The Beyond Einstein program is a NASA

NASA

The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

 project designed to explore the limits of Einstein's theory of General Relativity

General relativity

General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravitation in modern physics...

. The project includes two space observatories

Space observatory

A space observatory is any instrument in outer space which is used for observation of distant planets, galaxies, and other outer space objects...

, and several observational cosmology

Observational cosmology

Observational cosmology is the study of the structure, the evolution and the origin of the universe through observation, using instruments such as telescopes and cosmic ray detectors.-Early observations:...

 probes. The program culminates with the Einstein Vision probes, after completion of the Great Observatories program

Great Observatories program

NASA's series of Great Observatories satellites are four large, powerful space-based telescopes. Each of the Great Observatories has had a similar size and cost at program outset, and each has made a substantial contribution to astronomy...

.

Constellation-X

Constellation-X

The Constellation-X Observatory was a mission concept for an X-ray space observatory to be operated by NASA; in 2008 it was merged with ESA and JAXA efforts in the same direction to produce the International X-ray Observatory project, announced on July 24, 2008 .The intention of the Con-X project...

 and the Laser Interferometer Space Antenna

Laser Interferometer Space Antenna

The Laser Interferometer Space Antenna is a planned space mission to detect and accurately measure gravitational waves from astronomical sources. LISA was originally conceived as a joint effort between the United States space agency NASA and the European Space Agency...

 (LISA) been promoted by NASA as the Einstein Great Observatories, to differentiate them from the current generation. However, they are not a part of the Great Observatories program.

Einstein Great Observatories

• Constellation-X
  Constellation-X
  The Constellation-X Observatory was a mission concept for an X-ray space observatory to be operated by NASA; in 2008 it was merged with ESA and JAXA efforts in the same direction to produce the International X-ray Observatory project, announced on July 24, 2008 .The intention of the Con-X project...
  
   (HTXS) (2016): the next generation X-ray
  X-ray
  X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
  
   space observatory
• Laser Interferometer Space Antenna
  Laser Interferometer Space Antenna
  The Laser Interferometer Space Antenna is a planned space mission to detect and accurately measure gravitational waves from astronomical sources. LISA was originally conceived as a joint effort between the United States space agency NASA and the European Space Agency...
  
   (LISA) (2015): a gravitational wave
  Gravitational wave
  In physics, gravitational waves are theoretical ripples in the curvature of spacetime which propagates as a wave, traveling outward from the source. Predicted to exist by Albert Einstein in 1916 on the basis of his theory of general relativity, gravitational waves theoretically transport energy as...
  
   space observatory

Einstein Probes

• Inflation Probe: designed to examine the cosmic microwave background (CMB) polarization; a follow-up to COBE
  COBE
  The COsmic Background Explorer , also referred to as Explorer 66, was a satellite dedicated to cosmology. Its goals were to investigate the cosmic microwave background radiation of the universe and provide measurements that would help shape our understanding of the cosmos.This work provided...
  
   and WMAP
• Black-Hole Finder Probe (BHFP): a complement to HTXS
• Dark Energy Probe: the Joint Dark Energy Mission (JDEM) will select one of the following three:
  • Supernova/Acceleration Probe (SNAP)
  • Dark Energy Space Telescope
    Dark Energy Space Telescope
    The Dark Energy Space Telescope , was a planned project by NASA and DOE, designed to perform precision measurements of the universe to provide an understanding of dark energy...
    
     (Destiny)
  • Advanced Dark Energy Energy Physics Telescope (ADEPT)

Einstein Vision missions

• Big Bang Observer
  Big Bang Observer
  The Big Bang Observer is a proposed successor to the Laser Interferometer Space Antenna . The primary scientific goal will be the observation of gravitational waves from the time shortly after the Big Bang, but it will also be able to detect younger sources of gravitational radiation, like binary...
  
  , a follow-up mission to LISA and Inflation Probe, also a gravitational-wave observatory
• Black-Hole Imager (MAXIM): an X-ray observation of infalling gas at the event horizon of a black hole; a follow-up to HTXS and BHFP