1. PAU INSTRUMENT ABOARD INTA MICROSAT-1:
A GNSS-R DEMONSTRATION MISSION FOR
SEA STATE CORRECTION IN L-BAND RADIOMETRY
A. Camps1, J.F. Marchán1,5, E. Valencia1, I. Ramos1, X. Bosch-Lluis1, N. Rodriguez1, H. Park1,
A. Alcayde2, S. Chavero2, P. Martínez2, A. Mollfulleda2, J. Galindo2, M. Angulo3, and A. Rius4
1Dept.of Signal Theory and Communications, Universitat Politècnica de Catalunya and
IEEC CRAE/UPC, UPC Campus Nord, D4-016, 08034 Barcelona, Spain. E-mail: camps@tsc.upc.edu
2ADTelecom, Camí de la Pelleria, 12, P.I. Bonavista, 08915 Badalona, Spain
3INTA, Dept. Progrs. Espaciales y Ciencias del Espacio, Torrejón de Ardoz 28850, Madrid, España
4IEEC/ICE-CSIC, Campus UAB/Fac. Ciències, Torre C-5-parell-2a planta, 08193 Bellaterra, Spain
5Institut Cartogràfic de Catalunya, Parc de Montjuïc, 08038 Barcelona, Spain
IGARSS 2011, Vancouver, Canada, July 25-29, 2011 © UPC, ADTelecom 2011 1

2. Outline of the presentation:
1. Introduction
2. Measurement Concept
3. Instrument Heritage
4. PAU in INTA’s MicroSat-1
5. Preliminary Tests
6. Conclusions
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3. 1. Introduction
• L-band microwave radiometry is the best suited for
Sea Surface Salinity and Soil Moisture  e.g.: SMOS, Aquarius, SMAP missions
• The brightness temperature of the sea surface depends on:
Th ,v  ,SST,SSS  1  h ,v  ,  r f ,SST, SSS    SST  Th ,v  , param 
- salinity
- physical temperature
- sea state (surface roughness)
critical correction: . SMOS: aux. data + multi-angular information
. AQUARIUS: L-band scatterometer
• Potential solution = combination in a single instrument 3 different sensors:
- PAU-RAD: New type of radiometer  measure TB
- PAU-GNSS/R: GPS reflectometer  measure sea state (and altimetry)
- PAU-IR: IR radiometer  measure SST
(PAU concept proposed to ESF in 2003, granted in 2004, cont’ MICIIN projects)
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4. 2. Measurement Concept
• GNSS opportunity signals reflected over the sea
surface come from a larger area (“glistening zone”)
when the sea is rough  longer delays as compared
to specular reflection point + larger Doppler shifts
• The Delay Doppler Map (DDM) provides an indication of the “widening”
of the so-called glistening zone
 related to TB  may be used to correct for sea state
• Sample DDMs from UK-DMC (Tcoh.= 1 ms; Tincoh. = 200 ms)
over the ocean, land and ice
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5. 3. PAU Instrument Heritage (i)
DO-DEREC early tests (July 2002) griPAU ground-based instrument
40 km South of Barcelona (Gran Canaria, 2008 & 2009)
 sea state determination and impact on TB
• 24x32 DDM points (min =0.09 chips, fd=200 Hz)
• Tcoh. min = 1 ms / Tcoh. max = adjustable
• Tincoh. min = 1 ms / Tincoh. max = adjustable
PAU-ORA (One Receiver Airborne): ALTIMETRIC & SM applications
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6. 3. PAU Instrument Heritage (ii) TB Sensitivity to Normalized DDM Volume
Measured DDM and threshold applied 5
x 10
5
x 10
3 2.5
2 2
[au]
1.5
1
1
2000
1000 2.5 0.5
0 2
1.5
-1000 1
-2000 0.5
Doppler [Hz] Delay [chips]
TB Sensitivity to Waveform’s Tail Length
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7. 4. PAU in INTA’s MicroSat-1 (i):
Sponsored by Spanish Ministry of Science and Innovation
“Sistemas GNSS-R para Futuras Misiones SMOS: SUBPROYECTO UPC”, code: AYA2008-05906-C02-01/ESP
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8. 4. PAU in INTA’s MicroSat-1 (ii):
Simplified design:
• Radiometer operated as a TPR with frequent calibration,
• GNSS-Reflectometer operated while receiver is connected to the antenna,
• Combination of up-looking and down-looking channels through coupler
Frequency plan:
• fRF = 1575.42 MHz, fIF = 70 MHz, fs = 16.384 MHz
Architecture:
• Two cold redundant receivers and processing boards.
