  We study the characteristics of Near-Earth-Networks (NENs) of gamma-ray burst
(GRB) detectors, with the objective of defining a network with all-sky,
full-time localization capability for multi-messenger astrophysics. We show
that a minimum network consisting of 9 identical spacecraft in two orbits with
different inclinations provides a good combination of sky coverage with
several-degree localization accuracy with detector areas of 100 cm$^2$. In
order to achieve this, careful attention must be paid to systematics. This
includes accurate photon timing ($\sim$ 0.1 ms), good energy resolution ($\sim$
10\%), and reduction of Earth albedo, which are all within current
capabilities. Such a network can be scaled in both the number and size of
detectors to produce increased accuracy. We introduce a new method of
localization which does not rely on on-board trigger systems or on the
cross-correlation of time histories, but rather, in ground processing, tests
positions over the entire sky and assigns probabilities to them to detect and
localize events. We demonstrate its capabilities with simulations. If the NEN
spacecraft can downlink at least several hundred time- and energy-tagged events
per second, and the data can be ground-processed as they are received, it can
in principle derive GRB positions in near-real time over the entire sky.
