The Wheel In Space / The War Games
Tanya Lernov was an astronomer on Space Station W3. She was concerned about the sudden drops in air pressure on the station.
She liked to say that her nose never let her down, that it could smell trouble.
Lernov was worried that Zoe Heriot and Jamie McCrimmon would be killed during the shockwaves from exploding meteorites. She helped the Second Doctor defeat the Cybermen. (The Wheel in Space)
She bumped into Zoe after the Time Lords returned her to the station having wiped her memory of The Doctor. (The War Games)