Landsat, a remote sensing Earth Resources
Technology satellite, has been acquiring repetitive coverage of the
Earth since 1972 when Landsat 1 was launched. Since then, four
others have been in operation. Landsat 1, 2, and 3 flew in a
circular orbit 913 kilometers (570 miles) above the Earth's surface
and circled the Earth every 103 minutes, or about 14 times a day.
Landsat 4 and 5 fly about 705 kilometers (440 miles) above the Earth
and circle every 98 minutes.
Landsat 4 and 5 are still operating. Landsat 6
was launched in 1993 but did not achieve orbit and was lost. Landsat
7 is in planning stages. For more information on Landsat 7 status,
Landsat Program Home Page.
Data center only collected the data covering
the West China, especially the Himalayas regions. The main objective
is monitoring the glacier and snow cover in the cryoshpere of China.