SpaceX says Iridium satellite payload deploye

The private firm SpaceX on Friday said a partially-reused rocket successfully launched and deployed the latest group of satellites to upgrade communication networks for Virginia-based company Iridium. "We have successful liftoff of the Falcon 9," a SpaceX commentator said after the rocket roared off with a tail of fiery exhaust from Vandenberg US Air Force base in California. SpaceX confirmed on Twitter the "successful deployment of all 10 @IridiumComm NEXT satellites to low-Earth orbit." It was the fifth set of 10 satellites that SpaceX has launched for Iridium, whose $3 billion project is expected to include a total of 81 satellites -- with 75 launched by SpaceX. The first stage of the rocket sent aloft on Friday had been used in October for a previous launch as part of the project, known as Iridium NEXT. SpaceX did not attempt to make another recovery of the rocket's first stage after Friday's launch.

However, it did try to land the fairing -- the rocket's nose cone -- on a SpaceX-owned boat named "Mr Steven," which is equipped with a huge net.

SpaceX CEO Elon Musk said on Twitter the fairing "impacted water at high speed," without confirming explicitly if the landing was successful or not.

Musk aims to make rockets as reusable as commercial airplanes, bringing down the cost of spaceflight and boosting efficiency.

In February the company's Falcon Heavy, the world's most powerful rocket, blasted off on its maiden test flight carrying Musk's cherry red Tesla roadster car.

The Iridium project, though less flamboyant, will replace the world's largest commercial satellite network of low-Earth orbit satellites in one of the largest "tech upgrades" in history, improving mobile, voice and data networks, Iridium has said.

Some of the satellites are designed to help track ships and aircraft in real time.

Marsquakes could shake up planetary science

Starting next year, scientists will get their first look deep below the surface of Mars. That's when NASA will send the first robotic lander dedicated to exploring the planet's subsurface. InSight, which stands for Interior Exploration using Seismic Investigations, will study marsquakes to learn about the Martian crust, mantle and core. Doing so could help answer a big question: how are planets born?  Seismology, the study of quakes, has already revealed some of the answers here on Earth, said Bruce Banerdt, Insight's principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, California. But Earth has been churning its geologic record for billions of years, hiding its most ancient history. Mars, at half the size of Earth, churns far less: it's a fossil planet, preserving the history of its early birth. "During formation, this ball of featureless rock metamorphosed into a diverse and fascinating planet, almost like caterpillar to a butterfly," Banerdt said. "We want to use seismology to learn why Mars formed the way it did, and how planets take shape in general."

A Planetary CT Scan

When rocks crack or shift, they give off seismic waves that bounce throughout a planet. These waves, better known as quakes, travel at different speeds depending on the geologic material they travel through.

Seismometers, like InSight's SEIS instrument, measure the size, frequency and speed of these quakes, offering scientists a snapshot of the material they pass through.

"A seismometer is like a camera that takes an image of a planet's interior," Banerdt said. "It's a bit like taking a CT scan of a planet."

Mars' geologic record includes lighter rocks and minerals - which rose from the planet's interior to form the Martian crust - and heavier rocks and minerals that sank to form the Martian mantle and core. By learning about the layering of these materials, scientists can explain why some rocky planets turn into an "Earth" rather than a "Mars" or "Venus" - a factor that is essential to understanding where life can appear in the universe.

A Fuzzy Picture

Each time a quake happens on Mars, it will give InSight a "snapshot" of the planet's interior. The InSight team estimates the spacecraft will see between a couple dozen to several hundred quakes over the course of the mission. Small meteorites, which pass through the thin Martian atmosphere on a regular basis, will also serve as seismic "snapshots."

"It will be a fuzzy picture at first, but the more quakes we see, the sharper it will get," Banerdt said.

One challenge will be getting a complete look at Mars using only one location. Most seismology on Earth takes measurements from multiple stations. InSight will have the planet's only seismometer, requiring scientists to parse the data in creative ways.

"We have to get clever," Banerdt said. "We can measure how various waves from the same quake bounce off things and hit the station at different times."

Moonquakes and Marsquakes

InSight won't be the first NASA mission to do seismology.

The Apollo missions included four seismometers for the Moon. Astronauts exploded mortar rounds to create vibrations, offering a peek about 328 feet (100 meters) under the surface. They crashed the upper stages of rockets into the Moon, producing waves that enabled them to probe its crust. They also detected thousands of genuine moonquakes and meteorite impacts.

The Viking landers attempted to conduct seismology on Mars in the late 1970s. But those seismometers were located on top of the landers, which swayed in the wind on legs equipped with shock absorbers.

