If a couple divorces, FERS Basic Benefits are divided through something called a Court Order Acceptable for Processing (COAP) which is reviewed and approved by the Office of Personnel Management (OPM).  The division of benefits is done on a shared benefit basis. This means that the divorced spouse must wait until the FERS participant retires to receive their former spouse annuity benefit payments. The COAP also assigns the surviving spouse a share of the FERS death benefit in the event that the participant dies before retirement.
The division of the TSP, on the other hand, requires a Retirement Benefits Court Order (RBCO) which is filed with the court and then submitted to the Office of Thrift Supervision. The RBCO may only assign a specific dollar amount or a percentage of the TSP to the former spouse as of a specific date.