TERMO-LR Experiment on the Luna-27 Lander: Study of Thermophysical, Physicomechanical, and Electromagnetic Properties of the Lunar Soil

The device is being developed for the TERMO-LR experiment on the Luna-27 lunar lander; it is intended for contact geophysical measurements of various properties of the lunar soil on the surface and at a depth up to 3 m. We consider the scientific tasks of the experiment regarding the study of physicomechanical (density, mechanical and deformation characteristics), thermophysical (thermal conductivity, heat capacity), and electromagnetic (dielectric permittivity, magnetic susceptibility) properties of the lunar soil and the internal heat flow of the Moon. A description of the design and technical characteristics, functional diagram and operating modes of the device, which consists of three main units: a depth measurement unit with a deep logging probe, a surface measurement unit, and an electronics unit, are given. The logging probe includes a self-deepening penetrator hammer, a dielectric permittivity sensor, a magnetic susceptibility sensor, and a tape with temeprature sensors for measuring the temperature distribution in the soil and internal heat flow. The surface measurement unit includes temperature sensors for measuring the thermophysical properties of the lunar soil on the surface in passive and active modes. The tests and calibration of temperature sensors of the surface measurement unit are considered, which have confirmed the high performance characteristics of the sensor and the reliability of the measurement interpretation.