> On December 1, 2022, the FCC issued an approval for SpaceX[66] to launch the initial 7500 satellites for its second-generation (Gen2) constellation, in three low-Earth-orbit orbital shells, at 525, 530, and 535 km (326, 329 and 332 mile) altitude. Overall, SpaceX had requested approval for as many as 29,988 Gen2 satellites, with approximately 10,000 in the 525–535 km (326 to 332 mile) altitude shells, plus ~20,000 in 340–360 km (210 mile to 220 mile) shells and nearly 500 in 604–614 km (375 to 382 mile) shells.
https://www.spacex.com/updates/#sustainability
> SpaceX operates its satellites at an altitude below 600 km because of the reduced natural orbit decay time relative to those above 600 km. Starlink operates in \"self-cleaning\" orbits, meaning that non-maneuverable satellites and debris will lose altitude and deorbit due to atmospheric drag within 5 to 6 years, and often sooner, see Fig. 1. This greatly reduces the risk of persistent orbital debris, and vastly exceeds the FCC and international standard of 25 years (which we believe is outdated and should be reduced). Natural deorbit from altitudes higher than 600 km poses significantly higher orbital debris risk for many years at all lower orbital altitudes as the satellite or debris deorbits. Several other commercial satellite constellations are designed to operate above 1,000 km, where it requires hundreds of years for spacecraft to naturally deorbit if they fail prior to deorbit or are not deorbited by active debris removal, as in Fig. 1. SpaceX invested considerable effort and expense in developing satellites that would fly at these lower altitudes, including investment in sophisticated attitude and propulsion systems. SpaceX is hopeful active debris removal technology will be developed in the near term, but this technology does not currently exist.
> https://sxcontent9668.azureedge.us/cms-assets/assets/figure_...
> Fig. 1: Orbital lifetime for a satellite with a mass-to-area ratio of 40kg/m2 at various starting altitudes and average solar cycle.