Introduction

The ISTRA+ experiment being the development of ISTRA-M [1] started in 1999 at IHEP, Protvino. Its aim is the study of rare (on the level of $10^{-6}\div 10^{-8}$) decays of charged light mesons, such as $K\rightarrow e\nu\gamma$, $K\rightarrow e\nu\pi^0$, $\pi\rightarrow e\nu\gamma$ etc.