APPENDIX 4OVERVIEW OF
THE ADVANCED LAND OBSERVING SATELLITE-2(ALOS-2) MISSION

4-1

1. Introduction
The Advanced Land Observing Satellite-2 (ALOS-2) is succeeding to the radar mission of ALOS which had
contributed to cartography, regional observation, disaster monitoring, and resources surveys.
ALOS-2 is equipped with a SAR antenna just under its body and with two solar array paddles at both sides, as
shown in Figure 1. The observation data is transmitted directly to a ground station via X-band or through intersatellite communication via Ka-band. The transmission speed is 800 Mbps maximum for X-band and 278 Mbps forKa-band, respectively. Table 1 shows system specifications of ALOS-2. The local sun time of its orbit is at noon inorder to complement other SAR satellites which are in dawn-dusk orbits.

Fig. 1 ALOS-2 in-orbit configuration.
Observation mode
Orbit

LaunchDesign lifetime
Satellite mass
Downlink

Table 1 ALOS-2 specification.
Stripmap: 3 to 10 m resolution, 50 to 70 km swath
ScanSAR: 100 m/60 m resolution, 350 km/490 km swath
Spotlight: 1×3m resolution, 25 km swathSun-synchronous sub-recurrent orbit
Altitude: 628 km
Local sun time: 12:00 +/- 15 min
Revisit: 14 days
Orbit control: < +/-500 m
May 24, 2014 (JST), H-IIA launch vehicle
5 years (target: 7 years)
Approx. 2 tons
X-band: 800 Mbps (16QAM), 400/200 Mbps (QPSK)
Ka-band: 278 Mbps (QPSK)

2. PALSAR-2 Characteristic
ALOS-2 carries the state-of-the-art L-band Synthetic Aperture Radar (SAR) called PALSAR-2. PALSAR-2 hasa Spotlight mode (1×3m resolution in Az×Rg), a Stripmap mode (3 to 10 m resolution) and a ScanSAR mode. TheSpotlight mode and a high-resolution mode will allow providing users with more detailed data than ALOS/PALSAR.
The ScanSAR mode will allow us to acquire a 350 to 490 km width (depends on number of scans) of SAR images
at the expense of spatial resolution. The observation frequency of ALOS-2 will also be improved by greatly
expanding the observable areas (2,320km). Right-and-left looking function by satellite maneuvering and electricbeam steering using active phased array antenna establish the incidence angles from 8 to 70 degrees on both side ofthe satellite.

4-2Fig. 2 PALSAR-2 observation modes.
Table 2 PALSAR-2 specification.
Stripmap
Ultra-Fine
High-Sensitive
Fine

Observation mode

Spotlight

Incidence angle
Band width
Ground resolution

8 to 70 degrees
84 MHz84 MHz3mx1m
3m(Rg x Az)
25 km
50 km
SingleSingle/Dual

Swath
Polarization

42 MHz6m

50 km
Single/Dual/Full/Compact
NESZ-24 dB-24 dB-28 dB
S/ARg
25 dB
25 dB
23 dB
Az
20 dB
25 dB
20 dB
The parameters specified at 37degrees incidence angle above the equator.
* 28 MHz bandwidth in ScanSAR mode is used for only 350 km swath

