Tenma, known as ASTRO-B before launch (COSPAR 1983-011A, SATCAT 13829), was a Japanese X-ray astronomy satellite, developed by the Institute of Space and Astronautical Science. It was launched on February 20, 1983, using a M-3S rocket on the M-3S-3 mission.

Battery failure in July 1984 caused the operation to become limited, and continuing problems lead to the termination of X-ray observation in 1985. It reentered the atmosphere on January 19, 1989 (other sources, for example the NORAD catalog of satellites, say decay date (the day it stopped working) was 17 May 1988^[1]).