You are correct. There must be a cross (with a corpus) on or near the altar. If the sanctuary cross was designed and built before January 11, 2002, then it does not require a figure of Christ crucified upon it. However, the use of the crucifix remains obligatory during Mass, “positioned either on the altar or near it, and . . . clearly visible to the people gathered there.” (GIRM 308). In the case where a crucifix is not in the sanctuary, the processional cross with the figure of Christ crucified upon it would fulfill the obligation.
The new *General Instruction of the Roman Missal * states:
- There is also to be a cross, with the figure of Christ crucified upon it, either on the altar or near it, where it is clearly visible to the assembled congregation. It is appropriate that such a cross, which calls to mind for the faithful the saving Passion of the Lord, remain near the altar even outside of liturgical celebrations.
The document, Built on Living Stones, says:
§ 91 § The cross with the image of Christ crucified is a reminder of Christ’s paschal mystery. It draws us into the mystery of suffering and makes tangible our belief that our suffering when united with the passion and death of Christ leads to redemption.113 There should be a crucifix "positioned either on the altar or near it, and . . . clearly visible to the people gathered there."114 Since a crucifix placed on the altar and large enough to be seen by the congregation might well obstruct the view of the action taking place on the altar, other alternatives may be more appropriate. The crucifix may be suspended over the altar or affixed to the sanctuary wall. A processional cross of sufficient size, placed in a stand visible to the people following the entrance procession is another option. If the processional cross is to be used for this purpose, the size and weight of the cross should not preclude its being carried in procession. If there is already a cross in the sanctuary, the processional cross is placed out of view of the congregation following the procession.115
And, Father Edward McNamara, professor of liturgy at the Regina Apostolorum Pontifical Athenaem says,
“The use of the crucifix is obligatory during the celebration of Mass. The General Instruction of the Roman Missal in No. 308 requires the use of a “cross, with the figure of Christ crucified upon it, either on the altar or near it, where it is clearly visible to the assembled congregation. It is appropriate that such a cross, which calls to mind for the faithful the saving Passion of the Lord, remain near the altar even outside of liturgical celebrations.”
This specific call for the use of the crucifix was probably inserted into the new GIRM to counter a movement which favored the use of simple bare crosses or even images of the risen Christ.
While such symbols may have a role in churches, they may not substitute the crucifix. Use of the crucifix during Mass serves as a reminder and a sign that the Eucharistic celebration is the same sacrifice as Calvary.