Generally, the dominant attitude disturbance source for the low Earth orbit small satellites is the residual magnetic moment (RMM). The RMM should be estimated and compensated in orbit to increase the attitude estimation and control accuracy. Although the estimator is usually built with the assumption that these parameters are constant, the RMM changes with sudden shifts caused by the variations in the onboard electrical current. The estimator should quickly track these unobserved parameters in case of change and perform accurate estimation for the rest of the procedure. In this paper, we investigate applicability of the existing estimators, such as the particle filter, for the RMM estimation. We present the initial results for an extended Kalman particle filter (EKPF) based method which may be useful for improving the estimation accuracy and tracking capability. (C) 2015 The Authors. Published by Elsevier Ltd.