Jansen was a Masadan citizen and an officer of the Navy of Masada.

In 1903 PD, he held the rank of Admiral, and was in command of the light cruiser MNS Abraham, leading the Masadan task force against Grayson in the beginning of the Second Grayson-Masadan War. He missed his best chance to destroy the Grayson space station Orbital Four from beyond the station's range, and was killed when Orbital Four destroyed Abraham instead. (HH2)