Trans. JSASS Aerospace Tech. Japan
Vol. 8, No. ists27, pp. Tn_1-Tn_4, 2010

TopicsDevelopment of the Compact Infrared Camera (CIRC) for Earth Observation
By Haruyoshi KATAYAMA1), Masataka NAITOH1), Masahiro SUGANUMA1), Masatomo HARADA1),
Yoshihiko OKAMURA1), Koji NAKAU1) and Yoshio TANGE1)
1)

Earth Observation Research Center, Japan Aerospace Exploration Agency, Tsukuba, Japan(Received August 18th, 2009)
The Compact Infrared Camera (CIRC) is a technology demonstration payload of the Small Demonstration-Satellite
type-2 (SDS-2). The CIRC is an infrared camera equipped with an uncooled infrared array detector (microbolometer). The
main mission of the CIRC is to demonstrate the technology of wildfire detection using a microbolometer. The CIRC is asmall, lightweight, and low-cost thermal infrared imager for space applications. We employ athermal optics and shutter-lessimage correction to reduce the size, weight, and cost of the CIRC. In this paper, we show the details of the design of the
CIRC.
Key Words: Remote Sensing, Thermal Infrared Imaging, Wildfire, Uncooled Infrared Detector

1.

Introduction

SDS-1 are Multi-mode integrated Transponder (MTP), Space
Wire demonstration Module (SWIM), Advanced Microprocessing In-orbit experiment equipment (AMI), and so on.
The SDS-2 is scheduled to be launched as a piggybacksatellite in 2013 or later. Table 1 shows a baseline
specification of the SDS-2. The specifications of the SDS-2
are similar to those of the SDS-1. The attitude control of thesatellite is based on a three-axis stabilized attitude control.
The SDS-2 is a sun-pointing attitude control in a nominal
operation. However, it is possible to change to an
earth-pointing attitude control during an experiment.
The CIRC has been selected as a mission payload of theSDS-2. Other mission payloads are a next-generation star
tracker, a contamination monitor using quartz crystal
microbalance, and others.

Microbolometers 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 coolingsystem reduces the size, cost, and electrical power of thesensor. Although the sensitivity of microbolometers is lower
than that of HgCdTe-based photonic infrared detectors, theadvantage of not requiring a cooling mechanism is suitable forsmall satellites or resource-limited sensor systems.
JAXA has researched the application of microbolometers
for Earth observation since 2000. The Wide-Angle Multi-band
Sensor-Thermal Infrared (WAMS-TIR) 1), aboard thestation-keeping test airship (SPF-II) for the stratosphericplatform project, is a thermal infrared multi-band radiometerusing a microbolometer focal plane array.
In order to demonstrate the potential of microbolometers tothermal infrared imaging from space, the Compact Infrared
Camera (CIRC) is chosen as a technology demonstration
payload of the Small Demonstration Satellite (SDS) 2). The
SDS program is an activity of JAXA to demonstrate a varietyof new technologies and new missions.
In this paper, we show the details of the design of the
CIRC.

Table 1. Baseline specifications of the SDS-2.
Size

700 mm x 700 mm x 600 mm

Mass< 90 kg

Bus power> 110 W

Communication

S-bandOrbit

Sun-synchronous Orbit
600 km (TBD)

Mission resource

Size 600 mm x 550 mm x 250 mm
Mass ~ 30 kg
Power ~30 W (nominal)

2.

Small Demonstration Satellite Type-2

3.

The SDS program aims to improve the reliability ofpractical artificial satellites by demonstrating a wide range of
new space technologies covering everything from equipment
and elements to system engineering. The SDS-1, the firstsatellite in the SDS program, was launched in 2009 as a
piggyback satellite of the Greenhouse Gases Observing
Satellite “IBUKI” (GOSAT). The mission payloads of theMission of the CIRC

The main mission of the CIRC is to demonstrate thetechnology of wildfire detection using a microbolometer.
Wildfires are a major and chronic disaster affecting many
countries in the Asia-Pacific region, and some predictions arethat they will worsen with global warming and climate change.