ScanSAR

28 MHz
10 m

14 MHz/28 MHz*
100 m (60 m)

70 km
Single/Dual/
Full/Compact-26 dB
25 dB
23 dB

350 km (490 km)
Single/Dual-26 dB/-23 dB
25 dB (20 dB)
20 dB

PALSAR-2 is composed of two subsystems; Antenna subsystem (ANT) and Electric Unit (ELU). ANT is anactive phased array antenna, which steers a beam both in elevation and azimuth direction (plus-minus 30 degrees inelevation and plus-minus 3.5 degrees in azimuth). Figure 3 shows the antenna configuration of PALSAR-2. The sizeof ANT is 10 m in azimuth and 3 m in elevation, and is composed of five electrical panels, which have 180 TransmitReceive-Modules (TRMs) in total. The Spotlight mode and Ultra-Fine mode use the three of five panels to satisfy
resolution requirement and the other modes use all panels. The transmitted power is 3950 W and 6120 W
respectively.
Figure 4 shows the system diagram of PALSAR-2. Key components of the Electric Unit (ELU) are Exciter (EX),Transmitter (TX), Receiver (RX), Digital Processor (DP), and System controller (SC). As for RF signal, EXgenerates pulses, selects two chirp signals (up or down and phase modulation) with a selected center frequency
either 1257.5, 1236.5 or 1278.5 MHz in order to avoid interference to Radio Navigation Satellite Services which
use L-band, and stretches the signal to a selected bandwidth either 84 MHz, 42 MHz, 28 MHz or 14 MHz. Received
radar echo signals are compressed by BAQ or DS-BAQ algorithm. Compression mode is selected from 4 bit, 2 bit,or no compression.

4-3

Fig. 3 PALSAR-2 antenna configuration.
command and telemetry
from/to satellite

EXDPfor cal SAR ANTSCI/FUnit*TXRXTRM!
!180EA!
!
!
TRM

mission data
to satllite*: Dual receive antenna system is seleceted at I/F Unit

Fig. 4 PALSAR-2 system diagram.

3. ALOS-2 Data Products
3.1 Definition of ALOS-2 Data Products
Two categories of data products are defined - level 1 product and higher-level products.
3.1.1 Level 1Level 1 is radiometrically and geometrically calibrated data and is a standard JAXA product for ALOS-2 users.
3.1.2 Higher-level data productProducts above level 2 are higher-level data products. Higher-level data products are made more sophisticated byprocessing with digital elevation models. This is provided by JAXA's EORC as soon as ready.
3.2 Standard Data Products
Level
1.1

1.5

2.1

Table 3 PALSAR Standard data products.
Definition
Note
Range and azimuth compressed complex data on slant Beam modes: Full resolution mode, Low
range. Full resolution
data rate mode, Polarimetric mode
SLC: Single Look Complex used forinterferometry
Multi-look processed image projected to map
Map projection
coordinates.
ResamplingOption
Pixel spacing
G: Systematically Geo-coded (No option: Georeferenced)
Ortho-rectified and slope corrected products
Map projection
Resampling
Pixel spacing

4-4

4. ALOS-2 Operation Concept and Observation Strategy
ALOS-2 is operated based on the Basic Observation Scenario-3 (BOS-3) that is optimized as the background
mission while the emergency observation is the highly prioterized operation for the disaster mitigations. The BOS3 is open to the public through ALOS-2 i.e. https://www.eorc.jaxa.jp/ALOS/en/alos-2/obs/pal2_obs_guide_e.htm
The BOS-3 is designed to achieve the Earth observation using the several modes of the PALSAR-2, i.e. highresolution strip mode (84 MHz-singe polarization), Dual polarization mode (42 MHz-Dual Polarization), Quadmode (42 MHz-Full polarization), Dual Strip (28 MHz), and ScanSAR (14 MHz-Dual-350 Km /490 Km swath) forobserving the solid earth (deformation study), biosperic study (forest monitoring, carbon estimation) andCryospheric study (sea-ice, polarer monitoring), and map generation.

4-5

APPENDIX 5
OVERVIEW OF
THE ADVANCED LAND OBSERVING SATELLITE-4(ALOS-4) MISSION

7-1

1. Introduction
The Advanced Land Observing Satellite-4 (ALOS-4) will observe the Earth's surface using its onboard the Phased
Array type L-band Synthetic Aperture Radar-3 (PALSAR-3). The data will be utilized for monitoring disaster, forest,
sea ice, infrastructure, and many other applications with the advantages of Synthetic Aperture Radar (SAR) such as
all-weather and day-and-night observation capability. With further improved observation performance compared tothe predecessor PALSAR-2 aboard ALOS-2, the satellite aims at achieving both high resolution and a broader
observation swath.
ALOS-4 is equipped with a SAR antenna at the lower part of its body and with two solar array paddles at bothsides, as shown in Figure 1. The observation data is transmitted to a ground station via. Ka-band data downlink withmaximum rate of 3.6 Gbps. ALOS-4 will operate in the same orbit plane as ALOS-2. Table 1 shows system
specifications of ALOS-4.

