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IEICE Technical Report

地上検証用小型赤外カメラ(CIRC)を用いた校正試験結果報告
中村 良子†

片山 晴善†

内藤 聖貴†

加藤 恵理† 菅沼 正洋†

中右 浩二†

原田 昌朋†
佐藤 亮太††宇宙航空研究開発機構 〒305-8505 茨城県つくば市千現 2-1-1 筑波宇宙センター
E-mail: nakamura.ryoko@jaxa.jp
小型赤外カメラ(CIRC)は非冷却赤外検出器(マイクロボロメータ)を用いた技術実証センサでああらましる。非冷却式を採用することで小型軽量・低価格・低消費電力を実現している。CIRC の主要ミッションは、
森林火災検知である。森林火災はアジア太平洋諸国で頻発する主要な災害であり、衛星による初期検知が望まれている。我々は CIRC の打ち上げ前地上校正試験手順を確立するため、地上検証用モデルを製作した。これまでに検証用モデルを用いて結像性能を測り、アサーマル性を確認している。本公演では CIRC の開発状況とともに、詳細な校正試験結果について報告する。
キーワード

リモートセンシング、熱赤外イメージャー、非冷却検出器、森林火災

Calibration Results of the Compact Infrared Camera (CIRC)
Ground Test Model
Ryoko NAKAMURA† Haruyoshi KATAYAMA† Masataka NAITOH† Masatomo HARADA†
Eri KATO† Masahiro SUGANUMA† Koji NAKAU† and Ryota SATO††1)Japan Aerospace Exploration Agency, 2-1-1 Sengen, Tsukuba, Ibaraki, 305-8505, Japan
E-mail: nakamura.ryoko@jaxa.jp
Abstract

The compact infrared camera (CIRC) is a technology demonstration instrument equipped with an uncooled

infrared array detector (microbolometer). Eliminating the cooling system reduces the size, cost, and electrical power ofthe sensor. The main mission of the CIRC is the technology demonstration of the wildfire detection. Wildfires are major
and chronic disasters affecting many countries in the Asia-Pacific region. The CIRC ground test model was made toestablish a prelaunch calibration method. We have measured imaging quality in a vacuum environment. We also
confirmed the athermal characteristics of CIRC. In this paper, we show the current status of the CIRC development, andthe calibration results of the CIRC ground test model.
Keywordremote sensing, thermal infrared imaging, uncooled infrared detector, wildfire

1. Introductions

for Earth observation 1) . In order to demonstrate theMicrobolometers are widely used in commercial andmilitary
applications,
such
as
night
vision.
Microbolometers have the advantage of not requiring a
cooling mechanism, such as a mechanical cooler.
Eliminating the detector cooling system reduces the size,
cost, and electrical power of the sensor. Although thesensitivity of microbolometers is lower than that of
HgCdTe-based photonic infrared detectors, the advantage
of not requiring a cooling mechanism is suitable for small
satellites or resource-limited sensor systems.
JAXA has researched the application of microbolometers

potential of microbolometers to thermal infrared imaging
from space, the Compact Infrared Camera (CIRC) isdeveloped as a technology demonstration payload of theAdvanced Land Observing Satellite-2 (ALOS-2), andCALorimetric Electron Telescope (CALET) which will be
attached to the Japanese Experiment Module (JEM -EF) of
the International Space Station (ISS).
In this paper, we show the current development status of
CIRC. In §2, we briefly describe ALOS-2 and CALET.

This article is a technical report without peer review, and its polished and/or extended version may be published elsewhere.
Copyright ©20●●

by IEICEThe mission and the details of the CIRC are shown in §3

2.2 CALETand §4, respectively. In §5, we show the feasibility study

CALET 3 ) is an international program for the ISS thatof wildfire detection with CIRC spatial resolution. In §6,will search for signatures of Dark Mater and provide t heinitial calibration results of the CIRC ground test model

highest energy direct measurements of the cosmic raythat has been studied with laboratory experiments toelectron spectrum in order to observe discrete sources of

establish

high energy particle acceleration in our local region of thea prelaunch calibration

methodis shown.

