Artist's impression of a laser removing orbital debris, based on NASA pictures. Credit: Fulvio314/NASA/Wikipedia Commons
Orbital debris (aka. space junk) is one of the greatest problems facing space agencies today. After sixty years of sending rockets, boosters and satellites into space, the situation in the Low Earth Orbit (LEO) has become rather crowded. Given how fast debris in orbit can travel, even the tiniest bits of junk can pose a major threat to the International Space Station and threaten still-active satellites.
It’s little wonder then why ever major space agency on the planet is committed to monitoring orbital debris and creating countermeasures for it. So far, proposals have ranged from giant magnets and nets and harpoons to lasers. Given their growing presence in space, China is also considering developing giant space-based lasers as a possible means for combating junk in orbit.
One such proposal was made as part of a study titled “Impacts of orbital elements of space-based laser station on small scale space debris removal“, which recently appeared in the scientific journal Optik. The study was led by Quan Wen, a researcher from the Information and Navigation College at China’s Air Force Engineering University, with the help of the Institute of China Electronic Equipment System Engineering Company.
Graphic showing the cloud of space debris that currently surrounds the Earth. Credit: NASA’s Goddard Space Flight Center/JSC
For the sake of their study, the team conducted numerical simulations to see if an orbital station with a high-powered pulsed laser could make a dent in orbital debris. Based on their assessments of the velocity and trajectories of space junk, they found that an orbiting laser that had the same Right Ascension of Ascending Node (RAAN) as the debris itself would be effective at removing it. As they state in their paper:
“The simulation results show that, debris removal is affected by inclination and RAAN, and laser station with the same inclination and RAAN as debris has the highest removal efficiency. It provides necessary theoretical basis for the deployment of space-based laser station and the further application of space debris removal by using space-based laser.”
This is not the first time that directed-energy has been considered as a possible means of removing space debris. However, the fact that China is investigating directed-energy for the sake of debris removal is an indication of the nation’s growing presence in space. It also seems appropriate since China is considered to be one of the worst offenders when to comes to producing space junk.
Back in 2007, China conducted a anti-satellite missile test that resulted in the creation over 3000 of bits of dangerous debris. This debris cloud was the largest ever tracked, and caused significant damage to a Russian satellite in 2013. Much of this debris will remain in orbit for decades, posing a significant threat to satellites, the ISS and other objects in LEO.
The chip in the ISS’ Cupola window, photographed by astronaut Tim Peake. Credit: ESA/NASA/Tim Peake
Of course, there are those who fear that the deployment of lasers to LEO will mean the militarization of space. In accordance with the 1966 Outer Space Treaty, which was designed to ensure that the space exploration did not become the latest front in the Cold War, all signatories agreed to “not place nuclear weapons or other weapons of mass destruction in orbit or on celestial bodies or station them in outer space in any other manner.”
In the 1980s, China was added to the treaty and is therefore bound to its provisions. But back in March of 2017, US General John Hyten indicated in an interview with CNN that China’s attempts to develop space-based laser arrays constitutes a possible breach of this treaty:
“They’ve been building weapons, testing weapons, building weapons to operate from the Earth in space, jamming weapons, laser weapons, and they have not kept it secret. They’re building those capabilities to challenge the United States of America, to challenge our allies…We cannot allow that to happen.”
Such concerns are quite common, and represent a bit of a stumbling block when it comes to the use of directed-energy platforms in space. While orbital lasers would be immune to atmospheric interference, thus making them much more effective at removing space debris, they would also lead to fears that these lasers could be turned towards enemy satellites or stations in the event of war.
As always, space is subject to the politics of Earth. At the same time, it also presents opportunities for cooperation and mutual assistance. And since space debris represents a common problem and threatens any and all plans for the exploration of space and the colonization of LEO, cooperative efforts to address it are not only desirable but necessary.
Have you noticed that weather forecasting has gotten much better in the last few years? Thanks to weather satellites, weather stations, and better forecasting techniques. How do scientists predict the weather with any kind of accuracy days or even weeks in the future.
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
What’s the weather doing? Is it going to rain today? How much? What about temperatures? We depend on modern weather forecasting, thanks, in part to the vast network of weather satellites. What instruments do they have, what orbits do they use.
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity's first interstellar voyage. Credit: breakthroughinitiatives.org
In 2015, Russian billionaire Yuri Milner established Breakthrough Initiatives, a non-profit organization dedicated to enhancing the search for extraterrestrial intelligence (SETI). In April of the following year, he and the organization be founded announced the creation of Breakthrough Starshot, a program to create a lightsail-driven “wafercraft” that would make the journey to the nearest star system – Alpha Centauri – within our lifetime.
This past June, the organization took a major step towards achieving this goal. After hitching a ride on some satellites being deployed to Low Earth Orbit (LEO), Breakthrough conducted a successful test flight of its first spacecraft. Known as “Sprites”, these are not only the smallest spacecraft ever launched, but prototypes for the eventual wafercraft Starshot hopes to send to Alpha Centauri.