"It was a handicapped experiment," Banerdt said. "I joke that we didn't do seismology on Mars - we did it three feet above Mars."

InSight will measure more than seismology. The Doppler shift from a radio signal on the lander can reveal whether the planet's core is still molten; a self-burrowing probe is designed to measure heat from the interior. Wind, pressure and temperature sensors will allow scientists to subtract vibrational "noise" caused by weather. Combining all this data will give us the most complete picture of Mars yet.

Sentinel-3B launch preparations in full swing

With the Sentinel-3B satellite now at the Plesetsk launch site in Russia and liftoff set for 25 April, engineers are steaming ahead with the task of getting Europe's next Copernicus satellite ready for its journey into orbit. After arriving at the launch site on 18 March, the satellite has been taken out of its transport container and is being set up for testing. Kristof Gantois, ESA's Sentinel-3 engineering manager, said, "The satellite's journey from France was hampered slightly by the freezing winter weather here in Russia, but it's now safe in the milder cleanroom environment."With the aid of a crane, our baby has been removed from its transport container. We have also been very busy unpacking the array of equipment we need to test the satellite and make it ready to join its Rockot launcher." Sentinel-3B will join its twin, Sentinel-3A, in orbit. The pairing of identical satellites provides the best coverage and data delivery for Europe's Copernicus programme - the largest environmental monitoring programme in the world. The satellites carry the same suite of cutting-edge instruments to measure oceans, land, ice and atmosphere.

Feeding a new generation of data products, the Sentinel-3 mission is at the heart of operational oceanography.

For example, it provides measurements to monitor aquatic biological productivity and marine pollution, to map sea-level change and to forecast the sea state for efficient and safe ship routeing.

As well as measuring the oceans, the mission also delivers unique and timely information about changing land cover, vegetation, urban heat islands, and for tracking wildfires.

The Sentinel-3B will be lofted into orbit on a Rockot launcher on 25 April at 17:57 GMT (19:57 CEST).

Feature: Every second counts to trace a gravitational wave

When a gravitational wave reaches Earth, every second counts. The data processing speed will have a crucial impact on how much astronomers can learn from these space-time ripples, says computer scientist Cao Junwei. "In an era of multi-messenger astronomy, we have to shorten the time as much as possible so as to trigger the alert quickly enough for follow-up observations," says Cao, who leads the Chinese team in the international Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration. Last October, scientists from LIGO Scientific Collaboration, together with astronomers across the world, declared they had detected for the first time a gravitational wave from the collision of binary neutron stars and corresponding electromagnetic signals.The discovery was achieved with high data processing speed. Just 1.7 seconds after the gravitational wave detection network received the signal, a gamma-ray burst was detected by the Fermi space telescope. LIGO and Fermi immediately triggered alerts around the astronomical community, bringing about 70 ground and space detectors into follow-up observations of electromagnetic signals with various wave lengths, which helped locate the source of the gravitational wave more precisely.

Cao joined the LIGO Lab at the Massachusetts Institute of Technology (MIT) as a computer scientist in 2004. On returning to China, he led a team from Tsinghua University's Research Institute of Information Technology (RIIT) in joining the LIGO Scientific Collaboration in 2009.

"We were the only Chinese group in the collaboration. None of us specialized in astrophysics, but we were accepted," says Cao, who is vice dean of RIIT.

In the first five years, the Tsinghua team mainly helped build the computing platform and analyze data. Then they began devoting most of their efforts to speeding up data processing.

Few understood the importance of speed at the beginning.

"We suggested, from the outset, that fast computing should serve multi-messenger astronomy, which would require follow-up observations as soon as a gravitational wave signal is confirmed," Cao says. "The faster, the better."

In 2015, LIGO first detected gravitational waves from the collision of binary black holes, which verified the general relativity theory that Albert Einstein established a century ago. But it took scientists months to vet, validate and interpret the discovery before it was publicly announced.

LIGO detectors collect more than 16,000 data samples a second. To confirm a signal is generated by gravitational waves, scientists remove "noise" from the data, and then compare the data patterns with templates of gravitational waves.

More than 1,000 scientists are working for the LIGO Scientific Collaboration, more than half of them on data analysis. The data quality categories are defined by multiple analysis groups: Compact Binary Coalescence (CBC), Burst, Continuous Waves, Stochastic, and others.

"Our team, just a small group in the collaboration, is now focusing on GPU acceleration for CBC search and exploring the application of machine learning to real-time data analysis," Cao says.

Their accomplishments include a set of new data processing pipelines, in cooperation with the University of Western Australia.

