an estimation method for indirectly observable parameters for a typical low dynamic vehicle (ldv) is presented. the estimation method utilizes apparent magnitude, azimuth angle, and elevation angle to estimate the position and velocity of a typical ldv, such as a high altitude balloon (hab). in order to validate the accuracy of the estimated parameters gained from an unscented kalman filter, two sets of experiments are carried out to obtain the nonresolved photometric and astrometric data. in the experiments, a hab launch is planned; models of the hab dynamics and kinematics and observation models are built to use as time update and measurement update functions, respectively. when the hab is launched, a ground-based optoelectronic detector is used to capture the object images, which are processed using aperture photometry technology to obtain the time-varying apparent magnitude of the hab. two sets of actual and estimated parameters are given to clearly indicate the parameter differences. two sets of errors between the actual and estimated parameters are also given to show how the estimated position and velocity differ with respect to the observation time. the similar distribution curve results from the two scenarios, which agree within 3s, verify that nonresolved photometric and astrometric data can be used to estimate the indirectly observable state parameters (position and velocity) for a typical ldv. this technique can be applied to small and dim space objects in the future. (c) 2017 optical society of america