## 5 Conclusions  
To address fundamental open questions in the cloud-convective process, a sequence of polarimetric RO measurements collected from a closely spaced LEO satellite constellation is proposed. Currently, this process lacks observational constraints, due to the difficulty in obtaining accurate, vertically resolved pressure, temperature and water vapor structure inside and near convective clouds with global coverage over land and oceans. The recent launch of the COSMIC-2 (6-satellite, 24\({}^{\circ}\) inclination plane) RO constellation in mid-2019 may provide RO sampling internal and external to many convective systems, but relatively few close-time events at the short time scales of moisture transport in and near convective cloud processes. From the technology aspect, the polarimetric RO concept has been proven from space with the data collected from the modified IGOR receiver (ROHP) flying onboard the Spanish PAZ satellite since early 2018. An RO receiver (Cion) suitable in size and power requirements for small 6U-sized cubesats has been successfully flown and operated. The unique sampling offered by closely-spaced (p, q and T) profiles obtained from RO is complementary to other small satellite-based observations of the cloud structure as obtained from space-based radar, such as the RainCube Ka-band radar currently (mid-2019) being tested from space [46]. RO obtained by compact, low-power Cion-sized instruments could orbit together with small high-frequency (e.g., 183 GHz water vapor complex) passive MW sounders on the same platform, or separately in formation flying. Depending upon the orientation of the RO antenna on the receiving satellite, the RO tangent point locations can be tailored to lie outside of the MW sounder swath (effectively expanding the total coverage area), or more internal to the swath. In thelatter case, the coarse along-ray but high-vertical-resolution RO data are complementary to the finer horizontal scale, but the coarse vertical-resolution-passive MW data enables the potential tomographic reconstruction of 3-D water vapor structure [47]. In addition, knowledge of the moist thermodynamic profile within heavy precipitation is useful towards the improvement and evaluation of the microphysical parameterizations used in NWP forecast models, and advancement of the state of rain-affected data assimilation [48]. The use of PRO for NWP data assimilation will require a forward observation operator that can simulate all contributions to \(\Delta\Phi\) along realistic RO propagation paths [37]. In addition, other applications can benefit from such a constellation (e.g., inferring horizontal wavelengths of gravity waves from multiple RO temperature profiles) [49]. Conceptualization, F.J.T., R.P., C.O.A., M.d.l.T.J., G.W.F., S.T.L., S.M.H.-V., E.J.F., J.D.N. ; methodology, F.J.T., R.P., C.O.A., M.d.l.T.J., K.-N.W., G.W.F., S.T.L., S.M.H.-V., E.J.F., E.C.-H.K., J.D.N. ; software, F.J.T., R.P., C.O.A., M.l.T.J., K.-N.W., S.T.L., S.M.H.-V., E.C., Y.-H.K. ; validation, F.J.T., R.P., C.O.A., M.d.l.T.J., K.-N.W., G.W.F., S.T.L., S.M.H.-V., E.J.F., E.C., Y.-H.K. ; formal analysis, F.J.T., R.P., C.O.A., M.d.l.T.J., K.-N.W., G.W.F., S.T.L., S.M.H.-V., E.J.F., E.C., Y.-H.K. ; investigation, F.J.T., R.P., C.O.A., M.d.l.T.J., K.-N.W., G.W.F., S.T.L., S.M.H.-V., E.J.F., E.C., J.D.N. ; resources, F.J.T., R.P., C.O.A., M.d.l.T.J., K.-N.W., G.W.F., S.T.L., S.M.H.-V., E.J.F., E.C., J.D.N. ; data curation, R.P., M.d.l.T.J. ; writing--original draft preparation, F.J.T., R.P., G.W.F., C.O.A., K.-N.W., J.D.N. ; writing--review and editing, F.J.T. ; visualization, F.J.T., R.P., S.T.L. ; supervision, F.J.T., C.O.A., M.d.l.T.J., J.D.N. ; project administration, F.J.T., J.D.N. ; funding acquisition, F.J.T., M.d.l.T.J., C.O.A., J.D.N. FJT, COA, MTI and KNW acknowledge support from NASA US Participating Investigator (USPI) program element 14-ESUPIIA-0014.