Design and Concept of The Compact Infrared Camera (CIRC)
with Uncooled Infrared Detector
By Haruyoshi KATAYAMA1), Yoshihiko OKAMURA1), Yoshio TANGE1), and Koji NAKAU1)
1)

Earth Observation Research Center, Japan Aerospace Exploration Agency, Tsukuba, Ibaraki, JapanThe compact infrared camera (CIRC) is one of technology demonstration payloads of Small Demonstration-Satellite
type-3 (SDS-3). The CIRC is an infrared camera equipped with an uncooled infrared array detector (microbolometer).
Microbolometers have an advantage of no requirement of cooling mechanisms such as a mechanical cooler. The main
mission of the CIRC is the technology demonstration of the wildfire detection using the microbolometer. In this paper, weshow the details of the design and concept of the CIRC. We also show preliminary results of feasibility study of the wildfire
detection and other applications using thermal infrared images.
Key Words: Remote Sensing, Thermal Infrared Imaging, Wildfire, Uncooled Infrared Detector

In this paper, we show the details of the concept of theCIRC. We also show preliminary results of feasibility studyof the wildfire detection and other applications.

1. Introduction
Microbolometers are widely used in commercial andmilitary applications such as a night vision. Microbolometers
have an advantage of no requirement of cooling mechanisms
such as a mechanical cooler. The eliminating of detector
cooling system can reduce the size, cost and electrical powerof sensor. Although the sensitivity of microbolometers islower than that of HgCdTe-based photonic infrared detectors,
the advantage of no cooling mechanism is suitable for small
satellites or resource-limited sensor systems.
For this reason, microbolometers begin to be applied forvarious space applications. In planetary missions, theThermal Emission Imaging System (THEMIS) 1) onboard
Mars Odyssey spacecraft used a microbolometer focal planearray (FPA). The Longwave IR camera (LIR) onboard Venus
Climate Orbiter (PLANET-C) 2), which is scheduled to belaunched in 2010, also uses a microbolometer array.
In earth observation mission, the Infrared Spectral Imaging
Radiometer (ISIR) 3) experiment tests the potential of
microbolometer for application to thermal infrared imaging.
The ISIR was flown as a hitchhiker experiment on the space
shuttle in 1997. Recent missions to measure the atmospherevertical profiles like CALIPSO 4) and EarthCARE 5) also usea microbolometer as an imaging infrared instrument. JAXA
has started a research for application of microbolometer toearth observation since 2000. The Wide-Angle Multi-band
Sensor - Thermal Infrared (WAMS-TIR) 6), aboard thestation-keeping test airship (SPF-II) for the stratosphericplatform project, is a thermal infrared multi-band radiometerusing a microbolometer FPA.
In order to demonstrate the potential of microbolometer tothe thermal infrared imaging from space, the compact
infrared camera (CIRC) is chosen as one of the technology
demonstration payloads of Small Demonstration Satellite(SDS). The SDS program is one of activities of JAXA, todemonstrate a variety of new technologies and new missions.

2. Microbolometers
Microbolometers are detectors to detect infrared energy as
minutes change of the detector temperature. A
microbolometer consists of an array of pixels, each pixel
being made up of several layers. Although there are several
different structures from company to company, these layer
are consist of IR absorbing layer, reflection layer, andreadout integrated circuit (ROIC). The key technologies ofthe microbolometer are the IR absorber, the temperature
sensor to detect the temperature change of IR absorber, andthermal isolation structures of IR absorber.
In Japan, two companies are providing microbolometers.
One is Mitsubishi Electric Corporation (MELCO), and theother is NEC corporation. Uncooled infrared FPA ofMELCO is a device with series PN junction diodes
fabricated on Silicon-On-Insulator (SOI) wafer. On the otherhand, that of NEC uses vanadium oxide as IR absorbing
material. Both companies can provide a 640 x 480 large
format array with 23.5 or 25m pixel 7), 8). We are planning tochoose one of these devices. The 640 x 480 microbolometer
array is the largest format ever used in earth observations
from space.
3. Small Demonstration Satellite type-3
The Small Demonstration Satellite type-3 (SDS-3) is apiggybag satellite of HTV/HIIB launch vehicle. The SDS-3
is scheduled to be launched in 2010. Table 1 shows abaseline specification of the SDS-3. Although the details ofits system are still under discussion, the CIRC is one ofpossible candidates of the SDS-3 payloads. The ellipticalorbit of the SDS-3 is a disadvantage for the earth observation
1mission like the CIRC. However, we can observe a target
with different spatial resolutions from different orbital
altitudes. We thus think that this orbit is suitable for ourexperiments.

including forest fires, tundra fires, and peat fires.
Table 2. Baseline specifications of the CIRC.
Item

Table 1. Baseline specifications of the SDS-3.

