  We examine the detectability and interpretation of debris trails caused by
satellite disruption in external galaxies using semi-analytic approximations
for the dependence of streamer length, width and surface brightness on
satellite and primary galaxy characteristics. The semi-analytic method is
tested successfully against N-body simulations and then applied to three
representative astronomical applications. First, we show how streamer
properties can be used to estimate mass-to-light ratios $\Upsilon$ and streamer
ages of totally disrupted satellites, and apply the method to the stellar arc
in NGC 5907. Second, we discuss how the lack of observed tidal debris around a
satellite can provide an upper limit on its mass-loss rate, and, as an example,
derive the implied limits on mass-loss rates for M32 and NGC 205 around
Andromeda. Finally, we point out that a statistical analysis of streamer
properties might be applied to test and refine cosmological models of
hierarchical galaxy formation, and use the predicted debris from a standard
$\Lambda$CDM realization to test the feasibility of such a study. Using the
Local Group satellites and the few known examples of debris trails in the
Galaxy and in external systems, we estimate that the best current techniques
could characterize the brightest ($R < 29$ mag/ arcsec$^{2}$) portions of the
youngest (3 dynamical periods) debris streamers. If systematics can be
controlled, planned large-aperture telescopes such as CELT and OWL may allow
fainter trails to be detected routinely and thus used for statistical studies
such as those required for tests of galaxy formation.
