development of spaceborne dual- frequency precipitation ...development of spaceborne dual-frequency...
TRANSCRIPT
Development of Spaceborne Dual-frequency Precipitation Radar
and Its Role for the Global Precipitation Measurement
Shinsuke Satoh (1), Riko Oki (1), Nobuhiro Takahashi (2), and Toshio Iguchi (2)
(1) National Space Development Agency of Japan (NASDA)(2) Communications Research Laboratory (CRL), Japan
11 April 2003 in Nice, France
Core Satellite• Dual-frequency Precipitation
Radar (DPR)• Microwave Radiometer
High-sensitivity precipitation measurementCalibration for constellation radiometers
Constellation Satellites
• Microwave Radio-meters installed on each country’s satelliteFrequent precipitation measurement
NASDA (Japan) : DRP, H-IIA Launcher
NASA (US) : Spacecraft, MWR
Expected Partners: NASA, NOAA (US), ESA (EU), NASDA, China, Korea, others
3-hourly global
rainfall map
The Concept of Global Precipitation Measurement (GPM)
2 satellites
8 satellites
Blue: Inclination ~65º (GPM core)Green: Inclination ~35º (TRMM)
Range resolution= 250m
PR-U (13.6 GHz) swath width=245 km
PR-A (35.5 GHz)swath width=100 km
DPR GMI
Microwave radiometer swath width =800km
Flight direction
5km
Dual-frequency precipitation radar (DPR) consists of Ku-band (14GHz) radar (PR-U) and Ka-band (35GHz) radar (PR-A)
Concept of precipitation measurement
Design of the GPM Core Satellite and the DPR
Harness connectors
PR-A
Wave-guide connectors
PR-A Additional radiation panel (?)
Ant cant angle (0 to +4 deg)
S/C nadir
PR-U
(by NASA/GSFC)
+x
PR-UPR-A
GMI
Basic design of the PR-U and PR-A is the almost same as TRMM PR.
Wave-guide connectors
Concept of the DPR antenna scanPR-U footprint : ∆z = 250 mPR-A footprint (Matched with PR-U) : ∆z = 250 mPR-A footprint (Interlaced) : ∆z = 500 m
PR-U: 245 km (49 beams)
PR-A: 100 km (20 beams)
In the interlacing scan area ( ), the PR-A can measure snow and light rain in a high-sensitivity mode with a double pulse width.
The synchronized matched beam ( ) is necessary for the dual-frequency algorithm.
Precipitation measurement with DPR
Hei
ght
Radar reflectivity
PR-APR-U
Discrimination of snow and rain using differential attenuation
Sensitive observation by the PR-A
Accurate rainfall estimation using differential attenuation(DSD parameter estimation)
Detectable range of PR-U (14 GHz)( cannot measure light rain or snowfall)
Detectable range of PR-A (35 GHz)( cannot measure heavy rainfall )Matched beam of
PR-A and PR-U
Snowfall measurement in the frigid zones
Accurate rainfall measurement in the tropics and the temperate zones
ICE
SNOW
RAIN
MELTING LAYAR
Dynamic Database provided by DPR for MWR precipitation estimate algorithmsAnother role of DPR is to provide “Dynamic global Database”(every one day or a few days) for MWR algorithms. The precipitation parameters vary in seasons, times, and areas.
Database of precipitation parameter- DSD parameter (D0)- Melting level (0°C height)- Rainfall type (conv, strat, shallow,..)- Rainfall uniformity information- Storm height and mean profile
More accurate precipitation estimated by MWRs on the GPM constellation satellites
MWR algorithms
Rain-bands in a Typhoon
Stationary front and cloud clusters
Snow clouds in the winter monsoon
Tropical cloud clusters
DPR Specifications (Tentative)
Active Phased Array 20
100km1.67/3.34 micro sec. (x2)
250 m/500m0.7 Deg.
5 kmVPRF (4500 Hz±250 Hz)
144W [current] 12dBZ (0.2 mm/hr) [target]
95 kbps290kg
306 W [max 331 W]1.3 ×1.0 ×0.7m
Active Phased Array 49
245 km1.67 micro sec. (x2)
250 m0.7 Deg.
5 kmVPRF (4000 Hz±250 Hz)
1000W17dBZ (0.4 mm/hr)
95 kbps370 kg
334 W [max 352 W]2.4×2.4×0.6 m
Antenna TypeBeam NumberSwath WidthPulse WidthRange ResolutionBeam WidthHorizontal ResolutionPRFPeak PowerSensitivityData RateWeightPower ConsumptionSize
35.5GHz radar (PR-A)13.6GHz radar (PR-U)Item
Variable PRF (VPRF) Technique
1 2 3 4 9 10 11
Transmit Receive
Pulse num
1/PRF
Distance between S/C and the surface target
The observation range of spaceborneradar is only 20 km, while the distance between satellite and the surface is 392 ~ 440 km. For that reason, the receiving range window is located on after n-thtransmitting pulse. The Pulse Repetition Frequency (PRF) of the DPR make vary to increase the sampling number.
1.92.2
4.05.0
96 (n=11)112 (n=13)
2015
12
1.92.1
4.04.5
96 (n=11)104 (n=12)
2019
12
1.31.3
2.72.6
72 (n=8)72 (n=8)
2017
12
2020
H-obs(km)
60 (n=7)60 (n=7)
Sampling number(freq agility)
2.32.3
Center of PRF (Hz)
0.90.9
Gain(dB)
12
Mode
Examples of VPRF
1 2 3 4 9 10 11
Transmit Receive
Pulse num
1/PRF’
The distance is changed by Antenna scan angle (±9 km)
Proper PRF (±250 Hz) is determined on board
Satellite altitude (407 km±15 km)is measured by GPS data
Distance between S/C and a surface target* Mode-1: 245 km scan, Mode-2: 100 km scan
Current status of DPR development
TRMM/PR type
TRMM/PR type
TRMM/PR type with GPS
T/R module(128 elements)
TRMM/PR type but lighter weight(128 elements)
Concept
Alignment between PR-U and PR-A
PR-A: radiation panel
- variable PRF - synchronized pulses- data compression
PR-U: MMIC (PHS, SW, MPA, LIM)PR-A: High power SSPA (35 GHz)
Half thick wave-guide slot antenna
Need to develop/study
Depending on the RF unit chip development and DPR operation mode.
