Advanced Land Observing Satellite-2（ALOS-2）「 DAICHI-2 」
The Earth needs a health check.

The Earth needs a health check

L-band SAR Tradition and Evolution

The land underneath our feet is constantly changing even at this moment due to various reasons
including natural phenomena, such as earthquakes, floods, volcanic activity, landslides andman-made destruction.
On such a changing Earth, we hope to live as soundly as possible. For that, we need to understand thecurrent conditions of the Earth. It is the same as us taking a health check regularly, and a detailed
examination if necessary, to maintain our well-being.
JAXA has developed the Advanced Land Observing Satellite-2 “DAICHI-2” (ALOS-2), the successor of
the DAICHI, which observed the Earth between 2006 and 2011.
The DAICHI-2 is equipped with the Panchromatic L-band Synthetic Aperture Radar (PALSAR-2) asan observation device.
The Synthetic Aperture Radar (SAR) has a special feature of being able to observe regardless of time(day and night) and weather. With the L-band radar, the PALSAR-2 has an advantage in capturingconditions of land deformation, forestry and vegetation. Japan has been accumulating technology andknow-how for the L-band SAR field and has been leading the world in this area. Compared to the
DAICHI, on which three sensors (two optical and one microwave devices) were onboard, theDAICHI-2 is exclusively installed with the PALSAR-2 using microwaves to maximize its ability.
The DAICHI-2 can perform health checks on various targets in detail from space. It can grasp
conditions of a disaster-stricken area, and also examine the health conditions of forests, which are alifeline for us, and for the Earth. The DAICHI-2 can also watch over navigating ships, and support
agricultural development. Its application is broadly expanding with further possible utilization.
The new global eye, some 628 kilometers above us will open up a new future for us.

The Synthetic Aperture Radar (SAR) is an onboard radar on a moving vehicle such as an aircraft or asatellite to emit radio waves called microwaves towards observation targets, receive their reflection
from the target objects and process them in a special way for observation. Digital camera and otheroptical sensors usually perceive the Sun’s reflection from a target object, but in the case of the SAR, it
receives the reflection of the radio wave that is emitted from the SAR itself. That is why it can perform
observations day and night. In addition, the radio wave can penetrate rain and clouds to enable
observations regardless of weather. The L-ban is a radio wave whose wavelengths are especially longat about 24 cm. The SARs aboard oversea satellites use X-band (about 3 cm) and C-band (about 6 cm),and they reflect on leaves (forest canopy) when observing forests. On the other hand, the L-band has
an unique advantage of partially penetrating vegetation and reaching the ground to acquire
information on both vegetation and the ground. In addition, the L-band, which is not affected by thegrowth of vegetation, is suitable for technology called “Interferometry (SAR interference analysis),”which is useful for studying land deformation. The L-band is, therefore, highly beneficial forearthquake-prone Japan, where two-thirds of the land is covered by vegetation, and that was why wewant to apply the L-band at an early stage to lead the world. Beginning with its use on the Earth
Resource Satellite “FUYO-1” (JERS-1), the L-band SAR was also aboard the Land Observing Satellite“DAICHI” in 2006 and has been passed on to the DAICHI-2, during which the radar technology has
been evolving. Since the FUYO-1, we have accumulated data acquired by the L-band SAR for 11 years.
Using the DAICHI-2, the latest information will be further gained. Accumulation of such information
is essential to learn about changes in forests and predict their future, which is key for the Earth's
environment. As global warming progresses, Japan, which possesses the L-band SAR, will play a more
important role.

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2

The Earth needs a health。check2

L-band SAR Tradition and Evolution

3

Monitoring disasters for a safer life4

Tackling global-scale environmental problems

6

Overview of the Advanced Land Observing Satellite-2 “DAICHI-2”

8

Evolution of DAICHI-2 from DAICHI

9

Mission instrument

10

Satellite bus supporting DAICHI-2 and future satellite missions

12

Block diagram of the ALOS-2 system

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Satellite operation after separation from H-IIA

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Ground system and observation operation

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With longer wavelength(L-band)Penetrate clouds, rain,
and leaves to reflect
on tree trunks, objects,
and the ground©JAXA,METI

JERS-1（1992-1998）

JERS-1 SAR Image,
Resolution 16m

ALOS（2006-2011）

PALSAR Image,
Resolution 10m

ALOS-2

Simulation Image,
Resolution 3m

With mid-length wavelength(C-band)Penetrate clouds
and rain but reflect
on canopy andbranches©JAXA,METI

With shorter wavelength(X-band)Attenuate due torain and clouds andreflect on canopy

©JAXA

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3

Safe and secure life
How can we utilize DAICHI-2 observation data? We would like to introduce DAICHI-2’s missions and specificexamples of data application. Various possibilities proven by the L-band SAR aboard the DAICHI will befurther improved and achieved by the DAICHI-2.

Monitoring disasters for a safer life
To understand land deformation due to earthquakes
The land deformation due to the Great East Japan
Earthquake was clearly observed by the PALSAR
aboard the DAICHI (left figure.) The topographic
change and movement was drawn using a method called“interferometry” by observing one location multiple
times and finding differences through comparing (or“interfering”) such multiple data.
Data at the GPS-based control stations established by
the Geospatial Information Authority of Japan (GSI) is
used for measuring land deformation (right figure) but
GPS can measure changes and movement only by“points.” On the other hand, satellite data captureschanges by “areas”. Under collaboration between JAXA
and GSI, we can understand the changes and movement

more precisely by combining GPS and satellite data.
In addition, the DAICHI-2, whose precision in keeping
its orbit and position has improved, will be able toperform more accurate interferometry. The DAICHI-2
will help compile the base map for the interferometry
criteria in Japan and overseas. In the case of anearthquake in Japan, data for the interferometry will beacquired within three days to understand the land
deformation at an early stage. In addition, we cancapture high-resolution images by selecting a spotlightmode, or other means, to learn detailed conditions of adisaster-stricken area, such as finding if a skyscraper,
bridge, or other large building collapses, to determine
which routes should be taken for relief activities.
Analyzed by GSI：©JAXA,METI

Analyzed by GSI

Rainbow-colored stripes indicate
the scale and pattern of land
movement (protrusion, subsidence,or horizontal movement.) Stripes
with higher density show larger
land deformation in the samemanner as the contour lines.

