Image Caption: STS-46 Earth observation taken aboard Atlantis, Orbiter Vehicle (OV) 104, is of the Earth's limb near sunrise at an Orbiter altitude of 128 nautical miles, from a position just to the northeast of the Hawaiian Islands. The limb appears thicker than in most photographs from previous missions, due to the use of 350m focal length lens. The black parts of the image are the unlit Earth in the foreground and the darkness of space above. Uppermost layers of the atmosphere appear dark blue due to molecular scattering of solar rays. Beneath the blue is a white layer within which a thin, stratified layer of suspended scattering material can be identified. The greyish-red band is residue of the Mt. Pinatubo eruption of June, 1991, comprised of a combination of ash and sulfuric acid particles at an altitude of 20 to 27 kilometers above the Earth. The boundary between the grey-red and lighter colored red is the lower stratosphere. The clouds visible are cirrus at 40,000 ft altitude. Below the strat