The rocket contrails are colorful clouds that appear when the sun is below the horizon. The contrails can float so high in the atmosphere that the sun shines on them even if it is already completely dark on the ground. They stay visible noticeable quite long after the launch.
The colors are created by the scattering of sunlight in the small ice crystals. In Finland, rocket phenomena from two different locations have mainly been observed. One of them is the missile launches from the submarines from the White Sea and the Arctic Ocean. They use solid fuel that creates colorful clouds.
Another source of rocket phenomena is the Plesetsk Cosmodrome Area in Russia. There are a few launches from there every year. These fires usually use liquid fuels, making the clouds less spectacular.
The visibility of the rocket launch is affected by the time at which the launch is made and where the winds blow. The best of all is around 3-5 o'clock Finnish time, when the cloud has time to spread out a bit and shine in the morning sun coming from the east when it is still dark or dark in Finland.
During the first decade of the 2000s, rocket phenomena have been observed about twice per year in Finland. Since then, however, it has been quieter.
Rocket contrails from Oulunsalo, Photo by Jarmo Moilanen.