During the Great East Japan Earthquake on March 11, 2011,a large land deformation of about 5.3 meters in the horizontal
direction and about 1.2 meters (the numbers are the largest
on record) in the vertical direction was observed.

International cooperation through disaster information provision to the world
Swiftly acquiring observation images of a damaged area
is very important at the time of a disaster, but a satellite
belonging to a disaster-stricken country is notnecessarily flying over it in a timely manner. Therefore,
we now hold some international cooperation
frameworks to help provide appropriate observation
data for each other. One example is the “International
Charter”. The number of large-scale disasters that
require emergency relief operations, such as
earthquakes, floods, and typhoons, amounts to about
300 per year. For example, the International Charter
was mobilized 51 times for 330 such disasters in 2010.
Over 20 countries including the U.S., European
countries, China, South Korea, and Russia are Charter
members, and Japan joined it just after the launch of
the DAICHI.
The Sentinel Asia is an Asian version of the
4International Charter. Following Japan’s lead, Asian
countries such as India, Thailand, and Taiwan
participate in the framework. In addition, Japan has
made agreements with the Italian, German, andCanadian space agencies to exchange satellite data at
the time of disasters. Following the DAICHI’s
contribution to the International Charter and Sentinel
Asia, Japan is again expected to play an important role
after the launch of the DAICHI-2. Central government
ministries and municipalities ofeach member country will utilize
data from the DAICHI-2.

Vietnam flood water observed in
Oct. 2008
JAXA’s analyzed PALSAR data wasprovided to Vietnamese Academyof Science and Technology.

©JAXA,METI

Promptly responding to water disasters due to torrential rain and landslides
Totsugawa village in Nara Prefecture was heavily damaged by
Typhoon No. 12 in September 2011. Due to bad weather, only
partial amounts of information were acquired throughhelicopters, but by analyzing images acquired by the SAR
aboard the German satellite TerraSAR-X, we obtained
湛水池
information for determining evacuation orders. With the
DAICHI-2, observation requests can be filed as late as one hourprior to the observation time, with data provision taking as
little as one hour after observations are performed. We are
崩壊地
aiming at much prompter provision of data compared tooverseas satellites. The DAICHI-2 will exhibit its ability toacquire data of a disaster-hit area immediately after thedisaster when helicopters and aircrafts cannot observe it, anddata that covers broader areas to understand the hanks to images acquired by the SAR,
comprehensive situation. Using the DAICHI-2’s spotlight mode which can observe regardless of rain
by Kinki Regional
clouds or night. The images led to the Provided
Development Bureau, Ministry
and high resolution mode, we can provide disaster-related evacuation of the lower reaches.
of Land, Infrastructure andministries and agencies of the central government andTransport
municipalities with high-resolution high-quality images.
© 2014 Airbus Defence and Space / Infoterra GmbH, Distribution [PASCO]

Monitoring any kind of disaster
Images taken by the DAICHI-2 will contribute to monitoring andunderstanding situations of various disasters including land subsidence,
forest fires, and volcanic activities in addition to earthquakes andwater-related disasters. For example, in Japan, a volcanic country, 110
active volcanoes are regularly monitored by the Japan Meteorological
Agency (JMA) and other organizations, and images taken by the DAICHI
were also utilized for that purpose. After the completion of the DAICHI’s
operations, satellite monitoring of the volcanoes are currently performedby other overseas SAR satellites in response to requests by the JMA and
Coordinating Committee for Prediction of Volcanic Eruption. The DAICHI-2
will take over that duty with higher accuracy. Regarding land subsidence,
the DAICHI-2’s observation
data is expected to be usefulfor private infrastructure
related companies as they
will be helpful for degradationof large structures such as Oil spill in the Gulf of Mexico.
(Areas surrounded by yellow line mark the spills.)
dams.

©JAXA

©JAXA,METI©JAXA,METI

Images of the volcanic explosion of Mt. Kirishima (ShimoeDake) in January 2011. The left one is an optical image,and the right is a SAR image. You can see that the latter
penetrated not only clouds but also volcanic smoke.

Sea ice monitoring
Learning about the movement of sea ice is essential for boats to navigate safely incold districts. The Japan Coast Guard (JCG) publishes and updates the “Sea Ice
Condition Chart” of the Sea of Okhotsk every day in winter in cooperation withinformation from other related organizations.
The DAICHI observed the Sea of Okhotsk regularly by the Scan SAR mode of the
PALSAR from December to May every year to provide sea ice analysis information to
the JCG. With the strength of the SAR to be able to observe without any influence
from clouds, the DAICHI proved its observations over the rough winter ocean inharsh weather are effective. On the other hand, some issues were also raised such as
not having enough observation frequency and difficulty in identifying thin ice. The
DAICHI-2 will improve its observation frequency thus it can provide more sea ice
information in the Sea of Okhotsk in winter. In addition, a HV channel is also usedin the Scan SAR mode, thus a further increase in the amount of information on sea
ice is expected.

Floating sea ice on the Sea of Okhotskobserved by PALSAR (at 3rd February)©JAXA,METI

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Global-scale environmental problems

Tackling global-scale environmental problems

Economical and social contributions

Deforestation monitoring by global forest map

Uninterrupted food supply

The L-band SAR, whose special observation
feature is an ability to penetrate vegetationand to be less impacted by clouds, canefficiently observe forests, such as tropicalrainforests, which are often covered byclouds. Therefore, JAXA has constantly
monitored forests using the L-band SAR on
the FUYO-1 as well as on the DAICHI. Data
had been obtained for a prolonged time ofover 11 years between 1992 and 2010
although there were some blank periods.
The DAICHI-2, equipped with a HV channel(a channel that transmits a vibrating wave ina horizontal direction against the ground [H]©JAXA, METI Analyzes by JAXA
and receives it vertically [V]) even in the Scan
The color gets darker with more forests.
SAR mode, is expected to acquire more
We can find deforestation by comparing year-on-year images.
detailed observation data on forests. By fully
utilizing the different observation modes with polarimetry (four polarized waves) or with an operation that clarifies
differential interference, there is a possibility for the DAICHI-2 to observe the height and type of a tree. If we can learnsuch detailed information of forests, we can estimate carbon volume and CO2 absorption amounts in forests with moreaccuracy. Such details are very important for global warming solutions. Hence JAXA is aiming to establish L-band
SAR forest monitoring as a global standard through the DAICHI-2 project.

