Lowest quasi-circular orbit

The lowest near-circular orbit to be sustained for multiple days was achieved by the Chinese Lixing-1 research satellite. On 16 August 2016, Lixing-1 was lowered into an orbit with a perigee of 124 km and an apogee of 133 km. It remained in this orbit for three days before reentry on 19 August.

The Lixing-1 satellite was built for the Chinese Academy of Sciences to study the rarefied upper atmosphere. It had a cylindrical body with a mass of 110 kg (240 lb). Lixing-1 was launched as a ride-share with the larger QSS (Quantum Science Satellite) using a Long March 2D rocket from the Jiuquan Satellite Launch Center in Inner Mongolia, China.

Longer-term excursions to very low orbits are often carried out by reconnaissance satellites (also known as spy satellites), which have powerful rocket engines that can counteract atmospheric drag. The US National Reconnaissance Office GAMBIT-3 series satellites (in use from 1966 to 1984), for example, were frequently tracked in orbits with perigees as low as 123 km for weeks at a time (though their apogees were significantly higher than that of the Lixing-1).