Compact X band synthetic aperture radar on

100kg small satellite

Hirobumi Saito

Japan Aerospace Exploration Agency (JAXA), Institute of Space and Astronautical Science (ISAS),

IAA Small Satellite Berlin

Conventional SAR Satellite and Proposed 100kg SAR Satellite

TecSAR 300kg Resolution 1m

NovaSAR-S 400kg Resolution 6m

TerraSAR-X 1230kg Resolution 1m

Proposed MicroXSAR 100kｇ Resolution10-3 m Stowed 0.73m $10-20M.

3m

3m

5m

0.7m

RadarSat-2 2200kg Resolution 3m

15m

What Happens if $20M SAR Sat Available ?

・ Now - Only developed country governments can own $ 100s M SAR Satellites for Security & Gov. Use. ・ If $20M SAR Satellite available - Private companies & developing countries own SAR Sat for disaster monitering & business. - Frequent SAR observation with Constellation. “Anytime, anywhere Earth Imaging”

Scaling of SAR Observation

• Radar Equation

• Synthetic Integration Time • SNR per One Pixcell • （NESZ, Resolution） vs （RF Power, Antenna Size, wavelength）

ss

TXRX LR

AGR

PP 22 44 πησ

π=

.2 azst

D vRTδ

λ=

.8 3

22

stso

raveTXimagevNFLkTR

APSNRλπ

ση δ°= −

223 )()8(

ηλπσ

APNFLvkTR

aveTX

sstorNE

−

=° 　　δ

NESZ, Resolution, Satellite Size NESZ x Resolution ∝ λ ／（RF Power ｘ Ant

Area２） σNE

0δr ∝ λ／ PTX A2 SAR Performance Satellite Size

⇒Short Wavelength SAR is Suitable for Small Satellite .

100 300 1000 (kg)

10m

3m

1m

S(3GHz) X(9GHz)

C(5GHz)

L(1GHz)

ASNARO2 TecSAR

SAR-Lupe TerraSARX

Nova SAR

KOMSAT5

ALOS2

Cosmo-SkyMed

RADARSAT

JERS-1

ALOS

Satellite Mass

Reso

lutio

n at

σ0N

E =

-20d

B

-15dB

σ0NE= -20dB

MicroXSAR

Short Wavelength SAR is Suitable for Small Satellite .

σNE0δr ∝ λ／ PTX A2

SAR Performance Satellite Size

SAR System Specification for 100kg Satellite (Ground Resolution = 3 or 10m)

7

SAR System Block & Technology Strategy

Flexible Solar Panel

High – Speed X – band Transminitter

Deployable Antenna Feeder

RF Receiver

Data Processing & Storage

Li-Ion Bat

RF Transmitter

High Efficiency GaN Amp

Noncontact Wave Feed

Single Layer Slot Array

High – Rate Discharge Battery.

Thermal Management for High Peak Heat

500 Mbps Down Link for Small Satellite (Hodoyosh in 2014)

Flash Memory & Commercial FPGA

Flexible Solar Cell on backside of Antenna

Satellite Body

SAR Antenna.

Power & Heat

RF Amp.

Digital

Data Down Link .

Rectangular, Slot Array Antenna with Waveguide Feeder

Antenna size 4.9m x0.7m

Feeding Waveguide to three Panels

Feeder Waveguide

Satellite Body Deployed 3 Panels

Tournament Circuit

11

Honeycomb Single Layer Slot Array Antenna

Antenna Pattern

Ant Efficiency 55% Gain36.6dBic

One Polarization Antennal Dual Polarization Antenna being Tested Feeded from Both Sides Symmetric Pattern

Antenna & Feeder Composite Panel

-90 -60 -30 0 30 60 90-50

-40

-30

-20

-10

0XZ Plane

θ [deg]

Nor

mal

ized

Am

plitu

de [d

B] RHCP

LHCP 19.01 dB

9.6 9.65 9.731

32

33

34

35

36

37

0

1

2

3

Frequency (GHz)

Dire

ctiv

ity, G

ain

(dBi

c)

30%

40%

50%

60%

70%

80%

Directivity without back panel Directivity with back panel Gain (5.82 m) Gain (16.85 m) Axial ratio with (16.85 m)

Axial Ratio (dB)

RHCP LHCP

Noncontact RF Feed with Choke Flange at Hinge Position

・Waveguide Feeds RF to Deployable Antenna Panel ・Choke & Cover Flange at Hinge Position ・ Low RF Loss (<0.1dB) with Gap 1-2mm

λg/4

λg/4

short

open

Choke Flange Cover Flange Gap between Flanges (mm)

