First the relic...while there are relics of questionable status this one is worth reading about it bears a remarkable similarity to the Shroud of Turin in its features and may have been the other "cloth" mentioned in the Gospel when it tells us that the Beloved Disciple saw the cloths lying there and believed. The Veronica reference is something that arose later and of course means "true image."
Here is a story on the relic:
Scientific research carried out recently shows that the image on the Holy Shroud of Turin and the image which appears on the veil in Manoppello are of identical size and superimposable, the only difference being that on the relic of Manoppello the mouth and eyes are open.
Second the Pope and the Archbishop: two great theologians will meet to reverence this relic. Archbishop Bruno Forte is a great read if you haven't read him yet. Very quotable, here is one I read just the other day. Ubi amore, ibi oculus...where there is love the eye sees. Kind of goes along with the relic and the meeting.
From Zenit.org:
Benedict XVI will visit the shrine of the Holy Face in Manoppello, Italy, which houses what is said to be Veronica's veil.
The Vatican press office confirmed Saturday that the Holy Father's pilgrimage will take place Sept. 1, and will last two hours. The Pope will adore the Eucharist in silence, venerate the relic and deliver an address.
Archbishop Bruno Forte of Chieti-Vasto will welcome the Pope.
According to the shrine, the Holy Face is a veil of 17 by 24 centimeters (6.8 by 9.6 inches), on which an image is imprinted that to date has no scientific explanation. Studies carried out on the veil confirm that the image is not made from paint.
Iconographer B. Pascalis Shlömer has demonstrated that the image of the Holy Shroud of Turin coincides perfectly with the Holy Face of Manoppello, according to the shrine.
Father Heinrich Pfeiffer, professor of iconography and Christian art history at the Gregorian University in Rome, said that this image served as model for subsequent representations of the Holy Face, including portraits in the fourth-century Roman catacombs.
Some consider it to be Veronica's veil, imprinted as Jesus made his way to Calvary.