The RTEMS LEON Upgrade objectives were divided into three tasks. The first was the implementation of the requirements identified in the RTEMS Improvement Software Criticality Analysis of the RTEMS Improvement project. The second task was the verification and correction of a possible error in the GNU Compiler Collection (GCC)/Real-Time Executive for Multiprocessor Systems (RTEMS) in managing the Floating Point Unit (FPU) registers. The third task was the technical support for RTEMS Tailored in the European Space Agency IMA projects (Xtratum, AIR and PikeOS).