  We present an analysis of surveying the inner Solar System for objects that
may pose some threat to the Earth. Most of the analysis is based on
understanding the capability provided by Sentinel, a concept for an infrared
space-based telescope placed in a heliocentric orbit near the distance of
Venus. From this analysis, we show 1) the size range being targeted can affect
the survey design, 2) the orbit distribution of the target sample can affect
the survey design, 3) minimum observational arc length during the survey is an
important metric of survey performance, and 4) surveys must consider objects as
small as D=15-30 m to meet the goal of identifying objects that have the
potential to cause damage on Earth in the next 100 years. Sentinel will be able
to find 50% of all impactors larger than 40 meters in a 6.5 year survey. The
Sentinel mission concept is shown to be as effective as any survey in finding
objects bigger than D=140 m but is more effective when applied to finding
smaller objects on Earth-impacting orbits. Sentinel is also more effective at
finding objects of interest for human exploration that benefit from lower
propulsion requirements. To explore the interaction between space and ground
search programs, we also study a case where Sentinel is combined with the Large
Synoptic Survey Telescope and show the benefit of placing a space-based
observatory in an orbit that reduces the overlap in search regions with a
ground-based telescope. In this case, Sentinel+LSST can find more than 70% of
the impactors larger than 40 meters assuming a 6.5 year lifetime for Sentinel
and 10 years for LSST.
