Other satellite flares Many other controlled satellites also flare to magnitudes visible to the naked eye, i.e. larger than +6.5. MetOp-B and C, however, can produce predictable flares up to −5 magnitude (MetOp-A in no longer controlled) . Four COSMO-SkyMed satellites can produce flares up to -3 magnitude, and lasting much longer than the Iridium flares. The Terrasar X and Tandem X also can produce predictable flares up to -3 magnitude. The International Space Station (ISS) is known to cause bright ISS flares. Starlink flares can flare repeatedly in one area of the sky. This is due to the large number of Starlink satellites that are orbiting the Earth. The flares from Starlink have been misidentified as UFOs by airline pilots due to their strange repetitive nature which appears similar to an aircraft flying a racetrack holding pattern . Uncontrolled satellites When a satellite's orientation goes out of control, it becomes possible to predict only a trajectory of its pass, at any point of which it can flare up. These satellites are also described as "tumbling". This category includes many rotating rocket bodies, some failed Iridium satellites, ALOS satellite (which can produce flashes up to −10 mag), etc. The most important and valuable information about tumbling satellites is the period of flashes. It can vary from 0.3–0.5 seconds (rapidly rotating objects) to a minute or more (slowly rotating objects). Other important characteristics are the amplitude of changes in brightness and period of repetition of these changes. Humanity Star was a passive satellite which is primarily designed to produce satellite flares. Observation While satellites may be seen by chance, there are websites and mobile apps which provide location specific information as to when and where in the sky a satellite flare may be seen (for controlled satellites), or trajectory of a tumbling satellite's pass (for uncontrolled satellites) in the sky. Among others, reflections from satellites and other human space objects are often reported as unidentified flying objects (UFOs). See also NanoSail-D References External links – PreviSat software which calculates satellite flares (Iridium, MetOp, SkyMed) – schedule of upcoming Iridium flares – IridiumFlares prediction software (Java application) – "Catch a Flaring Iridium" at Visual Satellite Observer – SkyGuide Iridium 25 flare near the Moon Satellites Visibility