The document summarizes the proto-flight test of the Dual-frequency Precipitation Radar (DPR) for NASA's Global Precipitation Measurement (GPM) mission. The DPR consists of Ku-band and Ka-band radars that will provide accurate 3D precipitation measurements from space. Electrical performance, vibration, and thermal tests have been conducted on each radar. While the proto-flight test was interrupted by an earthquake, it has resumed and will be completed to verify the radars can function as intended in space. The DPR will improve global precipitation observations when launched aboard the GPM core observatory.

1. PROTO-FLIGHT TEST OF
THE DUAL-FREQUENCY PRECIPITATION
RADAR FOR THE GLOBAL
PRECIPITATION MEASUREMENT
Kinji FURUKAWA 1), Masahiro KOJIMA 1), Takeshi MIURA 1),
Yasutoshi HYAKUSOKU 1),
Toshio IGUCHI 2), Hiroshi HANADO 2), Katsuhiro NAKAGAWA 2),
and Minoru OKUMURA 3)
1) GPM/DPR Project Team, Japan Aerospace Exploration Agency
2) Applied Electromagnetic Research Institute, National Institute
of Information
and Communications Technology
3) NEC TOSHIBA Space systems, Ltd.
IGARSS2011

2. Contents
Overview of Global Precipitation
Measurement
Overview of Dual-frequency
Precipitation Radar
Development status of DPR
Schedule
Conclusion
IGARSS2011 P2

3. Overview of Global Precipitation Measurement
IGARSS2011 P3

4. Objective and Mission Requirements of GPM
Main objective
To establish accurate and frequent global precipitation
observing system from the space
Basic Mission Requirements of GPM
Global observation of precipitation
Accurate precipitation measurement
Frequent precipitation measurement
IGARSS2011 P4

5. Concept of GPM
GPM = follow-on mission of the Tropical Rainfall Measuring Mission (TRMM)
Core Observatory
• Dual-frequency Precipitation Constellation Satellites
Radar (DPR) • Microwave Radio-meters
• Microwave Imager (GMI) installed on each satellite
Frequent precipitation
Highly sensitive
precipitation measurement measurement
Calibration for constellation Expected Partners:
radiometers NASA, NOAA, CNES-ISRO,
China, others
2 satellites
JAXA and NICT: DPR and H2A Launcher
NASA : Spacecraft bus and GMI
3-hourly global
8 satellites
rainfall map
Blue: Inclination ~65º (GPM core)
Green: Inclination ~35º (TRMM)
IGARSS2011 P5

6. Overview of GPM Core Observatory
GPM Core Observatory
Dual-frequency precipitation radar GMI
(DPR) consists of Flight direction
DPR 407 km altitude,
Ku-band (13.6GHz) radar : KuPR 65 deg inclination
and Non-sun-synchronous circular orbit
Ka-band (35.55GHz) radar : KaPR
Range resolution
= 250m and 500m
KaPR GMI
KuPR Swath: 125 km
Swath: 245 km Swath: 800km
5km
IGARSS2011 P6

7. Overview of Dual-frequency Precipitation Radar
IGARSS2011 P7

8. Objectives of DPR
Three-dimensional observation of precipitation
High sensitivity measurement of light rainfall and
heavy snowfall in high latitude
Accurate estimation of rainfall rate by combining
the Ku- and Ka-band radar data.
Improvement of MWR’s precipitation estimation
accuracy using the precipitation parameters (DSD,
melting level, rain type, storm height, etc.)
estimated by using DPR data.
IGARSS2011 P8

9. Main Characteristics
KuPR KaPR
Frequency 13.597 , 13.603 GHz 35.547 , 35.553 GHz
Range Resolution 250 m 250 m / 500 m
Horizontal Resolution 5.2 km (at nadir) 5.2 km (at nadir)
Swath Width 245 km 125 km
Minimum Detectable Rainfall Rate 0.5mm/h 0.2mm/h
Beam-matching Accuracy < 1000 m
Observation altitude Up to 19 km Up to 19 km
- 5 dB below system noise
- 5 dB below system noise level
Dynamic Range level
+ 5 dB over surface echo level
+ 5 dB over surface echo level
Measurement Accuracy within ± 1 dB within ± 1dB
Data Rate < 108.5kbps < 81.5kbps
Mass < 472 kg < 336kg
Power Consumption < 446 W orbit average < 344 W orbit average
Size 2.5 × 2.4 × 0.6 m 1.4 × 1.2 × 0.8 m
IGARSS2011 P9

10. Outlook of KuPR and KaPR
KuPR KaPR
2.4m 2.5m
1 .4 m 1.2m
0.6m 0.8m
約400kg 約300 kg
IGARSS2011 P10

11. KuPR system block diagram
x8
128 ANT
x16
IGARSS2011 P11

12. KaPR system block diagram
IGARSS2011 P12

13. Precipitation Measurement by DPR
Detectable range of KaPR (35.55 GHz)
Matched beam of
KuPR and KaPR
Detectable range of KuPR (13.6GHz)
Height
ICE Sensitive observation by the KaPR
SNOW
Snowfall
Discrimination of snow and
measurements in
rain using differential
the frigid zones MELTING KuPR attenuation method
LAYAR
KaPR
RAIN
Accurate rainfall estimation using
differential attenuation method
(DSD parameter estimation)
Accurate rainfall measurements in the
tropics and the temperate zones Radar reflectivity
IGARSS2011 P13