For Asian countries, understanding their respective
agricultural status is important as food shortages havebecome a serious issue due to their population increase.
Agricultural statistical information for rice in detail is
especially important for Asian countries because Asia
accounts for 90% of rice production and consumption in
the world. The current survey on rice, however, is nothighly reliable. In addition, paddy rice is planted during
the rainy season which makes it difficult to observe fromspace. However, the SAR is very useful for its ability toobserve through clouds. Many people await the arrival of
the DAICHI-2.
In the images taken by the SAR, water surfaces lookdark. When paddy rice is planted, paddies are filled withwater, thus they look dark in the image. After rice grows,
they look brighter as water is covered by the green of theplant. In other words, if the darkness changes in a SAR
image when time elapses, that area with changing
brightness is where the rice paddies are. From the SAR
images, we can learn the area of rice paddies.
In some areas in Thailand, we have already used theabove method to verify the area of rice paddy area using
DAICHI’s data. We will further utilize DAICHI-2’s data
in other regions in Thailand as well as in other countries
to gradually move to a practical use of this method. We
are currently confirming its validity in cooperation with
Vietnam, Indonesia, Laos, and the Philippines, inaddition to Thailand. The DAICHI was used in a
relatively limited area, but the DAICHI-2 is expected tobe utilized by each country through a broader area
ranging from one prefecture/state to even-the wholecountry to compile basic data for food security measures.
SAR images are also expected to be able to identify somefairly large products such as corn and sugar cane, thus
we are also studying the possibility of such use.

Illegal deforestation frequently occurs in Brazilian forests,
and SAR images by the DAICHI played an important rolein the solution. In Brazil, forests were monitored byBy overlapping two PALSAR
satellites with an optical sensor such as the Landsat andimages taken at different
times, we can specify the area CBERS, but observations were hampered due to a rainythat was deforested duringseason that covers about a half of a year because opticalthat period. With the DAICHI,
newly grown bushes or
sensors do not see through rain clouds. Consequently, theexistence of water madenumber of deforestation cases increased. Once JAXA
difficulty to determine a
deforested area. The DAICHI-2 started to provide images acquired by the SAR aboard theis expected to offer us more
precise information to specify DAICHI, which can observe forests by penetrating rain andclouds, to the Instituto Brasileiro do Meio Ambiente e dos
the area.
Recursos Naturais Renováveis (IBAMA, Brazilian©JAXA,METI
environment agency) in 2007, deforestation cases havebeen decreasing. As a result, JAXA contributed to the reduction of the deforestation area (including legal cases) from12,000 km2 in 2008 to 7,000 km2 in 2009. The PALSAR-2 with higher performance aboard the DAICHI-2 is expected
to identify deforestation areas with more accuracy. In addition, in order to catch an illegal deforester red-handed, thepolice must be mobilized as soon as such an act was captured by the satellite. An illegal deforester is said to usually
stay at one site for about two weeks, thus the DAICHI, whose recurrent period was 46 days, did not have enoughopportunities to capture illegal deforestation activities. The DAICHI-2 will be more useful in this regard as its
recurrent period is 14 days. Apart from the IBAMA, many environment-related organizations in various countries
hold high expectations for the DAICHI-2

Monitoring deforestation

Polar ice reduction
The Polar Regions are vulnerable to global warming and entailingclimate changes, hence observing them for a prolonged period isimperative as an indicator for global warming. The SAR observation,
which is not affected by clouds, is very effective for the Polar Regions,which are always covered by clouds. Due to a reduction of sea ice, anavigation route through the Arctic Ocean to connect Europe and Asia
Monitoring regression of a glacier in Greenland.
seems a more likely development in the future. The DAICHI-2’s
accurate sea ice observation data will play an important role for the feasibility research and study of such a route.
Through an interferometry method, we can learn the movement of ice sheets and glaciers, thus it can be a very strong
tool for polar science.
©JAXA,METI
Analyzesby JAXA

6

A rice paddy filled with water before planting works as a mirror
which reflects microwaves in the opposite direction, thus the
microwaves do not come back to the satellite. As a result, it
appears dark in an image. Just after planting, the microwave
reflection on the paddy is weak, and the image is still dark. As
rice grows, the reflection becomes stronger to make thepaddy area on the image brighter. Using the changes in thedarkness, we can determine the area of rice paddies. Blue
represents the paddy rice and yellow represents the otherareas which are not paddy rice.
©JAXA,METI（RESTEC ホームページより）Probing underground resources and understanding land subsidence
Saudi Arabia had been leading the world in oil deposits for a long time, but in
2010, Venezuela took the top position by suddenly increasing its deposit
amount by 40.4% thanks to the remarkable evolution of resource mining
technology. In Japan, technological improvements in digging seabed resources
have attracted people’s attention in recent years to excavate in neighboringseas. The SAR can exhibit its ability in this area. At the location of a seabed oilfield, leaked oil often floats on the surface to create an oil slick. During an oil
slick, the sea surface is glassier than normal sea surface, thus an oil slick area
looks darker in a SAR image. If you can find an oil slick in multiple SAR
images taken at different times in a certain area, it means that oil is leaking
in that location, and that is one of the indicators for a seabed oil field.
Therefore, the DAICHI-2 possesses the high probability to exhibit its ability toacquire more accurate data for new resource development, and accordingly
energy related public organizations and private businesses are expected to use
its data. With the interferometry method, the DAICHI-2 can measure land
subsidence, due to oil digging, to a few centimeters, hence its data is also
expected to be utilized for environmental assessment operations to monitor
land subsidence.
J-spacesystems 提供

7Overview of Satellite

Evolution of DAICHI-2 from DAICHI

Overview of Advanced Land
Observing Satellite-2 “DAICHI-2”

1. More detailed

The configuration of satellite
Data Relay and Communication Antenna (DRC-ANT)
Solar Array Paddle (SAP)




X

-



The DAICHI-2’s resolution has been improved from theDAICHI to be able to observe more details using theL-band. The resolution of the DAICHI’s PALSAR was a
maximum of 10 meters, but that of the DAICHI-2’s
PALSAR-2 has been improved to 1 to 3 meters. This
improvement became possible by adding a “spotlightmode” which enables the satellite to change its radio
wave radiation direction to its moving direction (verticaldirection) while flying to keep observing one specifictarget location for a long time. In addition, a “Dualreceiving antenna system (explained later) is adopted tosecure enough observation band with high resolution. As
a result, the observation band is 50 km with 3-meter
resolution in the “strip map mode”, and 25 km with 1 to
3-meter resolution in the “spotlight mode”.

