Radio Occultation Science Plan EUMETSAT Polar System (EPS-SG) / Meteorological Operational Second Generation (MetOp-SG) prepared by the Radio Occultation Science Advisory Group and external experts GNSS Radio Occultation GNSS Radio Occultation mission on MetOp-SG Satellite A mission on MetOp-SG Satellite B Issue : v2C Date : 28 November 2018 v2C, 28 November 2018 Radio Occultation Science Plan Document Change Record Issue / Date DCN. Changed Pages / Paragraphs Revision No 1 Initial version 1B 21 December 2016 All contributor input provided, version for G. Kirchengast Review. 1C 11 January 2017 Added further ionosphere information (section 8.1) and executive summary. 1D 02 February 2017 Section 5.1, 7, 8.4, 8.5 updates 1E 14 March 2017 Section 4.3, 8.2.2 and 8.2.3, added 4.4, complete re-write of 10 1F 19 May 2017 Reviewed v1E document (by G. Kirchengast) 2 13 December 2017 Updated after RO SAG 04 meeting, including: general EPS-SG info added (orbit, mass, lifetime) references moved to the end acronym appendix place holder added several of 1F points included, some clean up of editorial updates Sub-sections, figures added to “Instrument and RO performance monitoring” chapter “RO related data processing and products” chapter moved to second to last, with “RO research & development and Outreach Need” now last chapter 2A 18 January 2018 Author update of Section 5, 9, RO SAG co-chair review, preparation for publication, removal of review comments 2B 11 October 2018 Cleaned up version for EUMETSAT website publication. 2C 28 November 2018 Updated Science Plan contributor, resend to RO SAG for re-check. Included RO hardware plot in Section 4. Page 2 of 125 v2C, 28 November 2018 Radio Occultation Science Plan Table of Contents 1 Executive Summary .................................................................................................................. 5 2 Introduction ............................................................................................................................... 6 2.1 The Role of RO SAG ......................................................................................................... 6 2.2 Purpose of the Science Plan ............................................................................................. 6 3 Mission Objectives .................................................................................................................... 7 3.1 EUMSATSAT Polar System–Second Generation (EPS-SG) ............................................. 7 3.2 Radio Occultation (RO) ................................................................................................... 10 4 EPS-SG RO Instrument ........................................................................................................... 12 4.1 Heritage .......................................................................................................................... 12 4.2 Instrument Hardware ....................................................................................................... 12 4.3 Observation Modes ......................................................................................................... 14 4.4 Bending Angle Requirements .......................................................................................... 15 5 POD for the RO Instrument and Future Signals [AH, JI] ...................................................... 16 5.1 Overview of GNSSs ........................................................................................................ 16 5.1.1 GPS .................................................................................................................... 17 5.1.2 GLONASS .......................................................................................................... 20 5.1.3 Galileo ................................................................................................................ 22 5.1.4 BeiDou ................................................................................................................ 24 5.1.5 QZSS .................................................................................................................. 26 5.1.6 Summary and Concluding Remarks on GNSS Status ........................................ 26 5.2 POD Processing Options ................................................................................................ 27 5.2.1 Ionospheric Propagation Effects ......................................................................... 27 5.2.2 Integer ambiguity fixing ....................................................................................... 30 5.2.3 Empirical Antenna Patterns ................................................................................ 31 5.3 Instrument Monitoring ...................................................................................................... 32 5.3.1 USO Characterization ......................................................................................... 32 6 Status and Outlook of RO Applications................................................................................. 36 6.1 NWP Applications ........................................................................................................... 36 6.2 Planetary Boundary Layer Height .................................................................................... 37 6.3 Tropopause Heights ........................................................................................................ 39 6.4 Gravity Waves ................................................................................................................. 41 6.5 Cloud Tops ...................................................................................................................... 42 7 Atmospheric RO Data Processing and Products.................................................................. 46 7.1 Processing of Atmosphere Products ............................................................................... 46 7.1.1 Level 2A Refractivity Profiles and Dry Temperature Profiles ............................... 47 7.1.2 Level 2B 1D-Var Products—Temperature, Humidity, Pressure Profiles .............. 48 7.1.3 Level 3 Gridded Data—Monthly Climatological Data Records ............................ 48 8 Ionospheric RO Data Processing and Products ................................................................... 50 8.1 Retrieval of Profiles and related Quantities from Ionospheric Occultations ...................... 50 8.1.1 Ne Profiling and hmF2 NmF2 hmE NmE Metrics ................................................ 50 8.1.2 Topside VTEC Estimation ................................................................................... 51 8.1.3 Profile Initialization .............................................................................................. 53 8.1.4 Bending Angles Estimation ................................................................................. 54 8.1.5 Lower Layers of the Ionosphere ......................................................................... 54 8.2 Monitoring Scintillations with RO Observations ............................................................... 56 8.2.1 Scintillation Indices from RO Observations ......................................................... 56 8.2.2 Scintillations to deduce Irregularities/Instabilities from RO Observations ............ 57 8.2.3 Effects on Receiver Hardware and Observables, and Countermeasures ........... 58 8.3 Assimilation of RO Ionospheric Observations into Ionospheric Models ........................... 58 8.3.1 Assimilation of Abel Transform Products with External Data .............................. 59 8.3.2 Assimilation of Augmented Abel Transform Products ......................................... 59 8.3.3 Assimilation of TEC Measurements .................................................................... 59 8.3.4 Assimilation of Bending Angle Measurements .................................................... 60 8.3.5 Development of Combined Neutral Atmosphere/Ionosphere Assimilation .......... 60 Page 3 of 125 v2C, 28 November 2018 Radio Occultation Science Plan 8.4 Model Assessment and Validation using RO-derived Data ............................................. 60 8.5 Improvement of Empirical Models using RO-derived Data (Bruno, ICTP) ....................... 61 9 Climate Use of RO data ........................................................................................................... 62 9.1 Quality of RO Data for Climate Use ................................................................................. 62 9.1.1 RO Data Characteristics for Climate ................................................................... 62 9.1.2 Uncertainty Characterization of RO Climatologies .............................................. 63 9.1.3 Structural Uncertainty of RO Climate Records from Different Data Centres ....... 64 9.2 RO Use for Monitoring Atmospheric Variability and Detecting Changes ......................... 66 9.2.1 Monitoring Atmospheric Variability and Extremes ............................................... 67 9.2.2 Monitoring and Detecting Climate Trends ........................................................... 69 9.2.3 RO for Evaluating Atmospheric Records and Climate Models ............................ 71 10 Instrument and RO Performance Monitoring ........................................................................ 73 10.1 EURD Requirements driving the Cal/Val Plan ................................................................