The Radio Occultation and Heavy Precipitation experiment aboard PAZ (ROHP-PAZ): after launch activities

Transcription

1 The Radio Occultation and Heavy Precipitation experiment aboard PAZ (ROHP-PAZ): after launch activities E. Cardellach¹ ², M. de la Torre-Juárez³, S. Tomás¹ ², S. Oliveras¹ ², A. Rius¹ ², B. Schreiner⁴, J. Weiss⁴, J. Clapp⁵, M. Seymour⁵, C.O. Ao³, F.J. Turk³, R. Padullés³, K-N Wang³, F. Cerezo⁶ ¹ Institute of Space Sciences (ICE-CSIC), Barcelona, Spain ²Institute of Space Studies of Catalonia (IEEC), Barcelona, Spain ³ Jet Propulsion Laboratory (JPL), Pasadena CA, U.S.A. ⁴ University Corporation for Atmospheric Research (UCAR), Boulder CO, U.S.A. ⁵ N.O.A.A., U.S.A. ⁶ Hisdesat, Madrid, Spain

2 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH AFTER LAUNCH ACTIVITIES

3 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH AFTER LAUNCH ACTIVITIES

4 Polarimetric RO PRODUCTS: VERTICAL PROFILES OF THERMODYNAMIC VARIABLES (typically temperature, pressure from refractivity)

5 Polarimetric RO PRODUCTS: VERTICAL PROFILES OF THERMODYNAMIC VARIABLES (typically temperature, pressure from refractivity) + VERTICAL PROFILES OF [INTENSE] RAIN

6 Polarimetric RO New measurement concept, to be proven aboard the PAZ Spanish LEO Similar to polarimetric weather radars, but FORWARD SCATTERING (propagation) rather than BACK-SCATTERING GNSS: Signals at L-band: ~1.5 GHz (this is ~1/2 of NEXRAD polarimetric radars, at 3 GHz)

7 ROHP-PAZ Spanish PAZ satellite: Main payload, X-band SAR Polar orbit (97.4 deg) at ~514 km altitude IGOR+ GNSS receiver A 2-pol (H/V) setting RO antenna

8 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH AFTER LAUNCH ACTIVITIES

9 STATUS On February 22nd 2018, at 6:17 a.m. PT, SpaceX successfully launched the PAZ satellite from Space Launch Complex 4E (SLC-4E) at Vandenberg Air Force Base in California

10 STATUS To launch on Falcon9 a new mechanical interface was installed (not needed in the original Dnepr launch).

11 STATUS POD data: RINEX fles received. Preliminary analysis seems to indicate that the SNR and amount of acquired satellites is slightly worse than TerraSAR-X PPP solution, Canada Geodetic Survey: POD-2, 29 hours test: - Aposteriori Phase Std: 1.2 cm - Aposteriori Code Std: cm - Rejected epochs: 2.22% POD-1, 8 hours test: - Aposteriori Phase Std: 1.2 cm - Aposteriori Code Std: 85.2 cm - Rejected epochs: 0.17% UCAR analysis, Yoke Yoon

12 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH AFTER LAUNCH ACTIVITIES

13 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH (polarimetric data) observables to be used retrieval concept separation step AFTER LAUNCH ACTIVITIES

14 PRO observable - Rain drop: fattered by air dragging. - Tangential propagation: asymmetric drops induce diferent propagation parameters in the vertical and horizontal polarization components. But at L-band: small signal! Diferent attenuation (amplitude): calibration issues. Diferent phase delay: GNSS very good at measuring phase-delay! - Simulation work: intense rain episodes induce several mm polarimetric phase delay. - Noise expected at mm (@1Hz) at surface level, better with altitude.

