Space agencies involved in GRACE, GRACE-FO, and subsequent missions
Satellite missions are usually planned, realised and operated by one or more space agencies, such as the national space agency of the German Aerospace Center (DLR RFA), the European Space Agency ESA, or the U.S.-American NASA. In the case of GRACE-FO, the GFZ has exceptionally taken on these tasks on the German side. The necessary funding for the German parts of the previous and planned GRACE missions was provided primarily by the Federal Ministry of Education and Research (BMBF) and the Federal Ministry for Economic Affairs and ClimateIn contrast to weather, which refers to daily or very short-term events, climate refers to an average condition in the atmosphere over a longer period of 30 to 40 years. All processes such as average temperature, precipitation, wind direction, wind s... Protection (BMWK), complemented by substantial contributions from the GFZ and the Max Planck Society MPG (GRACE-FO and GRACE-C).
GRACE
Foto: DLR
The realisation of GRACE was formally agreed in 1998 between DLR RFA and NASA in a Memorandum of Understanding (MOU). In this MOU, the responsibilities for the German and American sides were outlined, and further explained in a detailed Cooperative Project Plan (CPP) developed in parallel. For GRACE, DLR RFA was responsible for the realisation and implementation of mission operations, the provision of the launch vehicle, and contributions to the scientific evaluation of the data. NASA had overall mission responsibility and was specifically focusing on, among other things, the design, construction and necessary tests of the two satellites and the various instruments together with contributions to the scientific evaluation of the data.
Other components of the MOU were, for example, financial agreements, the definition of the overall schedule and important milestones, agreements on the transfer of components and technical data or the treatment of intellectual property rights. The MOU also stipulated the establishment of a Joint Steering Group to regularly review the project status and resolve any conflicts that might arise.
GRACE Follow-On
The arrangements were very similar with GRACE-FO, although the GFZ inself signed the MOU with NASA in 2014 instead of DLR RFA, and the responsibilities were extended to cover also the provision of German and American components of the Laser Ranging Interferometer (LRI) implemented as a technology demonstrator.
GRACE-C
For the next mission after GRACE-FO (launch planned for 2028), DLR RFA has taken over this role again from GFZ after the phase A planning period, and is now drafting an Implementation Arrangement (IA) with NASA corresponding to the previous MOU.
Realisation of responsibilities for the GRACE missions
After agreeing on the overarching documents, the two space agencies (or in the case of GRACE-FO, the GFZ) were/are then subsequently responsible for awarding the necessary contracts for the responsibilities specified in the MOU/IA to the industry or scientific institutes, and subsequently for monitoring progress in project meetings. During the Preliminary or Critical Design Reviews, the progress in planning and building the satellites and their instruments as well as the launch vehicle, the subsequent mission operation, or the evaluation of the scientific data is presented by the commissioned industrial partners or scientific institutes during the construction phase, discussed jointly between the space agencies and adjusted if necessary. After the final construction of the satellites and the integration of all instruments as well as various tests to demonstrate that the satellites can survive the launch and later function under space conditions, the launch and subsequent operation of the mission until re-entry into the Earth's atmosphere takes place.
European Space Agency ESA
The current situation is somewhat different at ESA, which is planning a Next Generation GravityGravity is also known as the force of gravity or mass attraction. Gravity is the force that two or more bodies exert on each other due to their mass. The best-known gravitational force is the Earth's gravitational pull. It causes bodies on earth to f... Mission (NGGM) with launch in 2032 as part of its Mission of Opportunity Programme. Together with GRACE-C, NGGM shall form the double-pair constellation MAGIC (Mass change And Geosciences International Constellation) in close cooperation with NASA and DLR RFA, so that not only data continuity is made possible, but in particular the spatial and temporal resolution of the gravity field products is significantly increased. To this end, ESA has been conducting two parallel Phase A feasibility studies with the industrial partners Airbus (Germany) and Thales Alenia (Italy) since June 2021. At the same time, further studies are underway, for example, to increase the accuracy of accelerometers for NGGM with ONERA (France), or to build Laser Tracking Instrument (similar to LRI) in Europe alone with SpaceTech (Germany). The Program Board Earth Observation (PB-EO) has already decided in May 2023 that, following Phase A, there will be further activities at Airbus and Thales Alenia in the framework of a Phase B1 starting around January 2024. In November 2024, the ESA Delegates Conference is set to decide on the further funding and realisation of NGGM. In parallel to thos industrialactivities, scientific studies (led by TU Munich and GFZ) are also underway, in which, for example, the subsequent accuracy of NGGM and/or MAGIC is being investigated depending on reasonable assumptions on errors of the instruments or geophysical correction models. These activities are accompanied by a Mission Advisory Group the assembles top-class European scientists working in the field.
Text: Prof. Dr. Frank Flechtner, GFZ