Hubble Space Telescope and Cassini spacecraft images have been analyzed in an attempt to characterize the ring particles based on their phase curves.
22.
The wide illumination scattering angle of clouds, as opposed to the narrower scattering of regolith, causes this flattening of the phase curve.
23.
As with Mercury, these new data are the major source of the phase curve used in the Astronomical Almanac for predicting apparent magnitudes.
24.
The phase curve of Mercury is very steep, which is characteristic of a body on which bare regolith ( soil ) is exposed to view.
25.
The phase curve of the Moon approximately resembles that of Mercury due to the similarities of the surfaces and the lack of an atmosphere on either body.
26.
In ephemeris generation, the phase curve is used in conjunction with the distances from the object to the Sun and the Earth to calculate the apparent magnitude.
27.
The shape of the phase curve indicates a mean slope on the surface of Mercury of about 16? which is slightly smoother than that of the Moon.
28.
The phase curve of the Earth has not been determined as accurately as those for Mercury and Venus because its integrated brightness is difficult to measure from the surface.
29.
The rotation of bright and dark surface markings across its disk and variability of its atmospheric state ( including its dust storms ) superimpose variations on the phase curve.
30.
Early visual observations contributing to the phase curve of Mercury were obtained by G . Muller in the 1800s and by Andr?Louis Danjon in the mid-twentieth century.
