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SUMMARY

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SUMMARY

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  1. ROSA INSTRUMENT AND ITS EVOLUTION (ROSA 2° GENERATION)A. Zin1, S. Landenna1, P. Ghibaudi1, E. Mangolini1, M. Bandinelli2, L. Mattioni2, V. De Cosmo31 Thales Alenia Space – Italia S.p.A., S.S. Padana Superiore 290, Vimodrone, Milano, Italy2 IDS, Ingegneria Dei Sistemi S.p.A. – Via Livornese, 1019, 56010 Pisa, Italy3 ASI, Agenzia Spaziale Italiana – Viale Liegi, 26, 00198 Roma, Italy

  2. SUMMARY • Context: GNSS Radio Occultation and Scatterometry / Altimetry Applications • Drivers for ROSA 2nd Generation Development • RO & SCAT Antenna concepts • ROSA 2nd Generation Instrument Concept

  3. SCIENTIFIC CONTEXT

  4. GNSS Radio Occultation • ROSA 1st Generation Domain: ( Source of media: JPL - UCAR - Wikipedia )

  5. GNSS Altimetry • ROSA 2nd Generation Domain: altimetry and scatterometry • GNSS-R altimetry: reflected signal arrives later than the direct one • Tracking of the specularly reflected coherent part of the signal allows the measurement of the arrival time difference, which is called the lapse or relative delay. (Source of media: StarLab - ES)

  6. GNSS Scatterometry • Scatterometry: a rougher surface reflects signals from a wider region around the specular point: the glistening zone. Dimension of glistening zone, depends on roughness/sea state

  7. ROSA 2nd GENERATION MOTIVATION - DRIVERS

  8. USER NEEDS… EASIER ACCOMMODATION ON HOST SATELLITE MORE OCCULTATIONS EVENTS BETTER QUALITY OF OCCULTATIONS: sounding to down to the surface BETTER IONOSPHERIC REMOVAL INNOVATION: multipurpose instrument, modularity of applications LOW LATENCY OF RO DATA

  9. USER NEEDS… EASIER ACCOMMODATION ON HOST SATELLITE • Accommodation of ROSA was a challenging issue for host satellites not specifically conceived for RO applications, main constraint are the RO antenna dimensions. Example: OceanSat II. • Reduction of mass, power, dimensions (both of receiver and antenna parts) are one of the main drivers for the development of a new generation instrument, ROSA 2nd Generation

  10. USER NEEDS… MORE OCCULTATIONS EVENTS • The user requirement of high number of occultation events translates into multi-constellation receiver. • Currently, the rough estimate for a single constellation receiver is ~500 occ/day using rising and setting antennas • Tracking of Galileo SV (when the constellation will be fully deployed) will increase the number to ~ 1000/day • Options to track COMPASS signals, as well as GLONASS may be an interesting opportunity to be evaluated in the near future. • Unclear ICD from COMPASS and future switch to CDMA for GLONASS are uncertain aspects that need to be considered. • Impacts at Rx: Correlator technology (GALVANI, AGGA-4), Number of channels, Processing power

  11. USER NEEDS… BETTER QUALITY OF OCCULTATIONS: sounding to down to the surface BETTER IONOSPHERIC REMOVAL • This requirement translates into better SNR at correlators, good frequency stability in the time interval of an occultation, robust tracking techniques and type signals to be tracked. • On receiver side, better SNR can be achieved by considering good LNA stage on one side (i.e. noise floor reduction) and gain on the antenna side. • Frequency stability in ROSA / ROSA 2° Gen is accomplished by using high-quality USO (currently < 5. e-11 @ 50 min, 2.e-12 @ 1 s)

  12. USER NEEDS… BETTER QUALITY OF OCCULTATIONS: sounding to down to the surface BETTER IONOSPHERIC REMOVAL • Robust tracking techniques: in parallel to classical closed loop operations, in the last years the focus has been put on open-loop techniques (high-frequency raw sampling). • An implementation of this technique, based on a collaboration between Italian Univiersity (Politecnico di Torino) and TAS-I was already implemented in ROSA • Modernized signals provide the opportunity to deal with pilot signals (i.e., signal components without data bit modulations), forgetting the current problems arosen in removal of Navigation Message Bit in Open Loop (see for example ** ). • Another important advantage of GPS Modernized signals and GALILEO Open Service is the opportunity to access the second frequency without the current drawbacks of L2P(Y) encription. (GPS L2-C, GAL E5a-b, GPS L5) ** S. Sokolovskiy, C. Rocken, D. Hunt, W. Schreiner, J. Johnson, D. Masters, S. Esterhuizen, Inversion of open-loop radio occultation signals at CDAAC, Second GPS Radio Occultation Data Users Workshop, National Conference Center, Lansdowne, VA, 2005

