ICSO 2010
International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

DEVELOPMENT OF THE COMPACT INFRARED CAMERA (CIRC)
FOR EARTH OBSERVATION
Masatomo Harada1, Haruyoshi Katayama1, Masataka Naitoh1, Masahiro Suganuma1,
Ryoko Nakamura1, Yoshio Tange1, Takao Sato2
1
Earth Observation Research Center, Japan Aerospace Exploration Agency, Japan.
2-1-1, Sengen, Tsukuba, Ibaraki, 305-8505, Japan.
2
Planetary Atmosphere Physics Laboratory, Tohoku University, Japan.
6-3, Aramaki-aza-Aoba, Aoba-ku, Sendai, Miyagi 980-8578, Japan
E-mail: harada.masatomo@jaxa.jp
ABSTRACTThe compact infrared camera (CIRC) is a technology demonstration instrument that Japanese Aerospace
Exploration Agency (JAXA) is developing by using commercial-off-the-shelf (COTS) technology in recentyears. CIRC is an infrared camera equipped with an uncooled infrared array detector (microbolometer). CIRC
will be utilized for various technology demonstrations. This paper introduces the current development status ofCIRC and the initial results of characteristics of the CIRC ground test model (Engineering Model; EM) that has
been studied with laboratory experiments.
Keywords: remote sensing, thermal infrared imaging, uncooled infrared detector, microbolometer.
Ⅰ. INTRODUCTION
Microbolometers are widely used in commercial and military 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 for Earth observation [1]. CIRC will be carried as atechnology demonstration payload for the Advanced Land Observing Satellite-2 (ALOS-2), which is asuccessor satellite to the Advanced Land Observing Satellite (ALOS). The main purpose of the technology
demonstration is to demonstrate the potential of microbolometers in thermal infrared imaging from space. The
second purpose of the CIRC project is the low-cost and early development of the thermal infrared imager.
This paper introduces the details of CIRC, the current development status of CIRC, and the initial results ofcharacteristics of the CIRC EM that has been studied with laboratory experiments to establish a prelaunchcalibration method.
Ⅱ. ADVANCED LAND OBSERVING SATELLITE-2 (ALOS-2)
The Advanced Land Observing Satellite-2 (ALOS-2) [2] is a follow-on mission from ALOS. ALOS has been
contributing to cartography, regional observation, disaster monitoring, and resource surveys, since its launch in2006. 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) Disastermonitoring of damage areas, both in considerable detail, and when these areas may be large 2) Continuous
updating of data archives related to national land and infrastructure information 3) Effective monitoring ofcultivated areas 4) Global monitoring of tropical rain forests to identify carbon sinks.
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. CIRC will be carried as a technology
demonstration instrument onboard ALOS-2. Fig.1 shows the mounting location of CIRC. CIRC will takeimages of the target area during the SAR pointing to the right at its off-nadir angle of 30 degrees.
Table 2 shows the mass budget of the ALOS-2 mission instruments. In comparison with the mass of the SAR
instruments, that of the CIRC sensor system is much lighter. This demonstrates one of the advantages of CIRC
when employing CIRC with other mission instruments of satellites.

ICSO 2010International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

Fig. 1. Schematic view of ALOS-2 and the mounting location of CIRC
Table 1.Baseline specifications of ALOS-2Parameter
Size
MassBus power
Communication
Orbit

Specification
9.9m x 16.5m x 3.4m
<2000kg>5200W<800Mbps
628km

Table 2.Mass budget of the ALOS-2 mission instruments
Unit
SAR-ANTSAR-ELU
CIRC

Unit Mass (kg)
547.7
109.1
2.6

Ⅲ. MISSION AND SPECIFICATION OF CIRC
The main mission of CIRC is a technology demonstration of a wildfire detection using the microbolometer.
Wildfires are one of the major and chronic disasters affecting many countries in Asia-Pacific region, and somesuggestions are that this will get worse with global warming and climate change. In Sentinel Asia project toshare the disaster information in near real-time across the Asia-Pacific region, the wildfire detection is chosen as
one of the important activities. It is possible to increase observational frequency of wildfires if CIRCs arecarried on various satellites by taking advantages of small size, light weight and low power consumption. The
other CIRC mission targets are volcanoes or heat island phenomena in a city. The observations of these targets
with thermal infrared imager will become a useful tool to monitor volcanoes or to solve the heat island problem.
Ⅳ.HARDWARE DESIGN AND BASELINE SPECIFICATIONS OF CIRC
CIRC is based on a commercial infrared camera developed by Mitsubishi Electric Corporation (MELCO). In
order to apply it for a space application, however, we add some modifications to the hardware design.
Baseline specifications of CIRC are shown in Table 3. We set the baseline specifications to meet requirements
for the wildfire detection. The detector is a large format (640 × 480) to obtain a wide field of view. The spatial
resolution is an important factor for the wildfire detection. The baseline specification of the spatial resolution is
200 m from the altitude of 600 km.
Fig. 2 shows a system block diagram of CIRC. In order to reduce the size, weight, and cost, we minimized thefunction of CIRC. The optics unit of CIRC is f/1.2 optics. We employ an athermal optics to keep the optical
performance in a wide range of temperature. This will be an advantage of CIRC because we don’t need an
active thermal control or a focus mechanism to the optics.

