European Space Agency (ESA) craft in Very Eccentric Elliptical LEO studying X-ray emissions, star-forming regions, galaxy clusters, environment of supermassive black holes, mapping dark matter, surpasses next full year in space today, launched 1999.
European Space Agency (ESA) craft in Very Eccentric Elliptical LEO studying X-ray emissions, star-forming regions, galaxy clusters, environment of supermassive black holes, mapping dark matter, surpasses next full year in space today, launched 1999.