"The new pipelines help speed up data filtering, so we can finish comparing data patterns with tens of thousands of templates within a second," says Tsinghua Associate Professor Du Zhihui.

"Now, the time between the arrival of a signal and the confirmation of it as gravitational waves has been shortened from several minutes to dozens of seconds. Next, we hope to shrink the time to three to five seconds," Du says.

Scientists began to enhance LIGO's detectors since 2008. The Advanced LIGO finished its second run in August 2017, and is expected to start its third in the middle of this year. Scientists will further upgrade its detectors between the two runs to improve its sensitivity, which might greatly increase the odds of discovering gravitational waves.

"With a higher sensitivity, the number of signals that are detected may soar from a few a year to several a day. We will fall far behind if we don't accelerate data processing," Cao says.

He hopes their work in the LIGO Scientific Collaboration will contribute to China's own gravitational wave detection projects. "China will participate in international cooperation actively to foster talent and accumulate experience," he says.

India to Experiment With Igloo-like Structures on the Moon

Indian scientists will use robots and 3D printers to build igloo-like structures using lunar soil and other suitable materials. Indian space scientists have already finalized five designs for such lunar habitats, according to a central minister. New Delhi (Sputnik) — In what could be India's biggest achievement in space exploration, the Indian Space Research Organisation (ISRO) is experimenting with potential structures for lunar habitation, the Indian space minister informed the nation's parliament on Wednesday.  "ISRO along with academic institutions are performing experiments on potential structures for lunar habitation," Jitendra Singh, Minister of State in the Prime Minister's Office, responsible for the Department of Space, informed the lower house of the parliament. Suman Balka, a member of the house, had asked him whether the ISRO had started working on building igloo-like habitats on the lunar surface for potential future missions and whether it was is planning to use the Moon as an outpost, like missions in Antarctica. 

  

"Various options are being studied about the requirements and complexities of habitats. The study is more towards futuristic developments," Singh responded.

The ISRO is planning to launch the Chandrayaan-II (Moon Mission-II) next month. This mission involves many complex elements like a soft landing, rover separation, and movement on the lunar surface, in addition to the operations of the Orbiter. The rover has been designed in such a way that it will have the power to spend a lunar day or 14 Earth days on the moon's surface and walk up to 150-200 meters. The rover will then send data and images of the lunar surface back to the Earth through the orbiter.

Several new technology elements have been developed indigenously and tests are being carried out for verification.

"Orbiter has completed the thermo-vacuum test, which is one of the major milestones. Lander sensors and actuators are tested on the ground to validate the performance and the results are satisfactory. The rover flight model is being assembled. Payloads are in various stages of delivery for spacecraft integration," Minister Jitendra Singh had said on 14 March when asked about the progress of the mission in Parliament.

ISRO had launched its first moon mission, Chandrayaan-I, in October 2008. Though the mission was expected to last for two years, it only lasted for roughly 10 months after the orbiter stopped communicating with the station in August 2009.

Predicting the Lifespan of Materials in Space

Almost every product we use has a shelf life. From milk and meat to laundry detergent and batteries, it's important to know when it's safe to use a product, and when it's time to replace it. But what about materials used for spacecraft? It is vital for scientists to know exactly how long a material will last in outer space; which is why Kim de Groh, a senior materials research engineer at NASA's Glenn Research Center in Cleveland, is gathering data from the Materials International Space Station Experiment (MISSE) missions. In April, de Groh will send 138 different material samples to the International Space Station as part of MISSE-9, which will be launched on SpaceX CRS-14 aboard a Dragon spacecraft. These samples will be part of the first MISSE mission to use the space station's new external materials testing platform, the MISSE-Flight Facility (MISSE-FF). De Groh wants to know how long these materials will last in outer space and will learn this by analyzing the affects atomic oxygen and radiation have on exposed polymers, composites and coatings. The flight data is needed to predict spacecraft performance and durability.

On Earth, the oxygen we breathe is made of two atoms of oxygen (O2), but in space the sun's rays break down (O2) into single oxygen atoms, creating atomic oxygen.

When spacecraft, such as the space station and resupply vehicles, travel in low-Earth orbit, atomic oxygen can react with its surfaces, causing materials, such as polymers, to erode. In addition, radiation can cause spacecraft materials to become brittle and crack.

De Groh has been involved with the MISSE missions since they began in 2001, and through this research, de Groh and her colleague Bruce Banks, have developed a model to predict the erosion of materials in space.

