The top photograph was taken by Apollo-7 crew in October 1968 during a mission to test control of a spacecraft moving into different orbits (AS07-8-1932). Based on photographs from Gemini and Apollo, the estimated open water area of Lake Chad was over 22,000 km2 (Mohler et al. 1989, Lulla et al. 1991). Although not known at the time, Lake Chad would not be observed this full again from orbit--it had significantly decreased in area when it was observed by Landsat in 1972.
In parallel with observations made from Landsat, NOAA-AVHRR and other Earth-observing satellites, Space Shuttle crews have continued to photograph dramatic fluctuations in Lake Chad. A sampling of this time series from 1982-2000 is below the apollo image. (STS005-39-1022, STS052-80-66, and STS092-34318.)
Lake Chad lies in a large basin of internal drainage which is located on the southern edge of the Sahara. During periods of adequate rainfall, runoff accumulates in the basin, filling Lake Chad and permitting extensive agriculture and local fishing. The position of Lake Chad and the sensitivity of the lake to changes in regional rainfall make the site an ideal focus for drought impact studies using satellite data and astronaut photography.
Images provided by the Earth Sciences and Image Analysis Laboratory http://eol.jsc.nasa.gov/, Johnson Space Center. Additional images taken by astronauts can be viewed at NASA-JSCs Gateway to Astronaut Photography of Earth http://eol.jsc.nasa.gov/sseop/.