Thank you for your valuable inputs Sastry ji. I would like to add few more points.
During the Mahalaya period, the ancestors are said to come close to the earth planet.
The most deadliest curse is ancestor's curse. Doing tarpanam duirng this Mahala period will pacify and liberate them .
People who have not done their tarpanam every year or on regular basis can make use of this period to pacify their ancestors and receive their blessings.