MISSE-9 will expose materials in each flight orientation on the space station. This includes forward facing known as "ram," rear-facing known as "wake," space-facing known as "zenith," and Earth-facing, known as "nadir." Flying samples in each orientation will show how the varying atomic oxygen and solar exposures in each position affect material.

"We will fly some of the same materials in different orientations as the same material can react differently in each flight direction," said de Groh.

The researchers expect the highest exposure to atomic oxygen for the ram samples and the least exposure to atomic oxygen for the wake samples. The highest solar exposure is likely for the zenith samples and the lowest solar exposure for the nadir samples. Monthly photos will be taken of the samples while in space showing color changes or sample cracking.

After a year in space, the MISSE-9 samples will be returned to Earth for post-flight analyses.

The data obtained from this mission will enable de Groh to make more accurate predictions of materials and component lifetimes in space, allowing engineers to build longer-lasting vehicles for spaceflight.

Airbus delivers new life support system for the ISS

Airbus has delivered the ACLS (Advanced Closed Loop System), an advanced life support system to purify air and produce oxygen for the International Space Station (ISS). The system also produces water, more or less as a by-product of the technology. ACLS was developed by Airbus for the European Space Agency (ESA) and is set to be used as a technology demonstrator on the ISS from summer 2018. The ACLS extracts a portion of the carbon dioxide in the cabin atmosphere and, using hydrogen obtained from splitting water molecules, converts it to methane and water in what is known as the Sabatier process. Oxygen is then produced from this water using electrolysis. This increases overall system efficiency and reduces the need for supplies from Earth.

The ACLS will now be installed in the HTV-7 space transporter at the Tanegashima Space Center in Japan and is due to be transported to the ISS in August 2018.

'Red and dead' NGC 1277 offers insights on the early universe

New analysis of a "relic galaxy" promises insights into the nature of the early universe. Formed some 12 billion years ago, the NGC 1277 galaxy birthed all of its stars within a span of 100 million years -- a star formation rate 1,000 times greater than that of the Milky Way. But nearly as quickly as the galaxy sprang to life, it died out. For the last 10 billion years, NGC 1277 has remained unchanged -- a relic of an earlier time in galactic evolution. To better understand the dynamics of the early universe, scientists used the Hubble Space Telescope to study NGC 1277. The lenticular galaxy is what's known as a "red and dead" galaxy. Most dead and red galaxies are found in the distant universe, too far away to be imaged in great detail. But at 240 million light-years away from Earth, NGC 1277 is close enough to offer insights. Most galaxies feature both red globular clusters, full of metal-rich stars, and blue clusters, globs of metal-poor stars. Models of galactic evolution suggest red clusters form during the earliest stages of a galaxy's formation, with blue clusters acquired later as new star forming material is pulled from the galaxy's surroundings. The lack of blue globular clusters is a sign that a galaxy stopped evolving -- that it is in a "state of arrested development."

Red and dead galaxies host mostly red clusters. NGC 1277 has only red clusters.

"I've been studying globular clusters in galaxies for a long time, and this is the first time I've ever seen this," Michael Beasley, a researcher with the Astrophysics Institute of the Canary Islands, said in a news release.

Scientists believe the massive black hole at the center of NGC 1277 grew quickly, pulling in stellar materials at a prodigious rate, inspiring the formation of the galaxy. But it's development stopped suddenly when it ran out of stellar material. As a result, the galaxy hosts a massive stellar popular but is extremely compact.

NGC 1277 is surrounded by other galaxies from which it could steal new material, but the latest Hubble findings show it is moving too fast to merge with other galaxies or acquire significant amounts of debris.

Described this week in the journal Nature, NGC 1277 is just one of 50 dense, compact relic galaxies identified by the Sloan Digital Sky Survey. Scientists hope future surveys of similar candidates will help astronomers better understand the nuances of galactic evolution in the early universe.

Scientists also hope newer, more powerful telescopes will help them study the role of dark matter in the formation and evolution of oddball galaxies like NGC 1277.

NASA Dawn Reveals Recent Changes in Ceres' Surface

Observations of Ceres have detected recent variations in its surface, revealing that the only dwarf planet in the inner solar system is a dynamic body that continues to evolve and change. NASA's Dawn mission has found recently exposed deposits that give us new information on the materials in the crust and how they are changing, according to two papers published March 14 in Science Advances that document the new findings. Observations obtained by the visible and infrared mapping spectrometer (VIR) on the Dawn spacecraft previously found water ice in a dozen sites on Ceres. The new study revealed the abundance of ice on the northern wall of Juling Crater, a crater 12 miles (20 kilometers) in diameter. The new observations, conducted from April through October 2016, show an increase in the amount of ice on the crater wall. "This is the first direct detection of change on the surface of Ceres," said Andrea Raponi of the Institute of Astrophysics and Planetary Science in Rome. Raponi led the new study, which found changes in the amount of ice exposed on the dwarf planet. "The combination of Ceres moving closer to the sun in its orbit, along with seasonal change, triggers the release of water vapor from the subsurface, which then condenses on the cold crater wall. This causes an increase in the amount of exposed ice. The warming might also cause landslides on the crater walls that expose fresh ice patches."

