 the way in which the false alarm event (state) is handled. Analogous to radar terminology, a false alarm in serial search PN code acquisition occurs when the detector (including the verification mode if it exists) erroneously decides that an in-sync condition has occurred and proceeds to direct the appropriate logic circuitry to initiate PN code tracking. Under normal cir- cumstances, an erroneous entry into the tracking mode of operation will be detected (by the code loop lock detector) and after a given amount of time (referred to as the false alarm penalty time), which, in reality, is a ran- dom variable but is often mathematically modelled as being fixed, the sys- tem will return to the acquisition mode and continue searching where it last left off. Such a recoverable false alarm state is referred to as a return- ing state. Occasionally, entry into the false alarm state is catastrophic in that the system cannot recover from this event. In this instance code acquisi- The Single Dwell Serial PN Acquisition System tion is completely lost and thus this type of false alarm state is referred to as absorbing. In the remainder of this chapter, we shall focus our attention on the ser- ial search strategy subclass of DS/SS acquisition schemes since, as previ- ously mentioned, these are most attractive in the low signal-to-noise ratio environments in which these systems normally operate. We begin with a detailed discussion of the simplest of the uniform stepping, serial search techniques, namely, the single dwell system where a single detector is used to examine each of the possible waveform alignments for a fixed period of time in a serial fashion until the correct one has been located [1]. A recent application of such a system was the code acquisition portion of the S-band despreader aboard the Space Shuttle Orbiter System [25]. In the succeeding sections we discuss the theoretical acquisition time and acqui- sition probability performance of such a system along with all of the prac- tical considerations required to 