  13. USER NEEDS… INNOVATION • The emerging concepts in the field of remote sensign using GNSS signals is GNSS altimetry and GNSS scatterometry. • The use of an integrated instrument aimed to the fulfillment of GNSS Navigation + GNSS Radio Occultation + GNSS Scatterometry/Altimetry (NAV + RO + SCAT/ALT) is an ambitious objective that TAS-I studied in the ROSA 2nd Gen Instrument Study • Modularity would allow, in principle, an unique design in which the RO and SCAT/ALT funtionalities are independent. NAV, of course, is the basis of the functioning. Options: • NAV • NAV + RO (single and dual-antenna) • NAV + SCAT/ALT • NAV + RO + SCAT/ALT

  14. USER NEEDS… LOW LATENCY • This issue impacts more on the ground stations displacement • At the receiver level, one of the possible improvements is to implement a mass memory in order to optimize the exchange with the satellite on-board memory

  15. STUDY CONTEXT • ROSA 2nd Generation concept was studied in the framework of a ASI Contract in 2008 (“Opportunity Mission “), with TAS-I acting as a prime contractor • The study was done in cooperation with Italian university for the scientific aspects and user requirements (Università La Sapienza, Tor Vergata, Politecnico di Torino, CETEMPS). Industrial partner (IDS) worked on Instrument feasibility aspects, together with TAS-I • In the framework of ROSA 2° Generation study, a survey of the state of the art technology in GNSS Radio Occultation and Scatterometry from space was carried out. • This allowed the identification of ROSA 2° generation user requirements and tradeoff among various instrument concepts, • The “less mature” scatterometry part (w.r.t RO) was analysed in detail

  16. ROSA 2nd GENERATION: RO & SCAT ANTENNA CONCEPTS

  17. SCATTEROMETRY ANTENNA Requirements 1Elliptical spots to be preferred with respect to circular ones 2Mainly interesting for altimetry applications Due to the fact that we are working in the frame of “mission of opportunity”, also requirements relevant to antenna encumbrance and mass have been considered as “main ones”  A < 0.35m2~ (0.6 x 0.6m)

  18. RADIO-OCCULTATION ANTENNA Requirements (secondary) (main) (limbo) Also in this case, requirements relevant to antenna encumbrance and mass have been considered as “main ones”

  19. SCATTEROMETRY ANTENNA Baseline antenna system The baseline configuration has been chosen having in mind the goal to minimize as much as possible antenna encumbrance (also if obviously at the cost of electric performance) • Antenna type: bi-dimensional array • Maximum size:  0.35 m2 (0.6m x 0.6m) • Radiating elements: patch-like antennas • Bands: GPS L1 – GALILEO E1 • BFN: Analog beam forming network • Beams: 4 fixed pencil shaped beams • Coverage: ±35° off-nadir (half-cone angle) • Maximum gain of each beam:  20 dBi • Polarization: LHCP

  20. RADIO-OCCULTATION ANTENNA receiving ant 1 receiving ant 2 receiving ant 3  (diplexer) Baseline antenna system The baseline configuration has been chosen having in mind the goal to minimize as much as possible antenna transversal encumbrance (also if at the cost of a greater longitudinal dimension) incoming GPS signals • Antenna type: 3 “combined” antennas • Maximum size:  0.6m long,  0.4 x 0.4m transv • Radiating elements: 2 helices, 1 patch-like • Bands: GPS L1 & L2, GALILEO E1 & E5b • Radiation pattern: main & secondary coverage • Maximum gain:  12 dBi (main cov.),  5 dBi (2nd cov) • Polarization: RHCP A diplexer is required at the output

  21. RADIO-OCCULTATION ANTENNA Baseline antenna system stacked patch RHCP metallic sheet (satellite body) elevation pattern azimuthal pattern Dq Df wire or printed helix dielectric support or quasi-aria Critical areas No special critical areas are identified for such baseline configuration, neither from the point of view of the design nor from the point of view of materials and manufacturing process

  22. RADIO-OCCULTATION ANTENNA Preliminary simulations DM 11.9 dBi D > 5.5 dBi -45° +45° DM 11.9 dBi D > 0 dBi elevation azimuth

  23. ROSA 2nd GENERATION: RECEIVER CONCEPT

  24. INSTRUMENT TRADE OFF

  25. INSTRUMENT TRADE OFF [1] ROSA reference data.

  26. INSTRUMENT CONCEPT • Modular Architecture allows flexibility for different instrument configurations: • NAV • NAV + RO • NAV + SCAT • NAV + RO + SCAT • Design “ITAR Free” • Main driver: accommodation on small missions • New technology involved: • GALVANI correlator (AGGA-4 ?) • Nemerix RF chip • OMNIA mp

  27. ROSA 2nd GEN CONCEPT NAV / POD PATCH ANTENNA ROSA SECOND GENERATION RECEIVER RADIO OCCULTATION / SPACE WEATHER VELOCITY ANTENNA SYSTEM RADIO OCCULTATION / SPACE WEATHER ANTI-VELOCITY ANTENNA SYSTEM SCATTEROMETRY / ALTIMETRY ANTENNA ARRAY

  28. THANK YOU!

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