arXiv subjects

Andreas Märki

Publications and source records attributed to Andreas Märki.

2 recordsLinked to original sources

arXiv2020

Radiation Analysis for Moon and Mars Missions

This paper provides an overview of the radiation aspects of manned space flight to Moon and Mars. The expected ionizing radiation dose for an astronaut is assessed along the Apollo 11 flight path to the Moon. With the two dose values, the expected and the measured total dose, the radiation shielding and the activity of the Sun are estimated. To judge the risk or safety margin the radiation effects on humans are opposed. The radiation from the Sun has to be set to zero in the computer model to achieve the published radiation dose value of the Apollo 11 flight. Galactic and cosmic particles have not been modelled either. The Apollo 11 astronauts must have been lucky that during their flight the Sun was totally quiet in the solar maximum year 1969 - and also their colleagues of the subsequent Apollo flights, i.e. until 1972, where the published dose values still require a quiet Sun. The here built mathematical model allows assessing the total dose of a journey to Mars by only changing the flight duration. Even if in the meantime much thicker and/or active radiation shielding is proposed the radiation risk of manned space flight to Moon and Mars remains still huge.

physics.space-ph↗

arXiv2020

A Critical Review of the Lunar Laser Ranging

This paper provides an overview of the Lunar Laser Ranging (LLR) experiments. The measurement principle is explained and its theory is derived. Both contributions, the direct reflected light from retroreflectors as well as the scattered light from the lunar surface are considered. The measurement results from the Sixties until 2007 are then compared between different LLR stations and with the theoretical forecast. The very first experiment was in 1962: a laser beam was directed to the Moon and the scattered light from the lunar surface was detected. The number of received photons was in line with the theory. Then from 1969 the laser beams were directed to retroreflectors placed by Apollo astronauts and Luna space crafts. Retroreflectors are on the one hand reference points for long term measurements; on the other hand they deliver a much stronger return signal compared to the scattered return. But none of the stations could measure the expected amplification of the retroreflectors. The number of received photons remained in line with measurements to the bare surface of the Moon. Therefore either all retroreflectors have degraded such that their return signals fit to the scattered return from the lunar soil or the measurements were indeed taken to the lunar surface only.

astro-ph.IM↗