Tsubame, an Earth Observation satellite developed by Japan’s space agency JAXA, has been registered by the Guinness World Records as having achieved the “lowest altitude by an Earth observation satellite in orbit,” for an altitude of 167.4 km. The 383kg satellite was decommissioned on Oct 1, 2019.
Tsubame maintained seven different orbital altitudes, and operated at an all-time low of 167.4 km. From this altitude, it managed to capture high-resolution satellite images despite the atmospheric drag and oxygen density, and propelled itself using an ion engine system and gas-jet thrusters. It also acquired data on atmospheric density, atomic oxygen density, and the level of deterioration of material samples that were exposed to the atmosphere.
For satellites, an altitude of between 200 km and 300 km is characterized as “super low”, which means the satellite will be exposed to 1,000 times more atmospheric resistance and concentrated atomic oxygen that can cause it to deteriorate.
Tsubame first maintained an orbital altitude of 271.5 km, which was gradually lowered to finally reach the 167.4 km altitude, where it stayed for 7 days. The satellite was launched on 23 December 2017, with a liftoff mass of 383 kg, and was designed to demonstrate operations in very low Earth orbit (below 200 km).