This paper presents a new method to determine the mass of an inactive space object from photometric and astrometric data. Typically the effect of solar radiation pressure is used to determine area-to-mass ratio for space objects from angles observations. The arca-to-mass ratio of a space object can greatly affect its orbital dynamics; therefore angles data are sensitive to this quantity. On the other hand, photometric data is not sensitive to mass but is a strong function of the albedo-area and the rotational dynamics of the space object. The albedo-area can be used to determine the amount of energy reflected from solar radiation. Since these two data types are sensitive to albedo-area and area-to-mass, then by fusing photometric data with angles data it is possible to determine the area and mass of a space object. This work employs an unscented Kalman filter to estimate rotational states, translational states, area states and mass of an inactive space object. Mass is not observerable with only angles data or only photometric data, but it is shown in this work that with the two combined data types mass can be recovered. Recovering this characteristic and trajectories with sufficient accuracy is shown in this paper. The performance of the new method is demonstrated via simulated scenarios.