  Gaia EDR3 has provided proper motions of Milky Way (MW) dwarf galaxies with
an unprecedented accuracy, which allows us to investigate their orbital
properties. We found that the total energy and angular momentum of MW dwarf
galaxies are much larger than that of MW K-giant stars, Sagittarius stream
stars and globular clusters. It suggests that many MW dwarf galaxies have had a
recent infall into the MW halo. We confirmed that MW dwarf galaxies lie near
their pericenters, which suggests that they do not behave like satellite
systems derived from Lambda-Cold-Dark-Matter cosmological simulations. These
new results require revisiting the origin of MW dwarf galaxies, e.g., if they
came recently, they were likely to have experienced gas removal due to the ram
pressure induced by MW's hot gas, and to be affected by MW tides. We will
discuss the consequences of these processes on their mass estimation.
