National Aeronautics and Space Administration

The Advanced Telescope for High ENergy Astrophysics (ATHENA) is an X-ray observatory planned for launch in the early 2030s aboard an Athena 6 expendable launch vehicle. The mission will be developed by the European Space Agency (ESA) as part of their Cosmic Vision program. As currently planned, ATHENA will have a 12 m focal length X-ray telescope with two instruments, the Wide Field Imager (WFI) and X-ray Integral Field Unit (X-IFU). A secondary mirror will direct X-rays from the telescope to one of the two instruments. The observatory will be placed in a halo orbit around the Earth-Sun L2 Lagrange point (The L1 point is a potential alternate destination.)

ATHENA is a down-sized verstion of the abandoned NASA/JAXA/ESA International X-ray Observatory (IXO), which itself was a merger of the ESA XEUS and NASA Constellation-X mission proposals.

In the current (as of 2020) instrumentation for ATHENA, there should be two different detectors, the Wild Field Imager (WFI) and X-ray Integral Field Unit (X-IFU), which share optics with a single 12 m focal length X-ray telescope. The telescope will have a large aperature and uses grazing incidence silicone pore optics to a provide 5-arcsec resolution at the center of the field of view. A secondary mirror will direct the focused beam of X-rays into one or the other of the two detector systems.

The WFI detector consists of a 2 x 2 array of depleted p-channel field-effect transistor (DEPFET) detector with a 40″ x 40′ field of view and 5″ angular resolution (512 x 512 pixels in each of four quadrants), known as the large DEPFET. The four large DEPFET has a timing resolution of less than 5 milliseconds. There is also a fast DEPFET for high rate count targets. This has an array of 64 x 64 pixels and 80 microsecond timing accuracy. WFI is sensitive to X-rays between 0.2 to 15 keV and has an energy resolution of ≤170 eV at 7 keV.

The X-IFU is an X-ray spectrometer using an array of cryogenically cooled transition edge detectors. It will have a 10 microsecond timing accuracy, a spectral resolution of 2.5 eV at or below 7 keV, and is sensitive across the spectral range 0.2–12 keV.

ATHENA will have an ambitious set of science goals for the mission. These include studying how matter assembles within galaxies and galaxy clusters, measuring the history of the chemical compisition of the Universe through time, studying acceration processing in compact objects, finding the earliest super-massive black holes and tracing their growth despite the obsurcation of heavy dust and gas, and studying transient phenomena such as gamma-ray burst sources with a fast target of opportunity system.