The concept for a wafercraft is simple. By leveraging recent developments in computing and miniaturization, spacecraft that are the size of a credit card could be created. These would be capable of carrying all the necessary sensors, microprocessors and microthrusters, but would be so small and light that it would take much less energy to accelerate them to relativistic speeds – in the case of Starshot, up to 20% the speed of light.
Artist’s illustration of a light-sail powered by a laser beam (red) generated on Earth’s surface. Credit: M. Weiss/CfA
As Pete Worden – Breakthrough Starshot’s executive director and the former director of NASA’s Ames Research Center – said in an interview with Scientific American:
“This is a very early version of what we would send to interstellar distances. In addition, this is another clear demonstration that it is possible for countries to work together to do great things in space. These are European spacecraft with U.S. nanosatellite payloads launching on an Indian booster—you can’t get much more international than that.”
Professor Abraham Loeb also has some choice words to mark this historic occasion. In addition to being the Frank B. Baird Jr. Professor of Science, the Chair of the Astronomy Department and the Director of the Institute for Theory and Computation at Harvard University, Prof. Loeb is also the chairman of the Breakthrough Starshot Advisory Committee. As he told Universe Today via email:
“The launch of the Sprite satellites marks the first demonstration that miniaturized electronics on small chips can be launched without damage, survive the harsh environment of space and communicate successfully with earth. The Starshot Initiative aims to launch similar chips attached to a lightweight sail that it being pushed by a laser beam to a fifth of the speed of light, so that its camera, communication and navigation devices (whose total weight is of order a gram) will reach the nearest planet outside the solar System within our generation.”
A prototype Sprite nanosatellite, showing its solar panel, microprocessors, sensors and transmitters. Credit: Zac Manchester
The craft were deployed on June 23rd, piggybacking on two satellites belonging to the multinational technology corporation OHB System AG. Much like the StarChips that Starshot is proposing, the Sprites represent a major step in the evolution of miniature spacecraft that can do the job of larger robotic explorers. They measure just 3.5 by 3.5 cm (1.378 x 1.378 inches) and weight only four grams (0.14 ounces), but still manage to pack solar panels, computers, sensors and radios into their tiny frames.
The Sprite were originally conceived by Zac Manchester, a postdoctorate researcher and aerospace engineer at Cornell University. Back in 2011, he launched a Kickstarter campaign (called “KickSat“) to raise funds to develop the concept, which was his way of bringing down the associated costs of spaceflight. The campaign was a huge success, with Manchester raising a total of $74,586 of his original goal of $30,000.
Now a member of Breakthrough Starshot (where he is in charge of Wafer design and optimization), Manchester oversaw the construction of the Sprites from the Sibley School of Mechanical and Aerospace Engineering at Cornell. As Professor Loeb explained:
“The Sprites project is led by Zac Manchester, a Harvard postdoc who started working on this during his PhD at Cornell. Sprites are chip-size satellites powered by sunlight, intended to be released in space to demonstrate a new technology of lightweight (gram-scale) spacecrafts that can communicated with Earth.”
Zac Manchester holding a prototype KickSat. Credit: Zac Manchester/kickstarer
The purpose of this mission was to test how well the Sprites’ electronics systems and radio communications performed in orbit. Upon deployment, the Sprites remained attached to these satellites (known as “Max Valier” and “Venta”) and began transmitting. Communications were then received from ground stations, which demonstrated that the Sprites’ novel radio communication architecture performed exactly as it was designed to.
With this test complete, Starshot now has confirmation that a waferocraft is capable of operating in space and communicating with ground-based controllers. In the coming months and years, the many scientists and engineers that are behind this program will no doubt seek to test other essential systems (such as the craft’s microthrusters and imagers) while also working on the various engineering concerns that an instellar mission would entail.
In the meantime, the Sprites are still transmitting and are in radio contact with ground stations located in California and New York (as well as radio enthusiasts around the world). For those looking to listen in on their communications, Prof. Loeb was kind enough to let us know what frequency they are transmitting on.
“The radio frequency at which the Sprites that were just launched operate is 437.24 MHz, corresponding to a wavelength of roughly 69 cm,” he said. So if you’ve got a ham radio and feel like tuning in, this is where to set your dials!
And be sure to check out Zac Manchester’s Kickstarter video, which showcases the technology and inspiration for the KickSat:
A ferrofluid is a magnetic liquid that turns spiky in a magnetic field. Add an electric field and each needle-like spike emits a jet of ions, which could solve micropropulsion for nanosatellites in space. Credit: MTU
When it comes to the future of space exploration, some truly interesting concepts are being developed. Hoping to reach farther and reduce associated costs, one of the overarching goals is to find more fuel-efficient and effective means of sending robotic spacecraft, satellites and even crewed missions to their destinations. Towards this end, ideas like nuclear propulsion, ion engines and even antimatter are all being considered.
But this idea has to be the strangest one to date! It’s known as a ferrofluid thruster, a new concept that relies on ionic fluids that become strongly magnetized and release ions when exposed to a magnetic field. According to a new study produced by researchers from the Ion Space Propulsion Laboratory at Michigan Tech, this concept could very well be the future of satellite propulsion.
