Removing the dose background from radioactive sources from active dose rate measurements in the Lunar Lander Neutron & Dosimetry (LND) experiment on Chang'E 4

The Lunar Lander Neutron & Dosimetry (LND) experiment is part of the scientific payload of the Chinese Chang'E 4 spacecraft which landed on the Moon on January 3, 2019. The LND measures the radiation environment on the surface of the moon in preparation of future manned missions to the Moon. There are, however, also four radioactive sources on the lander, a radioisotope thermoelectric generator (RTG) and three radioisotope heater units (RHUs) which provide heat and power for the instruments on the Chang'E 4 lander. The radiation emitted by these radioactive sources leads to a non-negligible background which interferes with the measurements of LND. The aim of this paper is to describe the method that how to remove the background from these radioactive sources on the Chang'E 4 lander. We measured the effect of the RTG and RHUs on LND in a laboratory on Earth which is a very different environment from that on the Moon. We discuss how to take these major differences into account using a combination of scaling laws and Monte-Carlo simulations.