Pitrus are our ancestors who have deceased.And "Tarpanam" means "to satiate". Pitru Tarpanam is done to please our deceased ancestors with offerings of black sesame seeds mixed with water.
It can be done yearly in the Pitru Paksha,monthly on each Amavasya Tithi(also known as the Pitru Tithi) or even daily.
Question-Usually done by sons of the family can it also be done by women of the family?Can women perform Shraddha or Pitru Tarpanam?
No @Rickross, they are not(allowed to do tarpanam). The only place they are allowed to do so is matru gaya, according to scholars.
As per Agasthiar.org ,Yes they can.
Can women do tharpanam? The answer is YES. Sathguru Venkataraman gave us the revolutionary idea (in the 1980s) that women can do pitru tharpanam just as well as men. Think of this key point: If there are no sons in a family, does that mean the ancestors should be starved of tharpanam? The answer is NO. The daughters can certainly do tharpanam. For a man who had daughters but no sons, will anyone do tharpanam with more mental involvement and dedication than his own daughters? NO. So these daughters can certainly do tharpanam for this (departed) man. Note further that if others do tharpanam for this (departed) man, it will be karunya tharpanam and not pitru tharpanam. Whereas, if his daughters do it, it will be direct, full fledged pitru tharpanam.However there is a condition viz :Women should use white sesame seeds in their tharpanam.
As per Sanatan.org Yes they can.:
Son (including the one whose threading ceremony has not been done), daughter, grandson, great grandson, wife, daughter’s son (if he is one of the heirs), real brother, nephew, cousin’s son, father, mother, daughter-in-law, son of elder and younger sisters, maternal uncle, anyone in the seven generations and from the same lineage (sapinda), anyone after the seven generations and belonging to the same family domain (samanodak), disciple, priests (upadhyay), friend, son-in-law of the deceased person can perform Shraddha in that order.However,The woman performing shraddha should place a clean cotton cloth on her shoulder while performing ‘Savya-Apasavya’
As per this PDF too,women are allowed to do Tarpanam.:
Facing south, Yagnopavit in Upsvena position (women should keep hair lock on left shoulder), left knee touching ground, right knee up, pavitri removed from anamika finger, one should hold tight two pieces of darbha, bent in the middle, by thumb and side of palm.