development of circularly polarized synthetic aperture radar onboard microsatellite for earth...

7/31/2019 Development of Circularly Polarized Synthetic Aperture Radar Onboard Microsatellite for Earth Diagnosis

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I. INTRODUCTION

ynthetic Aperture Radar (SAR) is well-known as a

multi-purpose sensor that can be operated in all-weather

and day-night time. Recently, many missions of SAR sensors

are operated in linear polarization (HH, VV and its

combination) with high power, sensitive to Faraday rotation

effect etc. In this research, we proposed the Circularly

Polarized Synthetic Aperture Radar onboard microsatellite

(PSAT CP-SAR) that will be launched in 2014 to retrieve the

physical information of Earth surface for Earth diagnosis [1].

Fig. 1 shows the illustration of PSAT CP-SAR that is being

developing in Center for Environmental Remote Sensing,

Chiba University, Japan. Table I shows the specification of the

PSAT CP-SAR, and Fig. 2 shows each sensor installed on the

pre-deploying condition ofPSAT CP-SAR. Fig. 3 shows the

PSAT CP-SAR system that is composed by attitude control

system (ACS), CDS (command and data handling system), EPS

(electrical Power Subsystem), and CMS (communication

subsystem). The detail components as listed in Fig. 3, CDS

composed by on-board computer (OBC), telemetry andcommand unit (TCU) and mission data storage unit (MDU).

ACS is composed by electromagnetic torque (EMT), GPS

receiver (GPSR), sun sensor (SS) and magnetometer (MAG).

EPS is composed by battery charge regulator (BCR), power

control unit (PCU) and power distribution unit (PDU). Finally,

CMS is composed by S-band transmitter (STX), S-band

receiver (SRX) and X-band transmitter (XTX).

In this research, the CP-SAR sensor is employing the

elliptical wave propagation and scattering phenomenon by

radiating and receiving the elliptically polarized wave,

This work was supported in part by the Japan Society for the Promotion of

Science (JSPS) for Grant-in-Aid for Scientific Research - Young Scientist (A)(No. 19686025) and Grant-in-Aid for Scientific Research (No. 19-07023);

Venture Business Laboratory - Chiba University for Project 10th Research

Grant; Chiba University President Research Grants 2008; National Institute of

Information and Communication Technology (NICT) for International

Research Collaboration Research Grant 2008 and other research grants to

support this research.

Josaphat Tetuko Sri Sumantyo is with the Center for Environmental

Remote Sensing (CEReS), Chiba University, Chiba, 263-8522 Japan

(corresponding author to provide phone: +81-43-290-3840; fax:

+81-43-290-3857; e-mail: jtetukoss@ faculty.chiba-u.jp).

(a) Principle of CP-SAR

(b) Illustration of CP-SAR onboard microsatellite

Fig.1. CP-SAR onboard microsatellite

Table I. Specification of CP-SAR onboard microsatelliteLaunched date 2014

Altitude 500 ~ 700 km

Inclination angle 97.6 degrees

Frequency / wavelength 1.27 GHz (L Band) / 24 cm

Polarization TX : RHCP+LHCP

RX : RHCP+LHCP

Gain / Axial ratio > 30 dBic / < 3 dB (main beam)Off-nadir angle 29 degrees (center)

Swath width 50 km

Spatial resolution 30 m

Peak power 90 ~ 300 W (PRF 2000~2500 Hz, Duty 6% :

average 5.6 W)

Bandwidth Chirp pulse : 10 MHz

Platform size 1 m x 1 m x 1 m

Weight 100 kg

Antenna size Elevation 2.0 m x Azimuth 5.0 m

Sensors CP-SAR, GPS SAR, GPS Radio Occultation

(RO)

Development of Circularly Polarized Synthetic

Aperture Radar onboard Microsatellite for

Earth Diagnosis

Josaphat Tetuko Sri Sumantyo,Member, IEEE

Sazimuth

929978-1-4577-1005-6/11/$26.00 2011 IEEE IGARSS 2011


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Fig.2. Pre-deploying CP-SAR onboard microsatellite : (a)

range direction view, (b) azimuth direction view, (c) top view,

and (d) bird eye view

including the special polarization as circular and linear

polarizations. In this mission we employ three microwave

sensors; there are CP-SAR, GPS-SAR and GPS-RO, as shown

in Fig. 4. CP-SAR is as active sensor that could transmit and

receive the L band chirp pulses for land deformation

monitoring. GPS-SAR is an experimental passive SAR sensor.

