Low-Latitude Ionospheric Sensor Network (LISN) is an international project that monitors the low, middle and high atmosphere in the equatorial region with the purpose of studying and forecasting the ionospheric phenomena, with special emphasis in dynamic and photochemical energy transport processes. For this purpose LISN is a permanent array of new geophysical instruments in South America, closely coordinated as a “Distributed Observatory”. All of these instruments have been installed near the position reference of the Magnetic Equator and the Meridian 70ºW. For this “Distributed Observatory”, LISN contemplates the set up of 50 GPS stations, 5 Magnetometers and 5 Ionosondes. We propose to establish a Low-Latitude Ionospheric Sensor Network across the western half of South America in order to answer key questions about the physics of the equatorial ionosphere and to develop forecasting capabilities concerning the onset of equatorial spread-F (ESF). The data acquired by LISN will be complemented with an assimilative physics-based model designed to “nowcast” the ionospheric state above the same geographical region. The model will be constrained with multipoint and multi-instrument observations from LISN to produce accurate estimates of ionospheric electron density distributions, conductivities, E×B plasma drifts, and neutral winds in near real time, and will also be integrated forward in time to make predictions about the onset of ESF. Developing an observatory capable of estimating plasma densities, ion drifts and neutral winds over a large geographic area constitute a logistical challenge with inherent intellectual merits. Additional merits of the proposed effort include its anticipated advances in equatorial Aeronomy, the development and testing of forecasting capability of ESF on a regional basis, and providing a prototype for distributed low-latitude observatories that may be established in other longitude sectors around the globe. Unique advantages of our plan for South America are the presence of incoherent scatter radar such as the Jicamarca Radio Observatory ─located in Peru─ and other instrumentation that can be used to calibrate and validate the distributed observatory. LISN data flow is managed through a Central Server ―located at the Instituto Geofisico del Peru― in order to receive, to process, to store and to distribute the scientific information. The real time information will be used in a Data Assimilation System of Ionosphere, for forecast using numerical models, and in deferred time the data will be available to users with investigation aims.