The Lunar Lander Neutron and Dosimetry (LND) Experiment on Chang’E 4

Abstract

Chang’E 4 is the first mission to the far side of the Moon and consists of a lander, a rover, and a relay spacecraft. Lander and rover were launched at 18:23 UTC on December 7, 2018 and landed in the von Kármán crater at 02:26 UTC on January 3, 2019. Here we describe the Lunar Lander Neutron & Dosimetry experiment (LND) which is part of the Chang’E 4 Lander scientific payload. Its chief scientific goal is to obtain first active dosimetric measurements on the surface of the Moon. LND also provides observations of fast neutrons which are a result of the interaction of high-energy particle radiation with the lunar regolith and of their thermalized counterpart, thermal neutrons, which are a sensitive indicator of subsurface water content.

Radiation Environment at the Surface and Subsurface of the Moon: Model Development and Validation

“…In particular, a large proton content (a strong indicator of subsurface water) may lead to a reduction of fast neutrons and an increase of the epithermal and thermal neutrons (Feldman et al., 1998). Comparison of our model with future studies of the thermal neutron flux measured by LND on the surface of the Moon (Wimmer‐Schweingruber et al., 2020) would be extremely interesting.…”

“…The Cosmic Ray Telescope for the Effects of Radiation (CRaTER, Spence et al., 2010) Experiment on the Lunar Reconnaissance Orbiter has been providing dose data and LET spectra since June 2009. Most recently, the Lunar Lander Neutron and Dosimetry instrument (LND, Wimmer‐Schweingruber et al., 2020) on‐board Chang’E−4 has been measuring the radiation environment on the lunar surface (Xu et al., 2020; Zhang et al., 2020). The radiation environment below the lunar surface has only been measured by the Lunar Neutron Probe Experiment (LNPE, Woolum et al., 1975) during the Apollo 17 mission, which provided the equilibrium neutron density distribution in the lunar soil in the declining phase of solar cycle 20.…”

First measurements of low-energy cosmic rays on the surface of the lunar farside from Chang’E-4 mission

“…More details of the CE-4 mission can be found in the literature ( 62 ). The LND instrument aboard the lander is developed to determine the dose rate and the linear energy transfer spectrum as well as the particle flux on the surface of the lunar farside, which contributes to the studies related to the lunar surface environment and heliospheric science ( 36 ). The results of the time series–based dose rate and the linear energy transfer spectrum have been reported on the basis of the data collected by the LND during the first two lunar days ( 37 ), and on 6 May 2019, the LND instrument measured its first SEP event on the lunar farside ( 63 ).…”

“…The door keeps open during working hours in the lunar daytime but closed during the cold lunar night to protect the payloads inside. The SH has a telescope configuration, a stack of ten 500-μm-thick dual-segment Si solid-state detectors labeled A through J as shown in figure 4 of ( 36 ), to ensure the detection of charged-particle radiations and the identification of its composition. The differential flux of a specific type of charged particles in a certain kinetic energy range can be obtained on the basis of the information of their count rate, geometric factor, and kinetic energy range interval.…”

“…The Chandrayaan-1/RADOM also observed the variation of the particle flux at lunar altitudes in the range between 92 and 118 km ( 27 ). On 3 January 2019, China successfully sent a lander (CE-4) and a rover (Yutu-2) to the Von Kármán crater in the South Pole Aitken basin, the largest known impact crater on the Moon and one of the largest in the solar system ( 36 ). They are both still active at the time of writing.…”