Thermal design
Note
For better sensitivity and reduction of downlink data.Common components
Signal processing unit design
According to “matched beam”requirements.
Mechanical design
PR-U: BBM of T/R module (2003-04)PR-A: BBM of T/R module(2002-03 in CRL)
RF unit design
PR-U: completed (2000)PR-A: completed (in CRL)
Antenna design
# The main aim is to develop light weight components (wave-guide antenna, T/R module)
DPR Development Schedule
Summary1. The Dual-frequency Precipitation Radar
(DPR) installed on the GPM core satellite, is currently being developed by NASDA and CRL.
2. The DPR will provide accurate estimates of rain rate,and light rain and snow data by high-sensitivity measurement.
3. The DPR will provide the dynamic global database of precipitation parameters (DSD, melting level, rain type, storm height, and so on) for the improvement of MWR’s precipitation estimate algorithms.
Backup Slides
Beam Matching
How well should the two beams match?- Answer depends on non-uniformity of rain- Matched Beam requirement on the IFOV: 0.1 ∼ 0.2 km- Pointing allocation in S/C < 0.1 deg (∼ 0.7 km)
Both radar should have the same foot print location (requires good alignment and synchronization)
Four kinds of mismatch:- Dimensions and shape- Cross-track direction- Along-track direction- Scan directionConcept for realizing matched beam.
- Cross-track direction : adjust the beam direction changing phase shifter control.
- Along-track direction : set delay for one radar system.
Post-launch checkout.- Active radar calibrator (ARC) experiment
from ground to know the alignment offset.
Requirements for the Cant angle
The radar beam direction is tilted to about 4 degrees off-nadir into the slot antenna direction in order to improve the VSWR.
Beam direction(= S/C nadir)<TRMM/PR case>
• The cant angle range will be 0 to 4 degrees (4 degrees in TRMM/PR case)• It depends on an examination of surface clutter reduction
Beam direction(≠ S/C nadir)→slight conical scan
or
Beam direction for the surface clutter reduction
Nadir direction from S/C
Main beam
Strong sidelobe (> -30 dB)
Weak sidelobe (-30 to -40 dB)
Main beam
Amount of scattering from a surface ring may contaminate the rain echoes detected by the main beam.
+X
+Y
2 dimensional antenna pattern
In case of the beam tilted about 4 degrees from the S/C nadir, the surface clutter may be reduced.
Improvement in the Accuracy of Rain Observation by TRMM
(TMI & PR)
Observation by Constellation Satellites with Microwave Radiometer
Observation area with MWRs in 3 hours(1, 2, 4 and 8 satellites from top to bottom)
Coverages byTRMM PR and
GPM DPR in a day
1
2
4
8
International Satellite Constellation
G
MP
8
7
6
5
4
3
2
1
90 98 1412100296 0088 92 94 04 06 08 16 18YearObs. Interval(Hour) ~16 ~11 ~7 ~5 ~4 ~3
DMSPSSM/I
DMSPSSMIS
NPOESSCMIS
TRMMPR,TMI
AQUAAMSR-E
ADEOS-IIAMSR AMSR Follow-on
GPM coreDPR,GMI
NPOESS-1,2,3CMIS
Num
ber o
f Sat
ellit
es
FY-3 (China)
Megha-Tropique
EGPS
NASA/Korea
Scientific and Social Significance of GPM
3-hourly global rain map by GPM– Climate change assessment– Improvement in weather forecasts– Flood forecasting (Flood Alert System)– Water resource management– Agricultural production forecasting
Precision brought by DPR– High sensitivity to detect light rain
and snow– Accurate estimation of rainfall rate– Separation of snow from rain
Concept of GPM Data Network
TDRS DRTS
GCOM-B1GPM COREEGPM Megha-Tripique NPOESS
ARTEMIS
FY3
GPM Data Network GPM Data Network (MWR L1 data)(MWR L1 data)
French Ground SystemsIndian Ground Systems Chinese Ground Systems
ESA Ground Systems
NASA Ground SystemsNASDA Ground Systems
Users
Users
Science & Research Weather Disaster Monitoring Education Public & Business
Users
Configuration of GPM Ground Systems
MWR ProcessingL1 ProductsL2 ProductsL3 Products
NASDA GPM Ground SystemsNASA
L2 Products
L1 Products
GMI Processing
DPR/GMIMatching
3H Rain Map Products
3hrs Rain Map Processing
Other Organizations
DPR L0
DPR L2
DRTS(NASDA)
DPR L1,L2
GMI L1
GMI L2
MWR L1 Products
GPM core satellite
TDRS
GPM sub satellites
GPM L1Network
SDPF
TSDIS
DPR Processing
DPR Processing
L1 ProductsL2 ProductsL3 Products
Data Archive
L1 ProductsL2 ProductsL3 Products
MWR ProcessingL1 ProductsL2 ProductsL3 Products
GPM L1Network
ARTEMIS(ESA)
MWR L1 GMI L2
Notes: Red marked products show TBD.
TDRS
Science Users
Operational Users
3H Rain Map Products
4DDA products
MWR Cal../ Processing
NASA PPS(Precipitation
Processing System)
3H Rain Map
JMA
IFnet