What can a 'spy satellite' do?





 Cradled by our film culture,
the satellites used in the service of armies around the world are often fantasized.
What are they for ? What about their abilities? They are not
public, but they too cannot match fiction.

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What is a spy satellite?

In reality, there is little that differentiates a 'spy' satellite from a commercial satellite at first glance. Of course, a state does not advertise as much as a company for its dedicated defense surveillance capabilities, so the exact characteristics of these units are not readily available. That said, even for those of whom we have no photographs (there are few), the rocket with which they are launched often gives a spectrum of their capacities: impossible for example to make take off a heavy telescope in a very small launcher. … And conversely, no need to order a heavy launcher for a trio of small electronic listening satellites.



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Once up there, however, those with a genuine interest in the subject don't have too much trouble identifying the orbital characteristics of these great tech gems. With the right equipment (all major nations have it, and even some amateurs) it is also possible to observe these satellites directly with a precision which easily reveals their nature. Depending on the antennas and their shape, it is easy to guess what a particular satellite is used for.



A 'spy' satellite therefore has only name to spy. It is its results that are espionage, because they are not hidden. Some, it is France's choice, make no secret of the role of their satellites (for example we know very well that the new generation of CSO satellites is a trio of optical observation satellites). Others hide the raison d'être of their new units under generic names.

This is the case of the United States (with their NROL satellites, renamed USA-XXX once in orbit) and of Russia (with the Cosmos satellites), but also of China, which regularly announces new satellites in its press releases ' observation of agricultural crops ”. At the rate at which the latter take off, the rice fields are well watched… In this little fool's game, all those who are really concerned (that is to say each other's armies) know what the satellites are doing in question.



Optics, all-purpose espionage

This is the most intuitive application: point a camera at the ground with a huge lens, and take pictures of your opponents. An application that will be talked about from the very first satellites at the end of the 1950s, and which will give rise to its own technological race. It will advance in giant leaps. First, telescopic optics that can be pointed precisely. Then, satellites with a wider sweep (often, an extraordinary resolution under the meter is paid in return with a very reduced field of view), better sensors.



In the mid-1980s, optical satellites embarked on digital technology which began to dispense with the need to send film back to the ground. A phenomenal saving of time… Although for certain resolutions, Russian film satellites will be used until the year 2010. Lately, the satellites are “agile”, they can rotate quickly to take pictures along their route, identify their target in advance to better calibrate their optics, store crazy quantities of high-resolution shots or films.



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This resolution, moreover, what is it? In some movies, it is possible to use the satellites to recognize someone, or read a license plate. In reality… It's more complex. Understand that with a resolution of 50 centimeters per pixel, a pedestrian seen from orbit is only one or two points. The best military units go under 30 centimeters (this is the commercial limit), and some (there is debate of course) would be under 10. Still too much to read a license plate, or recognize Uncle Michel, but enough to identify armed people, the equipment of a vehicle or the position of an antenna ...

However, it should be borne in mind that there is not only one important characteristic: the field of view (we speak of swath), the frequency of image capture, the time it takes to resume a photograph of the same area, the ability of the sensors to integrate color information, everything is important. To spot a pick-up in the desert, you don't need crazy resolution, you need the ability to photograph hundreds of kilometers of track ...



Radar, a very effective tool

Despite its very beautiful optics, there are many cases where optical satellites have shown their limits. At night, for example, or when a thick cloud layer covers an area. An optic too, we can deceive it with camouflage or decoys. Radars, more difficult to develop for space applications (especially for high resolutions) can compensate for these defects, regardless of the time and weather conditions.



Even more annoying, depending on the technologies used, a radar signal can “pass through” certain camouflage materials and… even the ground. Indirectly, these satellites are one of the tools that led to the reduction in the number of missile silos in the Eastern and Western blocs: it was simply becoming impossible to hide them.



Electronic intelligence, sub-domain.

It is a formidable tool, which the space powers jealously protect. Wiretapping satellites are passive, deploying their large antennas to pick up emissions from ground equipment. An anti-aircraft radar installed at the entrance to a valley? Beep. A camouflaged tank that acts as a command post? Beep beep. A submarine surfacing to get new orders? Beep beep. The list is long, and ranges from calls made by reckless terrorists to radio exchanges between a mechanized division and its artillery, including communications between an air patrol and its precious tanker plane ... Of course, these are not either satellites which can decipher everything, but the fusion of data with other indicators (such as an image of an optical or radar satellite, surveys on the ground or by drone, etc.) makes it an essential tool.



Early warning, satellites of the end of the world

Behind a popular name, 'early warning' satellites are the ultimate jewels of technology, which can cost close to two billion dollars apiece and… hardly ever be used. Indeed, they are there to detect and qualify ballistic and strategic launches in the world. Equipped with very sensitive infrared detectors, they react to intense sources of light and heat during takeoff, and can then follow the trajectory of these objects to estimate their function.



Because when a missile leaves its wheeled vehicle and engages on a parabola trajectory which can land 12,000 kilometers further on in a large city (American, for example) it is necessary to react very quickly. And if necessary, wake up military and political officials who can engage in 'mutually assured destruction'. Poetry. These early warning satellites also pick up orbital launches around the world, and can generate alerts during other disasters such as large fires, eruptions or accidental explosions.



Spy on ... satellites

In truth, they are rather the spy satellites. Indeed there are some observation satellites… satellites. A few go into low orbit to 'follow' a few hundred kilometers the largest and most imposing technological jewels of their opponents. To test a small interference, for example, or to capture the commands exchanged between satellite and ground stations… or quite simply to observe them to understand their role and or their capacities. Others will approach telecommunications satellites in geostationary orbit, to 'sniff' the signals they relay.



A dangerous game, which several space agencies denounce ... without always applying the same good behavior to their own satellites. The fear, of course, is to eventually have small approach and potentially attack satellites. France in particular has planned a defense nanosatellite program which will be able to act in a perimeter close to our most sensitive units.

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