Sub-Daily Global Gravity Mapping from Space

It has long been recognized that the primary limitation to science from single- or dual-pair SST gravity missions is temporal aliasing. As it can take 30 days to sample the globe at adequate density, prominent short-term phenomena, from sub-daily tides to multi-day weather events, are under-sampled and alias into lower frequencies. Such fast processes are often not well-modeled and tend to mask subtler long-term effects, confounding scientific interpretation. We can eliminate temporal aliasing by reducing the time needed for high-resolution global sampling to a day or less, capturing the full spectrum of gravity variations. That in turn requires an extended satellite array to cover the globe quickly. Today's smallsat technology makes this eminently practical while offering improved single-pair performance over GRACE-FO.

GeoOptics and its partners at Tyvak International, under sponsorship by NASA's Decadal Survey Mass Change Mission program, are developing a design for a smallsat gravity constellation known as the Earth Gravitational Observatory (EGO). Individual smallsat pairs will improve on the GRACE-FO K-band ranging precision by about 4x while offering comparable accelerometer accuracy. Other systematic measurement errors will be similar or lower. The target cost for spacecraft production is under $3M each. Up to 30 spacecraft pairs can be launched together in about ⅓ the capacity of a Falcon-9 rocket, then quickly dispersed to their final orbits for high-density daily and sub-daily global gravity mapping. The EGO spacecraft design has undergone a thorough update over the past year by the GeoOptics and Tyvak International teams and has been through a full preliminary design review. This presentation will describe the proposed end-to-end mission, key elements of the spacecraft design, and expected performance and costs.