  Symbiotic systems are interacting binary stars consisting of both hot and
cool components. This results in a complex environment that is ideal for
studying the latter stages of stellar evolution along with interactions within
binary systems. As a star approaches the end of its life, in particular the red
giant phase, it exhausts its supply of core hydrogen and begins burning its way
through successively heavier elements. Red giants lose mass in the form of a
dense wind that will replenish the interstellar medium with chemical elements
that are formed through nuclear processes deep in the stellar interior. When
these elements reach the interstellar medium they play a central role in both
stellar and planetary evolution, as well as providing the essential
constituents needed for life. The undoubted significance of these cool giants
means the study of their atmospheres is necessary to help understand our place
in the Universe. This thesis presents Hubble Space Telescope observations of
the symbiotic system EG Andromedae as an insight into red giant stars. EG And
is one of the brightest and closest symbiotic systems and consists of a red
giant primary along with a white dwarf. The presence of the white dwarf in the
system allows spatially resolved examination of the red giant primary. The
benefits of using such a system to better understand the base of red giant
chromospheres is shown. Along with the observations of EG And, new HST
observations of an isolated red giant spectral standard HD148349 are described.
The similarity between the isolated spectral standard and the red giant primary
of EG And is demonstrated, showing that much of the information gleaned from a
symbiotic system can be applied to the general red giant population. Using both
ultraviolet and optical spectroscopy, the atmosphere of EG And and HD148349 are
investigated and contrasted.