This mission plans to investigate the possibility to receive the

GPS pulse and process it to retrieve the SAR image. GPS Radio

occultation (GPS-RO) is an experimental four unit of patch

array antenna sensor to receive the GPS signal and process it to

retrieve the conditions of electron in the ionosphere to

investigate the coupling of electron density change and land

deformation. In the future, this coupling is used to predict the

earthquake activity and build the early warning system in Asian

countries. The sensor is designed as a low cost, light, low

power or safe energy, low profile configuration to transmit and

receive left-handed circular polarization (LHCP) and

right-handed circular polarization (RHCP), where the

transmission and reception are both working in RHCP+LHCP

as shown in Fig. 1 (a). Then these circularly polarized waves

are employed to generate the axial ratio image (ARI). This

sensor is considered not depending to the platform posture, and

it is available to avoid the effect of Faraday rotation during the

propagation in Ionosphere. Therefore, the high precision and

low noise image is expected to be obtained by the CP-SAR. For

this purpose, we are also developing the CP-SAR onboardunmanned aerial vehicle (CP-SAR UAV) for ground testing of

this sensor. In this paper, we also introduce the specification

and basic system of our CP-SAR UAV development.

II. PSAT CP-SAR MISSION

The main mission of this PSAT CP-SAR is to hold (1) the

basic research on elliptically polarized scattering and its

imaging technique, and (2) its application development.

Fig. 3. Block diagram ofPSAT CP-SAR system

In the basic research, we investigate the elliptical (including

circular and linear polarizations) scattering wave from the

Earth surface, circularly polarized interferometric technique

(CP-InSAR), axial ratio image (ARI) generation etc. We hold

the analysis and experiment on circularly polarized wave

scattering on vegetation, snow, ice, soil, rock, sand, grass etc to

investigate the elliptical scattering wave.

In experiment of CP-InSAR, we will hold some experiments

to compare the InSAR technique by using circular and linear

polarizations. This technique will be implemented to extract the

tree trunk height, DEM etc by using the elliptical polarization.

The axial ratio image (ARI) will be extracted by using the

received RHCP and LHCP wave, then this image is employed

to investigate the relationship between the characteristics of

ARI and vegetation, soils, snow, ice etc. The image of tiltedangle as the response of Earth surface also will be extracted to

mapping the physical information of the surface, i.e. geological

matters, contour, tree trunk structure and its characteristics,

snow-ice classification etc.

In application development, CP-SAR sensor will be

implemented for land cover mapping, disaster monitoring,

Cryosphere monitoring, oceanographic monitoring etc.

Especially, land cover mapping will classify the forest and

non-forest area, estimation of tree trunk height, mangrove area

monitoring, Arctic and Antarctic environment monitoring etc.

In disaster monitoring, CP-SAR sensor will be employed for

experiment of CP Differential InSAR in earthquake area,

monitoring of volcano activity, forest fire and flood monitoring

etc. In snow and ice monitoring, this sensor will be employed

for monitoring of ice berg, glacier, investigation of snow and

ice characteristic etc. The monitoring of oil spill, inner wave etc

will be done for Oceanographic monitoring. Especially in the

disaster monitoring, this mission has main target as shown in

Fig. 4.

Size : W1000D1000H1000

PAF239

M

Telemetry -Data Transfer X-band antenna

GPS

GPS-RO antenna

Azimuth directionSAP surface

(a) (b)

(c) (d)

GPS-RO

CDS (Command and Data handling Subsystem) ACS (Attitude Control Subsystem)-OBC:On-Board Computer -EMT:Electro Magnetic Torquer-TCU:Telemetry and Command Unit -GPSR:GPS Receiver-MDU:Mission Data Storage Unit -SS:Sun Sensor

-MAG: Magnetometer

EPS (Electrical Power Subsystem) CMS (Communication Subsystem)-BCR : Battery Charge Regulator -STX: S-band Transmitter-PCU: Power Control Unit -SRX:S-band Receiver-PDU: Power Distribution Unit -XTX:X-band Transmitter

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Fig. 4. PSAT CP-SAR mission

Fig. 5. Block diagram of Circularly Polarized Synthetic

Aperture Radar (CP-SAR) System

III. CIRCULARLY POLARIZED SYNTHETICAPERTURE

RADAR(CP-SAR) SYSTEMFig. 5 shows the circularly polarized synthetic aperture radar

(CP-SAR) system block. Basically, this system is composed by

transmitter, receiver, onboard signal processing, data

transmitter and ground segment. The transmitter is composed

by chirp generator, bandpass filter (BPF), local oscillator (LO),

power amplifier (PA), switch for RHCP and LHCP, and two

panel of CP microstrip array antenna (LHCP and RHCP panels).

