Photogeology: Part Y: physical and geological aspects of heiligenschein measurements

Heiligenschein is the upsurge in reflected brightness as zero-phase angle is approached. For the first time, an effort has been made to investigate the diagnostic value of the heiligenschein photometric magnitude on a statistically significant scale. This investigation was performed by using the vertical photography of the Apollo 16 metric camera. The brightness surge of reflected light near zero-phase angle was studied with the expectation that it might be related to lunar geologic setting. Although previous work suggests that a real effect is present (refs. 29-121 and 29-122), the data set was small, and no correlations with other lunar surface properties were attempted. The problem is complex enough to warrant massive effort. This subsection is merely a status report.