The GRACE Project is divided into five systems. Each of the five systems is shortly described in the following paragraphs.
Launch Vehicle System (LVS)
The LVS included the ROCKOT launch vehicle, a multi-satellite dispenser, and the personnel, test equipment and facilities for preparation, integration and launch of the satellites. The LVS was managed by the DLR Launch Vehicle System Manager and supported by the JPL Project and its contractors. GRACE was launched on March 17, 2002. Read more about “GRACE Launch”
Satellite System (SAT)
JPL led the development of the Satellite System in partnership with Space Systems/Loral (SS/L) and Astrium GmbH (GmbH). Astrium provided major elements of two flight satellites based on an existing small satellite designed for the CHAMP mission. SS/L provided the attitude control system, microwave instrument electronics and system and environmental testing. Read more about “GRACE Satellites”
Science Instrument System (SIS)
The SIS included all elements of the inter-satellite ranging system, the GPS receivers required for precision orbit determination and occultation experiments, and associated sensors such as the Star Cameras. This System also coordinated the integration activities of all sensors, assuring their compatibility with each other and the satellite. Read more about “GRACE Payload”
Mission Operations System (MOS)
The MOS consists of facilities and resources of the German Space Operations Center, tracking antennas at Weilheim and Neustrelitz, and other stations and facilities needed for supporting LEOP (Launch and Early Mission Operation) and contingency operations. These facilities are used to monitor and control the satellite, perform initial processing of the telemetry data, and deliver all data to the SDS for further processing and generating science products. In addition to real-time operations, the MOS function provides the Central Checkout System for ground testing using command and data interfaces. The operations team also monitors satellite performance and health throughout the duration of the mission. Mission operations are conducted at the GSOC control center in Oberpaffenhofen, Germany. Read more about “GRACE Operations”
Science Data System (SDS)
The SDS functions include science data processing, distribution, archiving and product verification. The SDS is a distributed entity and managed in a cooperative approach by JPL and UTCSR in the US and GFZ in Germany. The cooperative approach includes sharing of processing tasks, harmonization of product archives and validation/comparison of products. Data and products to be processed and archived by the SDS include corrected inter-satellite range and accelerometer measurements, GPS orbit and occultation data, orbit, gravity field and GPS occultation products. The SDS also receives, processes and archives ancillary data (e.g. meteorological fields) necessary for data processing and verification. Further information is given in other pages such as “Products” or “Gravity Field Results”.