  Space based gravitational wave astronomy will open a completely new window on
the Universe and massive black holes binaries are expected to be among the
primary actors on this upcoming stage. The New Gravitational-wave Observatory
(NGO) is a space interferometer proposal derived from the former Laser
Interferometer Space Antenna (LISA) concept. We describe here its capabilities
of observing massive black hole binaries throughout the Universe, measuring
their relevant parameters (masses, spins, distance to the observer) to high
precision. The statistical properties of the population of detected systems can
be used to constrain the massive black hole cosmic history, providing deep
insights into the faint, high redshift Universe.