This study, which was recently published in the journal Physics of Fluids, presents an entirely new method for creating microthrusters – tiny nozzles that are used by small satellites to maneuver in orbit. Thanks to improvements in technology, small satellites – which are typically defined as those that weight less than 500 km (1,100 lbs) – can perform tasks that were once reserved for larger ones.
As the magnetic field is applied, the ferrofluid forms “peaks”, which disappear once the field is removed. Click to animate. Credit: MTU
As such, they are making up an increasingly large share of the satellite market, and many more are expected to be launched in the near future. In fact, it is estimated that between 2015 and 2019, over 500 small satellites will be launched to LEO, with an estimated market value of $7.4 billion. Little wonder then why researchers are looking at various types of microthrusters to ensure that these satellites can maneuver effectively.
While there are no shortage of possibilities, finding the one that balances cost-effectiveness and reliability has been difficult. To address this, an MTU research team began conducting a study that considered ferrofluids as a possible solution. As noted, ferrofluids are ionic liquids that become active when exposed to a magnetic field, forming peaks that emit small amounts of ions.
These peaks then return to a natural state when the magnetic field is removed, a phenomena known as Rosenweig instability. Led by Brandon A. Jackson – a doctoral candidate in mechanical engineering at Michigan Technological University – the MTU research team began to consider how this could be turned into propulsion. Other members included fellow doctoral candidate Kurt Terhune and Professor Lyon B. King.
Prof. King, the Ron & Elaine Starr Professor in Space Systems at Michigan Tech, has been researching the physics of ferrofluids for many years, thanks to support provided by the Air Force Office of Scientific Research (AFOSR). In 2012, he proposed using such ionic fluids to create a microthruster for modern satellites, based on previous studies conducted by researchers at the University of Sydney.
Without a magnetic field, ferrofluids look like a tarry, oil-based fuel. With a magnetic field, the propellant self-assembles, raising into a spiky ball. Credit: MTU
As he explained in a MTU press release, this method offers a simple and effective way to create a reliable microthruster:
“We’re working with a unique material called an ionic liquid ferrofluid. When we put a magnet underneath a small pool of the ferrofluid, it turns into a beautiful hedgehog structure of aligned peaks. When we apply a strong electric field to that array of peaks, each one emits an individual micro-jet of ions.”
With King’s help, who oversees MTU’s Ion Space Propulsion Laboratory, Jackson and Tehrune began conducting an an experimental and computational study on the dynamics of the ferrofluid. From this, they created a computational model that taught them much about the relationships between magnetic, electric and surface tension stresses, and were even surprised by some of what they saw.
“We wanted to learn what led up to emission instability in one single peak of the ferrofluid microthruster,” said Jackson. “We learned that the magnetic field has a large effect in preconditioning the fluid electric stress.”
Cubesats being launched from the International Space Station. Credit: NASA
Ultimately, what they had created was a model for an electrospray ionic liquid ferrofluid thruster. Unlike conventional electrospray thrusters – which generate propulsion with electrical charges that send tiny jets of fluid through microscopic needles – a ferrofluid electrospray thruster would be able to do away with these needles, which are expensive to manufacture and vulnerable to damage.
Instead, the thruster they are proposing would be able to assemble itself out of its own propellant, would rely on no fragile parts, and would essentially be indestructible. It would also present advantages over conventional plasma thrusters, which are apparently unreliable when scaled down for small satellites. With the success of their model, the AFOSR recently decided to award King a second contract to continue studying ferrofluids.
With this funding secured, King is confident that they can put what they learned with this study to good use, and scale it up to examine what happens with multiple peaks. As he explained:
“Often in the lab we’ll have one peak working and 99 others loafing. Brandon’s model will be a vital tool for the team going forward. If we are successful, our thruster will enable small inexpensive satellites with their own propulsion to be mass produced. That could improve remote sensing for better climate modeling, or provide better internet connectivity, which three billion people in the world still do not have.”
In the coming years, small satellites are expected to make up an ever-increasing portion of all artificial objects that are currently in Low Earth Orbit. Credit: ESA
Looking ahead, the team wants to conduct experiments on how an actual thruster might perform. The team has also begun working with Professor Juan Fernandez de la Mora of Yale University, one of the world’s leading experts on electrospray propulsion, to help bring their proposal to fruition. Naturally, it will take many years before a prototype is ready, and such a thruster would likely have to be able to execute about 100 peaks to be considered viable.
Nevertheless, the technology holds promise for a market that is expected to grow by leaps and bounds in the coming years and decades. Facilitating everything from worldwide internet access and telecommunications to scientific research, there is likely to be no shortage of smallsats, cubesats, nanosats, etc. taking to space very soon. They will all need to have reliable propulsion if they want to be able to stay clear of each other do their jobs!
Michigan Tech also has patents pending for the technology, which has applications that go beyond propulsion to include spectrometry, pharmaceuticals, and nanofabrication.
Composite image of continental U.S. at night, 2016.
Credits: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA's Goddard Space Flight Center
NASA strives to explore space and to expand our understanding of our Solar System and beyond. But they also turn their keen eyes on Earth in an effort to understand how our planet is doing. Now, they’re releasing a new composite image of Earth at night, the first one since 2012.
