Navigation Department 5 Feb. 2009 - Meeting ASI / EUMETSAT All rights reserved, 2008, Thales Alenia Space ROSA INSTRUMENT AND ITS EVOLUTION (ROSA 2° GENERATION)

Navigation Department

5 Feb. 2009 - Meeting ASI / EUMETSAT All rights reserved, 2008, Thales Alenia Space

ROSA INSTRUMENT AND ITS EVOLUTION (ROSA 2° GENERATION)

A. Zin1, S. Landenna1, P. Ghibaudi1, E. Mangolini1, M. Bandinelli2, L. Mattioni2, V. De Cosmo3

1 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, Italy

3 ASI, Agenzia Spaziale Italiana – Viale Liegi, 26, 00198 Roma, Italy

All rights reserved, 2008, Thales Alenia Space


5 Feb. 2009 - Meeting ASI / EUMETSAT

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SUMMARY

Context: GNSS Radio Occultation and

Scatterometry / Altimetry Applications

Drivers for ROSA 2ROSA 2ndnd Generation Generation Development

RO & SCAT Antenna concepts

ROSA 2ROSA 2ndnd Generation Generation Instrument Concept



SCIENTIFIC CONTEXT




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GNSS Radio Occultation

( Source of media: JPL - UCAR - Wikipedia )

ROSA ROSA 11stst Generation Generation Domain:




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GNSS Altimetry

ROSA ROSA 22ndnd Generation Generation Domain: altimetryaltimetry and scatterometryscatterometry

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)




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GNSS Scatterometry

ScatterometryScatterometry: 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



ROSA 2nd GENERATION

MOTIVATION - DRIVERS




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USER NEEDS…

INNOVATION: multipurpose instrument, modularity of applications

EASIER ACCOMMODATION ON HOST SATELLITE

MORE OCCULTATIONS EVENTS

BETTER QUALITY OF OCCULTATIONS: sounding to down to the surface

LOW LATENCY OF RO DATA

BETTER IONOSPHERIC REMOVAL




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USER NEEDS…

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 2ROSA 2ndnd

GenerationGeneration

EASIER ACCOMMODATION ON HOST SATELLITE




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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




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USER NEEDS…

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)






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USER NEEDS…

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





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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:

NAVNAV

NAV + RO (single and dual-antenna)NAV + RO (single and dual-antenna)

NAV + SCAT/ALTNAV + SCAT/ALT

NAV + RO + SCAT/ALTNAV + RO + SCAT/ALT




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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




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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



ROSA 2nd GENERATION:

RO & SCAT ANTENNA CONCEPTS




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2 Mainly interesting for altimetry applications

1 Elliptical spots to be preferred with respect to circular ones

SCATTEROMETRY ANTENNA

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)

Requirements




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RADIO-OCCULTATION ANTENNA

Requirements

(limbo)

(main)

(secondary)

Also in this case, requirements relevant to antenna encumbrance and mass have been considered as “main ones”




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SCATTEROMETRY ANTENNA

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)

Baseline antenna system

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




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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)

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

receivingant 1

receivingant 2

receivingant 3

(diplexer)

A diplexer is required at the output

incomingGPS signals




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Critical areasNo 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



elevation pattern azimuthal pattern

dielectric support or quasi-aria

wire or printed helix

stacked patchRHCP

metallic sheet(satellite body)




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-45° +45°

azimuth

D > 5.5 dBi

elevation

DM 11.9 dBi

D > 0 dBi

DM 11.9 dBi


Preliminary simulations



ROSA 2nd GENERATION:

RECEIVER CONCEPT




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INSTRUMENT TRADE OFF




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INSTRUMENT TRADE OFF

Requirement Signals # of Multi Frequency channels

RF Section Tracking Data storage Sampling Rate

On board processing

Comments

OPTION A GPS L1 C/A+ GPS L2C +GALILEO (L1, E5b)

Up to 16 nav, Up to 16 VA occultations, up to 16 AVA occultations.

RF Asic CL / OL ~440 MB TBC 1-10-50 Hz @ <200 / <50 / <, 50 Hz (space weather),>= 100 Hz OL

No Occultation processing on-board. Only raw data collection. Occultation predictions necessary.

~ 1000 occ / day expected with antenna azimuth of 45 deg, ~ 650 with azimuth of 30 deg

OPTION B GPS + GPS modernized (L2C + L5 - TBC)

8 nav, 8 occ (GPS) CL+ OL,

RF Asic CL / OL ~220 MB TBC

1-10-50 Hz 200-50- , 1-Hz space weather



OPTION C GPS + GPS modernized (L2C)

8 nav, 8 occ (GPS)

RF Asic CL / OL No storage 1-10-50 Hz 200-50- , 1-Hz space weather



[1] ROSA reference data.




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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 p




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ROSA 2nd GEN CONCEPT

RADIO OCCULTATION / SPACE WEATHER VELOCITY ANTENNA SYSTEM

SCATTEROMETRY / ALTIMETRY ANTENNA ARRAY

RADIO OCCULTATION / SPACE WEATHER ANTI-VELOCITY ANTENNA SYSTEM

NAV / POD PATCH ANTENNA

ROSA SECOND GENERATION RECEIVER




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THANK YOU!THANK YOU!

Documents

Navigation Department 5 Feb. 2009 - Meeting ASI / EUMETSAT All rights reserved, 2008, Thales Alenia Space ROSA INSTRUMENT AND ITS EVOLUTION (ROSA 2° GENERATION)