©METI, JAXA©JAXAPALSAR Image
Resolution 10m

PALSAR-2 Simulation Image
Resolution 3m

Nadir

2. Much faster
Flight Direction

Direct Transmission X-band Antenna (XANT)

L-band SAR Antenna (PALSAR-2)

Nadir

As the name indicates, the DAICHI-2 is the successor of
the DAICHI, but the structure of the new satellite isquite different from its predecessor. The DAICHI isequipped with three sensors namely the Advanced
Visible and Near Infrared Radiometer type 2 (AVNIR-2),
Panchromatic Remote-sensing Instrument for Stereo
Mapping (PRISM), and Phased Array type L-band
Synthetic Aperture Rader (PALSAR), but the DAICHI-2
is specialized for the SAR. By focusing on one specificinstrument, we can maximize the SAR’s performance forthe DAICHI-2 to be best suited for its primary purposeof monitoring disasters regardless of the time of day andweather conditions. PALSAR-2 of the DAICHI-2, hasbeen significantly improved from the DAICHI’s PALSAR
in all aspects including resolution, observation band,and time lag fordata provision.In addition, the satellite’s

Shape

LaunchConfiguration Approx. 4.5m (X) x 3.5m (Y) x 3.1m (Z)On-orbit
Configuration Approx. 10m (X) x 16.5m (Y) x 3.7m (Z)basic capability has also been enhanced for supporting
the radar performance such as data transmission speed
and high position retention accuracy thanks to newtechnology.
While the DAICHI-2 is equipped with the necessary
ability for swift disaster monitoring, its development
has also generated a variety of new technologies thatcan be applied for future satellite development.

Type

Sun-synchronous sub-reccurent orbit

Satellite

Altitude

628km above the equator

Mission Data Downlink

Direct Transmission or
via Data Relay Satellite

SAR Frequency range

L band (1.2GHz)

5 years (target: 7 years)

Spotlight

Resolution: 1-3m
Swath: 25km

TargetLaunch Date May 24, 2014 (Nominal)

Observation Strip map
Mode+/- 15min above the equator,
Local sun time 12:00
at descending nodeLife time
Launch8

LaunchvehicleH-IIA launch vehicle #24[ALOS]

Mass

Flightdirection

Scan SAR(N+1)th orbit
Nadir Track

Electric beam steering:
Incidence angle 8~70deg

Approx. 2t

Resolution: 3m, 6m or 10m
Swath: 50 or 70km

30deg

Nadir
[Right Looking][Earth pointing attitude(without observation)]

Flightdirection

revisit time is how many daysa satellite on Earth's orbit
takes to come back to thesame location. It isdetermined mainly by two
factors, the altitude and theinclination of a satellite.
The altitude of DAICHI and
DAICHI-2 is different, 691 km
for the former, and 628 km forthe latter. This difference
results in the DAICHI-2’s revisit
time of 14 days compared tothat of the DAICHI at 46 days.

Electric beam steering:
Incidence angle 8~60deg[Earth pointing attitude(with observation)][ALOS-2]

Main characteristics of ALOS-2

Orbit

High responsiveness is required for monitoring disasters. In order to copewith requests from DAICHI users, the DAICHI-2 has been improved invarious ways. First of all, the DAICHI’s SAR antenna was fixed to face thelower right direction toward the moving direction of the satellite, thus it
observed only one orientation. To broaden the observable area, theDAICHI-2’s antenna plane is upgraded to face to the nadir direction of thesatellite, thus, by changing the satellite‘s attitude right or left duringobservations, both sides of the satellite can be observed. Accordingly, theobservable area was drastically improved from 879 km to 2,320 km. In
addition to this right and left looking function (meaning monitoring a vast
area from one orbit,) the revisit time is also significantly reduced from 46
days to 14 days (so that the satellite can go back to the target location
sooner-), and data transmission capability is strengthened to be more
efficient (to transmit data faster.) As a result, when a disaster monitoring
request comes in within Japan, we can provide images of the stricken area as
fast as two hours from request.

Q: How is the revisit time
determined？

30deg

Nadir
[Left Looking]

Incidence angle : 8~70 deg.

Nth orbit
Nadir Track

Distance between orbits
2200 km

Pink width：Swath 50 km (Ultra-Fine and High-sensitivity)
Green width：Swath 70 km (Fine mode)
Red width：Swath 350 km (ScanSAR nominal mode)
Yellow width：Swath 490 km (ScanSAR wide mode)

Resolution: 100m
Swath: 350km
9Mission instrument
Observations are possible day and night regardless of weather:Phased Array type L-band Synthetic Aperture Rader (PALSAR)

Attaining high resolution by spotlight mode
A new observation mode called a “spotlight mode” wasadded to the PALSAR-2, which enables it to gain highresolution. As the name shows, this mode works like a
spotlight by moving beams to keep aiming at a specificobservation target along the flight path of the satellite.
More information can be acquired by emitting beams to
the same location for a prolonged time (13 to 26 seconds)

in the same manner as we can receive more knowledge
when we keep looking at one spot while moving. As aresult, high resolution of 1 to 3 meters can be achieved.
In other words, we will be able to specify an object or ashape of something that cannot be distinguishedby the DAICHI/PALSAR, whose resolution was about
10 meters.