We’ve grown accustomed to seeing these types of images in our social media feeds, especially night-time views of Earth from the International Space Station. But this new image is much more than that. It’s part of a whole project that will allow scientists—and the rest of us—to study Earth at night in unprecedented detail.
Night-time views of Earth have been around for 25 years or so, usually produced several years apart. Comparing those images shows clearly how humans are changing the face of the planet. Scientists have been refining the imaging over the years, producing better and more detailed images.
The team behind this is led by Miguel Román of NASA’s Goddard Space Flight Center. They’ve been analyzing data and working on new software and algorithms to improve the quality, clarity, and availability of the images.
This new work stems from a collaboration between the National Oceanic and Atmospheric Administration (NOAA) and NASA. In 2011, NASA and NOAA launched a satellite called the Suomi National Polar-orbiting Partnership (NPP) satellite. The key instrument on that satellite is the Visible Infrared Imaging Radiometer Suite (VIIRS), a 275 kg piece of equipment that is a big step forward in Earth observation.
VIIRS detects photons of light in 22 different wavelengths. It’s the first satellite instrument to make quantitative measurements of light emissions and reflections, which allows researchers to distinguish the intensity, types and the sources of night lights over several years.
Composite image of Mid-Atlantic and Northeastern U.S. at night, 2016. Credits: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA’s Goddard Space Flight Center
Producing these types of maps is challenging. The raw data from SUOMI NPP and its VIIRS instrument has to be skillfully manipulated to get these images. The main challenge is the Moon itself.
As the Moon goes through its different phases, the amount of light hitting Earth is constantly changing. Those changes are predictable, but they still have to be accounted for. Other factors have to be managed as well, like seasonal vegetation, clouds, aerosols, and snow and ice cover. Other changes in the atmosphere, though faint, also affect the outcome. Phenomenon like auroras change the way that light is observed in different parts of the world.
The newly released maps were made from data throughout the year, and the team developed algorithms and code that picked the clearest night views each month, ultimately combining moonlight-free and moonlight-corrected data.
A glittering night-time map of Europe. Looks like there’s a Kraftwerk concert happening in Dusseldorf! NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA’s Goddard Space Flight Center
The SUOMI NPP satellite is in a polar orbit, and it observes the planet in vertical swaths that are about 3,000 km wide. With its VIIRS instrument, it images almost every location on the surface of the Earth, every day. VIIRS low-light sensor has six times better spatial resolution for distinguishing night lights, and 250 times better resolution overall than previous satellites.
What do all those numbers mean? The team hopes that their new techniques, combined with the power of VIIRS, will create images with extraordinary resolution: the ability to distinguish a single highway lamp, or fishing boat, anywhere on the surface of Earth.
Composite image of Nile River and surrounding region at night, 2016. Credits: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA’s Goddard Space Flight Center
Beyond thought-provoking eye-candy for the rest of us, these images of night-time Earth have practical benefits to researchers and planners.
“Thanks to VIIRS, we can now monitor short-term changes caused by disturbances in power delivery, such as conflict, storms, earthquakes and brownouts,” said Román. “We can monitor cyclical changes driven by reoccurring human activities such as holiday lighting and seasonal migrations. We can also monitor gradual changes driven by urbanization, out-migration, economic changes, and electrification. The fact that we can track all these different aspects at the heart of what defines a city is simply mind-boggling.”
These three composite images provide full-hemisphere views of Earth at night. The clouds and sun glint — added here for aesthetic effect — are derived from MODIS instrument land surface and cloud cover products. Credits: NASA Earth Observatory images by Joshua Stevens, using Suomi NPP VIIRS data from Miguel Román, NASA’s Goddard Space Flight Center
These maps of night-time Earth are a powerful tool. But the newest development will be a game-changer: Román and his team aim to provide daily, high-definition views of Earth at night. Daily updates will allow real-time tracking of changes on Earth’s surface in a way never before possible.
Maybe the best thing about these upcoming daily night-time light maps is that they will be publicly available. The SUOMI NPP satellite is not military and its data is not classified in any way. They hope to have these daily images available later this year. Once the new daily light-maps of Earth are available, it’ll be another powerful tool in the hands of researchers and planners, and the rest of us.
These maps will join other endeavours like NASA-EOSDIS Worldview. Worldview is a fascinating, easy-to-use data tool that anyone can access. It allows users to look at satellite images of the Earth with user-selected layers for things like dust, smoke, draught, fires, and storms. It’s a powerful tool that can change how you understand the world.
CubeSats NODes 1 & 2 and STMSat-1 are deployed from the International Space Station during Expedition 47. Image: NASA
We’re accustomed to the ‘large craft’ approach to exploring our Solar System. Probes like the Voyagers, the Mariners, and the Pioneers have written their place in the history of space exploration. Missions like Cassini and Juno are carrying on that work. But advances in technology mean that Nanosats and Cubesats might write the next chapter in the exploration of our Solar System.