By combining chemical, geological and geophysical observations, the Dawn mission is producing a comprehensive view of Ceres. Previous data had shown Ceres has a crust about 25 miles (40 kilometers) thick and rich in water, salts and, possibly, organics.

In a second study, VIR observations also reveal new information about the variability of Ceres' crust, and suggest recent surface changes, in the form of newly exposed material.

Dawn previously found carbonates, common on the planet's surface, that formed within an ocean. Sodium carbonates, for example, dominate the bright regions in Occator Crater, and material of similar composition has been found at Oxo Crater and Ahuna Mons.

This study, led by Giacomo Carrozzo of the Institute of Astrophysics and Planetary Science, identified 12 sites rich in sodium carbonates and examined in detail several areas of a few square miles that show where water is present as part of the carbonate structure. The study marks the first time hydrated carbonate has been found on the surface of Ceres, or any other planetary body besides Earth, giving us new information about the dwarf planet's chemical evolution.

Water ice is not stable on the surface of Ceres over long time periods unless it is hidden in shadows, as in the case of Juling. Similarly, hydrated carbonate would dehydrate, although over a longer timescale of a few million years.

"This implies that the sites rich in hydrated carbonates have been exposed due to recent activity on the surface," Carrozzo said.

The great diversity of material, ice and carbonates, exposed via impacts, landslides and cryovolcanism suggests Ceres' crust is not uniform in composition. These heterogeneities were either produced during the freezing of Ceres' original ocean - which formed the crust - or later on as a consequence of large impacts or cryovolcanic intrusions.

"Changes in the abundance of water ice on a short timescale, as well as the presence of hydrated sodium carbonates, are further evidence that Ceres is a geologically and chemically active body," said Cristina De Sanctis, VIR team leader at the Institute of Astrophysics and Planetary Science.

Arianespace lofts 4 more O3b sats for SES led constellation

Arianespace has successfully launched four additional O3b satellites for the constellation operated by SES Networks. The launch took place on Friday, March 9 at 2:10 pm (local time) from the Guiana Space Center (CSG), Europe's Spaceport in French Guiana (South America).This mission was the second of the year for Arianespace, the first in 2018 using a Soyuz rocket and the second launch since January for the global operator SES. With this fourth launch for O3b fleet since 2013, all 16 spacecraft in the current O3b constellation have been orbited by Arianespace. With this latest mission, Arianespace has demonstrated that its family of launchers is extremely well suited to the deployment of communications, navigation and Earth observation satellite systems. This mission was the fourth for the O3b satellite fleet operated by global operator SES, following three previous launches to orbit the constellation's first 12 satellites performed on June 25, 2013, July 10, 2014 and December 18, 2014. With this latest successful launch of four more O3b satellites, Arianespace supports SES Networks' continued development of its constellation, which started commercial service in September 2014.

The four Ka-band O3b satellites will join the other O3b satellites already in Medium Earth Orbit (MEO) to provide low latency, fibre-like connectivity in the booming mobility, fixed data and government markets.

By expanding its O3b fleet, SES will be able to offer 38% more capacity worldwide, and extend its potential market from 45 to 50 degrees north and south latitude.

These new satellites will enable SES Networks to offer more capacity, extended coverage, greater efficiency and higher reliability. At the same time, they will provide operator-class services to businesses, government customers, telecommunications companies, mobile network operators and internet service providers.

Arianespace will launch four more O3b satellites into Medium Earth Orbit for this constellation in 2019.

Arianespace launches 57 satellites for SES in a 30-year partnership

SES, a world-leading satellite operator, is the first to deliver a differentiated and scalable GEO-MEO offering worldwide, with more than 50 satellites in geostationary Earth orbit (GEO) and 12 satellites in Medium Earth Orbit (MEO).

Arianespace and SES have developed an exceptional partnership over the last 30 years, made even stronger by this latest successful launch. Because of its versatile and complementary family of launchers, Arianespace is perfectly suited to address SES's GEO/MEO strategy and the requirements of its future programs.