Copyright© 2010 by the Japan Society for Aeronautical and Space Sciences and ISTS. All rights reserved.

Tn_1

Trans. JSASS Aerospace Tech. Japan Vol. 8, No. ists27 (2010)

In the Sentinel Asia1 project to share disaster information innear real-time across the Asia-Pacific region, wildfire
detection has been chosen as an important activity. It is
possible to increase observational frequency of wildfires if
CIRCs are carried on various satellites. The other CIRC
mission targets are volcanoes and heat island phenomena incities. The observations of these targets with a thermal
infrared imager will become a useful tool in monitoring
volcanoes or solving the heat island problem.
4.

introduce the hardware design of the CIRC.
㻯㼛㼙㼜㼍㼏㼠㻌㻵㼚㼒㼞㼍㼞㼑㼐㻌㻯㼍㼙㼑㼞㼍㻌㻔㻯㻵㻾㻯㻕㼀㼑㼙㼜㼑㼞㼍㼠㼡㼞㼑㻌㼟㼑㼚㼟㼛㼞㼟

Baseline Specifications of the CIRC

< 150 mm × 100 mm × 200 mm

Mass< 3 kgDetector

Uncooled infrared detector

Wavelength

8 - 12 ȝm

Number of pixels

640 × 480

Spatial resolution

198mm

12°× 9° (128 ×96 km)
33 ms

Dynamic range

180 K - 400 K

NEDT

0.2 K@300 K

5.1

Detector unit

The Focal Plane Array (FPA) of the CIRC is a
Silicon-On-Insulator (SOI) diode uncooled infrared (IR) FPA
developed by MELCO 5, 6). The characteristic of the SOI diodeuncooled IR FPA is its use of single-crystal silicon
pn-junction diodes as a temperature sensor. The single-crystal
sensor, which is based on silicon LSI technology, offers alow-noise characteristic.
We use a 640 × 480 pixel SOI diode uncooled IR FPA ofwhich pixel size is 25 Pm2. The NEDT is 40 mK with f/1
optics. Drive and readout circuits are almost the same as thoseof a commercial IR camera. For space applications, we areplanning to perform a radiation damage test, and a screeningof commercial devices.
The thermal time constant of the SOI diode uncooled IR FPA
is 24 ms. Although this thermal time constant is shorter than the
exposure time of 33 ms, it affects the Modulation Transfer
Function (MTF) due to the satellite motion. We estimate theeffect of the thermal time constant to the MTF. The thermal time
constant of 24 ms reduces the MTF in the along track direction byalmost 40%. However, as the MTF of the optics is 0.6 (see next
section), the total MTF including the detector MTF and thesatellite disturbance effect is above 0.1 even in the along track
direction.
5.2 Optics unit

Hardware Designs of the CIRC

Figure 2 shows a schematic view of the CIRC. The CIRC isbased on a commercial infrared camera developed by
Mitsubishi Electric Corporation (MELCO). However, in order
to utilize it for space applications, we added somemodifications to the hardware design. In this section, we
1

149.5mmFig. 2. Schematic view of the CIRC.

< 200 mExposure㻮㼡㼟㻌㼜㼛㼣㼑㼞

95mm

observed from 600 km (< 0.33 mrad)
Field of View㻵㼙㼍㼓㼑㻌㼐㼍㼠㼍㻴㻷㻌㼠㼑㼘㼑㼙㼑㼠㼞㼥Fig 1. System block diagram of the CIRC.

