NASA has announced the Earth Radiation Budget Satellite (ERBS) reentered the atmosphere at 11:04 pm EST on Sunday, January 8. The timing put it over the Bering Sea, so even if any pieces survived re-entry, the chance of damage to people or property was minimal. However, this was pure luck. The uncontrolled nature of the re-entry meant it could have come down over densely populated Korea if the timing had been only slightly different.
In recent years, multiple Long March 5B rockets have made uncontrolled re-entries, putting a wide range of equatorial and temperate regions at risk. Although most of the pieces have fallen into the ocean, some have come disturbingly close to villages. Many shorter-range rockets have fallen over China, sometimes quite dramatically. An international incident is probably only a matter of time.
Although Space X theoretically makes controlled re-entries over the ocean, several failures have seen pieces land in Australia and the United States. Today, NASA’s satellites are equipped to make controlled reentries when their time comes, if they are large enough to be dangerous, but this has not always been the case.
The ERBS was launched in 1984 with an intended two-year lifespan. Scientifically, it was an enormous success, observing the Earth’s reflected radiation and its stratospheric gasses such as ozone for 21 years before operations failed. It also dramatically expanded our understanding of environmental threats such as ozone depletion and global heating. However, no provision was made for safe reentry, so when atmospheric drag caused its orbit to decay, the planet was playing a form of Russian Roulette with falling metal.
Nevertheless, there is a difference of scale between the ERBS and the falling Long March rockets. The ERBS weighed 2.4 tonnes, a size which means most of its mass was expected to burn up in the atmosphere, with only small pieces likely to reach the ground, even if it had come down over land. Long March 5Bs weigh 21.6 tonnes, most of which reaches sea level.
