The NASA Goddard Space Flight Center's Wallops Flight Facility (GSFC/WFF)
was responsible for specifying and providing the dual-frequency altimeter (ALT) which is the prime instrument for the TOPEX/Poseidon mission. The ALT hardware was developed and built for GSFC/WFF by the Johns Hopkins University's Applied Physics Laboratory
. Within the GSFC Hydrospheric and Biospheric Sciences Laboratory
, the WFF TOPEX group has been continuously involved in altimeter design studies and data analysis from the middle 1970's through the present time. The WFF TOPEX group has been involved throughout the entire life of the TOPEX project.