| Parameter Name | Units | Type | Default | Description |
| X | long | 1 | center x coordinates? | |
| XP | long | 1 | center x' coordinates? | |
| Y | long | 1 | center y coordinates? | |
| YP | long | 1 | center y' coordinates? | |
| ONCE_ONLY | long | 0 |
compute centering offsets for first beam only, apply to all? |