The sequential estimation (SE) proposed by Ward for rapid acquisition of pseudo-noise (PN) sequences performs well only at moderate chip signal-to-noise ratios (SNRs). In this paper, a seed accumulating sequential estimation (SASE) method based on accumulated seeds of the received IN sequence is proposed, which performs well at low chip SNR also. The mean acquisition time performance of the SASE method is investigated. Numerical results show that the SASE performs dramatically better than the SE at low chip SNR and the improvement becomes larger as the period of PN sequence increases. (C) 2002 Elsevier Science B.V. All rights reserved.