  The combination of deep exposures and high resolution offered by telescopes
in space allows the detection of lensing over a wide range of source redshifts
and lens masses. As an example, we model a lens candidate found in the southern
Hubble Deep Field. The system consists of a source galaxy lensed into an arc,
0.9 arcseconds from an elliptical galaxy with an implied mass-to-light ratio of
order 15 in solar units. This lens system may be a preview of the large number
of lensed high-redshift galaxies that will be detected with the Next Generation
Space Telescope (NGST). Popular models of structure formation imply that
roughly 3% of observed sources at z>5 should be multiply imaged. Thus, NGST
should detect several lensed objects in each field of view. In addition, NGST
will be a valuable tool for weak lensing measurements if it can resolve the
background galaxies. We estimate the angular size distribution of high redshift
sources within hierarchical models of structure formation and find that most
will be resolved. (abridged)
