  The Photogravitational Restricted Three Body Problem with oblateness has been
studied to obtain halo orbits around the Lagrangian points $L_1$ and $L_2$ of
the Sun-Earth system in which the Sun is taken as radiating and the Earth as an
oblate spheroid. The halo orbits corresponding to fourth and fifth order
approximations around $L_1$ and $L_2$ for actual oblateness of the Earth and
for different radiation pressures for the Sun are displayed graphically. The
time period of halo orbits around $L_1$ decreases with increase in oblateness
and increases with increase in radiation pressure. A reverse effect is observed
due to increase in oblateness and radiation pressure on time period of orbits
around $L_2$. It is also observed that halo orbits around $L_1$ shifts towards
the source of radiation due to increase in both radiation pressure and
oblateness. However, halo orbits around $L_2$ shifts towards the source of
radiation due to increase in radiation but recedes with increase in oblateness.
