Artificial aperture radar makes the Earth’s surface visible throughout the week | Science

In June 1794, almost a decade after the Montgolfier brothers invented the hot-air balloon, humans first observed a battlefield from a single point of view. The French Air Corps, a diverse team of chemists and carpenters, today launched a hydrogen balloon on the battlefield in Flores, Belgium, to inform their colleagues below of the moves of their Austrian enemies 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 Low Countries in 1914, the aircraft had already begun to give way to aircraft, and by the end of the war it was no longer in use. By the time NATO shifted its military headquarters to Mons, 40 kilometers west of Floros, satellites had entered the field in the 1960s.

The sensors remained intact with two obvious problems: darkness and clouds at night (Getty Images).

Sensor challenges

But despite the change in flight mode, the sensors remained the same, with two obvious problems: darkness and clouds at night; Half of the world is dark at any time of the day, and in most parts the sky is cloudy at times or always.

More than half of Europe is covered by clouds at any time of the year. In some parts of South America, cloudless images only appear every decade or so, says Adam Maher of Ursa Space, a startup based in Ithaca, New York, which uses satellite imagery for business intelligence.

Aiming to capture the entire surface of the Earth with a resolution of one meter per day, Planet Planet claims that about 70% of the Earth’s surface is cloudy at any given time.

But in the last few years, there has been tremendous progress in replacing visible wavelengths. Orbital radars illuminate the surface using wavelengths hundreds of thousands of times longer than visible light. These wavelengths penetrate easily into clouds, fog and smoke.

Among the advantages of long wavelengths; Permeability. The accuracy of the sensor depends on the wavelength and size of the aperture, the camera or telescope and the glass or lens depending on the antenna on the radar. As you stretch the wavelength, you increase the size of the hole you need to reach a certain clarity.

Synthetic aperture radar

Synthetic-aperture radar provides a way to deal with this problem. Satellites move very fast, usually in low orbit, at about 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 in use since the 1980s, but it is limited, expensive and highly classified. In the late 2000s, when both India and Israel had their own military satellites, the Pentagon’s right-hand man, the U.S. 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 routine way 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 carrying satellite aperture radar. Realizing that it was futile to try to stop their use because other countries had similar capabilities, the Pentagon backed them to increase its influence.

Finding milestones when they occur can be useful in combat (Getty Images)

Industry kings

Jack O’Connor, who has retired from the National Geo-Intelligence Agency since 2013, says artificial aperture radar coverage is not enough to provide a normal analysis.

The newspaper noted that even if the weather is bad – whether it is day or night – it allows the ability to monitor 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 from the phase of the waves they use in ways that exceed the capabilities of photovoltaic systems that use ambient light, changes at a specific location are analyzed with remarkable accuracy. Perception of communication change can also show temporary differences.

When the United States discovered the loss of troops in Iraq and Afghanistan by roadside bombs, scientists at the Sandia National Laboratory, one of the facilities responsible for the US nuclear weapons, developed a copperhead system, an artificial aperture radar-equipped drone, to detect changes. On the ground, “insurgents” (according to the newspaper’s description) detonated explosives or wires. Similar technologies allow satellites to detect small falls on the Earth’s surface when building 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 when fighting a battle.

Following the airstrikes on Pakistan in February 2019, India used its Emerging Satellite Radar (SAR) satellites for this purpose.
The U.S. Air Force did the same in tests conducted in December 2020, explicitly claiming that their use was triggered by weather conditions in Europe and the Pacific.

Ability to view location regardless of weather allows Armed Forces to create useful archives (Getty Images)

Population at all times and places

The magazine stressed that the ability to view 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 keep track of the members of the team in charge by re-watching the videos recorded after the attack.

The newspaper quoted Capella Founder Fear Benazir Bhutto as saying that the six satellites his company now owns in orbit could check anywhere on the planet every 6 hours. As the company’s consortium of satellites grows, it plans to reduce the re-viewing 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 run 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 it takes to transfer information from space to those in need is declining. Joe Morrison of Umbra, California, says he can order a satellite image in 5 years and get it in minutes.

Umbra hopes to promote the growth of an industry that sells analysis based on artificial aperture radar data to civilian and government clients to make that data cheaper. It plans to sell images over an area of ​​16 square kilometers, with one meter of clarity, for $ 500, under a license that allows buyers to do whatever they want with the product.

Large quantities of satellite images, at relatively low cost, provide excellent input to machine learning methods that are the basis for the latest advances in artificial intelligence.

The magazine noted that artificial aperture radar capabilities are an example of how much progress is being made with all kinds of sophisticated sensors and data processing systems needed to interpret its output.