Then the generated chirp pulses are transmitted by using these

antennas.

The receiver is composed by two panels of CP microstrip

array antenna (LHCP and RHCP), low noise amplifier (LNA),

switch to reduce the coupling between antenna of transmitter

and receiver, bandpass filter (BPF), I/Q demodulator to

generate the in-phase and quadrature data (phase),

analog/digital (A/D) converter, temporary memory for data

processing, onboard signal processing (OSP) unit, data

transmitter system. In the OSP unit, the SAR signal processing

as range compression, corner turn, azimuth compression etc is

processed to produce the SAR image. Then this image will be

sent to the ground segment by using X band data transmitter.

This data is received by ground segment for further process.

Fig. 6. Josaphat Experimental CP-SAR onboard Unmanned

Aerial Vehicle (JX-1)

Fig. 7. Size and sensors: (a) front view, (b) side view, (c)

bottom view, and (d) Concept of SAR sensors. Size in

millimeter.

IV. CP-SAR ONBOARD UNMANNED AERIAL VEHICLE

(CP-SAR UAV)

In this research, the CP-SAR onboard unmanned aerial

vehicle (CP-SAR UAV) as shown in Fig. 6 is developed for

CP-SAR ground testing before it is installed on the

microsatellite. The platform called Josaphat Laboratory

Experimental UAV (JX-1) has 25 kg of payload availability for

various microwave sensors (CP-SAR, GPS SAR, and GPS RO)

and optic sensors (visible cameras). The operation altitude is

1,000 m to 4,000 m. The three linear polarization of P-, L- and

X-bands SAR sensors are also installed on the tail wing of

UAV as shown in Fig. 7 (c).

The concept of CP-SAR UAV is shown in Fig. 7 (d), then the

size and sensor position are shown in Fig. 7 (a)-(c). The

specification of CP-SAR sensor for UAV : frequency 1.27

GHz, ground resolution 1m, pulse length 3.9 to 23.87 ms, pulse

bandwidth 61.14 to 244.69 MHz, off nadir angle 40o to 60o,

swath width 1 km, antenna size 1.5 m x 0.4 m for LHCP and

RHCP, azimuth beamwidth 6.77o, range beamwidth 29.78o,

antenna radiation efficiency >80%, PRF 1000 Hz, and peak

power 8.65 W (1 km) to 94.38 W (4 km). The CP-SAR has

receiver antenna composed by LHCP and RHCP antenna. The

GPS-Sat

GPS-SAR

GPS-RO

CP-SAR

Earthquake

Land deformation

Electron Density Change

GPS-Sat

GPS-Sat

CP-SAR

LP-SAR

(a)

(c)

(b)

(d)

CP-SAR

P,L,X bands

LP-SAR

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data retrieved by LHCP and RHCP antenna is employed to

generate the axial ratio image. This image is used to retrieve the

physical information of Earth surface , i.e. soil mois ture ,

biomass, Cryosphere, agr iculture, ocean dynamics, land

deformation, disaster monitoring, digital elevation model etc.

In this UAV, we also install the linearly or horizontally

polarized SAR (LP-SAR) in frequency P-, L-, and X-Bands.

The Linearly polarized SAR data will be compared with

CP-SAR data , and employ for some appl icat ions .

V. SUMMARY

In this paper, we proposed the circularly polarized Synthetic

aperture radar onboard microsatellite (PSAT CP-SAR). The

CP-SAR is designed as the small, light in weight and low

power consumption system. The CP-SAR sensor is developed

to radiate and receives circularly polarized wave. This CP-SAR

sensor will be applicable for land cover, disaster monitoring,

snow cover, and oceanography mapping, etc. We also proposed

the CP-SAR UAV for ground experiment at Shikabe airport(Japan) and Sulaiman airport (Indonesia) in 2011-1012.

REFERENCES

[1] J.T. Sri Sumantyo et al.: "Development of Circularly

Polarized Synthetic Aperture Radar onboard

Microsatellite", PIERS Proc., 2A3, Beijing, 2009.

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development of circularly polarized synthetic aperture radar onboard microsatellite for earth...

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