14. Scanning Method
KuPR footprint : Dz=250m
KaPR footprint (Matched with KuPR) : Dz=250m
KaPR footprint (Interlaced) : Dz=500m
49
26
3725 49
13 1 25
1
KaPR: 125km (25+24beams)
KuPR: 245km (49beams)
The synchronized In the interlacing scan area ( ), the
matched beam ( ) is KaPR can measure snow and light
necessary for the dual- rain in a high-sensitivity mode with a
frequency algorithm. double pulse width.
IGARSS2011 P14

15. Beam Matching
Both radars should have the same foot print locations (requires good
alignment and synchronization between KuPR & KaPR)
For post-launch checkout;
Active radar calibrator (ARC) experiment will be done
from ground to estimate the beam mismatch.
To match the beams in;
Cross-track direction : control the phase shifters
ARC
Scan direction
Along-track direction : set delay of pulse transmitting timing for one radar system.
IGARSS2011 P15

16. Variable Pulse Repetition Frequency
VPRF is to change the transmitting and receiving pulse interval according
to the distance to a target.
Beam swings Satellite altitude
TRMM PR Fixed Fixed
DPR (KuPR, KaPR) Variable Variable
Purpose
Efficient sampling for higher sensitivity
To deal with more altitude variation, compared with TRMM
Method
Use different timing for transmitting (Tx) pulses and receiving (Rx)
pulses.
Tx Tx Tx
Rx Time
Earth Time
orbit
target (rain)
Range
Range
IGARSS2011 P16

17. Development status of DPR
IGARSS2011 P17

18. Proto-flight Test Flow of DPR
KuPR
Mass
EPT Acoustic Vibration TBT/TVT EMC EPT
Property
Nov. 2010
EPT: Electric Performance Test KuPR/KaPR
TBT: Thermal Balance Test Co-operation
TVT: Thermal Vacuum Test
KaPR
Mass
EPT Acoustic Vibration EMC TBT/TVT EPT
Property
Dec. 2010
March 11, 2011
Japan Earthquake Occurred.
IGARSS2011 P18

19. Test Configurations
KuPR
Electrical Performance Test Vibration test TBT/TVT
KaPR
Acoustic Test
Electrical Performance Test (Covers are attached in this picture.
They are removed during test)
IGARSS2011
ISTS2011 P19

20. Example of PFT data (1/2)
KuPR Initial Electrical Performance Test
TX Antenna Pattern - Nadir
IGARSS2011 P20

21. Example of PFT data (2/2)
External Calibration Scan Pattern
Max hold measurement,
including 17 beams for
external calibration
IGARSS2011 P21

22. Recovery Activities on DPR
Inspection
KuPR is contaminated by the particles of the wall
material (plasterboard) .
Cleaning
Vacuum cleaner, Low adhesive tape, wiping
Health Check
Power consumption, Receiving characteristic,
Transmitting characteristic, SSPA LNA current
Hold the PFT re-start review on May 19.
Re-start PFT.
IGARSS2011 P22

23. Current Status
KuPR/KaPR co-operation test was completed.
This test is intend to verify the following items.
Co-operation by using one SCDP
No interference between KuPR and KaPR
Confirmation of the commanding based on the operation
scenario.
Relative location between KuPR and
KaPR during co-operation test simulates
actual location on GPM core observatory.
Flight harnesses connecting KuPR and
KaPR are used.
KaPR TBT/TVT is on going
IGARSS2011 P23

24. Schedule
KuPR
Mass
EPT Acoustic Vibration TBT/TVT EMC EPT
Property
Nov. 2010
EPT: Electric Performance Test KuPR/KaPR
TBT: Thermal Balance Test Co-operation
TVT: Thermal Vacuum Test
KaPR
Mass
EPT Acoustic Vibration EMC TBT/TVT EPT
Property
Dec. 2010 Change the test order
March 11, 2011
Japan Earthquake Occurred.
KuPR
EMC EPT
KuPR/KaPR
Re-start Co-operation
May 20, 2011
EMC TBT/TVT EPT
KaPR NOW
IGARSS2011 P24

25. Conclusion
The DPR that will be installed on the GPM core observatory
is being developed by JAXA and NICT.
The main objective of the DPR is to measure the three-
dimensional structure of precipitation including light rainfall
and snowfall.
Though Proto-flight test was interrupted due to Japan
Earthquake on March 11, 2011, there is no significant impact
to DPR from technical and schedule point of view.
Proto-flight test has been restarted, and will be completed in
the near future. After completion of all PFT, the DPR
instrument will be verified as a space borne radar.
IGARSS2011 P25