Nanosats and Cubesats are different than the probes of the past. They’re much smaller and cheaper, and they offer some flexibility in our approach to exploring the Solar System. A Nanosat is defined as a satellite with a mass between 1 and 10 kg. A CubeSat is made up of multiple cubes of roughly 10cm³ (10cm x 10cm x 11.35cm). Together, they hold the promise of rapidly expanding our understanding of the Solar System in a much more flexible way.
A cubesat structure, made by ClydeSpace, 1U in size. Credit: Wikipedia Commons/Svobodat
NASA has been working on smaller satellites for a few years, and the work is starting to bear some serious fruit. A group of scientists at JPL predicts that by 2020 there will be 10 deep space CubeSats exploring our Solar System, and by 2030 there will be 100 of them. NASA, as usual, is developing NanoSat and CubeSat technologies, but so are private companies like Scotland’s Clyde Space.
NASA has built 2 Interplanetary NanoSpacecraft Pathfinder In Relevant Environment (INSPIRE) CubeSats to be launched in 2017. They will demonstrate what NASA calls the “revolutionary capability of deep space CubeSats.” They’ll be placed in earth-escape orbit to show that they can withstand the rigors of space, and can operate, navigate, and communicate effectively.
Following in INSPIRE’s footsteps will be the Mars Cube One (MarCO) CubeSats. MarCO will demonstrate one of the most attractive aspects of CubeSats and NanoSats: their ability to hitch a ride with larger missions and to augment the capabilities of those missions.
In 2018, NASA plans to send a stationary lander to Mars, called Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight). The MarCO CubeSats will be along for the ride, and will act as communications relays, though they aren’t needed for mission success. They will be the first CubeSats to be sent into deep space.
So what are some specific targets for this new class of small probes? The applications for NanoSats and CubeSats are abundant.
Other NanoSat and CubeSat Missions
NASA’s Europa Clipper Mission, planned for the 2020’s, will likely have CubeSats along for the ride as it scrutinizes Europa for conditions favorable for life. NASA has contracted 10 academic institutes to study CubeSats that would allow the mission to get closer to Europa’s frozen surface.
The ESA’s AIM asteroid probe will launch in 2020 to study a binary asteroid system called the Didymos system. AIM will consist of the main spacecraft, a small lander, and at least two CubeSats. The CubeSats will act as part of a deep space communications network.
ESA’s Asteroid Impact Mission is joined by two triple-unit CubeSats to observe the impact of the NASA-led Demonstration of Autonomous Rendezvous Technology (DART) probe with the secondary Didymos asteroid, planned for late 2022. Image: ESA
The challenging environment of Venus is also another world where CubeSats and NanoSats can play a prominent role. Many missions make use of a gravity assist from Venus as they head to their main objective. The small size of NanoSats means that one or more of them could be released at Venus. The thick atmosphere at Venus gives us a chance to demonstrate aerocapture and to place NanoSats in orbit around our neighbor planet. These NanoSats could take study the Venusian atmosphere and send the results back to Earth.
NanoSWARM
But the proposed NanoSWARM might be the most effective demonstration of the power of NanoSats yet. The NanoSWARM mission would have a fleet of small satellites sent to the Moon with a specific set of objectives. Unlike other missions, where NanoSats and CubeSats would be part of a mission centered around larger payloads, NanoSWARM would be only small satellites.
NanoSWARM is a forward thinking mission that is so far only a concept. It would be a fleet of CubeSats orbiting the Moon and addressing questions around planetary magnetism, surface water on airless bodies, space weathering, and the physics of small-scale magnetospheres. NanoSWARM would target features on the Moon called “swirls“, which are high-albedo features correlated with strong magnetic fields and low surficial water. NanoSWARM CubeSats will make the first near-surface measurements of solar wind flux and magnetic fields at swirls.
This is an image of the Reiner Gamma lunar swirl from NASA’s Lunar Reconnaissance Orbiter. Credits: NASA LRO WAC science team
NanoSWARM would have a mission architecture referred to as “mother with many children.” The mother ship would release two sets of CubeSats. One set would be released with impact trajectories and would gather data on magnetism and proton fluxes right up until impact. A second set would orbit the Moon to measure neutron fluxes. NanoSWARM’s results would tell us a lot about the geophysics, volatile distribution, and plasma physics of other bodies, including terrestrial planets and asteroids.
Space enthusiasts know that the Voyager probes had less computing power than our mobile phones. It’s common knowledge that our electronics are getting smaller and smaller. We’re also getting better at all the other technologies necessary for CubeSats and NanoSats, like batteries, solar arrays, and electrospray thrusters. As this trend continues, expect nanosatellites and cubesats to play a larger and more prominent role in space exploration.
A view from Earth orbit of the Longyangxia Dam Solar Park in China. Credit: NASA/Landsat 8.
While the Great Wall of China is not readily visible from space (we debunked that popular myth here) there are several other human-built structures that actually can be seen from space. And that list is growing, thanks to the large solar farms being built around the world.
The solar farm with the current distinction of being the largest in the world — as of February 2017 – is the Longyangxia Dam Solar Park in China. These new images from NASA’s Landsat 8 satellite show the farm’s blue solar panels prominently standing out on the brown landscape of the western province of Qinghai, China. Reportedly, the solar farm covers 27 square kilometers (10.42 square miles), and consists of nearly 4 million solar panels.
