PARIS — The European Space Agency (ESA) has selected X-ray and gravity-wave observatories as the agency’s second and third Large-Class missions for launch in 2028 and 2034, respectively, with a call for mission concepts to begin in 2014.

The 20-nation ESA polled Europe’s space science community starting in March on what should be the focus areas for the next two L-Class missions. ESA said in a Nov. 28 statement that the winning missions were judged the best of the 32 proposals received and then discussed with science organizations.

“We believe that missions to study the hot, energetic universe and gravitational waves will result in discoveries of the greatest importance to cosmology, astrophysics, and physics in general,” Catherine Cesarsky, chair of the Senior Survey Committee, which assessed the proposals, said in a statement.

ESA will issue a formal call for concepts for the X-ray observatory in 2014, and sometime later will issue a second call for the gravity-wave mission, which the agency said will “require the development of a spaceborne gravitational wave observatory, or extreme precision ‘gravitometer’, an ambitious enterprise that will push the boundaries of current technology.”

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.