However the probe will be conducted under solemn 'Pontifical' secrecy until the Holy See announces its decisions.
The probe, which was ordered by Pope Benedict in his letter to the Catholics of Ireland last March, will conduct rigorous inquiries into the state of religion in the four main archdioceses of Armagh, Dublin, Cashel and Tuam.
It may decide later to examine the country's other 24 dioceses, such as Cloyne and Raphoe. Cloyne is being examined for the cover-up of paedophile priests in a government inquiry, while Raphoe has also been subjected to claims of abuse cover-ups.
Billed as the Vatican's response to the shocking Ryan and Murphy reports, the probe will also investigate how priests are trained at seminaries including St Patrick's College in Maynooth, Co Kildare, and the Pontifical Irish College in Rome.
Although the full terms of what is officially called 'an Apostolic Visitation' have still to be communicated to the Hierarchy by Rome, no role has been provided for an input from clergy and laity.
The Vatican's aim is to explore more deeply questions concerning the handling of cases of abuse and the assistance owed to the victims by monitoring its effectiveness, as well as seeking possible improvements to procedures for preventing abuse.
This will involve assessing how two different sets of guidelines are being followed -- a 2001 directive from the Congregation for the Doctrine of the Faith signed by the late Pope John Paul II, and the Irish Church's Safeguarding Children guidelines patrolled by its National Board under Ian Elliott.
In an elaborate 'octopus' procedure under strict Vatican control, two religious priests and two nuns have been further mandated to survey Ireland's 137 religious orders and congregations and make recommendations for their regulation.
Assistance
In a statement the Vatican described the Visitation as offering assistance to bishops, clergy, religious and lay faithful "as they seek to respond adequately to the situation caused by the tragic cases of abuse perpetrated by priests and religious upon minors".
It intends "to contribute to the desired spiritual and moral renewal that is already being vigorously pursued by the church in Ireland."
Simultaneously, in Maynooth Irish bishops welcomed the Visitation's autumn start and pledged their full cooperation.
But the bishops said they looked forward "to receiving further details of the precise terms of reference of the Apostolic Visitation in due course".
The Vatican named five senior prelates to conduct different parts of the investigation.
Cardinal Cormac Murphy-O'Connor, the retired Archbishop of Westminster, is to look at the archdiocese of Armagh, the diocese of Cardinal Sean Brady.
Cardinal Sean O'Malley, Archbishop of Boston, is to look at the archdiocese of Dublin led by Archbishop Diarmuid Martin.
Archbishop Thomas Collins, Archbishop of Toronto, will oversee Cashel run by Archbishop Dermot Clifford.
Archbishop Terrence Prendergast, Archbishop of Ottowa, will look at Archbishop of Tuam Michael Neary's diocese.
Archbishop Timothy Dolan, Archbishop of New York, will head the section of the inquiry into seminary training and will report to the Vatican Congregation for Catholic Education.
All five prelates are of Irish descent and have played leading roles in investigating allegations of sexual abuse and church mishandling of abuse in their own countries.
SIC: II