When it was discovered, a limitation of the radial velocity method used to detect Upsilon Andromedae d is that the orbital inclination is unknown, and only a lower limit on the planet's mass can be obtained, which was estimated to be about 4.1 times as massive as Jupiter. However, by combining radial velocity measurements from ground-based telescopes with astrometric data from the Hubble Space Telescope, astronomers have determined the orbital inclination as well as the actual mass of the planet, which is about 10.25 times the mass of Jupiter.