The Arianespace family: especially well-suited to constellation launches

With its current family of launchers (Ariane 5, Soyuz and Vega) and its future family (Ariane 6 and Vega C), Arianespace enjoys an excellent position in the growth market of satellite constellations, whether for navigation, telecommunications or Earth observation; and for initial deployment, as well as subsequent replacement launches.

Right from its service entry in 2020, Ariane 6 will offer three major advantages for constellations: larger payload capacity, a restartable Vinci upper stage engine, and the Auxiliary Power Unit (APU), allowing the sequential release of satellites to prevent any collisions.

To address the specific needs of constellations with small satellites (0-400 kg.) - primarily for Earth observation - two multiple launch systems for Ariane 6 and Vega C are now being developed with the European Space Agency and the European Commission.

Shortly after the official announcement of the orbital injection of the O3b satellites on Flight VS18 mission, Stephane Israel, CEO of Arianespace, said: "With this second launch of the year, and the first by Soyuz, Arianespace is proud to help its long-standing customer SES meet its ambitious goals, for the second time in 2018. We are honored by the renewed confidence placed in us by SES, for whom we have launched 57 satellites since 1988, including the entire O3b constellation. I also would like to congratulate Thales Alenia Space, another loyal partner, which built all four O3b satellites. I would like to thank the Russian space agency Roscosmos for their commitment to our partnership based on Soyuz. My thanks go as well to CNES/CSG, our ground segment partners and all employees at the launch base, who continue to support us as we go from success to success. And of course, congratulations to all Arianespace staff, for this 18th Soyuz launch from CSG."

Quantum vacuum may allow stars to exist in unconventional configurations

A new kind of star comes up from a study by SISSA's postdoctoral researcher Raul Carballo-Rubio. In a piece of research recently published in Physical Review Letters, Carballo-Rubio has developed a novel mathematical model that combines general relativity with the repulsive effect of quantum vacuum polarization. The inclusion of this repulsive force allows describing ultracompact configurations of stars, which were previously considered by scientists not to exist in equilibrium. "As a consequence of the attractive and repulsive forces at play, a massive star can either become a neutron star, or turn into a black hole" says Carballo-Rubio. In neutron stars, stellar equilibrium is the result of the "fight" between gravity, which is an attractive force, and a repulsive force called degeneracy pressure, of quantum mechanical origin. "But if the star's mass becomes higher than a certain threshold, about 3 times the solar mass, the equilibrium would be broken and the star collapses due to the overwhelming pull of the gravitational force".

In this study, the researcher has investigated the possibility that additional quantum mechanical forces that are largely expected to be present in nature, permit new equilibrium configurations for stars above this threshold. The additional force that has been taken into account is a manifestation of the effect known as "quantum vacuum polarization", which is a robust consequence of mixing gravity and quantum mechanics in a semiclassical framework.

"The novelty in this analysis is that, for the first time, all these ingredients have been assembled together in a fully consistent model. Moreover, it has been shown that there exist new stellar configurations, and that these can be described in a surprisingly simple manner".

There are still several important issues that remain to be studied, including the observational applications of these results. "It is not clear yet whether these configurations can be dynamically realized in astrophysical scenarios, or how long would they last if this is the case".

From an observational perspective, these "semiclassical relativistic stars" would be very similar to black holes. However, even minute differences would be perceptible in the next generation of gravitational wave observatories: "If there are very dense and ultracompact stars in the Universe, similar to black holes but with no horizons, it should be possible to detect them in the next decades".

BlackSky readies to launch its first Earth Imaging Smallsat

BlackSky, the geospatial intelligence service of Spaceflight Industries, has announced the first of its next generation of small Earth observation satellites is complete, qualified, and awaiting launch. This spacecraft, called Global-1, is the first of four smallsats that are scheduled to launch in in the next year on both US and foreign launch vehicles.The Global series of spacecraft builds on the success of BlackSky's initial technology demonstration spacecraft, called Pathfinder, which was launched in September 2016. The Global spacecraft provides 1-meter resolution and features improved image quality, geolocation accuracy, and on-orbit lifetime. The spacecraft is complemented by an enhanced ground system to minimize the latency between image tasking and receipt."The Global satellites are an important step forward for the satellite industry," said Nick Merski, vice president of space operations at Spaceflight Industries. "We are continuing to advance the boundaries of what can be achieved in terms of price point, capability and form factor, and these improvements ultimately help to make space more accessible for a broader set of business applications."

BlackSky's Global smallsats will join the virtual constellation of commercial imaging satellites accessible through the BlackSky geospatial platform. Within the platform, users can access BlackSky Spectra's on-demand imagery service to search, purchase, task, and download visual imagery and multi-spectral data from a global collection network.

