BOAC,
TERPS and PANOPS both group aircraft into categories based on VREF.
PANOPs is using higher speeds for circling (ie cat C up to 180kts) hence a larger radius required (max 4.2 rather than 1.7NM for USTERPS).
Min vis PANOPS circling is 2NM , USTERPS is less(1.3NM).
I cannot find TERPS. Posters above (9.g + westhawk) are suggesting that TERPS max circling speeds are the same as the TERPS approach category speeds - is this correct?
I believe it is ,as there is no mention of any difference and required visibility is lower for USTERPS,which makes sense as your radius clearance is also lower.