ICSO 2010
International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

Table 3.Baseline specifications of CIRC
Parameter
Size
MassDetector
Wavelength
Number of pixels
Spacial resolution
Field of View
Exposure
Dynamic range
NEdTSpecification< 180mm x 100mm x 200mm< 3kg
Uncooled infrared detector
8 - 12 μm
640 × 480
< 200 m @ 600 km (< 0.33 mrad)
12°× 9° (128 ×96 km)
33 ms
180 K - 400 K
0.2 K@300 K

Fig. 2. System block diagram of the CIRC.

Fig. 3. Optical design of CIRCICSO 2010
International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

The optics of the CIRC is a f/1.2 refractive optics. A focal length of the optics is 78 mm. The temperature of theCIRC is changed on orbit. The temperature change of the optics will cause a defocus because refractive indicesof lens materials are highly dependent on temperature. In order to compensate for this defocus, we have toemploy a focus mechanism or a heater to keep the optics’ temperature constant. However, such mechanisms
increase sensor resources. An athermal optics can compensate for the defocus due to the temperature change
without such mechanisms. CIRC can operate in a temperature range from -15℃ to 50℃ while maintaining its
performance. Fig. 3 shows the optical design of the CIRC. The athermal optics of the CIRC compensates for thedefocus by a combination of different lens materials and diffractive lenses. The optics of the CIRC uses agermanium and a chalcogenide glass (GASIR) [3].
Ⅴ. LABORATORY EXPERIMENT OF THE CIRC ENGINEERING MODELIn this section, we report the initial result of the laboratory experiment of the CIRC EM. The CIRC EM isshown in Fig.4.

Fig.4.Picture of the CIRC EM
A. Measurement setup
In the laboratory experiment at JAXA Tsukuba Space center, we measured the Modulation Transfer Function(MTF), which is one of the important image capture performance parameters of the optical sensor systems, ofthe CIRC EM in both atmosphere and vacuum to evaluate the image capture performance of the sensor system.
The schematic diagram of the experimental setup is shown in Fig.5 and the configuration of the measurement
setup is shown in Fig.6.
CIRC is placed inside of the vacuum chamber in the laboratory and surrounded by a shroud which controls theambient temperature of CIRC by using a heater and a cooler. The infrared-ray is emitted by the black body (CISystems SR800) and passes through the 4-bar targets (shown in Fig.7) mounted inside of the reflective
collimator system (CI Systems ILET-5-1.1). The intervals of the slits of the 4-bar targets is equivalent to 1-, 1/2-,
1/4- and 1/8-nyquist frequency. The collimated infrared-ray pass through a germanium window, which ismounted on to the side of the vacuum chamber and transmits the infrared-ray from outside of the vacuumchamber, and is detected by CIRC.

Fig.5. Schematic diagram of the experimental setup

ICSO 2010
International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

Fig.6. Configuration of the measurement setup

AT-direction

CT-direction
Fig.7. (left) 4-bar targets mounted on the collimator system. (right) Image of the 4-bar target taken with CIRC.
B. results
The MTF of CIRC corresponding to each nyquist frequency is measured for both the Along-Track (AT) andCross-Track (CT) direction at the center of the field of view. Fig.8 (a) and Fig.8 (b) show the results of the MTF
measurement for the AT and CT direction, respectively. The color of each line corresponds to the conditions of
the measurements in Table 4. The ambient temperature of CIRC was changed from room temperature to 50℃.
The difference in each measurement is large in the AT direction. One of the reasons for the difference is theaccuracy of the alignment of the measurement. In the experiment setup, we can align the target position for theCT direction using the rotation stage under CIRC (see Fig. 6). However, there is no alignment mechanism forthe AT direction.
As an initial result of the measurements, we confirmed the athermal characteristic of the lens of CIRC as wedesigned, though we need some improvement of the alignment for the MTF measurement in the AT direction.

ICSO 2010
International Conference on Space Optics

Rhodes, Greece
4 - 8 October 2010

Fig.8. MTF of CIRC for the AT direction (a) and the CT direction (b).
Table 4. Conditions of the measurements
color of the line
bluegreenorangeredmeasurement condition-5vacuum (P=10 Torr), 40℃-5vacuum (P=10 Torr), 50℃-5vacuum (P=10 Torr), room temperature (~20℃)
atmosphere, room temperature (~20℃)

Ⅵ. SUMMARY
We measured the MTF characteristic of CIRC and confirmed the athermal characteristics of the lens of CIRC as
it was designed. In a future experiment, we will measure the radiometric performance of the CIRC EM.
Through these experiments, we establish a prelaunch calibration method for the CIRC Proto-Flight Model(PFM) onboard ALOS-2.
REFERENCES[1] H. Katayama, M. Naitoh, M. Suganuma, M. Harada, Y. Okamura, Y. Tange, and K. Nakau,“Development of the Compact Infrared Camera (CIRC) for Wildfire Detection”, Proc. SPIE, vol 7458, pp.
745806-1-745806-8, August 2009[2] S. Suzuki, Y. Osawa, Y. Hatooka, Y. Kankaku, and T. Watanabe, “Overview of Japan's Advanced Land
Observing Satellite-2 Mission”, Proc. SPIE, vol 7474, pp. 74740Q-1-10, August 2009[3] M. Naitoh , H. Katayama, M. Harada, M. Suganuma, Y. Okamura, Y. Tange and Kenny Rogers andYann Guimond, “The Radiation Tolerance of Chalcogenide Glasses”, Proc. SPIE, Vol. 7660, 766028 ;doi:10.1117/12.850146, April 2010