Dual receiving antenna system to broaden observable area

The PALSAR-2 aboard the DAICHI-2 is a microwave
sensor that emits L-band radio waves and receives theirreflection from the ground to acquire information. It
does not rely on other sources of light such as the sun,thus its strongest point lies in its ability to observe theEarth regardless of the time of day.
The bandwidth of the transmitting and receiving radio
waves are in microwaves, hence they are less affected byclouds or small water drops and can penetrate them. As
it is an all-weather sensor it is best suited formonitoring disasters, which are very difficult to predict
when and where they occur. In addition, the wavelengthof the L-band is relatively long among microwaves,allowing it to travel all the way down to the groundthrough vegetation. Not only can information be,
obtained about vegetation but information of the groundsurface can be obtained as well.
Japan’s L-band SAR debuted aboard the FUYO-1
launched in 1992, and was inherited on the
DAICHI/PALSAR
in2006,
leadingup
DAICHI-2/PALSAR-2 today. The PALSAR-2 now
becomes a unique and highly useful sensor in the world
by expanding its radio-frequency bandwidth-, andadopting the “Dual receiving antenna system,” which
can control two separate receiving radio waves, andachieve a high resolution and broader observation band.

Achieving the phased array antenna with various cutting-edge technologies
The thousand antennas observing the Earth

The PALSAR-2 adopts the “Dual receiving antenna
system”, the leading-edge technology in the world, toenable itself to maintain a broader observation swath
with high resolution. In this method, the whole antenna
plane works as one aperture plane (or one radio
frequency transmission plane) when it emits radio
waves, while the antenna plane plays as two apertureplanes consisting of front and back antennas when
receiving the radio waves. By dividing the antenna into
two for receiving, two separate waves can be accepted atonce, and reception time for each beam can be kept
longer. One characteristic of a synthetic aperture radaris that the observation band becomes broader when thereception time gets longer. Therefore, using thismethod, we can secure a broader observation band of 50
km with a resolution of 3 meters.

tion

tion

irec
Flight D

irec
Flight D[ALOS][ ALOS−2]

Expanding bandwidth and higher power transmission
In order to achieve the high observation resolution andimage quality required for the PALSAR-2 aboard theDAICHI-2, the radio wave strength must be improved
from that of the PALSAR. For the improvement we needeither to enlarge an antenna to concentrate radio waves(in the case of a phased array, increase the number ofantennas) or to enhance transmitting power. We applied

the latter method by using the world’s first antenna
amplifier made of GaN HEMT to expand the radar
bandwidth for transmitting radio waves with higher
output. This improvement will support the DAICHI-2’s
detailed observation.

Variety of observation modes

Q: What is the phased array antenna？

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wave front

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TargetInstead of a parabolic antenna,
which looks like a hugeumbrella, PALSAR-2’s phasedarray antenna consists ofmultiple small antennas lined up
in rows. A radio wave emitted
from an antenna is
electronically controlled tochange its direction so thatbeams can freely shift theirdirection although the antenna
is fixed. A phased array
antenna, which can open inspace, is suitable to expand to
become a large-size antenna ofa size of about 10 meters by 3
meters with swinging beams,
hence this method is widelyused in space.

Beamdirection
Ground surface

Another special feature of the PALSAR-2 is theavailability of various observation modes. Apart fromthe “spotlight mode” (observation band of 25 km), which
achieves the most detailed observation of 1 to 3 metersin resolution, the PALSAR-2 is also equipped with the“strip map mode” (band of 50 or 70 km), which isinherited from the PALSAR with more choices ofresolution of 3, 6, or 10 meters, and the “scan SAR
mode” (band of 350 or 490 kilometers, resolution of 60 to
100 meters), which can observe a broader area at theObservation Mode
Spotlight

アンテナ

B
direeacmGtion
surrfoaucnd
e
アンテナ

Strip map

Scan SAR

same time. By selecting one observation mode fromthese options according to the objective, the mostsuitable monitoring method can be performed.
Furthermore, the HV channel can be used at the scan
SAR mode (in the case of the PALSAR, only the HH
channel was available) thanks to the achievement of the“full polarimetry” (observation with four polarizedwaves) of 6-meter resolution, so that we will be able togain more information from one observation location(for example, a type of tree in a forest can be detected.)

Resolution
1m(Az)×3m (Rg)Swath
25km×25km (Rg)

Ultra Fine

3m

50km

High sensitivity

6m

70km

Fine

10m

70km

Nominal

100m

350km

Wide

60m

490km
11

Satellite bus supporting DAICHI-2 and future satellite missions
Every satellite requires a main body that preforms basic needs to achieve its special mission. Thatbody is called a “bus.” The DAICHI-2’s bus has been actively incorporated with various newtechnologies as we foresee future applications to other satellites.

Improvement of datatransmission capacity

More promptly
X-bandModulator

FasterMore efficientHigh speed transmission is imperative for promptly
delivering large-volume observation data acquired by
the DAICHI-2 to users. For fulfilling our responsibility,
the “X band Multi-mode High Speed Modulator(XMOD)” is installed. In addition to the QPSK method,
modulation with 16QAM method is also available toenable transmission of 800 Mbps. This transmission
speed is the fastest in the world as a communication
method using a single X-band wave, and over five times
faster than that of the DAICHI (138 Mbps.)

The XMOD is available only when the DAICHI-2 isflying within the view area of a ground station, but datatransmission is possible through a data relay satellite“KODAMA” in areas outside the view path. Although
the data relay transmission speed is about 278 Mbps
(QPSK method), we can achieve efficient datatransmission with the help of the XMOD.

Improved data acquisition
opportunity andstorage capacity
Reaction
Wheel

Mission Data Processor

More agility

More voluminous

The DAICHI-2 can rotate its attitude right and left
against its moving direction. Using this function, the
PALSAR-2 beam can be emitted in broader areas toincrease image shooting opportunities. For quicker
attitude shifting, five “high torque reaction wheels” areonboard. Dynamic movement of 30 degrees rotation in
120 seconds is attained through the generation of large
torque.

Data volume for one observation by the DAICHI-2/
PALSAR-2 is larger than that of the DAICHI/PALSAR
as the former is higher in resolution and broader inobservation band. In addition, image shooting opportunities
are increased thanks to its right-and-left observation
function, thus data storage until completing datatransmission to the ground will increase. The ALOS-2
data recorder volume is expanded to a maximum of 128
Gbyte (96 Gbyte for the ALOS) of memory storage.