Characteristics

Size< 150mm x 150mm x 300mm

Mass

< 5kg
Uncooled infrared detector

Size280mm x 280mm x 500mm

Detector

Mass< 50 kg

Wavelength

8 - 12 μm

Bus power> 52 W

Number of pixels

640 x 480

16.8-22.4V (unstable)

Spatial resolution

Powersupply< 200 mvoltage

5.0V (stable)

Communication

S-bandField of View

16° x 12°Orbit

300-1000 km

Frame rate

30Hz

elliptical orbit (TBD)

Dynamic range

Hi gain : 180 K - 340 K

observed from 450 km (< 0.44 mrad)

Low gain : 180 K - 450 K

4. Mission and specifications of the CIRC

NEdT

The main mission of the CIRC is the technology
demonstration of the wildfire detection using themicrobolometer. Wildfires are one of the major and chronic
disasters affecting many countries in Asia-Pacific region, andsome suggestions are that this will get worse with global
warming and climate change. In Sentinel Asia 1 project toshare the disaster information in near real-time across theAsia-Pacific region, the wildfire detection is chosen as one of
the important activities.
A baseline specification of the CIRC is shown in Table-2.
We set the baseline specification to meet requirements for thewildfire detection. The detector is a large format (640 x 480)
to obtain wide field of view. The spatial resolution is an
important factor for the wildfire detection. The baseline
specification of the spatial resolution is 200m from thealtitude of 450km.
Fig. 1 shows a system block diagram of the CIRC. In orderto reduce the size, weight, and cost, we minimized thefunction of the CIRC. The optics unit of the CIRC is f/1-f/1.5
optics. We are discussing to employ an athermal optics tokeep the optical performance in a wide range of temperature.
This will be an advantage of the CIRC for small satellites,
because we don’t need an active thermal control to the optics.

Compact Infrared Camera (CIRC)

Temperature
sensors

Optics Unit

Detector
Unit

Calibration
Unit (TBD)

Satellite Bus
SystemSignal
Processor
Unit

Power
SupplyUnitCommandImage data
HK telemetry

Bus power

Heater()Signal I/FPower I/F

Fig 1. System block diagram of the CIRC.

Table 3. Analyzed wildfire data of the ASTER/TIR.

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) 9) data. ASTER has a significant advantage
over previous datasets because of the combination of highspatial resolutions (15–90 m) and enhanced multispectral
capabilities, particularly in the TIR. The spatial resolution
and swath of the ASTER/TIR are 90m and 60km. The 90m
spatial resolution in thermal infrared band is useful tosimulate various case of a spatial resolution.
In order to check the delectability of wildfire, we obtained
the wildfire data taken by ASTER. Table 3 shows the list ofwildfire data we checked. These are typical wildfire data
10.2 K@300 K

Location

Date

TypeAlaska

2004-07-17

Forest fire

Alaska2007-09-08

Tundra fire

California

2003-10-26

Forest fireIndonesia

2006-10-12

Peat fire

5.1 Spatial resolution
In order to investigate the difference of the wildfire
detectability depending on the spatial resolution, we madesimulated images of which spatial resolutions are 180m and
270m from the original ASTER/TIR image.
Fig. 2 and Fig. 3 show simulated images of the forest firein California and the peat fire in Indonesia. We searched theimage for regions of anomalously high brightness to detect
wildfires. In general, the wildfire detection using satellite
data uses short or medium infrared images. However, byoptimizing a threshold level, we can detect a wildfire only
from the thermal infrared image.
Hotspots are detected by contextual threshold method. Apixel is defined as hotspot if the anomaly in 11m brightness

http://dmss.tksc.jaxa.jp/sentinel/2

is higher than 3, where  is standard deviation of brightness
in pixels within 1km radius. Details of this algorithm will bepublished in 10).

heat power plants. So we are planning to apply this algorithm toother various dataset and check the detectability.

90m
90m

180m
180m

270m
270m
Fig 3. ASTER/TIR images of peat fire in Indonesia on October 12, 2006.
Fig 2. ASTER/TIR images of forest fire in California on October 26,

The spatial resolutions are 90m (top), 180m (middle), and 270m

2003. The spatial resolutions are 90m (top), 180m (middle), and 270m

(bottom). Red filled squares and yellow open squares are the same in Fig.

(bottom). Red filled squares are the results of wildfire detection using1.

thermal infrared data only. Yellow open squares are the results using
MOD14.

