of Mars' axis of rotation varies much more than Earth's, over rhythms of millions of years.

Today the two planets' tilts are about the same. When Mars tilts more, climate conditions may favor buildup of middle-latitude ice. Dundas and co-authors say that banding and color variations apparent in some of the scarps suggest layers "possibly deposited with changes in the proportion of ice and dust under varying climate conditions."

This research benefited from coordinated use of multiple instruments on Mars orbiters, plus the longevities at Mars now exceeding 11 years for MRO and 16 years for Odyssey. Orbital observations will continue, but future missions to the surface could seek additional information.

"If you had a mission at one of these sites, sampling the layers going down the scarp, you could get a detailed climate history of Mars," suggested MRO Deputy Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, California. "It's part of the whole story of what happens to water on Mars over time: Where does it go? When does ice accumulate? When does it recede?"