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12-01-2017
1
OVERVIEW OF
INDIAN SAR MISSIONS
Deepak PutrevuHead, Microwave Sensors System Division
DPD-Chandrayaan-2 Dual Frequency SAR
DPD- RISAT-1A SAR
Microwave Remote Sensors Area
Space Applications Centre, Ahmedabad
19
80
s TO
PR
ESEN
T
X-BAND SLAR
C-BAND ASAR
C-BAND DMSAR
X-BAND MINISAR
L&S-BAND AIRBORNE SAR
C-BAND RISAT-1
C-BAND RISAT-1A
X-BAND RISAT-2A
L&S-BAND NISAR
CHANDRAYAAN-2 L&S-BAND SAR
SAR ACTIVITIES AT SAC
20
03
TO
20
20
9.6 GHZ, HH 25 KW PEAK POWER ALTITUDE 3 KM SWATH 5 Km DAKOTA DC-10 (Aircraft)
SIDE-LOOKING AIRBORNE RADAR (SLAR)
(1983-89)
C-BAND AIRBORNE SAR (ASAR)
First Flown On May 20th, 1992
Operating frequency 5350 MHz
Polarisation HH, VV
Antenna pattern Cosec2
Back scattering coefficient -30 to +7 dB
Instantaneous dynamic range ~ 20 dB
Slant range resolution 6 m
Azimuth resolution 6 m
Radiometric resolution < 2.5 dB
Swath coverage 25 Km
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ROBUST ASAR PROCESSOR (2000-2001)
• On Ground Motion Sensing And Compensation
• Can Generate Images In Large Disturbances
• Enabled Reduction In On-board Hardware Significantly
• Generated Much Improved Understanding Of SAR Processing
C-BAND AIRBORNE SAR (ASAR)Kansi
Jalwara
Rampur
*
*
*
Sabhan*
DARBHANGA
LAHERIA SARAI
Kamrauli
*
Baliya*
Banauli *Yaunga *
Dih Rampur *
Panchobh * Mahnauli*
Kamalpur *Baghla *
Baghia*
Taralahi * Chandih *
Ekmighat*
Badhbasti
* Simra *
Bajrdpur*
Ballapur*
Baluwahi
*
Manlari
*Ganawli*
Kadaria*
Bharaul
*
Chatiriya*
FLOOD INUNDATION
During Floods - ASAR data of 24-Jul-2003
Affected Embankment
During Floods - ASAR data of 24-Jul-2003
Karja
Belsandi
Chhecahauni
Lad Kapasiya
Salaha Buzurg
Phuhiya
Bardaum
Sohma
*
*
**
NirpaSughrain
Sukhasan
*
*
*
*
**
Chandauli
*
*
Flood InundationRiver / Water Bodies
Submerged RoadRoad Embankment
Karja
Belsandi
Chhecahauni
Lad Kapasiya
Salaha Buzurg
Phuhiya
Bardaum
Sohma
*
*
**
NirpaSughrain
Sukhasan
*
*
*
*
**
Chandauli
*
*
Flood Map
C-BAND AIRBORNE SAR (ASAR)
DMSAR Rack Inside The AircraftC-BAND DMSAR
DMSAR SPECIFICATIONS
Parameters Specifications
Frequency 5.35 GHz (C-band)
Polarization HH/VV (Single polarization at a time)
Nominal Altitude
8 km
Nominal Velocity
120 m/s
Slant Range Resolutions
<2m 3m 5m 10m 30m
Swath 6 km 25 km 50 km 75 km 75 km
Minimum Normalised RCS
-20 dB -24 dB -27 dB -30 dB -33 dB
DMSAR INSTALLED IN THE BEECHCRAFTBEECHCRAFT
AHMEDABAD AIRPORT
C-BAND DMSAR
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Radar Imaging Satellite
RISAT - 1
• C-BAND SYNTHETIC APERTURE RADAR (SAR)
• FIRST SPACEBORNE SAR FROM INDIA, LAUNCHED IN 2012
