the name of Soviet unmanned high-altitude ionospheric laboratories that were launched with domestic, series-production geophysical rockets to study the performance of electrostatic rocket engines in space. During testing, measurements were taken of the flux density of the ionospheric ions striking the surface of the laboratory, the electric potential of the laboratory’s surface, engine discharge current, and the ion-beam current. Four Iantar’-l’s were launched between 1966 and 1971. Propellant for the engines consisted of argon, nitrogen, and air, with exhaust velocities fixed at 40 km/sec, 120 km/sec, and 140 km/sec, respectively. (See also.)