The photo published by the Ukraine Weapons Tracker Twitter account depicts one of the upgraded Polish S-125 Newa-SC systems. That shows that although no official communications were released, pointing to the delivery of this system to Ukraine from Poland, it is being used by Poland's eastern neighbours to defend their country. The tweet mentions the fact that the Polish system has been upgraded with new electronics, and is based on the T-55 MBT platform.
The Newa system dates to the late 1950s, and it has been developed in the USSR to eliminate low-flying enemy aircraft. The system can launch 5V27U and 5V27D missiles, with a range of 25 kilometres, and is capable of eliminating targets flying at an altitude of 18 kilometres. The SC suffix stands for Samobieżny and Cyfrowy (Self-propelled and Digital). It is a Polish modification of its Soviet prerequisite. The main portion of the Polish S-125 upgrades began in the late nineties, and WZE Zielonka was the main entity engaged in the project, working with the Military University of Technology (WAT).
#Ukraine: The first photo of a Polish 🇵🇱 S-125 Newa SC air-defense system in use with the Ukrainian army. Main difference of the Polish modernization is the WZT-1 tank chassis and updated electronics.— 🇺🇦 Ukraine Weapons Tracker (@UAWeapons) December 5, 2022
Previously Poland didn't report any deliveries of such systems to Ukraine. pic.twitter.com/0HHgtKjoTC
The upgrades were aimed at increased lethality, improved mobility, changed combat employment methods, easier training, implementation of an A/C system, digital data recorders, and achieving a diminished number of launchers within a single battery - from 4 to 3 systems. Replacement of analogue systems with digital ones has been a key element of the upgrade, also rendering the whole system less exposed and vulnerable to jamming. Modernization was also applied when it comes to the SNR radar deployment hydraulics.
The whole upgrade did not, however, concern the missiles. The launchers have been based on the previously decommissioned T-55 MBTs, while command cabins with antenna columns were integrated on MAZ-543 vehicles, that had been used in the surface-to-surface SCUD systems before. Noteworthy, Ukraine also developed and implemented its own, original upgrades for the Newa system. The fact that Newa has been well known to the Ukrainian soldiers surely contributed to easier training, when it comes to the use of the Polish systems.
The Polish Armed Forces currently operate modernized Newa SC SAMs that are a part of air defence missile squadron units. Starting this year (as deliveries have begun when it comes to the first IBCS/Patriot squadron for phase I of the Wisła programme, with that squadron soon expected to be integrated and achieve readiness), a process aimed to replace the Newa SCs with new systems began. Some of the Newa systems are also expected to be replaced by the Narew system.