Many thanks to Dick Brown & Rich Beckwell of the Test Services Section, Simulation Operations Center (SOC) who compiled the below information.
Building 25 joined the Goddard facility in 1966 as the Network Testing and Training Facility (NTTF). The building was divided into two separate equipment laboratories, one for the Manned Space Flight Network (MSFN) and one for the Satellite Tracking and Data Acquisition Network (STADAN). These laboratories designed, developed and tested prototype equipment destined for their respective network stations.
The training group was moved from the STADAN station at Blossom Point and was responsible for the development and conduction of all training for both the MSFN and the STADAN.
The Interferometer Tracking System, commonly called MINITRACK, was housed on the STADAN side of the facility and was, for many years, the only area that was a real-time operational facility, supporting daily tracking operations.
In the early 70's, the two networks were joined into the Spaceflight Tracking Data Network (STDN). This resulted in a consolidation of tracking stations. Many stations that had overlapping ground tracks were closed and the remaining ones reconfigured with "standardized" equipment and support requirements. At NTTF, this meant that the area previously designated to MSFN was converted to an operational tracking station and was named the Engineering Test Center (ETC) by the new network. The STADAN area was transformed into a network development and compatibility test center known as the Program Development Center (PDC).
The training effort increased in its scope to respond to the new equipment being developed. A multimedia laboratory was developed to tape training material that would be sent to the ground stations by mail to train site personnel.
In the late 70's, the compatibilty section was separated from the development area and a new group, the Compatibility Test Vans joined the building facilities. Parking spaces were specially built to place the test vans, fabricated to support their mission, next to the building.
The Simulations Operations Center joined the building at this time. The section was formed to provide an operational test facility for all mission operations, including simulators if required.
From 1973 to 1986, ETC supported the STDN in all its operational requirements. At one time it could support 4 different tracking missions at once. In addition to the operational support it provided the STDN, it also provided equipment used by both the PDC and Training groups. During this era, it changed names from ETC to BLT. This was teletype shorthand for the Greenbelt Tracking Station.
With the development and ultimate success of the TDRS network came the decline of BLT and the ground stations in general. In 1986, all the operational tracking requirements and much of the equipment was transferred to the Wallops facility and the station was officially closed. The operations area was converted to a engineering Test Bed. In 1989, the building name was changed to Network Technical Training Facility.
In 1997, Network Training was moved from Building 25, and the NTTF designate was dropped. Today, the building houses a diverse group of users that consist of the Simulation Operations Center (SOC), Compatibility Test Laboratory and Van (CTV), Data Evaluation Lab (DEL), RF Systems (RFS) development, Communications Link Analysis Simulation System (CLASS), and the Microsystems Repair Laboratory (MRL). In addition, an engineering test bed area has been set aside to provide for the development and testing of unique equipment in a controlled environment. Other areas have been converted to office facilities and are occupied by the SEB, QSS and other functions.