ASCA (Advanced Satellite for Cosmology and Astrophysics), also known as ASTRO-D, was a Japanese X-ray astronomy satellite developed and operated by the Institute of Space and Astronautical Science (ISAS), which later became part of JAXA (Japan Aerospace Exploration Agency). The primary purpose of the ASCA mission was to study X-ray emissions from astronomical objects, including stars, galaxies, black holes, and supernova remnants. The mission aimed to enhance the understanding of high-energy astrophysical phenomena and contribute to the field of X-ray astronomy.