voy2_v_c_o_TPMBK (P-34709, Voyager 2-N55, PIA00058 eq)
“This Voyager 2 high resolution color image, taken 2 hours before closest approach, provides obvious evidence of vertical relief in Neptune's bright cloud streaks. These clouds were observed at a latitude of 29 degrees north near Neptune's east terminator. The linear cloud forms are stretched approximately along lines of constant latitude and the sun is toward the lower left. The bright sides of the clouds which face the sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the sun. These shadows are less distinct at short wavelengths (violet filter) and more distinct at long wavelengths (orange filter). This can be understood if the underlying cloud deck on which the shadow is cast is at a relatively great depth, in which case scattering by molecules in the overlying atmosphere will diffuse light into the shadow. Because molecules scatter blue light much more efficiently than red light, the shadows will be darkest at the longest (reddest) wavelengths, and will appear blue under white light illumination. The resolution of this image is 11 kilometers (6.8 miles per pixel) and the range is only 157,000 kilometers (98,000 miles). The width of the cloud streaks range from 50 to 200 kilometers (31 to 124 miles), and their shadow widths range from 30 to 50 kilometers (18 to 31 miles). Cloud heights appear to be of the order of 50 kilometers (31 miles). This corresponds to 2 scale heights. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.”
Above & image at:
photojournal.jpl.nasa.gov/catalog/PIA00058
Credit: JPL Photojournal website
And/or, with the photograph’s impeccable provenance, the description possibly used in Mr. Burgess’s book “Far Encounter: The Neptune System”:
“Figure 4-6: Taken two hours before the spacecraft’s closest approach to Neptune, this image shows vertical relief in the cloud streaks. The linear cloud forms are stretched approximately along lines of constant latitude, and the Sun is toward the lower left. The bright sides of the clouds which face the Sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the Sun. These shadows are less distinct at short ultraviolet wavelengths because they are cast on a lower cloud deck and scattering of light by the atmosphere above them diffuses light into the shadow. The shadows are darkest when observed in red light because molecules scatter the longer waves of red light less than blue or ultraviolet light. The widths of the cloud streaks range from 30 to 125 miles (50 to 200 km) and their heights appear to be about 30 miles (50 km) above the main cloud deck.”
The image was also the cover of the 1990 issue of “NASA Spinoff” magazine, by James Haggerty.
voy2_v_c_o_TPMBK (P-34709, Voyager 2-N55, PIA00058 eq)
“This Voyager 2 high resolution color image, taken 2 hours before closest approach, provides obvious evidence of vertical relief in Neptune's bright cloud streaks. These clouds were observed at a latitude of 29 degrees north near Neptune's east terminator. The linear cloud forms are stretched approximately along lines of constant latitude and the sun is toward the lower left. The bright sides of the clouds which face the sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the sun. These shadows are less distinct at short wavelengths (violet filter) and more distinct at long wavelengths (orange filter). This can be understood if the underlying cloud deck on which the shadow is cast is at a relatively great depth, in which case scattering by molecules in the overlying atmosphere will diffuse light into the shadow. Because molecules scatter blue light much more efficiently than red light, the shadows will be darkest at the longest (reddest) wavelengths, and will appear blue under white light illumination. The resolution of this image is 11 kilometers (6.8 miles per pixel) and the range is only 157,000 kilometers (98,000 miles). The width of the cloud streaks range from 50 to 200 kilometers (31 to 124 miles), and their shadow widths range from 30 to 50 kilometers (18 to 31 miles). Cloud heights appear to be of the order of 50 kilometers (31 miles). This corresponds to 2 scale heights. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.”
Above & image at:
photojournal.jpl.nasa.gov/catalog/PIA00058
Credit: JPL Photojournal website
And/or, with the photograph’s impeccable provenance, the description possibly used in Mr. Burgess’s book “Far Encounter: The Neptune System”:
“Figure 4-6: Taken two hours before the spacecraft’s closest approach to Neptune, this image shows vertical relief in the cloud streaks. The linear cloud forms are stretched approximately along lines of constant latitude, and the Sun is toward the lower left. The bright sides of the clouds which face the Sun are brighter than the surrounding cloud deck because they are more directly exposed to the sun. Shadows can be seen on the side opposite the Sun. These shadows are less distinct at short ultraviolet wavelengths because they are cast on a lower cloud deck and scattering of light by the atmosphere above them diffuses light into the shadow. The shadows are darkest when observed in red light because molecules scatter the longer waves of red light less than blue or ultraviolet light. The widths of the cloud streaks range from 30 to 125 miles (50 to 200 km) and their heights appear to be about 30 miles (50 km) above the main cloud deck.”
The image was also the cover of the 1990 issue of “NASA Spinoff” magazine, by James Haggerty.