Improving position accuracy
and recurrent precision
A data analysis method called the “interferometry” of the PALSAR-2 is expected
to be applied in various fields. In order to utilize this method with high precision,
the satellite has to observe exactly the same location twice or more. Therefore, it
is important to know the satellite position accurately to use this method. The
GPS aboard the DAICHI-2 can determine a position within one meter of themargin by using technology called the “dual-frequency GPS receivers for L1 andL2 band.” A satellite’s orbit is gradually shifting due to outside forces such as
altitude decrease due to atmospheric resistance and orbit plane change by solar
attraction. The new “precise autonomous orbit maintenance technology” isadopted for the DAICHI-2 to correct its orbit by itself. The orbit is autonomously
maintained within a 500 meter radius from the basic orbit.
12

GPS Antenna

500mMore precisely

Enhanced operability
The DAICHI-2 adopts an “observation table.” This is apattern or a sample of a series of pre-registeredinformation for each specific operation, such as turning
on/off a certain device for observations. Eachobservation mode has its own table. When we start a
new observation mode, we simply pick up the table forthat mode and set up the parameter unique for thatobservation plan. With this clear procedure, we canpromptly cope with an emergency disaster monitoring
request without any incorrect commands.

Improved survivability
From one paddle to two paddles

Safety mode for emergencies

The DAICHI was installed with only one set of solar arraypaddles which extended long to the left side against it moving
direction. With one paddle, each onboard mission sensor cansecure a broader view, but there is no alternative if that one
paddle is broken. The DAICHI-2 does not have any issues withthe onboard radar’s view because it faces toward the nadir
direction, thus the satellite is equipped with two sets of paddles
to be advantageous for securing electricity even when one of
paddle is broken. In the case that power generation is reducedin half if one of the paddles fails, the mission can continue in the“degenerate mode” meaning conducting limited observation
operation by reducing the burden on power.

If an emergency occurs with a satellite andobservations have to be halted or continuing
observations may induce a serious problem withthe satellite system, the satellite stops
observations and shifts to the “safety mode.”This is a mode to reduce its power burden to theminimum level to study the satellite’s condition.
The DAICHI-2 increases its survivability byappropriately and automatically shifting to the“safety mode” when a problem arises.

Development for the future
Lithium-ion battery

Unified Driver Electronics

The NiCd (nickel cadmium) battery aboard the DAICHI had a memory
effect, which means that a rechargeable battery gradually loses its
maximum energy capacity if it is repeatedly recharged after being only
partially discharged. Therefore, reconditioning to recover its capacity
had to be performed for the DAICHI from time to time by discharging
more than its capacity. The DAICHI-2 adopts a lithium-ion battery
which does not entail a memory effect as part of design developmentthat can be applied for future satellites, hence reconditioning is notnecessary anymore. In addition, we successfully made the battery
lighter.
MDP

Development of the Unified Driver Electronics
(UDE)

GPSA

XMOD

RW

In order to make the DAICHI-2 lighter by reducing the number of
onboard devices, we reviewed the function of onboard devices. As aresult, we integrated some driving functions into one, namely driving UDE
functions of propellant valves, latch valves, SADM, SAR deployment
motor, XANT deployment motor, and MTQ. The integrated driver iscalled the “Unified Driver Electronics (UDE.)” We will apply the UDE
for future satellites.

ALOS-2 Satellite bus skeleton model
13

1553B

CIR C

CIR C

Subsystem Constitution

DM（SAP-1 ） CAM-H1

Observation Data
（Low Speed To CDMS ）Primary PWR（28V fm PDCU-1 ）CAM-CNT（SAP-2 ） CAM-H2