• 5.35 GHz FREQUENCY WITH MULTIPOLARIZATION CAPABILITY
• CATERS TO WIDE RANGE OF APPLICATIONS FROM AGRICULTURE TO LAND
MAPPING
• MULTIMODE CONFIGURATION TO MEET APPLICATION REQUIREMENTS
• ACTIVE ANTENNA CONFIGURATION WITH STATE-OF-THE-ART TECHNOLOGY
PHASED ARRAY RADARS
•WIDE SWATH REQUIREMENT CALLS FOR
ELECTRONIC BEAM STEERING IN ELEVATION
•THIS LEADS TO PHASED ARRAY RADARS
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
-1.5-1-0.5 0 0.5 1 1.5
0 5
10 15
20
sin(x)
DIRECTION OF ANTENNA BEAM POINTING
DIRECTION OF ANTENNA
BEAM POINTING
PHASE,
φ
PHASE,
φ
ELEMENT, x ELEMENT, x
PHASE IS SWITCHED IN FEW MICROSECS, HENCE HIGHLY AGILE SYSTEM
ACTIVE PHASED ARRAY RADARS
•PHASE SHIFTERS ARE LOSSY (6-7dB) AND DEGRADE SNR SIGNIFICANTLY. LARGE PATH
LENGTHS ADD TO THE WOES.
RxTx
•TRANSMIT-RECEIVE MODULES WITH PHASE-SHIFTERS DELIVER REQD GAIN AND
REDUCE NF DURING TRANSMIT AND RECEIVE, TO IMPROVE SNR OF THE SYSTEM
•FOR BOTH PASSIVE AND ACTIVE PHASED ARRAYS,
SEPARATION OF THE ANTENNA ELEMENTS SHOULD
BE CLOSE TO AVOID GRATING LOBES
• IDEALLY, SEPARATION < 0.5λ;
PRACTICALLY, ~0.7-0.8λ SUFFICES (AND PREFERRED!)
Equi-Phase
Reference
•FOR SWATH SELECTION
WITHIN 100km – 700km
OFF-NADIR DISTANCE
•FOR SCANSAR MODE
OF OPERATION, TO
INCREASE SWATH36°
RISAT-1: ELECTRONIC BEAM STEERING
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6m
2m
EACH PANEL OF 2M X 2M DIMENSIONS
EACH PANEL HAS 4 TILES (EACH OF 1m x 1m)
12 TILES (= 3PANELS) MAKE FULL ANTENNA OF 6M X 2M
ACTIVE ARRAY CONFIGURATION
576 TR-MODULES (288 EACH FOR H & V)
FRS1/FRS2 Mode
536
km
HRS Mode
CRS Mode
MRS Mode
RISAT Specifications – Imaging Modes & Swath
HRS ModeResolution = 1 - 2 m, o = -16dB
FRS-1 ModeResolution = 3 - 6 m, o = -17dB
FRS-2 ModeResolution = 6-9m (Quad Pol), o = -20dB / -19dB
MRS ModeResolution = 25 m, o = -17dB
CRS ModeResolution = 50 m, o = -17dB
Look Angle Varies from 11.280– 49.090
RISAT-1
H
VRx-H
SSPA
Rx-V
BASIC SYSTEM CONFIGURATION
LOReceiver
DistributedActive
Antenna
Chirped Carrier
LO
PRF
I & Q8 bit
Sampling Clock
To BDH
Clock Ref
IF
FEEDER SSPA
FREQUENCY GENERATOR
(BW X 9)
2/3/4/5/6 BITBAQ
ADC
DIGITAL CHIRP GENERATOR (DCG)
225/9, 75/9, 37.5/9 & 18.75/9MHZ
CAL SWITCHING
MATRIX
MGCLNA+DOWN CONVERTER
ISOLATION SWITCH
ISOLATION SWITCH
CLOCK REF
PRF
SAMPLINGCLOCK
TILE CONTROL
PAYLOAD CONTROLLER
LPF 112.5MHz
LPF 37.5MHz
LPF 18.75MHz
LPF 9.40MHz
I/Q DEMOD
IF
CONFIGURATION OF RF & BASEBAND SYSTEMS
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TILE CONFIGURATION
TILE CONTROL UNIT
(1 PER TILE)
1:12 RF DISTR N/W
FOR SIGNAL(V&H), CAL (V&H)(2 PER TILE)
PCPU (POWER
CONDITIONING AND PROCESSING
UNIT)(24 PER TILE)
TRM-V
TRM-H