Fig. 1 ALOS-4 in-orbit configuration.
Table 1 ALOS-4 current specifications (under designed).
Mission Instruments

Orbit

LaunchMission lifetime
Satellite mass
Data downlink

・ PALSAR-3 (Phased Array-type L-band Synthetic Aperture Radar-3)
・ SPAISE3 (SPace based AIS Experiment 3)
・ Sun-synchronous sub-recurrent orbit
・ Altitude: 628 km
・ Inclination angle: 97.9 degree
・ Local sun time at descending: 12:00 ± 15 min.
・ Revisit time: 14 days (15-3/14 rev/day)(Same orbit as ALOS-2)
June 30, 2024 by H-3 Flight 3 as planned
7 years
Approx. 3 tons
3.6 Gbps/1.8 Gbps (Ka-band)

2. PALSAR-3 Specification
ALOS-4 carries the state-of-the-art L-band SAR called PALSAR-3. For the continuity of ALOS-2 data, PALSAR3 will inherit the major function and performance (NESZ, S/A, etc.) of PALSAR-2 aboard ALOS-2. The observation
swath width of PALSAR-3 will be expanded from PALSAR-2 without spoiling the spatial resolution by using thedigital beam-forming (DBF) technique.
Fig. 2 and Table 2 show geometries and specifications of PALSAR-3, respectively. Spotlight and Stripmap modes
will provide high resolution data. ScanSAR mode will observe wider area with 700 km swath width at the expenseof spatial resolution. The observation repetition frequency of ALOS-4 will also be improved owing to the expanded
swath width.
7-2

Fig. 2 Geometry of PALSAR-3 observation modes.
Table 2 PALSAR-3 observation modes and specifications.
Observation mode

Spotlight

SAR mode

Slidingspotlight

Center frequency(MHz)1257.51257.5

Bandwidth (MHz)

84

84

4228

3

6103x1(Rg x Az)
35 x 35(Rg x Az)

Resolution (m)Swath width (km)Polarization(HV basis)

1, 2Stripmap 3m

Stripmap 6m

Stripmap 10m

Stripmap

ScanSAR
ScanSAR1236.5 or 1257.5 or 1278.5
2825(1 look)
700(4 scan)

200

100

200100200

100

1, 2

1, 2, 4

1, 2

1, 2, 4

1, 2

1, 2, 4

1, 2

8-70

8-70

N/A

N/A

Incidence angle
8-70
30-56
8-70
30-56
8-70
29-56
range (degree)
Split-band option
28+10(for ionospheric
N/A
N/A
N/A
N/A
N/A
MHzcorrection)*Items in red color represent improvements or modifications from PALSAR-2

3. Standard Product
PALSAR-3 Standard Data Products (Level 1) are radiometrically and geometrically calibrated data and will be
provided for ALOS-4 users. Table 3 shows the definitions of the Standard Data Products. In addition, higher-level
data products including global mosaic and disaster map are planned to be released.
Table 3 PALSAR-3 standard data procucts.
Level
1.1
1.5
2.1Definition
Range and azimuth compressed single-look complex (SLC) data on slant range
Geo-coded or geo-referenced amplitude image projected to map coordinate
Ortho-rectified amplitude image projected to map coordinate

7-3

4. ALOS-4 Operation Concept and Observation Strategy
To achieve these mission objectives of ALOS-4, it is necessary to establish a common observation scenario tomake effective use of the limited observation resources, and to conduct systematic observations in time and space.
In ALOS-4, the "Basic Observation Scenario (BOS)" is defined as a common observation scenario as in ALOS andALOS-2, and observations are performed based on this scenario. For emergency observations required to grasp thedisaster situation, or for observations required by individual users, individual observation requests are drafted
separately from the BOS and observations are performed according to the priority level defined with the BOS.
Since ALOS-4 is expected to be operated simultaneously with ALOS-2, the observation plan will beappropriately discussed and updated so that it will be integrated and consistent between ALOS-2 and 4.
More detail of the ALOS-4 BOS is presented on the public through EORC ALOS seriese website i.e.,
https://www.eorc.jaxa.jp/ALOS/en/alos-4/a4_observation_e.htm

7-4