Primary PWR（28V fm PDCU-1 ）Observation Data

Data BUs（SAR-PX/XANT-PY ） CAM-H3

PALSAR-2

Antenna development
Power（fm UDE ）SAR 外部搭載機器（SAR-MX ） CAM-H4SPAISE-2

Observation Data
（High Speed ）（SAR-PX/XANT-MY ） CAM-H5SPAISE-2

Guard Pulse（to GPSP ）Primary PW R
（fm PCU ）Primary PWR（50V fm PDCU-1 ）AIS-RXDATA

Low Speed Line to CDMS
High Speed Line to CDMS

MDP

SAR-ANT

DRC

SF-CNT
Observation Data

KTWTA-A
KMOD

KHYB

KFIL
KTWTA-B

TLM（High Speed ）CSS-A

Drive Signal/Encoder

APE-A

DRC-ANT
CSS-B
ESH-1

ESE-1

ESH-2

ESE-2

WDE-1

RW-1

APE-B
RW-2

WDE-2
WDE-3

RW-3

Drive Signal/Encder

IRU
GPSA-1A

GPSL-1A

AOCE

GPSP-A
GPSL-2A

GPSA-2B

DT
RW-5

UDE-A

MTQ-1

UDE-B

MTQ-2

XANT-PY

GPSL-1B
GPSP-B
GPSL-2B

XATT-ASTT-1

SAR Deployment
Motor Drive Signal

STT-2

XANT Deployment
Motor Drive Signal

STT-3

SAP Drive Signal（to SADM ）XHYB-AXMOD

XSSPA-A

XFIL-AXSSPA-B

XFIL-B

XATT-BXHYB-B

XANT-MY

Boot Signal（fm BIM ）Satellite Separation Signal

SAP Deployment Pulse(to ODC)SAP Potentiometer （fm SADM ）TCS

Launch Lock
Release Signal（fm ODC ）

RW-4

WDE-4
WDE-5

GPSA-2ASAR Guard Pulse
GPSA-1B

CMD / TLM
to Equipment

AOCE TLM

RIM-ATime Marker, Clock

RIM-B

SHYB-3①

MTP-A

SDIP-ASHYB-2②②

SLPF-B
MTP-B

CDMS-B
HeaterControl
to Equipment

SDIP-B

EPS

Attitude & Orbit Control System

PDCU-250V PWR
to Mission Equipment
50V or 28V PWR
to Bus Equipment／ Heater

PDCU-1

CAM-H1
CAM-H1
SADM-1

BAT-1

BAT-2

SAP Deployment Pulse（fm AOCE ）
STR

■ PCU

Power Control Unit

■ BIM

Battery Interface Module■ ESH

Earth Sensor Head

■ BAT

Battery■ STTStar Tracker■ ODC

Ordnance Controller■ GPSP

Global Positioning System Processor■ GPSA

Global Positioning System Antenna■ UDE

Unified Driver Electronics■ WDE

Wheel Driver Electronics■ RW

Reaction Wheel■ MTQ

Magnet Torquer

Telemetry Tracking and Control Subsystem■ SANTS-band AntennaDT■ XANTEPS

SPSS-band HybridElectrical Power System

Solar Paddle Subsystem■ SAP

Solar Array Paddle■ SADM

Solar Array Drive Mechanism

DM

Deployment Monitor■ CAM-CNT

Monitor Camera-Controller■ CAM-H

Monitor Camera-HeadTCS

Thermal Control System

RCS

Reaction Control Subsystem■ THR

4N-Thruster■ TNK

Fuel Tank■ LV

Latching Valve■ FDVFill and Drain Valve■ PFD

Propellant Fill and Drain Valve

Direct Transmission Subsystem■ GFD

Gass Fill and Drain Valve

X-band Antenna■ FLT

Filter■ PT

Pressure Transducer

THR-1B■ XFILX-band Filter

THR-2B■ XHYB

X-band Hybrid

THR-3B■ XSSPAX-band Solid State Power Amplifier

THR-4B■ XMODX-band Modulator■ XATT

X-band Attenuater

LV-1

Mission Data Processing Subsystem
Mission Data Processor

Earth Sensor Electronics■ SHYBPFD

CAM-H1

Data Relay and Communication Antenna

Coarse Sun Sensor

S-band Low Pass Filter

FDV-2■ DRC-ANT■ ESE■ SLPF

THR-4AK-band Filter■ CSS

S-band Diplexer

FLT

K-band Traveling Wave Tube Amplifier■ KFIL

Inertial Reference Unit

■ SDIP

THR-3ATNKBoot signal（to AOCE ）Launch Lock
Release Signal

K-band Hybrid■ KTWTA

Attitude & Orbit Control Electronics

Multi-mode integrated Transponder

LV-1■ KHYB■ IRU

THR-2A

50V PWRto Bus Equipment

PDCU-2

K-band Modulator■ AOCE■ MTP

PT

Antenna Pointing Electronics■ KMOD■ MDP

Remote Interface Module

FDV-1

Data Relay and Communication

■ APE

MDHS

Command & Data Management System

RC S

GFD

14

AOCS

■ CDM S

SANT-1INT

SADM-1SAP Potentiometer（to AOCE ）Space based AIS Experiment -2■ RIM

SANT-4

SHYB-1DM Observation Data
Time Marker, ClockPCU

SA Ｐ-2SPAISE- 2

SANT-2

THR-1ASA Ｐ-2Compact Infrared Camera

SANT-3MDP①

SAP Drive Signal（fm UDE ）

CIRC

TT&C

SLPF-A

CDMS-A

Thermistor

SPS

SOI FPGA In-orbit Experiment

TT&C①Low Speed Line – Record & Reproduced Data
②High Speed Line – Record Data

DM Observation Data

Temperature
sensor

SOFI EDATA

Primary PWR（50V fm PDCU-1 ）AOCS

Phased Array type L-band Synthetic Aperture Radar

Observation Data

SOFIE

SOFIE

SAR 内部搭載機器

MDHS

PALSAR- 2

DRC

STR

Structure

IN T

Integration Hardware■ PDCUPower Distribution Control Unit

15

Satellite operation after separation from H-IIA
The DAICHI-2 will be launched from the Tanegashima Space Center by the H-IIA Launch Vehicle. It will beseparated from the H-IIA about 16 minutes after liftoff to be injected into orbit at an altitude of 628
kilometers with an inclination of 97.9 degrees. The DAICHI-2 will perform a series of post-separation
operations automatically, namely a rate damping to stop its rotation (angular velocity) caused by theseparation, solar array paddle deployment, and sun acquisition. After that, it will acquire the Earth,establish its stable attitude to face to the Earth (three-axis stabilization in the Earth orientation mode), thentrack the sun to face solar array paddles toward the sun all the time. The onboard equipment will then beunder function verification following the deployment of the L-band SAR antenna and direct transmission
antennas, while correcting orbit to the observation orbit.

Fine normal mode
As the L-band SAR antenna and direct transmission
antennas are deployed, the DAICHI-2 shifts to the finenormal mode (FNM) following a command sent from theground. In the FNM, the attitude is controlled using a wheel
to face toward the Earth. After moving to the FNM, onboard
equipment is functionally verified and the DAICHI-2 orbit
is corrected to start observation operations.

Fine normal mode

Satellite separation to rate damping
After being separated from the launch vehicle, theDAICHI-2 automatically shifts to the Rate Damping
Mode (RDM). In this mode, the satellite stops its
rotation (angular velocity) caused by separation fromthe launch vehicle to be stable by jetting the thrusters
installed onto the satellite.

Satellite
separation

Direct transmission
antenna deployment

Solar array paddle deployment tosun acquisition
Upon completion of the rate damping, the solar
array paddle is automatically deployed to move tothe sun acquisition mode (SAM). In this mode, thesatellite is rotating around the sun's orientation
axis (the direct line connecting the sun and thesatellite) while facing the solar array paddle’s cellside (the side which solar batteries are lined on)
toward the direction of the sun.

Main Event ScheduleRate
damping

PALSAR-2
deployment

Earth acquisition
mode

Solar arraypaddledeployment

Time from liftoff

Satellite Event
Rate Damping
Approx. 30 min
Solar Array Paddle deployment
Start the Sun Acquisition Mode (SAM)
Start the Earth Acquisition Mode (EAM)
Approx. 8-9 hourandfollowed by the Earth Pointing Mode (EAM)16
16

Approx. 13 hour

SAR Antenna deployment #1(package deployment)

Approx. 24 hour

SAR Antenna deployment #2(first wing deployment)

Approx. 34 hour

SAR Antenna deployment #3(first wing deployment)

Approx. 37 hour

Direct Transmission Antenna
PY deployment

Approx. 47 hour

Direct Transmission Antenna
MY deployment

Approx. 51 hourStart the Fine Normal Mode

Sun
acquisition

Q: What is the advantage of the revisit time of 14 days？
The DAICHI-2 flies back to the same location every 14 days bycircling around the Earth in the south-north direction for 97. 3
minutes per cycle while gradually shifting its orbit to west andeast directions. The revisit time of the DAICHI-2 is about a one
third of the DAICHI’s 46 days, hence it can answer an
emergency call for disaster monitoring much quicker.