Characteristics

Size㻯㼛㼙㼙㼍㼚㼐

㻿㼕㼓㼚㼍㼘㻌㻵㻛㻲㻼㼛㼣㼑㼞㻌㻵㻛㻲

Table 2. Baseline Specifications of the CIRC.
Item

㻿㼕㼓㼚㼍㼘㻌
㻼㼞㼛㼏㼑㼟㼟㼛㼞
㼁㼚㼕㼠
㻼㼛㼣㼑㼞
㻿㼡㼜㼜㼘㼥
㼁㼚㼕㼠

The baseline specifications of the CIRC are shown in Table
2. We set the baseline specifications to meet requirements forthe wildfire detection 3, 4). The detector uses a large format(640 × 480) to obtain a wide field of view. The spatial
resolution is an important factor for wildfire detection. The
baseline specification of the spatial resolution is 200 m fromthe altitude of 600 km. Noise Equivalent Differential
Temperature (NEDT) is related to the contrast between abackground area and a burning area. If NEDT is smaller, thedetectability of the wildfire is increased. Considering thedetector performance and the optical design, we set the NEDT
is 0.2K at 300K background.
Figure 1 shows a system block diagram of the CIRC. To
reduce the size, weight, and cost, we minimized the functionsof the CIRC. The optics unit of the CIRC uses f/1.2 optics. We
employ athermal optics to maintain optical performance in awide range of temperatures. This will be an advantage of the
CIRC for small satellites, because we do not need an active
thermal control or a focus mechanism for the optics.

5.

㻰㼑㼠㼑㼏㼠㼛㼞
㼁㼚㼕㼠㻻㼜㼠㼕㼏㼟㻌㼁㼚㼕㼠㻿㼍㼠㼑㼘㼘㼕㼠㼑㻌㻮㼡㼟㻌㻿㼥㼟㼠㼑㼙

The optics of the CIRC is f/1.2 refractive optics. The focal

http://dmss.tksc.jaxa.jp/sentinel/

Tn_2

H. KATAYAMA et al.: Development of the Compact Infrared Camera (CIRC) for Earth Observation

length of the optics is 78 mm.
The temperature of the CIRC is changed on orbit. The
temperature change of the optics will cause a defocus because
refractive indices of lens materials are highly dependent on
temperature. In order to compensate for this defocus, we haveto employ a focus mechanism or a heater to keep the optics
temperature constant. However, such mechanisms increase
sensor resources. Athermal optics 7) can compensate for the
defocus due to the temperature change without suchmechanisms.
Figure 3 shows the optical design of the CIRC. The
athermal optics of the CIRC compensate for the defocus by
utilizing a combination of different lens materials anddiffractive lenses. The optics of the CIRC use a germanium
and a chalcogenide glass (GASIR®1). Figure 4 shows thecalculated MTF of the CIRC optics versus the ambient
temperature from -15°C to 50°C. The MTF is constant over
the wide range of temperatures.

corrections of the CIRC are a coarse correction of the analog
offset level of the detector and a DC level correction to avoid
a deviation from an ADC input range. Thus, the CIRC data is
downlinked without compression and corrected on the groundusing the data taken during a ground calibration. In order tocorrect effects of stray light or an analog drift of the CIRC
electronics, we also monitor the temperatures of the optics, thedetector, and the electrical circuit of the CIRC.
Image data of the CIRC are 14-bit images. The size of one
frame data is 4.3M bits. The frame data is transferred to thesatellite bus system with RS-422. The CIRC can also store
16-frame data in its frame memory.
6.

The CIRC is a mission to demonstrate the potential of the
microbolometer to thermal infrared imaging from space. We
thus are planning to observe various targets, such as wildfires,volcanoes, and heat island phenomena. We are also planningto observe calibration targets, like deep space, the moon, andthe ocean, to demonstrate the on-orbit performance of the
CIRC. Although there is a restriction of downlinking
resources of the SDS-2, we will be able to observe one target
per day from these targets.
Figure 5 shows an observational sequence of the CIRC. In
order to stabilize the temperature of the CIRC, the CIRC isturned on 30 minutes prior to the observation. After the heatrun, we observe a calibration target that has a uniform
temperature distribution, like deep space or the ocean. The
satellite maneuvers from a sun-pointing attitude to an
earth-pointing one to observe the target area. The frame rate of
the CIRC is 30Hz (33ms/frame). The CIRC can store theimage of the target area up to 16 frames on its memory. The
time between stored frames (exposure interval) can bechanged from 33 ms to 8.45 s as shown in Figure 6. If the
exposure interval is 33 ms, the CIRC observes almost thesame area displaced about 200 m with each exposure. By
combining these data on the ground, the signal-to-noise ratioof the image can be increased. If we combined 16 frames data,
the signal-to-noise ratio is expected to increase by 4 times. We
are planning to confirm this on the ground calibration. This isan experiment of the Time Delay and Integration (TDI). If the
exposure interval is longer, we can observe a wider area. The
maximum area the CIRC can observe is about 128 km (crosstrack) × 1000 km (along track) in one observation.

