Career
Rantaseppä-Helenius began studying mathematics in hopes of becoming a teacher. Finnish astronomer Yrjö Väisälä inspired her to become an astronomer instead. Rantaseppä-Helenius worked on observing minor planets.
She worked as an assistant at Tuorla Observatory from 1956 to 1962.
In 1962 she became an observer when a vacancy became available. She remained an observer until 1975.
She was also involved in building the Kevola Observatory by Tähtitieteellis-optillinen seura (Astronomy-Optical Society) on her own property in 1963. Rantaseppä-Helenius died at age 50 in an accident.
The asteroid 1530 Rantaseppä is named after her.