Poland has requested four TARS (Tethered Aerostat Radar System) systems from United States. TARS is a tech pioneered by and heavily used by American forces since September 11, 2001. Israel and the U.S. are major developers of and suppliers of such systems. Systems like TARS have been around for decades but have become more useful since the 1990s as radar and other sensors became smaller, lighter, more capable and reliable. Poland wants a TARS using a very powerful radar and electronic countermeasures system. The Polish TARS has a radar with a range of about 400 kilometers and the aerostat carrying the radar aloft can carry about a ton of sensors. The Polish border with Ukraine is only about 520 kilometers but if you add the borders with Belarus and the Russian enclave of Kalinin grade, you have over 1,200 kilometers of potentially hostile borders to monitor. Russia is close enough to attack Poland with low flying cruise missiles or UAVs along all these borders. Poland first discussed obtaining TARS from the Americans five years ago and aerostat use in Ukraine convinced Poland aerostats were viable surveillance tech that could survive a surprise attack and remain operational.
Aerostats are helium-filled blimp-like vehicles designed to always turn into the wind and stay in the same place. The U.S. developed larger aerostat systems (JLENS) to detect cruise missiles but the U.S. Army, since 2004 used dozens of smaller and cheaper aerostat systems for local security in Iraq and Afghanistan. These aerostats operated at about 330 meters (a thousand feet) up, tethered by a cable that provides power and communications to the day and night cameras up there. Larger aerostats can hover at 3,000 meters altitude and carry up to two tons of sensors. These blimps can stay up for about 30 days at a time before being brought down for maintenance.
Often two radars are carried on larger systems like JLENS and TARS. One is a surveillance radar and the other is a precision track and illumination radar (PTIR). The surveillance radar provides long-range coverage (up to 500 kilometers) while the PTIR, which is a steerable system capable of tracking multiple targets, can focus in on items of interest. TARS will give Poland persistent surveillance of border areas.