You can see in the image below from 2013 that the farm has been growing over the years. The project has cost the amount of 6 billion yuan ($889.5 million).
The orbital view from April 16, 2013 of the Longyangxia Dam Solar Park in China. Credit: NASA/Landsat 8.
China wants to shed its title of the biggest polluter in the world and is now investing in clean, renewable energy. It has a goal of producing 110 GW of solar power and 210 GW of wind power by the year 2020. That sounds like a lot, but in a country of 1.4 billion people that relies heavily on coal, it amounts to less than 1 percent of the country’s more than 1,500 gigawatts of total power generation capacity, says Inside Climate News.
According to NASA, China is now the world’s largest producer of solar power, however Germany, Japan, and the United States produce more solar power per person.
China has another solar farm in the works that will have a capacity of 2,000 MW when it is finished.
Here’s another wider-angle view from Landsat 8 of the Longyangxia Dam and lake near the solar farm.
The Longyangxia Dam Solar Park as seen from orbit on January 5, 2017. Credit: NASA/Landsat 8.
The Millennium Tower luxury skyscraper in San Francisco is sinking and tilting. Image by MichaelTG - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=51657571
The Millennium Tower is a luxury skyscraper in San Francisco. It has been sinking and tilting since it’s construction 8 years ago. In fact, the 58 story building has sunk 8 inches, and tilted at least 2 inches. San Francisco is experiencing a building boom, and planners and politicians want to know why the Millennium Tower is having these problems.
Now they’re getting a little help from space.
The European Space Agency’s (ESA) Copernicus Sentinel-1 satellites have trained their radar on San Francisco. They’ve found that the Millennium Tower is sinking, or subsiding, at the alarming rate of almost 50 mm per year. Although the exact cause is not yet known for sure, it’s suspected that the building’s supporting piles are not resting on solid bedrock.
An artist’s illustration of the Sentinel-1. Image: ESA/ATG Medialab
The Sentinel-1 satellites are part of the ESA’s Copernicus Program. There are two of the satellites in operation, and two more are on the way. They employ Synthetic Aperture Radar to provide continuous imagery during the day, during the night, and through any kind of weather.
The satellites have several applications:
Monitoring sea ice in the arctic
Monitoring the arctic environment and other marine environments
Monitoring land surface motion
Mapping land surfaces, including forest, water, and soil
Mapping in support of humanitarian aid in crisis situations
Though the Sentinels were not specifically designed to monitor buildings, they’re actually pretty good at it. Buildings like the Millennium Tower are especially good at reflecting radar. When multiple passes are made with the satellites, they provide a very accurate measurement of ground subsidence.
Radar data from Sentinel-1 shows the displacement in San Francisco’s Bay Area. Yellow-red areas are sinking, while blue areas are rising. Green areas are not moving. Image: ESA SEOM INSARAP study / PPO.labs / Norut / NGU
The Millennium Tower is not the only thing in San Francisco Bay Area that Sentinel-1 can see moving. It’s also spotted movement in buildings along the Hayward Fault, an area prone to earthquakes, and the sinking of reclaimed land in San Rafael Bay. It’s also spotted some rising land near the city of Pleasanton. The recent replenishing of groundwater is thought to be the cause of the rising land.
Now other parts of the world, especially in Europe, are poised to benefit from Sentinel-1’s newfound prowess at reading the ground. In Oslo, Norway, the train station is built on reclaimed land. Newer buildings have proper foundations right on solid bedrock, but the older parts of the station are experiencing severe subsidence.
Sentinel-1 data shows that the Oslo train station, the red/yellow area in the center of the image, is sinking at the rate of 12-18mm per year. Image: Copernicus Sentinel data (2014–16) / ESA SEOM INSARAP study / InSAR Norway project / NGU / Norut / PPO.labs
John Dehls is from the Geological Survey of Norway. He had this to say about Sentinel: “Experience and knowledge gained within the ESA’s Scientific Exploitation of Operational Missions programme give us strong confidence that Sentinel-1 will be a highly versatile and reliable platform for operational deformation monitoring in Norway, and worldwide.”
As for the Millennium Tower in San Francisco, the problems continue. The developer of the building is blaming the problems on the construction of a new transit center for the city. But the agency in charge of that, the Transbay Joint Powers Authority, denies that they are at fault. They blame the developer’s poor structural design, saying that it’s not properly built on bedrock.
Now, the whole thing is before the courts. A $500 million class-action lawsuit has been filed on behalf of the residents, against the developer, the transit authority, and other parties.
It’s a good bet that data from the Sentinel satellites will be part of the evidence in that lawsuit.
Look up at the night sky, and what do you see? Space, glittering and gleaming in all its glory. Astronomically speaking, space is really quite close, lingering just on the other side of that thin layer we call an atmosphere. And if you think about it, Earth is little more than a tiny island in a sea of space. So it is quite literally all around us.
By definition, space is defined as being the point at which the Earth’s atmosphere ends, and the vacuum of space begins. But exactly how far away is that? How high do you need to travel before you can actually touch space? As you can probably imagine, with such a subjective definition, people tend to disagree on exactly where space begins.
