Realization of a Satellite Mission “GRACE-I” for parallel Observation of Changing Global Water Resources and Biodiversity

Abstract:

The actual NASA Earth Science Decadal Survey Report highlights mass transport monitoring as one of five top priorities in Earth Observation for the next decade. To realize such as Mass Change Mission (MCM) NASA is seeking for international partnership. A future continuation of the very successful technological and scientific GRACE/GRACE-FO partnership between the U.S. and Germany is in the involved partners’ highest interest and would be based on a strong heritage in the fields of satellite manufacturing, laser ranging interferometry (LRI) or science data utilization.

The goal of a study, jointly performed in summer 2020 between DLR, industry and HGF and MPG scientists, was to bundle up an attractive scientific and technological German package for further discussions with NASA which 1) compares the cost and benefit of technical modifications with respect to GRACE-FO, 2) is not only attractive for a future MCM but also for the Laser Interferometer Space Antenna (LISA) and 3) strengthens at the same time Germany´s role towards ESA´s Next Generation Gravity Mission (NGGM) implementation.

An ICARUS (International Cooperation for Animal Research Using Space) payload system on a future polar-orbiting GRACE-like “GRACE-ICARUS” (or short “GRACE-I”) mission could provide a much-desired scientific extension of biodiversity monitoring, which is another designated observable in NASA´s Decadal Survey.

Three mission options have been investigated:

• A reference design based on the GRACE-FO platform and technology with a redundant LRI as the main satellite-to-satellite tracking instrument, ready for delivery in late 2027.
• Add-on of the ICARUS payload, and
• Implementation of further technology options such as (i) spacecraft and mission related enhancements, (ii) LRI related issues and (iii) inclusion of technology demonstrators based on quantum technologies.

The nominal spacecraft separation for all options was 220 km at an altitude of 490 km with free-decay (Options 1a, 2a and 3a), or alternatively 420 km maintained using electric propulsion (Options 1b, 2b and 3b).

The presentation summarizes the most important findings of our study and discusses possible steps forward towards implementation with NASA.