L-band SAR antenna/direct transmission antenna deployment
The stowed L-band SAR antenna (PALSAR-2) is deployed after the DAICHI-2
shifts its mode to the EPA. The deployment of the PALSAR-2 is in three stages, 1)
a package deployment to release the stowed panels as a whole from the satellite
main body, 2) the first wing deployment, and 3) the second wing deployment. The
deployment is performed while the sun shines on the satellite, and each stage
takes less than five minutes. Following the PALSAR-2 deployment, the directtransmission antennas on both sides on the satellite are deployed.

ALOS-2 orbit
Earth acquisition mode
After the sun is successfully acquired, the DAICH-2
progresses to the Earth acquisition mode (EAM)
following a command from the ground to acquire theEarth, then automatically shifts to the Earth pointing
mode (EPM.) In the EPM, the satellite controls its
attitude to face its L-band SAR antenna side to the
Earth while it starts sun acquisition to always direct
its solar array paddles toward the sun.

The DAICHI-2 will utilize the sunsynchronous sub-recurrent orbit, which makes
a north-south circle around the Earth. In thisorbit, the positional relationship between theorbit plane of a satellite and the sun are
constant (sun-synchronous) while a satellite
flies over the same location on the Earth every
recurrent period of days (subrecurrent.) The
time of passing the equator is also constant inthis orbit, thus the satellite flies over one
location at around the same time of day. The“local sun time” is the time when a satellite Orbit
passes over the equator, and it is 12:00 (a.m. planeand p.m.) +/- 15 minutes for the DAICHI-2.

North Pole

「だいち2号」軌道概要 Alos-2 Orbit

Directionof sunSouth Pole

Orbit

軌道種類

太陽同期準回帰軌道

軌道高度

628km

軌道傾斜角

97.9deg

降交点通過地方時

12:00 ± 15mi n

回帰日数

14 日

軌道周期

97.3 分17
17

Ground system and observation operation
The ground system for the DAICHI-2 consists of the following four major systems: “Spacecraft Control andMission Operation System,” “Earth Intelligence Collection and Sharing System”, “Tracking Network System ,”and “Data Analysis System.” They are at the Tsukuba Space Center.

1 Receiving requests, compiling observation requests

コマンド
Command

Receiving requests from users at the “Earth Intelligence Collection and Sharing System ,” and compiling observation requests.

コマンド
Command[ALOS-2]

Commandtelemetry / Mission data

Command[Data Relay Satellite]
Command2

Operation planning

3

Satellite control and tracking operation

Planning observations according to requests by the “Spacecraft Control andMission Operation System.”

telemetry

telemetry / Mission data

Ground network systemtelemetry / Mission data

telemetry / Mission data

Extension Network Station

Svalvard Station

Space Network Station

Performing telemetry and command operations and ground station operations
using the “Tracking Network System .”4 Observations

Data acquisition through satellite observations.

Masuda station

5 Observation data reception

Compiling various products by the “Earth Intelligence Collectionand Sharing System ”

7 Observation data delivery

Katsuura station

Range data

Receiving and recording observation data by the“Mission data Network Infrastructure for Tracking network.”

6 Observation data processing

Okinawa station

Katsuura S/X station Hatoyama X station

CommandCommandCommandtelemetry

telemetry

telemetry

Command

GPS data
Orbit Data

telemetry

Integrated Network Interface for Tracking network System

Spacecraft Control and Mission
Operation System

Earth Intelligence Collection andSharing System

A system for compiling an observation plan; generating
a command, monitoring and controlling satellite conditions;transmitting observation data of the mission instrument
and processing them with the level 0 process; and processing
emergency observation data with the level 1 process.

A system for users to apply observation data; user interface
for observation requests, product orders, search and provisions; observation data storage and management; andvarious processes for compiling products.

18

Product

Product

Observation Request
Observation & Processing plan
Product(L0,L1,L3)
Observation parameter

Data reception request

Command

Orbit Data

telemetry

Mission data

Spacecraft Control and Mission Operation System

Observation Request

Data Analysis System
A system for calibration and verification of SAR observation
data; constructing and evaluating sensor models; developing
and evaluating higher-order processing software.

Data provision and utilization
during disasters
The approximate observation time frame of the DAICHI-2
over Japan is at 12:00 a.m. and 12:00 p.m. (with a marginof about one hour before and after the top of the hour.)
The DAICHI-2 can cope with an emergency observation
request an hour prior to the observation time at the latest,

Earth Intelligence Collectionand Sharing System

Mission data

Mission data Network Infrastructure for Tracking network
Trajectory Information

A system for compiling the network operation plan forsatellite control operations; orbit determination; monitoring
and controlling ground stations; monitoring and controlling
ground stations for observation data receiving operations.

Hatoyama station

Unified Flight Dynamics System

Providing products to users from the “Earth Intelligence Collectionand Sharing System .”Tracking Network System

Tsukuba station

thus, if a disaster occurs around 11:00 o’clock, the satellite
can observe the disaster-stricken area in an hour in thebest-case scenario. Then, one hour after the observation,
the data (with standard process) can be provided. In twohours after the observation, a quick analyzed product canbe compiled and sent to the damaged area. In the case ofa disaster within Japan, data can be provided within 12hours.

Data Analysis System

User agencies

Overseas space agencies

Q: How will the DAICHI-2 operations start after the launch, and around when will theDAICHI-2 data be available？

The DAICHI-2 will first move into the fine normal mode (FNM, which is the regular operation mode) after launch,then, in the FNM, it will take about three months for initial functional verification of the satellite bus and the
PALSAR-2. After that, it requires three more months of the initial calibration and verification period to calibrate
and verify the PALSAR-2. The data provision to users will then begin about six months after launch.
19

ALOS-2 Project Team
Satellite Applications Mission Directorate I
Japan Aerospace Exploration Agency
Tsukuba Space Center
2-1-1, Sengen, Tsukuba, Ibaraki, 305-8505 Japan
http://global.jaxa.jp/
DAICHI-2 special site
http://global.jaxa.jp/projects/sat/alos2/index.html
April 2014