102
Chalcogenide
glass

Ge+Diffractive
lens
Ge

Ge

φ65

Ge

(mm)

Fig. 3. Optical design of the CIRC.

MTF(@20lp/mm)

1.0
On-axis CT
On-axis AT
Vertical CT
Vertical AT
Horizontal CT
Horizontal AT
Corner CT
Corner AT
Specification

0.5

0.1
-20

0

20
Temperature(℃)

40

Fig. 4. Calculated MTF of the CIRC optics in the ambient temperaturefrom -15°C to 50°C.

5.3

On-orbit Operation Plan of the CIRC

Signal processor unitTime

The CIRC has no calibration equipment, like a shutter or an
onboard blackbody, to avoid the use of mechanical equipment.
Commercial IR cameras correct a nonuniformity of an image
using data while the shutter is closed. The onboard data

Heat run[30min TBD]CIRC ON

Calibration target（16 frame）[20s TBD]

Target area
Calibration target（16 frame）（16 frame）[0.5-135s TBD]
[20s TBD]

maneuver(sun→earth pointing)[TBD]

maneuver(earth→sun pointing) CIRC OFF[TBD]

Fig. 5. Observational sequence of the CIRC.

Tn_3

Trans. JSASS Aerospace Tech. Japan Vol. 8, No. ists27 (2010)

shutter-less image correction to reduce the size, weight, andcost of the CIRC.
We will finish the design of the CIRC and start fabricationof the ground test model (engineering model) of the CIRC by
the end of FY 2009.

exposure interval
8.45s

exposure interval
33ms

direction of movement

References
480 pixel
~96km

1)
135s
~1000km

640 pixel
䡚128km2)

3)
Fig.6. Observational area in case of the different exposure intervals ( 33
ms and 8.45 s).

7.

4)Conclusion

The Compact Infrared Camera (CIRC) onboard the Small
Demonstration Satellite type-2 (SDS-2) is a thermal infrared
imager using a microbolometer. The main mission of the
CIRC is to demonstrate the technology of wildfire detection
using a microbolometer.
The hardware design of the CIRC is ongoing. The CIRC isa small, lightweight, and low-cost thermal infrared imager for
space applications. We employ athermal optics and

5)
6)
7)

Tn_4

Okamura, Y., Matsuyama, H., Kasahara. M., Yoshida, S. and Tange,
Y.: Development of the WAMS-TIR Instrument for SPF-II, Proc.
SPIE, 5659 (2005), pp. 105-114.
Nakamura, Y. and Hirako, K.: Research and Development of Small
Demonstration Satellite, Report on Research Achievements for
FY2006 Institute of Space and Astronautical Science, Institute of
Aerospace Technology, Japan Aerospace Exploration Agency,(2006), pp. 21-26.
Katayama, H., Okamura, Y., Tange. Y. and Nakau, K.: Design andConcept of The Compact Infrared Camera (CIRC) with Uncooled
Infrared Detector, Proc. 26th ISTS, (2008), in press.
Katayama, H., Suganuma, M., Okamura, Y., Naitoh, M., Tange. Y.
and Nakau, K.: Design and Concept of The Compact Infrared
Camera (CIRC) with Uncooled Infrared Detector, Proc.
International Conference of Space Optics, (2008).
Ueno, M. et al.: 640 x 480 Pixel Uncooled Infrared FPA with SOI
Diode Detectors, Proc. SPIE, 5783 (2005), pp. 566-577.
Kimata, M., et al.: SOI Diode Uncooled Infrared Focal Plane
Arrays, Proc. SPIE, 6127 (2006), pp. 61270X-1-11.
Tamagawa, Y., Wakabayashi, S. and Tajime, T.: New Design
Method for Athermalized Optical Systems, Proc. SPIE, 1752
(1992), pp. 232-238.