The Economist March 20th 2021 pp71-72|Science & technology| Espionage (1) “Ears in the sky” “By listening for radio and radar signals, a new generation of satellites can track human activity, both licit and illicit”
Source unseenlabs.space
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Summary of the article
As we have reported before there are a new generation of low-orbit miniature satellites dubbed cubesats that can cover the earth using various sensing devices. This article features those that detect radio and radar signals on land or sea. As an example, they can detect ships, through clouds and whether or not they have enabled required Automatic Identification Systems (AIS). In doing so, organizations including navies or governments can track the whereabouts of seagoing vessels some of which through data analysis systems have been identified using unique attributes they have cataloged previously. HawkEye 360, Virginia U.S.A., “announced it had detected vessels inside Equador’s EEZ (Exclusive Economic Zone) on 14 occasions when the boats in question were not transmitting AIS.” This is accomplished by “listening for faint signals emanating from their navigation radars and radio communications. While vessels might turn off AIS it is unlikely they will disable radar and radio. Systems have also been used to identify, best sites for mobile phone towers, illegal gold mines, elephant poachers, “guerilla camps and mobile missile launchers, and to track both conventional and unconventional craft like the weaponized speedboats sometimes deployed by Iran. Hawkeye now has two tracking stations one in the Arctic Ocean (Svalbard Island, Norway) and a ground station in Antarctica. There are “at least six other companies operating or developing similar systems.”
Radio frequency (RF) intelligence satellites use two methods to detect where “a transmission is coming from.” One method uses trilateration “measuring minute differences in a signal’s arrival time at each member of a cluster of satellites. A cluster of satellites can sweep 2,000 km wide, circling the earth every 90 minutes “revisiting areas several times a day." The other method “uses the Doppler effect-the shift in a signal’s frequency if the transmitter is moving relative to the receiver.” Hawkeye claims a resolution of 500 meters. The receivers can “see through clouds”, are not fooled by bogus/fabricated AIS signals and are sensitive enough to detect satellite phones, walkie talkies and all radar but not standard cell phone communication. RF cubsats are relatively inexpensive, another firm know as Horizon “says that building, insuring and launching its August mission should cost no more than $1.4 million.”
The technology is rapidly improving from clusters to single satellites (Unseenlabs, France). The single satellites work by “accessing differences in the angles at which a target’s signals arrive during the satellite’s arc across the sky.” Horizon, “plans to compile a library of unique radar-pulse ‘fingerprints’ of the world’s vessels.” Unseenlabs “has already cataloged the radar fingerprints of many thousands of vessels” without relying on AIS.