Discussion and Summary are shown in §7.

Galaxy. CALET will address many of the outstanding
questions including (1) the nature of the sources of highenergy particles and photons, through the high energy

2. ALOS-2 and CALET
2.1 ALOS-2

spectrum, (2) the details of particle transportation in the2)

ALOS-2 is a follow-on mission from ALOS, which has
been contributing to cartography, regional observation,
disaster monitoring, and resource surveys, since its launch
in 2006. JAXA is conducting research and development
activities to improve wide and high -resolution observation
technologies developed for ALOS in order to further
fulfill social needs. These social needs include: 1)
Disaster monitoring of damage areas, both in considerable
detail, and when these areas may be large 2) Continuous
updating of data archives related to national land andinfrastructure information 3) Effective monitoring ofcultivated areas 4) Global monitoring of tropical rain
forests to identify carbon sinks. Alos -2 will be launched in
2013.
ALOS-2 succeeds the L-band Synthetic Aperture Radar(SAR) observation of ALOS PALSAR with enhanced
capabilities. Table 1 shows the baseline specifications of
ALOS-2. The mounting location of CIRC is shown infigure 1. Basically, CIRC will take images of the target
area during the SAR pointing to the right at its off -nadir
angle of 30 degrees.

Galaxy, and (3) signatures of dark matter, in either thehigh energy electrons or gamma ray spectrum. It will also
be capable of monitoring gamma ray transients and solar
modulation. CALET will be launched in 2013.
The baseline specifications of CALET are shown intable 2. CIRC will be mounted on the bottom of CALET,
shown in figure 2.

Fig. 2 Sc he mat ic view o f C AL ET and the mo unt ing locat io n o f CIRC

Table. 2 baseline specifications of CALET

Parameter
Mass
Bus power
Communication
Orbit

Specification< 500 kg
< 500W< 300kbps
407 km (nominal)

3. Mission of CIRC
The

main

demonstration

missionofofwildfire

a

CIRC

is

a

detectiontechnology
using

the

microbolometer. Wildfires are one of the major andchronic disasters affecting many countries in Asia-PacificFig. 1 Sc he matic view o f ALO S -2 a nd the mo unting locatio n o f CIRC

region, and some suggestions are that this will get worsewith global warming and climate change. In Sentine l Asia

Table 1. Baseline specifications of ALOS-2

Parameter
Size
Mass
Bus power
Communication
Orbit

Specification
9.9m x 16.5m x 3.4m
< 2000 kg> 5200W< 800Mbps
628 kmproject to share the disaster information in near real -timeacross the Asia-Pacific region, the wildfire detection ischosen as one of the important activities. It is possible toincrease observational frequency of wildfires i f CIRCs arecarried on various satellites by taking advantages of small
size, light weight and low p ower consumption. The otherCIRC mission targets are volcanoes or heat island

wildfire data including forest fires, tundra fires, and peat

phenomena in a city. The observations of these targets

fires.

with thermal infrared imager will become a use ful tool tomonitor volcanoes or to solve the heat island problem.

Table 4. Analyzed wildfire data of the ASTER/TIR

4. Baseline specifications of the CIRC
Baseline specifications of the CIRC are shown in Table

Location

Date

Type

Alaska2004-07-17

Forest fire

Alaska2007-09-08

Tundra fire

3. We set the baseline specification s to meet requirements

California

2003-10-26

Forest fire

for the wildfire detection. The detect or is a large format

Indonesia

2006-10-12

Peat fire(640 × 480) to obtain a wide field of view. The spatial.

resolution is an important factor for the wildfire detection.

In order to investigate the difference of the wildfire

The spatial resolution is 200 m from the altitude of 600 km

detectability depending on the spatial resolution, we made(ALOS-2), and 130 m from the altitude of 400 km

simulated images of which spatial resolutions are 180m

(CALET), respectively. Eliminating the cooling systemand 270m from the original ASTER/TIR image.

reduces the size (110mm x 180mm x 230mm) and

Fig. 3 show simulated images of the forest fi re inelectrical power (<20 W).

