NewAthena is an observatory that is currently planned by ESA for 2038, to be launched into orbit at the L1 point. It should be able to detect sources down to ~1 x 10⁻¹⁶ erg cm⁻² s⁻¹.
It will have two X-ray instruments, the X-ray Integral field Unit (X-IFU) that will have a FoV of 4’ x 4’ and operate in the 0.2-12 keV range. It will have a 0.5 eV spectral resolution and temporal resolution of 10 microseconds.
The Wide-Field Imager will be sensitive in the 0.2-15 keV domain. It will have a 40’ x 40’ FoV and a 5’’ HEW PSF and an energy resolution of <170 eV.
For more information see https://www.the-athena-x-ray-observatory.eu/en