UP-looking antenna
Processing
board #1
Processing
board #2
DOWN-looking antenna
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9. 4. PAU in INTA’s MicroSat-1 (iii): Antenna Array Design
1. Antenna array optimized for lowest possible ohmic losses and maximum gain
Planar structure (microstrip patches + stripline 8:1 power combiner < 6 mm thick)
Patch GPS R4360
f= 1575.42 MHz
r = 6.15
l = 36.6 mm
h = 2.54 mm
S11 = -25 dB
G = 5.37 dB
 = 86%
Array
G = 15 dB
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10. 4. PAU in INTA’s MicroSat-1 (iv):
All boards (Engineering Model – final version pending)
DPU VOLTAGE
MAIN SUPPLY
RF
BOARD BOARD
BOARD
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11. 4. PAU in INTA’s MicroSat-1 (v): RF/IF chain
2. RF / IF chain to provide G ~ 110 dB gain, NF ~ 2 dB, B ~ 2.2 MHz
G [dB]
Gcum [dB]
IP3 [dB]
IP3cum [dB]
NF [dB]
NFcum [dB]
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12. 4. PAU in INTA’s MicroSat-1 (vi): DPU
3. Signal Processor
• Virtex-4 FPGAs + in-orbit reconfiguration capability
• Interfaces: CAN (commands & reconfigurability), Space-Wire (data)
• DDM size: 4096* samples in delay x 16 samples in Doppler
• “Dummy” processing: Sequential search of all GPS satellites using
1 ms coherent integration time + > 10 incoherent avg. (100 typ.)
• On-board NRT processing or raw data acquisition
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13. 4. PAU in INTA’s MicroSat-1 (vii): DPU
Data Processing Unit Main Board (x 2: space-qualified + commercial compts.)
CAN
interface SRAM
ADC
IF
Input
signal
Back-
PROM panel
SpaceWire connector
Interface
FPGA
CLOCK
GENERATION
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14. 4. PAU in INTA’s MicroSat-1 (viii): Boards being stacked
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15. 4. PAU in INTA’s MicroSat-1 (ix): Boards being stacked
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16. 5. Preliminary Tests: (i)
R&S SMU-200A
arbitrary signal
generator + GPS module Acquisition Set-up
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17. 5. Preliminary Tests: (ii)
Sampling = 6-bit
Level = GPS L1 C/A at ground level
Tcoh =1 ms
Nincoh =1
fDoppler
[Hz]
Doppler [lags]
Delay [lags]
Delay [lags]
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18. 5. Preliminary Tests: (iii)
Sampling = 6-bit
Level = GPS L1 C/A at ground level -15 dB
Tcoh = 2 ms
Nincoh =50
Doppler [lags]
Delay [lags]
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19. 6. Conclusions
• PAU in INTA MicroSat-1 is a small secondary payload to test sea state
correction in L-band radiometric observations (TB vs Volume under the
normalized DDM).
• Combination of direct and reflected signals will allow also to “explore”
other scatterometric and altimetric measurements
• Planar antenna size limited by available space: trade-off between low
ohmic losses (~86%), “high” gain (~15 dB), side lobes (-11 dB at 90º), mass
and thickness (< 6 mm).
• Computes real-time DDMs or stores raw data for ground processing
• Engineering Model finished and first tests performed.
• Current basic processing scheme: Tcoh = 1 ms, Nincoh. avg = 100
+ blind sequential search of GPS satellites in view
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20. Acknowledgements:
Activities sponsored by ESF – EURYI 2004 grant and the Spanish Ministry
of Science and Innovation “Sistemas GNSS-R para Futuras Misiones
SMOS: SUBPROYECTO UPC”, code: AYA2008-05906-C02-01/ESP
IGARSS 2011, Vancouver, Canada, July 25-29, 2011 © UPC, ADTelecom 2011 20