What part of the atmosphere did sputnik 1 burn up?

Sputnik 1, the first artificial satellite launched by the Soviet Union in 1957, re-entered the Earth's atmosphere and burned up primarily in the thermosphere. This layer of the atmosphere, located between about 80 to 550 kilometers (50 to 342 miles) above the Earth's surface, contains very thin air and is where the majority of satellite re-entries occur. The satellite completed its mission and began to lose altitude due to atmospheric drag before disintegrating upon re-entry.