They can also subscribe to BlackSky Events, the platform's global event monitoring service that fuses news, social media, industry data services, and physical sensor networks to provide early warning and insights on risks, threats, and opportunities that can impact their business.

The platform is currently in use by several large government and commercial organizations to actively monitor global assets.

"This is an important milestone for Spaceflight Industries and for our BlackSky geospatial information business," said Jason Andrews, chairman and CEO of Spaceflight Industries.

"Qualifying the Global generation of spacecraft paves the way for mass production and launch of our full constellation, as well as achieving our vision of deploying a high revisit rate constellation in the near future."

World-first firing of air-breathing electric thruster

In a world-first, an ESA-led team has built and fired an electric thruster to ingest scarce air molecules from the top of the atmosphere for propellant, opening the way to satellites flying in very low orbits for years on end. ESA's GOCE gravity-mapper flew as low as 250 km for more than five years thanks to an electric thruster that continuously compensated for air drag. However, its working life was limited by the 40 kg of xenon it carried as propellant - once that was exhausted, the mission was over. Replacing onboard propellant with atmospheric molecules would create a new class of satellites able to operate in very low orbits for long periods. Air-breathing electric thrusters could also be used at the outer fringes of atmospheres of other planets, drawing on the carbon dioxide of Mars, for instance. "This project began with a novel design to scoop up air molecules as propellant from the top of Earth's atmosphere at around 200 km altitude with a typical speed of 7.8 km/s," explains ESA's Louis Walpot. A complete thruster was developed for testing the concept, which was performed in a vacuum chamber by Sitael in Italy, simulating the environment at 200 km altitude.

A 'particle flow generator' provided the oncoming high-speed molecules for collection by the Ram-Electric Propulsion novel intake and thruster.

There are no valves or complex parts - everything works on a simple, passive basis. All that is needed is power to the coils and electrodes, creating an extremely robust drag-compensation system.

The challenge was to design a new type of intake to collect the air molecules so that instead of simply bouncing away they are collected and compressed.

The molecules collected by the intake designed by QuinteScience in Poland are given electric charges so that they can be accelerated and ejected to provide thrust.

A two-step design ensures better charging of the incoming air, which is harder to achieve than in traditional electric propulsion designs.

"The team ran computer simulations on particle behaviour to model all the different intake options," adds Louis, "but it all came down to this practical test to know if the combined intake and thruster would work together or not.

"Instead of simply measuring the resulting density at the collector to check the intake design, we decided to attach an electric thruster. In this way, we proved that we could indeed collect and compress the air molecules to a level where thruster ignition could take place, and measure the actual thrust.

"At first we checked our thruster could be ignited repeatedly with xenon gathered from the particle beam generator."

As a next step, Louis explains, the xenon was partially replaced by a nitrogen-oxygen air mixture: "When the xenon-based blue colour of the engine plume changed to purple, we knew we'd succeeded.

"Finally, the system was ignited repeatedly solely with atmospheric propellant to prove the concept's feasibility.

"This result means air-breathing electric propulsion is no longer simply a theory but a tangible, working concept, ready to be developed, to serve one day as the basis of a new class of missions."

The PI's Perspective: Why Didn't Voyager Explore the Kuiper Belt?

New Horizons is in good health and cruising closer each day to our next encounter, an end-of-the-year flyby of the Kuiper Belt object (KBO) 2014 MU69 (or "MU69" for short). Currently, the spacecraft is hibernating while the mission team plans the MU69 flyby. During hibernation, three of the instruments on New Horizons-SWAP, PEPSSI and SDC-collect data every day on the charged particle, ionized plasma and dust environment in the Kuiper Belt at a solar distance of 41-42 astronomical units (AU), where our spacecraft is traveling. (1 AU is the distance from the Earth to the Sun, about 93 million miles or 140 million kilometers; for comparison, Pluto is about 34 AU from the Sun, so we're about 750 million miles farther out than Pluto now.) A role of all NASA mission principal investigators is to communicate with the public. I typically give 20 to 30 public New Horizons talks per year, and a question I used to get a lot is whether Voyager could have explored Pluto. I addressed that really interesting question in this column in June 2014, shortly before our Pluto encounter began.

Now people often ask why the Voyagers didn't explore the Kuiper Belt, since both Voyager 1 and 2 clearly transited this region after passing the giant planets. That's a really good question with a number of facets, so I thought I'd address it in this PI Perspective.

