**5. Conclusions**

Large constellations of smallsats in low Earth orbit can provide spatial and temporal coverages with greater sampling density relative to constellations with fewer large satellites. This increase in coverage is primarily characterized by three factors and quantified by zonal and global measurements. The selection of satellite inclinations allows designers to choose which latitude zones are receiving more coverage while also optimizing global visibility. Meanwhile, dividing a constellation into multiple orbit planes allows designers to further improve global and zonal temporal coverage figures. Additionally, the quality and quantity of the permissible sensed data can be controlled by selecting an appropriate RCG threshold in accordance with constellation's onboard GNSS-R instruments. Ultimately, these parameters allow for designers to iteratively evaluate constellation prototypes and maximize spatial and temporal coverage both globally and in regions of interest.

When designing a constellation, each mission will have its own set of objectives where it wants to maximize its coverage. However, the most generic definition of a successful constellation design would be maximizing global coverage metrics while keeping zonal coverage metrics evenly distributed. Through an iterative process of adjusting the satellite inclinations of 3-plane constellations, it has been found that a constellation with planes of 8 satellites orbiting at inclinations of 50◦, 75◦ and 80◦ meet these design goals. Although it may be possible to adjust the definition of success to meet specific mission requirements, this constellation has been found to provide quite good overall coverage both globally and zonally.

**Author Contributions:** Conceptualization, C.R. and S.G.; methodology, J.W., C.R. and S.G.; software, J.W.; validation, J.W., C.R. and S.G.; formal analysis, J.W., C.R. and S.G.; investigation, J.W., C.R. and S.G.; resources, C.R.; data curation, C.R.; writing—original draft preparation, J.W., C.R. and S.G.; writing—review and editing, J.W., C.R. and S.G.; visualization, J.W.; supervision, C.R. and

S.G.; project administration, C.R.; funding acquisition, C.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research and the APC were funded by NASA contract number 80LARC21DA003.

**Data Availability Statement:** No new data were created in performance of the work presented here.

**Conflicts of Interest:** The authors declare no conflict of interest.
