Quoted from: https://ccmc.gsfc.nasa.gov/models/models_at_glance.php 

Model Description
The Earth-Moon-Mars Radiation Environment Module (EMMREM) provides a tool to completely characterize time-dependent radiation exposure in the Earth-Moon-Mars and Interplanetary space environments. The numerical module integrates numerous sub-routines that describe radiation transport and planetary interactions, yielding predictions of exposure.

EMMREM has been developed using contemporary state-of-the-art particle radiation models, designed with well-established, working codes, including the BRYNTRYN (BaRYoN TRaNsport) and HZETRN (High-Z (charge) and Energy (TRaNsport) code developed at NASA and the HETC-HEDS (High Energy Transport Code - Human Exploration and Development of Space), Monte Carlo code developed at Oak Ridge National Laboratory and the University of Tennessee. We have created the Energetic Particle Radiation Environment Module (EPREM), which traces individual nodes along magnetic field lines as they are carried out with the Solar Wind, and solves the energetic particle transport equations in the Lagrangian field aligned grid. The energetic particle solutions include both the field aligned transport solutions and contributions from cross-field diffusion and drift.

The module has the capability to incorporate new and improving models as they become available, giving continually more accurate estimates of radiation hazards and effects. Moreover, it is constantly validated to significantly reduce uncertainties in predictions, using previous measurements from the International Space Station (ISS) and the Space Shuttle; LET spectra observed by LRO/CRaTER for Lunar scenarios; observations from MSL/RAD and MARIE on Odyssey for Mars scenarios; and an extensive data-base of Accelerator Beam Measurements. The results of EMMREM will improve risk assessment models, enabling adequate planning of future missions.

Model Input
The model takes simulated events and time series, observed events and time-series, or user-specified input for the energy and angular distributions of particles incident from interplanetary space. Users specify: (1) LEO, Moon, and Mars scenarios including altitudes and (2) shielding depths. In the future, users will have the option of specifying spacecraft, habitat, spacesuit, human CAF/CAM models, and surface (albedo) effects.

Model Output
EMMREM outputs currently include time-dependent dose-related quantities (accumulated dose and dose-equivalent rates). Linear Energy Transfer (LET) spectra will soon be available. Events, time-series, and case-studies for validation are also collected into the online data-base.

BRYNTRN is a radiation transport model that takes an energy spectrum and derives the energy spectrum after passing through layers of different materials (e.g., water, aluminum shielding). BRYNTRN calculates doses and dose rates of radiation experienced inside a spacecraft and within human tissue layers.[Null]

Relevant links
EMMREM website

CCMC Contact(s)
Masha Kuznetsova
301-286-9571

Developer Contact(s)
Nathan Schwadron
phone: 603-862-3451

Harlan Spence
phone: 603-862-0322

Kamen Kozarev
phone: 857-277-4873