In order to check the detectability, we used theMODerate-resolution Imaging Spectroradiometer (MODIS)
Thermal Anomalies/Fire products (MOD14v4). MOD14
algorithm detects fire locations using 4m and 11m brightness
temperatures with spatial resolution of 1km.
From this simulation, we find that the detectability of forest
fire or tundra fire using thermal infrared images of which spatial
resolution of 180m is comparable to that of MOD14 algorithm.
On the other hand, the detection of the peat fire needs higher
spatial resolution. Because the burning temperature of peat fires
is lower than that of other wildfires.
Although further improvements of the detection algorithm areneeded especially for peat fires, we find that 200m spatial
resolution is almost appropriate for the wildfire detection. The
detectability of wildfires should have a dependency to theburning area. In addition to that, there is a possibility to detect a“false alarm” wildfire in a city due to various heat sources likeFig 4. A histogram of the radiation temperature of a wildfire taken by
ASTER/TIR 11m band.

3

We set the baseline specification to meet requirements forthe wildfire detection and other applications. The feasibility
study shows that the CIRC baseline specification is almost
suitable for these purposes. We start the development of theCIRC based on the specification this year.

5.2 Dynamic range
For the detection of wildfires, the dynamic range of sensor isalso important. If the burning temperature is too high, the outputof sensor is saturated.
Fig. 4 shows a histogram of the radiation temperature of awildfire taken by ASTER/TIR 11m band. The radiation
temperature of 370K is the saturation level of the ASTER/TIR.
This implies that the dynamic range needed for the CIRC is400K-450K.

References
1)

Schueler, C. F, Silverman, S. H, and Christensen, P. R. : ThermalEmission Imaging System (THEMIS), the International Workshop on
thermal detectors (TDW03).
2) Nakamura, M. et al. : Planet-C: Venus Climate Orbiter mission ofJapan, Planetary and Space Science, 55, Issue 12, (2007), pp.
1831-1842.
3) Spinhirne, J. D. et al. : Preliminary spaceflight results from theuncooled infrared spectral imaging radiometer (ISIR) on shuttle
mission STS-85, Proc. SPIE, 3379 (1998), pp. 14-21.
4) CALIPSOIMAGINGINFRAREDRADIOMETER
http://smsc.cnes.fr/CALIPSO/GP_iir.htm.
5) EarthCARE – Earth Clouds, Aerosols and Radiation Explorer
Technical and Programmatic Annex
http://esamultimedia.esa.int/docs/EEUCM/EarthCARE_TPA.pdf.
6) Okamura, Y. et al. : Development of the WAMS-TIR instrument for
SPF-II, Proc. SPIE, 5659 (2005), pp. 105-114.
7) Ueno, M. et al. : 640 x 480 pixel uncooled infrared FPA with SOI
diode detectors, Proc. SPIE, 5783 (2005), pp. 566-577.
8) Tohyama, S. et al. : New thermally isolated pixel structure forhighresolution 640x480 uncooled infrared focal plane arrays : OpticalEngineering, 45 (2006), pp. 014001 1-10.
9) Ohmae, H. et al. : Preflight test results of the ASTER TIR flightmodel, Proc. SPIE, 3220 (1997), pp. 210-219.
10) Nakau, K. et al. : In preparation.

6. Other possible applications
The other CIRC mission is to demonstrate the possibilityof microbolometers as a thermal infrared imager to otherobservation targets like volcanoes or heat island phenomena
in a city.
Fig 5. shows the image of Mt. Merapi volcano, Indonesia
taken by ASTER on June 6, 2006. We can see fumes andvolcanic ash at the crater and its surrounding area from theVNIR image. Fig 6. shows TIR images around crater withdifferent spatial resolution. Two streaks are relics of thepyroclastic flow. We can see these features from the imagesof 90m and 180m spatial resolution. However it is difficult toresolve from 270m or 360m spatial resolution.
As well as the wildfire detection, the visibility of thesefeatures has a dependency of the scale of observation target.
We will continue this kind of work to check the feasibility.

Fig 5. ASTER/VNIR image of Mt. Merapi volcano, Indonesia taken by
ASTER on June 6, 2006.

Fig 6. ASTER/TIR images of the crater of Mt. Merapi. The spatial
resolutions of images are 90m, 180m, 270m, and 360m from left to right.

7. Summary
The compact infrared camera (CIRC) onboard the Small
Demonstration Satellite type-3 (SDS-3) is a thermal infrared
imager using microbolometer. The main mission of the CIRCis the technology demonstration of the wildfire detection
using the microbolometer.
4