Our New Horizons extended mission to explore the Kuiper Belt and KBOs runs to mid-2021, when the spacecraft will be at a distance of 50 AU. This mission consists of three primary scientific investigations: studying the ionized plasma and dust environment of the Kuiper Belt with our charged-particle and dust sensors, studying numerous KBOs in the distance with our Long Range Reconnaissance Imager (LORRI), and exploring one ancient KBO (2014 MU69) in a close flyby.

Voyager carried many spectacular instruments through the Kuiper Belt, including imagers, spectrometers, magnetometers and charged-particle detectors. Those instruments have contributed a lot to our understanding of the Sun's heliosphere and the Kuiper Belt plasma environment, even though the Kuiper Belt wasn't discovered until 1992, when Voyager 1 was almost all the way across the region and Voyager 2 was deep within it. So even though the Voyager team didn't know their spacecraft was in the Kuiper Belt until 1992, the Voyagers themselves collected a lot of data about the region. Now, New Horizons is transiting the region with more advanced charged particle spectrometers and a dust detector, making new and more sensitive studies of this aspect of the Kuiper Belt's environment.

Regarding the images we're taking of KBOs our spacecraft passes in the distance, however, Voyager's imagers would have not been able to do what New Horizons can-such as search for KBO satellites, or determine KBO rotation periods and shapes. Why not? First, with very few known KBOs at the time, and certainly no small ones known close to Voyager's trajectory, it would have been impossible to put together a Kuiper Belt target observing list. But even had the team been able to somehow craft such a list, Voyager's cameras used older-technology Vidicon detectors instead of the charge-coupled devices (CCDs) that LORRI uses (and are found in most digital cameras). As a result, Voyager's imagers were not anywhere near as sensitive as those aboard New Horizons, and they could not have detected faint KBOs like the telescopic LORRI can.

But, perhaps most important is the question: could Voyager have flown by a small KBO as New Horizons will do this December and January? Again, regrettably, the answer is no, for a number of reasons. First, even once the Kuiper Belt had been detected in 1992, the Hubble Space Telescope (the only telescope capable of finding such distant flyby targets, even today) hadn't been repaired to properly focus light. That repair didn't occur until December 1993. By then, Voyager 1 was exiting the Kuiper Belt near 55 AU, and Voyager 2 was near 42 AU. But even after its repair, the Hubble wasn't sensitive enough to detect KBOs as small and common as MU69, so there would have been no way to find a flyby target-that capability only came in 2009, when a more advanced and sensitive wide-field camera was placed aboard the Hubble during a servicing mission.

And even if those limitations weren't the case, it might have been hard to find a KBO along the Voyagers' paths. That's because both Voyagers 1 and 2 traveled far out of the plane of the solar system, on which the heart of the Kuiper Belt resides. Unlike New Horizons, which is traveling directly through the densest region of the Kuiper Belt, the Voyagers were literally a billion or more miles above (Voyager 1) or below (Voyager 2) most of the KBO population; they were closer to the fringes of the population where there are fewer flyby candidates. Of course, had the Kuiper Belt been known in the 1980s, the Voyagers could have been targeted to fly through its heart, but that would have adversely affected the targeting of and scientific return from their final flybys at Saturn and Neptune, respectively, something I doubt the science teams would have favored because their prime objectives were to study the giant planets and their satellites.

It's too bad, because their cameras and spectrometers and other instruments could have made very nice observations of a flyby target had they been able to find one. But alas, there's wrinkle to that too: Voyager's cameras also weren't sensitive enough to navigate to a close flyby the way New Horizons can, snapping pictures to home in on MU69 even from distances of over 100 million miles (or 160 million kilometers), so it would have been very difficult to target a close flyby using Voyager. In sum, a Voyager KBO flyby was simply not in the cards, given the lack of knowledge of the Kuiper Belt back then, the Hubble's capabilities when Voyager crossed the region, the spacecraft trajectories and their onboard optical imaging and navigation limitations.

So, all in all, practical limitations meant that Voyager really could not have done the Kuiper Belt exploration mission New Horizons is now performing. But no matter, New Horizons is exploring the Kuiper Belt, and the Voyagers left an amazing legacy of truly opening our eyes to the giant planets and their rings, satellites and magnetospheres-both amazing outcomes!

I wonder when the next, even farther explorations will take place out in the Kuiper Belt, and how will people compare those future missions to what we accomplish with New Horizons?

Well, that's my update for now. For more mission news, stay tuned to the many websites and social media channels listed below.

I'll write again around the time we wake up New Horizons in early June. Until then, I hope you'll keep on exploring-just as we do!