RF L

oss (

dB)

13

Deployed Antenna Needs Surface Accuracy of λ/20

Thermal Deformation Analysis

Deployment Mechanism (patented) smooth on antenna surface Angle Accuracy

Deployment Test with Air Bearings

Flexible Solar Cell on Back Side Thermally Isolated with Antenna by MLI

Stow

Deploy

14

GaN HEMT Pulse Amp 100/200W (Commercial)

600-1000W Amplifier 100/200W x 6 RF Combiner

600-1000W Power Combiner Input :Microstrip Line Combiner :Circular WG Resonator Output: Waveguide

600W Output Combiner

Φ27mm x 3mm

100/200W Input ｘ ６

Measuement Heat Management

60W 5min

Module

15

SAR Data

Pluse Sharping Filter

Pre- Distortion D/A RF Amplifier

Ground Demodulator

SCCC Turbo Decoder S/X Dual Band 3.8m Parabola

SAR Data

Com Parameter Bit Rate 3480Mbps Orbit 600km RF Trans, Power 2W RF Power 22W RF Bandwidth 150MHz＠8GHz Modulation 1 6QAM/64APSK Onboard Antenna MGA（15dBi) Ground Antenna dia 3.8m

500Mbps (64APSK) Down Link for 50kg Satellite Demonstrated in Hodoyoshi #4

Small Ant MGA/ Isoflix

Satellite

Ground Antenna

X band Transmitter

Hodoyoshi #4 in 2014

1.3kg, 22WDC, 2WRF, GaN Amplifier 2.5 oversampling parallel processing

Soon 64APSK 500Mbps

Demonstrated 16QAM 348Mbps

Conceptual Design of 100kg SAR Satellite Based on SDS-4 , 100kg Satellite at JAXA

Rocket H2A ALOS3 piggy - back

Orbit 618km, Sun – Synchronous, inclination 98°, 10:30@d.n.

Mass 100kg

Size 70x70x70cm3(with rocket), 4.6m x 0.7m (antenna in operation)

SAR Observation Strip-map Mode, Resolution 3～10m @NESZ=-15～-20dB, 5-10 min observation in a orbit, 460W DC for observation

SAR Antenna 4.6m x 0.7m, deployable system of single layer slot array panel x 6 non-contact waveguide feeding

Power 400W generation by flexible solar panel on antenna backside , Li-Ion 2.7Ah(Bus), 5.6Ah(SAR 3C fast discharge )

Attitude Control 0.06deg accuracy for SAR, coarse tracking for down link station, coarse sun-pointing for other period

Communication S band for TT&C, X-band 500Mbps

Data Storage 100 GB, Read 400Mbps

100kg SAR Satellite Block Diagram & Layout

図e-3-2 衛星の搭載機器配置の一例

Conclusions 1. We start development of small SAR compatible with

100kg satellite. 2. Applications are constellation (>10 Sats) with short

revisit time for natural disaster & ocean monitoring for Asian countries, and real time earth image from space.

3. Technologies: deployable single layer slot array antenna, non-contact waveguide feeding, GaN pulse amplifier Power & heat management

Outlook of SAR Satellite

図８ 検討中の多偏波合成開口レーダを搭載した100kg級衛星の概観図。ロケット収納時（左上）と軌道上で合成開口レーダアンテナを展開した状態（右下）。

Slot Array Antenna

Waveguide Feed & Flexible Solar Panel

Specifications of 100 kg – Class SAR Satellite

Vehcle H2A Piggy-Back

OrbitAltitude 618km, Sun-Synchronous,Inclination 98°,　10:30＠Desending Node

Mass 100kg（120kg with Separation Gear）Size 0.7mx0.7mx0.7m Stowed in Rocket

4.6mx0.7m Antenna DeployedSAR Observation X-band, Compact Polarimetric (TX: R, RX: R and L)

Strip-Map / Spot-Light ModeResolution 3～10m @ NESZ=-15～‐20ｄB5 min per revolution, 460W Consumption

SAR Antenna4.6m x 0.7m, Single Layer Slot-Array　Antenna3 panels x 2 WingsNon-Contact Waveguide Feed

PowerThin Film Solar Panel at Antenna Rear210 W generationLi-Ion 2.7Ah (Bus),　Olivine-type 5.6Ah（SAR）

AttitudeTarget Pointing：Pitch 0.06°,Maneuver １°/sData Down Link & Sun Pointing：5deg

CommunicationsSatellite Operation S bandData Down Link X band 320Mbps

Data Storage100Gbytes, Write Speed :150Mbps x 4channelRead Speed :100Mbps x 4 channel