California and the peat fire in Indonesia. We searched theimage for regions of anomalously high brightness to detect

Table 3.

Baseline specifications of the CIRC

wildfires. In general, the wildfire detection using satellite

Parameter

Specification

data uses short or medium infrared images in addition toSize

110mm x 180mm x 230mm

the TIR image. However, by optimizing a threshold level,

Mass

~3kg

we can detect a wildfire only from the thermal infrared

Detector

Uncooled infrared detector

image. Hotspots are detected by contextual threshold

Wavelength

8 - 12 μm

method. A pixel is defined as hotspot if the anomaly in

Number of pixels

640 × 48011m brightness is higher than 3 , where Special resolution< 200 m @ 600 km (ALOS-2)

deviation of brightness in pixels within 1km radius.

< 130m @ 400km (CALET)

In order to check the detectability, we used the(< 0.33 mrad)

MODerate-resolution Imaging Spectroradiometerstandard

Field of View

12°× 9°(MODIS) Thermal Anomalies/Fire products (MOD14v4).

Exposure

33 ms

MOD14 algorithm detects fire locations using 4 m andDynamic range

180 K - 400 K

11m brightness temperatures with the spatial resolution

NEdT

0.2 K@300 K

of 1km.

Power

< 20W

From this simulation, we found that the detectability offorest fire or tundra fire using thermal infrared images ofwhich spatial resolution of 180m is comparable to that of

5. Feasibility study of wildfire detection
For feasibility study of the wildfire detection and otherpossible application, we used Advanced Spaceborne
Thermal Emission and Reflection Radiometer (ASTER) /thermal infrared (TIR)
advantage

over

4)

data. ASTER has a significant

previous

datasets

becauseofthecombination of high spatial resolutions (15 –90 m) andenhanced multispectral capabilities, particularly in the
TIR. The spatial resolution and swath of the ASTER/TIR
are 90m and 60km,

respectively.

The 90m spatial

resolution in the thermal infrared band is useful tosimulate various case of a spatial resolution.
In order to check the detectability of wildfire, we
obtained the wildfire data taken by ASTER. Table 4 shows
the list of wildfire data we checked. These are typical

MOD14 algorithm. On the other hand, the detection of thepeat fire needs higher spatial resolution. Because theburning temperature of peat fires is lower than that ofother wildfires.
Although further improvements of the detection
algorithm are needed especially fo r peat fires, we find that
200m spatial resolution is almost appropriate for thewildfire detection. The detectability of wildfires shouldhave a dependency to the burning area. In addition to that,
there is a possibility to detect a “false alarm” wildfire in acity due to various heat sources like heat power plants. So
we are planning to apply this algorithm to other various
dataset and check the detectability.

Fig. 3. ASTER/TIR images of forest fire in California on October 26, 2003 (left) and peat f ire in Indonesia on October 12,
2006(right). The spatial resolutions are 90m (top), 180m (middle), and 270m (bottom). Red filled squares are the results ofwildfire detection using thermal infrared data only. Yellow open squares are the results using MOD14 .

6. Calibration of the CIRC ground test model

chamber, and is detected by CIRC.

In this section, we present the calibration results of the
CIRC ground test model. Figure 4 shows the picture of the
CIRC ground test model.

200mm
mm

Fig. 4 Picture of the CIRC ground test model

In the laboratory experiment at JAXA Tsukuba Space
center, we measured the Modulation Transfer Function(MTF) of the CIRC ground test model in a v acuum toevaluate the image capture performance of the sensor
system.

6.1 Measurement setup
The schematic diagram of the experimental setup is
shown in Fig. 5.

Fig. 6 (top) 4-bar target mounted on the collimator system.
1/6-, 1/4-, 1/2-, 1-nyquist frequency from the left. (bottom)
image of the 4-bar target taken with CIRC

6.2 Data
We have measured MTF under a vacuum environment.
The detector positions of measurements are at the center,±5 degrees in the Cross-Track (CT) direction, and ±3.5
degrees in the Along-Track (AT) direction, shown infigure 7. In order to measure the MTF at ±3.5 degrees,
the CIRC is able to be replaced to the side panel of the
shroud, because only one rotating stage is set in thevacuum chamber (see figure 5). MTF for CT/ AT direction
were measured by rotating the 4-bar target. The
temperatures of the shroud are set to -10 to 50 degrees C.

