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Multi Layer Insulation (MLI) is very commonly used in all spacecraft for heat conservation. In most instances one has to deal with MLI facing space or other cold surfaces while protecting the thermally controlled surface at more moderate temperatures than the heat sink. But in some instances, either in steady state or transient modes, one has to deal with the MLI facing the sun. Examples of such situations are during spacecraft turns, deliberate or inadvertent, when the MLI is exposed to solar insolation for short or extended periods. The effective emittance of MLI is commonly used to describe its heat loss behavior in the absence of solar incidence and is well documented in widespread literature based on measurements and rules of thumb from practice. However, when MLI faces the sun, its effective solar absorptance comes into play to determine its effectiveness in controlling the temperature of the object that it was designed to protect thermally.