15 INVERSION

16 INVERSION STATISTICAL INVERSTION APPROACH: Which are the chances that a RO ray with a given altitude of its tangent point has cross a rain cell of certain characteristics? To answer this questions we have artifcially co-located 'RO rays' along the GPM mission swath (>200,000 profles) and obtained (ht) to produce Lookup Tables (LUT): our the inversion tools. We have generated LUT for most probable mean rain rate along the ray <R>*, most probable maximum rain rate along the ray path Rmax*, and several percentiles of <R> and Rmax

17 INVERSION How to build the LUT? Up to ~ profiles Most probable <R> th percentile: 75% is larger than this value

18 INVERSION Final PAZ RO product: hydrometeor products Height of TP Standard RO Thermodynamic products

19 SEPARABILITY Accepted for publication at IEEE Trans. Geosc. Remote Sensing

20 SEPARABILITY Transmitted ellipticity + Faraday rotation + receiver efects mix up with hydrometeor efects observable contains these efects How to separate these efects and isolate the hydrometeorinduced 1) Calibration of the receiving system 2) Diferential approach

21 SEPARABILITY Diferential approach: extrapolation of the polarimetric diferential phase measured above the rain (e.g. 20 km) down to the surface, assuming it will contain the efects dur to: transmitter + iono1 + iono2 + receiver initial phase subtraction of this extrapolated profle

22 Contents INTRODUCTION TO THE ROHP-PAZ EXPERIMENT STATUS PROCESSING APPROACH AFTER LAUNCH ACTIVITIES

23 After launch Standard RO data (non-pol) Downlink to NOAA s Fairbanks tests started this week frst step towards NRT data UCAR to test the quality UCAR & NOAA NRT processing and dissemination of standard RO products (GTM & CDAAC) SCHEDULE: dissemination expected later Polarimetric RO data Understanding of the data and their main efects Co-location of RO profles with precipitation and cloud missions, atmospheric, ionospheric, magnetic feld models data fagging Calibration fag: RO free of hydrometeors and expected moderate Faraday rotations Validation fag: RO well colocated with GPM mission and presenting intense precipitation Proceed to receiver calibration and retrieval validation SCHEDULE: 6-12 months before making pol-ro data publicly available at

24 Conclusions PAZ carries a polarimetric RO payload, to prove the concept. Launched: Feb 22, POD data looks fne. Possible issues due to satellite mechanical interface, especially for PolRO. Selected polarimetric observable: phase-delay diference between H and V linear polarizations, with expected noise at 1.5 mm (1 Hz). A statistical inversion approach provides the probability of rain (diferent percentiles and most probable) as a function of altitude polarimetric product. Isolation of the hydrometeor component diferential approach + calibration standard non-pol products UCAR, NRT (after quality checks) Polarimetric data/products through IEEC, 6-12 months

25 Thank you for your attention! More info and data access:

26 INVERSION Examples of a few LUT

27 INVERSION How to use the LUT for data inversion?

28 CALIBRATION H-pol and V-pol components captured at the receiver are afected by rain, but also by other efects: Common H/V propagation effects Receiver Initial phase Calibrable Rcv systems Hydrometeors effect Ionosphere after hydrometeors Emitted field Ionosphere before hydrometeors Only affect polarimetric differential phase if input field is not circular

29 SEPARABILITY H-pol and V-pol components captured at the receiver are afected by rain, but also by other efects: Common H/V propagation effects Calibrable Rcv systems Hydrometeors effect If emitted field is RCHP Receiver Ionosphere-2 Ionosphere and hydrometeors after Ionosphere before Initial phase hydrometeors hydrometeors can be separated if either - both polarimetric differential amplitude and phase Only canaffect be measured polarimetric differential phase if input is not circular - or only differential phase is measured but field Faraday rotation in ionosphere-2 is within +-15 deg.

30 SEPARABILITY How often the Faraday rotation at iono-2 will be < 15 deg? Solar minimum ( ) Solar maximum ( ) 95% of the cases among >220,000 RO COSMIC rays below 20 km along GPM swath simulated

31 SEPARABILITY Simulations based on 30,000 'fake' RO rays artifcially co-located with GPM rain events ABSOLUTE ERROR in the estimated hydrometeor induced polarimetric phase shift (5% worst cases removed) GNSS transmission assumed 1.8dB ellipticity 5 diferent orientations of the ellipse L1, L2, combined