  In recent years, a number of observations have been made of the transits of
'Hot Jupiters', such as HD 189733b, which have been modelled to derive
atmospheric structure and composition. As measurement techniques improve, the
transit spectra of 'Super-Earths' such as GJ 1214b are becoming better
constrained, allowing model atmospheres to be fitted for this class of planet
also. While it is not yet possible to constrain the atmospheric states of small
planets such as the Earth or cold planets like Jupiter, this may become
practical in the coming decades and if so, it is of interest to determine what
we might infer from such measurements. Here we have constructed atmospheric
models of the Solar System planets from 0.4 - 15.5 microns that are consistent
with ground-based and satellite observations and from these calculate the
primary transit and secondary eclipse spectra (with respect to the Sun and
typical M-dwarfs) that would be observed by a 'remote observer', many light
years away. From these spectra we test what current retrieval models might
infer about their atmospheres and compare these with the 'ground truths' in
order to assess: a) the inherent uncertainties in transit spectra observations;
b) the relative merits of primary transit and secondary eclipse spectra; and c)
the advantages of directly imaged spectra. We find that secondary eclipses
would not give sufficient information, but that primary transits give much
better determination. We find that a single transit of Jupiter in front of the
Sun could potentially be used to determine temperature and stratospheric
composition, but for the Earth the mean atmospheric composition could only be
determined if it were orbiting an M-dwarf. For both planets we note that direct
imaging with sufficient nulling of the light from the parent star provides the
best method of determining the atmospheric properties of such planets.
