  Earth is the only known habitable planet and it serves as a testbed to
benchmark the observations of temperate and more Earth-like exoplanets. It is
required to observe the disc-integrated signatures of Earth for a large range
of phase angles, resembling the observations of an exoplanet. In this work, an
AOTF (Acousto-Optic Tunable Filter) based experiment is designed to observe the
spectro-polarimetric signatures of Earth. The results of spectroscopic and
polarimetric laboratory calibration are presented here along with a brief
overview of a possible instrument configuration. Based on the results of the
spectro-polarimetric calibration, simulations are carried out to optimize the
instrument design for the expected signal levels for various observing
conditions. The usefulness of an AOTF based spectro-polarimeter is established
from this study and it is found that, in the present configuration, the
instrument can achieve a polarimetric accuracy of $<0.3$\% for linear
polarization for an integration time of 100 ms or larger. The design
configuration of the instrument and the planning of conducting such
observations from Lunar orbit are discussed.
