Post-Decadal White Paper: A Dual-Satellite Dark-Energy/Microlensing
  NASA-ESA Mission
  A confluence of scientific, financial, and political factors imply that
launching two simpler, more narrowly defined dark-energy/microlensing
satellites will lead to faster, cheaper, better (and more secure) science than
the present EUCLID and WFIRST designs. The two satellites, one led by ESA and
the other by NASA, would be explicitly designed to perform complementary
functions of a single, dual-satellite dark-energy/microlensing ``mission''. One
would be a purely optical wide-field camera, with large format and small
pixels, optimized for weak-lensing, which because of its simple design, could
be launched by ESA on relatively short timescales. The second would be a purely
infrared satellite with marginally-sampled or under-sampled pixels, launched by
NASA. Because of budget constraints, this would be launched several years
later. The two would complement one another in 3 dark energy experiments (weak
lensing, baryon oscillations, supernovae) and also in microlensing planet
searches. Signed international agreements would guarantee the later NASA
launch, and on this basis equal access of both US and European scientists to
both data sets.
