The GMDN, is a Global Muon Detector Network (GMDN) of ground based multi-directional detectors, and an international collaboration consisting of 10 institutions from 6 countries, with real time data generated by the GMDN, which was developed at Shinshu University, Japan. The Brazilian GMDN’s contribution was the installation in 2001, of a Multi-Directional Muon Detector prototype (MMD) for detection of high-energy galactic cosmic rays (GCRs), through an international cooperation between Brazil, Japan and USA, and has been in operation since then at the Southern Space Observatory - SSO/CRS/INPE - MCTI, (Latitude 29o, 26’, 24”S, Longitude 53o, 48’, 38”W, 492m above sea level), S˜ao Martinho da Serra, RS, in southern Brazil. The SSO-MMD detector’s capability and sensitivity were twice upgraded, in 2005 and 2012. The Brazilian contribution for Space Weather forecasting is through the observations conducted by the SSO-MMD which are used for forecasting the arrival of the geomagnetic storm and their Interplanetary Coronal Mass Ejection (ICME) drivers in the near-Earth geospace. The detector measures GCRs by detecting secondary muons produced from the hadronic interactions of primary GCRs (mostly protons) with atmospheric nuclei. Since muons have a relatively short life-time (about 2.2 microseconds at rest), it can reach the ground level due to the relativistic effect, and can preserving the incident direction of primary particles, because its high energy, the SSO-MMD detector can measure the GCRs intensity in 17 directions as a multidirectional detector at a single location, the SSO in southern Brazil.