LF may not stand out clearly from the background. Fluctuations during and across missions Apollo astronauts reported that they observed the phenomenon more frequently during the transit to the Moon than during the return transit to Earth. Avdeev et al. (2002) suggested that this might be due to a decrease in sensitivity to the LF over time while in space. Astronauts on other missions reported a change in the rate of occurrence and intensity of the LF during the course of a mission. While some noted that the rate and intensity increased, others noted a decrease. These changes were said to take place during the first days of a mission. Other astronauts have reported changes in the rate of occurrence of the LF across missions, instead of during a mission. For example, Avdeev himself was on Mir for six months during one mission, six months during the second mission a few years later and twelve months during a third mission a couple of years after. He reported that the LF were seen less frequently with each subsequent flight. Orbital altitude and inclination have also correlated positively with rate of occurrence of the LF. Fuglesang et al. (2006) have suggested that this trend could be due to the increasing particles fluxes at increasing altitudes and inclinations. Experiments ALFMED experiment During the Apollo 16 and Apollo 17 transits, astronauts conducted the Apollo Light Flash Moving Emulsion Detector (ALFMED) experiment where an astronaut wore a helmet designed to capture the tracks of cosmic ray particles to determine if they coincided with the visual observation. Examination of the results showed that two of fifteen tracks coincided with observation of the flashes. These results in combination with considerations for geometry and Monte Carlo estimations led researchers to conclude that the visual phenomena were indeed caused by cosmic rays. SilEye-Alteino and ALTEA projects The SilEye-Alteino and Anomalous Long Term Effects in Astronauts' Central Nervous System (ALTEA) projects have investigated the phenomenon aboard the International Space Station, using helmets similar in nature to those in the ALFMED experiment. The SilEye project has also examined the phenomenon on Mir. The purpose of this study was to examine the particle tracks entering the eyes of the astronauts when the astronaut said they observed a LF. In examining the particles, the researchers hoped to gain a deeper understanding of what particles might be causing the LF. Astronauts wore the SilEye