Fig. 5 Schematic diagram of the experimental setup

CIRC is placed inside of the vacuum chamber in thelaboratory and surrounded by a shroud which controls theambient temperature of CIRC by using a heater and acooler. The pressure in the vacuum chamber is ~ 10 - 5 Torrduring the experiment. The infrared-ray is emitted by theblack body (CI Systems SR800) and passes through the
4-bar targets (shown in Fig.6) mounted inside of thereflective collimator system (CI Systems ILET-5-1.1). Theintervals of the slits of the 4 -bar targets are equivalent to1-, 1/2-, 1/4- and 1/6-nyquist frequency. The collimatedinfrared-ray pass through a germanium window, which ismounted on to the side of the vacuum chamber andtransmits the infrared-ray from outside of the vacuum

Fig. 7 The positions of MTF measurement

6.3 Procedure of analysis
We have taken 4-bar target image for each frequency. By
using the image, we obtained MTF. MTF is defined asshown below;
MTF = ( V ma x +V min ) / (V ma x － V min ) ,where V ma x , V min are peak and a bottom of digital numberof 4-bar image. (see Fig. 8)

Fig. 8 (Top) Image of 4 -bar target at the detector center.
(Bottom) DN of 4 -bar target. We correct the offset (red line),and calculate MTF with Vmax and Vmin show n in blue line.

6.4 Result
We have measured MTF for CT/AT direction at 5detector positions. Main results are shown in figure 9.
CT-direction at the detector position has same trend withseveral temperature. Athermal characteristics at nyquist
frequency measurement are shown in Fig. 9 middle(CT)and bottom(AT). CT direction MTF at the detector centerand ±5 degrees are constant regardless of temperatures.
CT at ±3.5 degrees and AT direction MTF has gradient,lower in low temperature environment.

7. Discussion and Conclusion
Results of MTF measurement are summarized asfollows;
 MTF is lower at low temperature environment
 The variation of AT-direction MTF is large
Possible reason for small MTF at low temperature caseis due to the gap of focal length. Alt hough an alignment offocal length of CIRC ground test model was adjusted in
atmosphere, focal length changes due to the variation ofreflective index in the vacuum environment. The variationof AT-direction MTF is also due to the misalignment offocal length. We are planning to adjust focal length of
CIRC PFM for vacuum environment.
We measured the MTF characteristic of CIRC, which isone of the important image capture performanceparameters of the optical sensor systems, and confirmed
the athermal characteristics of the CIRC. We input theresults to development process of CIRC PFM. In a future
experiment, we will measure the radiometric performanceof the CIRC ground test model. Through theseexperiments, we establish a prelaunch calibration method

Fig. 9 (Top) Results of CT-direction MTF measurement at thedetector center. In the room temperature (black), lowtemperature (blue) and high temperature ( magenta or red)environment results are shown. (Middle, Bottom) Athermal
characteristics at nyquist frequency at CT/AT-direction.
Difference in color shows the detecto r position; center is inblack, +5 degrees is in red, -5 degrees is in blue, +3.5 degrees isin cyan, and -3.5 degrees is in magenta, respectively.

for the CIRC PFM onboard ALOS -2 and CALET.

References[1]

H. Katayama, M. Naitoh, M. Suganuma, M. Harada, Y.
Okamura, Y. Tange, and K. Nakau, : Development of theCompact Infrared Camera (CIRC) for Wildfire Detection,
Proc. SPIE, vol 7458, 2009, pp. 745806-1-745806-8[2]

S. Suzuki, Y. Osawa, Y. Hatoo ka, Y. Kankaku, and T.
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S. Torii, et al, : CALET mission on ISS, Proc. SPIE, vol7021, 2008, pp. 702114-1 -11[4] Ohmae, H., Maekawa, T., Aoki, Y., and Kitamura, S.,"Preflight test results of the ASTER TIR flight model,”Proc.