Definition:
The first official definition of space came from the National Advisory Committee for Aeronautics (the predecessor to NASA), who decided on the point where atmospheric pressure was less than one pound per square foot. This was the altitude that airplane control surfaces could no longer be used, and corresponded to roughly 81 kilometers (50 miles) above the Earth’s surface.
The Bell X-1, in which Chuck Yeager “broke” the sound barrier in 1947. Credit: NASA
Any NASA test pilot or astronaut who crosses this altitude is awarded their astronaut wings. Shortly after that definition was passed, the aerospace engineer Theodore von Kármán calculated that above an altitude of 100 km, the atmosphere would be so thin that an aircraft would need to be traveling at orbital velocity to derive any lift.
This altitude was later adopted as the Karman Line by the World Air Sports Federation (Fédération Aéronautique Internationale, FAI). And in 2012, when Felix Baumgartner broke the record for the highest freefall, he jumped from an altitude of 39 kilometers (24.23 mi), less than halfway to space (according to NASA’s definition).
By the same token, space is often defined as beginning at the lowest altitude at which satellites can maintain orbits for a reasonable time – which is approximately 160 kilometers (100 miles) above the surface. These varying definitions are complicated when one takes the definition of the word “atmosphere” into account.
Earth’s Atmosphere:
When we talk about Earth’s atmosphere, we tend to think of the region where air pressure is still high enough to cause air resistance, or where the air is simply thick enough to breath. But in truth, Earth’s atmosphere is made up of five main layers – the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere – the latter of which extend pretty far out into space.
Space Shuttle Endeavor silhouetted against Earth’s atmosphere. The orange layer is the troposphere, the white layer is the stratosphere and the blue layer the mesosphere. Credit: NASAThe Thermosphere, the second highest layer of the atmosphere, extends from an altitude of about 80 km (50 mi) up to the thermopause, which is at an altitude of 500–1000 km (310–620 mi). The lower part of the thermosphere, – from 80 to 550 kilometers (50 to 342 mi) – contains the ionosphere, which is so named because it is here in the atmosphere that particles are ionized by solar radiation.
Hence, this is where the phenomena known as Aurora Borealis and Aurara Australis are known to take place. The International Space Station also orbits in this layer, between 320 and 380 km (200 and 240 mi), and needs to be constantly boosted because friction with the atmosphere still occurs.
The outermost layer, known as the exosphere, extends out to an altitude of 10,000 km (6214 mi) above the planet. This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules (nitrogen, oxygen, CO²). The atoms and molecules are so far apart that the exosphere no longer behaves like a gas and the particles constantly escape into space.
It is here that Earth’s atmosphere truly merges with the emptiness of outer space, where there is no atmosphere. Hence why the majority of Earth’s satellites orbit within this region. Sometimes, the Aurora Borealis and Aurora Australis occur in the lower part of the exosphere, where they overlap into the thermosphere. But beyond that, there is no meteorological phenomena in this region.
Interplanetary vs. Interstellar:
Another important distinction when discussing space is the difference between that which lies between planets (interplanetary space) and that which lies between star systems (interstellar space) in our galaxy. But of course, that’s just the tip of the iceberg when it comes to space.
If one were to cast the net wider, there is also the space which lies between galaxies in the Universe (intergalactic space). In all cases, the definition involves regions where the concentration of matter is significantly lower than in other places – i.e. a region occupied centrally by a planet, star or galaxy.
In addition, in all three definitions, the measurements involved are beyond anything that we humans are accustomed to dealing with on a regular basis. Some scientists believe that space extends infinitely in all directions, while others believe that space is finite, but is unbounded and continuous (i.e. has no beginning and end).
In other words, there’s a reason they call it space – there’s just so much of it!
Exploration:
The exploration of space (that is to say, that which lies immediately beyond Earth’s atmosphere) began in earnest with what is known as the “Space Age“, This newfound age of exploration began with the United States and Soviet Union setting their sights on placing satellites and crewed modules into orbit.
The first major event of the Space Age took place on October 4th, 1957, with the launch ofSputnik 1 by the Soviet Union – the first artificial satellite to be launched into orbit. In response, then-President Dwight D. Eisenhower signed the National Aeronautics and Space Act on July 29th, 1958, officially establishing NASA.
Photograph of a Russian technician putting the finishing touches on Sputnik 1, humanity’s first artificial satellite. Credit: NASA/Asif A.
Immediately, NASA and the Soviet space program began taking the necessary steps towards creating manned spacecraft. By 1959, this competition resulted in the creation of the Soviet Vostok program and NASA’s Project Mercury. In the case of Vostok, this consisted of developing a space capsule that could be launched aboard an expendable carrier rocket.
Along with numerous unmanned tests, and a few using dogs, six Soviet pilots were selected by 1960 to be the first men to go into space. On April 12th, 1961, Soviet cosmonaut Yuri Gagarin was launched aboard the Vostok 1spacecraft from the Baikonur Cosmodrome, and thus became the fist man to go into space (beating American Alan Shepard by just a few weeks).
