Tenma, known as ASTRO-B before launch, was a Japanese X-ray astronomy satellite developed by the Institute of Space and Astronautical Science. It was launched on 20 February 1983, using a M-3S rocket on the M-3S-3 mission. It was the second X-ray observatory successfully operated by Japan after Hakucho (CORSA-B), and it had a superior temporal and spectral sensitivity compared to its predecessor.