THIS PROPOSAL COVERING THE THREE YEARS PERIOD OF FEBRUARY 1ST. 2010 TO JANUARY 31ST,2013, PRESENTS A TANDEM APPROACH FOR THE DEVELOPMENT OF SPATIAL AND TIME DEPENDENT RADIATION ENVIRONMENTAL MODELS FOR THE LOW EARTH ORBIT (LEO) TRAJECTORIES. IT PROPOSES THE DEVELOPMENT OF ACCURATE TIME DEPENDENT MODELS OF THE RADIATION ENVIRONMENTS TO BE FOUND AT LEO IN THE RANGE OF400 - 2000 KILOMETERS (KM). THE MODELS ARE TO BE USED IN THE SPACE RADIATION ANALYSIS STUDIES. THE WORK WILL DEAL WITH THE IMPROVEMENT OF THE PARTICLE ABSORPTION AND SCATTERING ALGORITHMS NEEDED AS INPUT TO THE RADIATION TRANSPORT CODES, ACCOUNTING FOR THE PRESENCE OF IONS, MESON AND NEUTRONS; WITH THE IMPROVEMENT OF THE MODELS FOR THE ELECTRONS. THE MODELS WILL ALSO ACCOUNT FOR THE EFFECTS ON THE INCOMING PARTICLE FIELDS OF GALACTIC COSMIC RAYS (GCR), BOTH AT THE SURFACE AND WITHIN THE INTERIOR OF A SPACECRAFT. THE MODELS WILL BE COUPLED TO AN AVAILABLE ATMOSPHERIC ATTENUATION IONIZATION MODEL, TO ACCOUNT FOR THE PRESENCE OF ATMOSPHERE ON THE INCOMING PARTICLE FIELDS OF BOTH GCR AND SOLAR ORIGIN AT THE LEO ALTITUDES. THE WORK WILL BE PERFORMED IN A 3-YEARS EFFORT.