On June 16th, 1963, Valentina Tereshkova was sent into orbit aboard the Vostok 6 craft (which was the final Vostok mission), and thus became the first woman to go into space. Meanwhile, NASA took over Project Mercury from the US Air Force and began developing their own crewed mission concept.
Yury Gagarin before a space flight aboard the Vostok spacecraft. April 12, 1961 Credit: RIA Novosti
Designed to send a man into space using existing rockets, the program quickly adopted the concept of launching ballistic capsules into orbit. The first seven astronauts, nicknamed the “Mercury Seven“, were selected from from the Navy, Air Force and Marine test pilot programs.
On May 5th, 1961, astronaut Alan Shepard became the first American in space aboard the Freedom 7 mission. Then, on February 20th, 1962, astronaut John Glenn became the first American to be launched into orbit by an Atlas launch vehicle as part of Friendship 7. Glenn completed three orbits of planet Earth, and three more orbital flights were made, culminating in L. Gordon Cooper’s 22-orbit flight aboard Faith 7, which flew on May 15th and 16th, 1963.
In the ensuing decades, both NASA and Soviets began to develop more complex, long-range crewed spacecraft. Once the “Race to the Moon” ended with the successful landing of Apollo 11 (followed by several more Apollo missions), the focus began to shift to establishing a permanent presence in space.
For the Russians, this led to the continued development of space station technology as part of the Salyut program. Between 1972 and 1991, they attempted to orbit seven separate stations. However, technical failures and a failure in one rocket’s second stage boosters caused the first three attempts after Salyut 1 to fail or result in the station’s orbits decaying after a short period.
Skylab, America’s First manned Space Station. Photo taken by departing Skylab 4 crew in Feb. 1974. Credit: NASA
However, by 1974, the Russians managed to successfully deploy Salyut 4, followed by three more stations that would remain in orbit for periods of between one and nine years. While all of the Salyuts were presented to the public as non-military scientific laboratories, some of them were actually covers for the military Almaz reconnaissance stations.
NASA also pursued the development of space station technology, which culminated in May of 1973 with the launch of Skylab, which would remain America’s first and only independently-built space station. During deployment, Skylab suffered severe damage, losing its thermal protection and one of its solar panels.
This required the first crew to rendezvous with the station and conduct repairs. Two more crews followed, and the station was occupied for a total of 171 days during its history of service. This ended in 1979 with the downing of the station over the Indian Ocean and parts of southern Australia.
By 1986, the Soviets once again took the lead in the creation of space stations with the deployment of Mir. Authorized in February 1976 by a government decree, the station was originally intended to be an improved model of the Salyut space stations. In time, it evolved into a station consisting of multiple modules and several ports for crewed Soyuz spacecraft and Progress cargo spaceships.
The Mir Space Station and Earth limb observed from the Orbiter Endeavour during NASA’s STS-89 mission in 1998. Credit: NASA
The core module was launched into orbit on February 19th, 1986; and between 1987 and 1996, all of the other modules would be deployed and attached. During its 15-years of service, Mir was visited by a total of 28 long-duration crews. Through a series of collaborative programs with other nations, the station would also be visited by crews from other Eastern Bloc nations, the European Space Agency (ESA), and NASA.
After a series of technical and structural problems caught up with the station, the Russian government announced in 2000 that it would decommission the space station. This began on Jan. 24th, 2001, when a Russian Progress cargo ship docked with the station and pushed it out of orbit. The station then entered the atmosphere and crashed into the South Pacific.
By 1993, NASA began collaborating with the Russians, the ESA and the Japan Aerospace Exploration Agency (JAXA) to create the International Space Station (ISS). Combining NASA’s Space Station Freedom project with the Soviet/Russian Mir-2 station, the European Columbus station, and the Japanese Kibo laboratory module, the project also built on the Russian-American Shuttle-Mir missions (1995-1998).
With the retirement of the Space Shuttle Program in 2011, crew members have been delivered exclusively by Soyuz spacecraft in recent years. Since 2014, cooperation between NASA and Roscosmos has been suspended for most non-ISS activities due to tensions caused by the situation in the Ukraine.
However, in the past few years, indigenous launch capability has been restored to the US thanks to companies like SpaceX, United Launch Alliance, and Blue Origin stepping in to fill the void with their private fleet of rockets.
The ISS has been continuously occupied for the past 15 years, having exceeded the previous record held by Mir; and has been visited by astronauts and cosmonauts from 15 different nations. The ISS program is expected to continue until at least 2020, but may be extended until 2028 or possibly longer, depending on the budget environment.
As you can clearly see, where our atmosphere ends and space begins is the subject of some debate. But thanks to decades of space exploration and launches, we have managed to come up with a working definition. But whatever the exact definition is, if you can get above 100 kilometers, you have definitely earned your astronaut wings!
![Space Shuttle Endeavour sillouetted against the atmosphere. The orange layer is the troposphere, the white layer is the stratosphere and the blue layer the mesosphere.[1] (The shuttle is actually orbiting at an altitude of more than 320 km (200 mi), far above all three layers.) Credit: NASA](https://www.universetoday.com/wp-content/uploads/2012/03/Endeavour_silhouette_STS-130.jpg)
