Artificial Aperture Radar Makes Earth’s Surface Visible All Week Long
In June 1794, nearly a decade after the invention of the hot air balloon by the Montgolfier brothers, humans first observed a battlefield from a single vantage point. The French Air Force, a diverse team of chemists and carpenters, today launched a hydrogen balloon over the battlefield of Flores, Belgium, to inform their colleagues below of the movements of their enemies Austrians through the semaphore.
The British newspaper The Economist said: A statement The success of the hot air balloon is not surprising, its importance is short-lived. When war broke out again in the Netherlands in 1914, the airplane had already begun to give way to airplanes, and by the end of the war it was no longer in use. By the time NATO moved its military headquarters to Mons, 40 kilometers west of Floros, satellites had entered the field in the 1960s.
But despite the change in flight mode, the sensors remained the same, with two obvious problems: darkness and clouds at night; Half the world is dark at all times of the day, and in most areas the sky is sometimes or always cloudy.
More than half of Europe is covered in clouds at all times of the year. In parts of South America, cloud-free images only appear about every ten years, says Adam Maher of Ursa Space, an Ithaca, New York-based startup that uses satellite imagery for intelligence. economic.
Aiming to capture the entire surface of the Earth with a resolution of one meter per day, Planet Planet claims that around 70% of the Earth’s surface is cloudy at any given time.
But in recent years, considerable progress has been made in replacing visible wavelengths. Orbital radars illuminate the surface using wavelengths hundreds of thousands of times longer than visible light. These wavelengths easily penetrate clouds, fog and smoke.
Among the advantages of long wavelengths; Permeability. The accuracy of the sensor depends on the wavelength and the size of the aperture, the camera or telescope and the glass or lens depending on the antenna of the radar. As you stretch the wavelength, you increase the size of the hole you need to achieve some clarity.
Synthetic Aperture Radar
Synthetic aperture radar solves this problem. Satellites move very quickly, usually in low orbit, at around 25,000 kilometers per hour. By taking all its radar shots when passing a specific target and processing them into a single image, the artificial aperture radar gives an accurate result.
This technology has been available since the 1960s and spy satellites have been used since the 1980s, but it is limited, expensive and highly classified. In the late 2000s, when India and Israel had their own military satellites, the Pentagon’s right arm, the US National Intelligence Service, classified the existence of such satellites.
Civilian space agencies in the United States, Canada and Europe have used this technology for a variety of environmental tasks, but not as a common means of monitoring human activities. Advances in electronics, space engineering, and orbital computing have made it possible to place artificial aperture radar systems with an accuracy of a few meters or less on smaller satellites at an affordable price.
In 2018, two start-ups – Capella Space in California and ICEYE in Finland – launched commercial satellites equipped with satellite aperture radar. Realizing that trying to stop their use was futile because other countries had similar capabilities, the Pentagon backed them to increase its influence.
kings of industry
Jack O’Connor, who retired from the National Geo-Intelligence Agency in 2013, says artificial aperture radar coverage is not sufficient to provide normal analysis.
The newspaper noted that even if the weather is bad – whether day or night – it allows monitoring of moving objects such as the military concentration on the border with Ukraine. The pictures may not be enough to determine the type of armor, but they are good enough to count the number.
Thanks to radar systems that collect data on the phase of the waves they use in a way that exceeds the capabilities of photovoltaic systems that use ambient light, changes at a specific location are analyzed with remarkable precision. The perception of communication change may also show temporary differences.
When the United States discovered the loss of troops in Iraq and Afghanistan to roadside bombs, scientists at Sandia National Laboratory, one of the facilities responsible for American nuclear weapons, developed a Copperhead system, a drone equipped with an artificial aperture radar, to detect changes. On the ground, “insurgents” (according to the newspaper’s description) detonate explosives or wires. Similar technologies allow satellites to detect small drops on the Earth’s surface during the construction of tunnels for nuclear testing.
It is useful to quickly identify whether the bombs hit the right targets and what damage they caused, and it will be useful to find different components during a battle.
Following the airstrikes on Pakistan in February 2019, India used its Emerging Satellite Radar (SAR) satellites for this purpose.
The US Air Force did the same in tests conducted in December 2020, explicitly stating that their use was triggered by weather conditions in Europe and the Pacific.
Population anytime, anywhere
The magazine pointed out that being able to consult a site on a regular basis – regardless of weather conditions – allows the Armed Forces to create archives that will be useful in the future.
An example of this is another system developed by the Pentagon to counter advanced explosive devices called the Gorgon Star System, which allowed drones to capture video clips of entire cities for weeks and months. The idea was to find out when the IEDs were buried and to keep track of the team members responsible by reviewing the videos recorded after the attack.
The newspaper quoted Capella founder Fear Benazir Bhutto as saying that the six satellites his company now has in orbit could check anywhere on the planet every 6 hours. As the company’s satellite consortium grows, it plans to reduce the review time to a maximum of 15 minutes, which is less than the time it would take a country to launch a ballistic missile.
He pointed out that the satellites could not operate 24/7 because the antennas were powered by solar panels and their batteries were not large enough to operate continuously at night.
The magazine said that with the increase in the number of data companies and ground stations such as “Amazon Web Services”, the time required to transfer information from space to those who need it is decreasing. Joe Morrison of Umbra, California says he can order a satellite image in 5 years and have it in minutes.
Umbra hopes to promote the growth of an industry that sells analytics based on artificial aperture radar data to civilian and government customers to make that data cheaper. It plans to sell 16 square kilometer images, with one meter of clarity, for $500 under a license that allows buyers to do whatever they want with the product.
Large amounts of satellite imagery, at a relatively low cost, provide an excellent contribution to machine learning methods that are the basis of the latest advances in artificial intelligence.
The magazine noted that the capabilities of the artificial aperture radar are an example of the advances made with all sorts of sophisticated sensors and data processing systems needed to interpret its output.