TRM-SET (2TRM + 1TRC)
(24 PER TILE)
TRC (TR CONTROL UNIT)
1:2 RF POWER DIVIDER
(4 PER TILE)
•48 TR-MODULE PAIRS ALONG ANTENNA WIDTH TO CONTROL BEAM POINTING AND BEAMWIDTH
•TOTAL 288 TRM PAIRS OVER ENTIRE ANTENNA
TR MODULE
EPC FOR TR MODULEMULTILAYER DUAL
POLARISED PRINTED
ANTENNA
ASIC FOR TRC
TILE ELECTRONICS
OVERALL SCHEMATIC OF RF SIGNAL FLOW
Tile
Aperture
Tile
Aperture
Tile
Aperture
Tile
Electronics
Tile
Electronics
Tile
Electronics
Panel
Panel
Panel
To 12 TR
Pairs
To 12
TR Pairs
To 12 TR
Pairs
To 12 TR
Pairs
To 12 TR
Pairs
To 12 TR
PairsFEEDER SSPA
RECEIVER
TR(V)TO 20
ANTENNA
PATCHES
TR(H)
1:24 DNW
1:24 DNW
TR(V)TO 20
ANTENNA
PATCHES
TR(H)
1:24 DNW
1:24 DNW
TR(V)TO 20
ANTENNA
PATCHES
TR(H)
1:24 DNW
1:24 DNW
ACTIVE ANTENNA SIGNAL DISTRIBUTION
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Ground Station
RISAT Antenna
Tile Controller
BMU PLC
RF Sub-Systems
Digital Sub-Systems
TR Controller
TR Module
RIS
AT
De
ck
COMMUNICATION PROTOCOL - ONBOARD
1. Data Transformation during Holographic Back-Projection
2. Axis transformation during NF – FF transformation
3. Generation of Far-field antenna patterns
NEAR-FIELD CHARACTERIZATION
Measured Illumination Profile and Antenna Pattern Before
Equalisation
Measured Illumination Profile and Antenna Pattern After
Equalisation
Performance Improvement Of Antenna Pattern Of DVM Tile Of RISAT After Introducing The Concept Of Equalisation
Amplitude PhaseAmplitude Phase
LHS beams from 24° to -13°
Total 128 antenna beams were characterized for Tx and Rx, for V & H polarizations
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RISAT-1 SAR Payload flagged off from SAC on 29th July, 2010,
to be integrated with spacecraft at ISAC, Bangalore
PSLV-C19 lifted off RISAT-1 on 26 April 2012 at 05.47hrs IST.
Andaman Sea Pali, Rajasthan Antarctica Sea IceTunisia
SABARMATI OIL SPILL, NORWAY AHMEDABADAndaman Sea
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L-band SAR for greater depth of penetration;
S-band for MiniSAR continuity
Hybrid & Full Polarimetry with 2 – 75m resolutions
(First fully-polarimetric SAR for lunar observations)
L- and S-band SAR operation in standalone and
simultaneous modes
Programmable pulsewidth, BW to meet power &
data-rate constraints
Configuration supports Lander TTC
communication
CHANDRAYAAN-2 DUAL-FREQ SAR
NASA-ISRO SAR (NISAR) SWEEPSAR CONCEPT
World’s first space-borne SweepSAR
Repeat pass interferometry and polarimetry
Array-fed reflector (transmitting a fan beam, and receiving with multiple pencil beams)
Shared reflector for both L- and S-band SAR
Separate L- and S-band feeds
F/D = 0.75
Sweep SAR Technique
