Transcript ROSA SECONDA GENERAZIONE

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, Italy
2 IDS, Ingegneria Dei Sistemi S.p.A. – Via Livornese, 1019, 56010 Pisa, Italy
3 ASI, Agenzia Spaziale Italiana – Viale Liegi, 26, 00198 Roma, Italy
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SUMMARY
Page 2
 Context: GNSS Radio Occultation and Scatterometry
/ Altimetry Applications
 Drivers for ROSA 2nd Generation Development
 RO & SCAT Antenna concepts
 ROSA 2nd Generation Instrument Concept
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SCIENTIFIC CONTEXT
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GNSS Radio Occultation
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ROSA 1st Generation Domain:
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GNSS Altimetry
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 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.
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GNSS Scatterometry
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 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
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ROSA 2nd GENERATION
MOTIVATION - DRIVERS
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USER NEEDS…
Page 8
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
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Page 9
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
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USER NEEDS…
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MORE OCCULTATIONS EVENTS
 The user requirement of high number of occultation events translates into multiconstellation 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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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)
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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
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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
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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
Page 15
 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
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ROSA 2nd GENERATION:
RO & SCAT ANTENNA CONCEPTS
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SCATTEROMETRY ANTENNA
Requirements
1
Elliptical spots to be preferred with respect to circular ones
2
Mainly interesting for altimetry applications
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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)
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RADIO-OCCULTATION ANTENNA
Requirements
Page 18
(secondary)
(main)
(limbo)
Also in this case, requirements
relevant to antenna encumbrance
and mass have been considered
as “main ones”
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SCATTEROMETRY ANTENNA
Baseline antenna system
Page 19
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
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RADIO-OCCULTATION ANTENNA
Baseline antenna system
Page 20
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
incoming
GPS signals
receiving
ant 1
receiving
ant 2
receiving
ant 3

(diplexer)
A diplexer is required at the output
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RADIO-OCCULTATION ANTENNA
Baseline antenna system
stacked patch
RHCP
Page 21
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
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RADIO-OCCULTATION ANTENNA
Preliminary simulations
DM  11.9 dBi
Page 22
D > 5.5 dBi
-45°
+45°
DM  11.9 dBi
D > 0 dBi
azimuth
elevation
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ROSA 2nd GENERATION:
RECEIVER CONCEPT
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INSTRUMENT TRADE OFF
Page 24
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[1]
INSTRUMENT TRADE OFF
ROSA reference data.
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Requirement Signals
# of Multi
Frequency
channels
Up to 16 nav,
Up to 16 VA
occultations, up
to 16 AVA
occultations.
RF Section Tracking
Data storage Sampling On board
Rate
processing
Comments
RF Asic
CL / OL
~440 MB TBC 1-10-50
Hz @
<200 /
<50 / <,
50 Hz
(space
weather),
>= 100 Hz
OL
~220 MB TBC 1-10-50
Hz 20050- ,
1-Hz
space
weather
~ 1000 occ / day
expected with
antenna azimuth of
45 deg, ~ 650 with
azimuth of 30 deg
OPTION A
GPS L1
C/A+
GPS L2C +
GALILEO
(L1, E5b)
OPTION B
GPS +
GPS
modernized
(L2C + L5 TBC)
8 nav, 8 occ
(GPS) CL+ OL,
RF Asic
CL / OL
OPTION C
GPS +
GPS
modernized
(L2C)
8 nav, 8 occ
(GPS)
RF Asic
CL / OL
No storage
1-10-50
Hz 20050- ,
1-Hz
space
weather
No
Occultation
processing
on-board.
Only raw data
collection.
Occultation
predictions
necessary.
No
Occultation
processing
on-board.
Only raw data
collection.
Occultation
predictions
necessary.
No
Occultation
processing
on-board.
Only raw data
collection.
Occultation
predictions
necessary.
~ 500 occ / day
expected with
antenna azimuth of
45 deg, ~ 300 with
azimuth of 30 deg
~ 500 occ / day
expected with
antenna azimuth of
45 deg, ~ 300 with
azimuth of 30 deg
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INSTRUMENT CONCEPT
Page 26
 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
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ROSA 2nd GEN CONCEPT
Page 27
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
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Page 28
THANK YOU!
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