Spectroscopic characterization of GEO satellites with Gunma LOW resolution
SpectrographTakao Endo, Hitomi Ono, Mana Hosokawa and Toshiyuki Ando

Mitsubishi Electric Corporation, Information Technology R&D Center
Takashi Takanezawa

Mitsubishi Electric Corporation, Communication Systems Center
Osamu Hashimoto

Gunma Astronomical Observatory
ABSTRACTThe spectroscopic observation is potentially a powerful tool for understanding the Geostationary Earth Orbit (GEO)
objects. We present here the results of an investigation of energy spectra of GEO satellites obtained from a groundbased optical telescope. The spectroscopic observations were made from April to June 2016 with the Gunma LOW
resolution Spectrograph and imager (GLOWS) at the Gunma Astronomical Observatory (GAO) in JAPAN. The
observation targets consist of eleven dierent satellites: two weather satellites, four communications satellites, and vebroadcasting satellites. All the spectra of those GEO satellites are inferred to be solar-like. A number of well-known
absorption features such as H-alpha, H-beta, Na-D, water vapor and oxygen molecules are clearly seen in the wavelength
range of 4,000 - 8,000 Å. For comparison, we calculated the intensity ratio of the spectra of GEO satellites to thatof the Moon which is the natural satellite of the earth. As a result, the following characteristics were obtained. 1)
Some variations are seen in the strength of absorption features of water vapor and oxygen originated by the telluric
atmosphere, but any other characteristic absorption features were not found. 2) For all observed satellites, the intensity
ratio of the spectrum of GEO satellites decrease as a function of wavelength or to be at. It means that the spectralreectance of satellite materials is bluer than that of the Moon. 3) A characteristic dip at around 4,800 Å is found in
all observed spectra of a weather satellite. Based on these observations, it is indicated that the characteristics of thespectrum are mainly derived from the solar panels because the apparent area of the solar cell is probably larger thanthat of the satellite body.

1.

INTRODUCTIONSpace Situational Awareness (SSA) is a concept about security in the outer space, in order to ensure the safety ofthe space ight, understand the current status of the satellites, prevent collision, or understand the status of the spacedebris, etc. The motions of the space debris are mainly observed by radio wave (radar) and optic (telescope), and thencataloged as the orbital elements.
On the other hand, the Geostationary Earth Orbit (GEO) objects cannot be spatially resolved even by current large
aperture ground-based optical telescopes since they are located at a long distance from the ground. Therefore,
unresolved optical measurements such as spectroscopy can be a good tool for understanding individual characteristics
of each GEO object. In practice, optical properties other than motion, such as luminance, time variation of luminance,or spectral reectance, are regarded as media to guess the size, materials, and rotation of the target. In this paper,
we report the results of investigations of energy spectra of eleven GEO satellites: weather satellites, communications
satellites, and broadcasting satellites obtained with the use of the 1.5 m telescope at Gunma Astronomical Observatory(GAO).

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

2.
2.1.

OBSERVATION PLAN

INSTRUMENTATION

The 1.5 m telescope at GAO which is located about 120 km northwest of Tokyo was used for a spectral analysis of
GEO objects because a telescope with a large aperture enables to collect a large amount of light. The specications andperformances of the 1.5 m telescope at GAO are listed in Table 1 [1; 2]. This telescope has no tracking capability forhigh-speed moving objects such as the Low Earth Orbit (LEO) objects, because the alt-azimuth mount was designed
only for sidereal tracking.
In case of the GEO object observation, the pointing direction of the reector (AZ: azimuth angle, EV: elevation angle)
is xed, and then GEO object remains stationary in the camera eld of view. The GEO object is therefore observed
without any type of tracking. In practice, a manual adjustment for object tracking is required because the position of
GEO object slightly drifts during the exposure for about 10 minutes or less.

Fig. 1.

1.5 m reector at Gunma astronomical observatory.

For various scientic research, three kinds of instruments are placed at the three dierent focal planes of the 1.5 m
reector. In the following observations, we used the Gunma LOW resolution Spectrograph and Imager for optical
wavelength (GLOWS). Specications and performances of GLOWS are listed in Table 2.
GLOWS is the spectroscopic instrument combined grism and CCD camera. It provides a λ/∆λ = 300 ∼ 500 resolving
power in the visible wavelength range of λ = 4, 000 ∼ 8, 000 Å. Grism is the optical element which is composed ofdiraction grating and prism, and is useful in spectrometers that requires in-line presentation of the spectrum. The
light diracted by the grating is bent back in line by the refracting eect of the prism.
In order to avoid the contamination source close to the observation target, the target should be located in the center ofnarrow slit at the spectrographs entrance. Then the grism creates a dispersed spectrum centered on the location of theobject in the camera eld of view. The dispersion direction is perpendicular to the slit and the spatial direction along
the slit. In the GLOWS instrument, arc line lamps (FeNeAr) are contained for the pixel-to-wavelength conversion.

2.2.

SOLAR RADIATION SPETRUM

The red line in Figure 2 shows an example of solar radiation spectrum obtained at Tsukuba 12:10 (JST) on 11 May
2012 at the elevation corresponding to the airmass = 1.1 [3]. The horizontal axis shows the wavelength, the vertical

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Table 1. 1.5 m reector at Gunma astronomical observatory.
Item

Specication

Optics . . . . . . . . . . . . . . . . . . . . . . . . . .
Diameter of primary mirror . . . . . .
Eective diameter . . . . . . . . . . . . . . .
Focal length . . . . . . . . . . . . . . . . . . . .
Hartmann constant . . . . . . . . . . . . . .
Mounting . . . . . . . . . . . . . . . . . . . . . . .
Pointting accuracy . . . . . . . . . . . . . . .
Tracking accuracy . . . . . . . . . . . . . . .
Diameter of Dome . . . . . . . . . . . . . . .
Establish . . . . . . . . . . . . . . . . . . . . . . .
Manufacturer . . . . . . . . . . . . . . . . . . .

Ritchey-Chretien
160 cm150 cm1830 cm (F/12.2)
0.3′′
Altazimuth
3′′ (rms)
0.7′′ (rms) (15 min)
11 m
March 1999
Mitsubishi Electric Corp.

1000

axis shows spectral irradiance. Absorption features such as Hα, H β, Na-D (λ = 5, 896 Å) and iron are clearly seen
in solar spectrum. It is well known that such spectral features are originated from the solar atmosphere. On the other
hand, absorption features such as O2 and H2 O are also clearly seen, which are caused by the absorption of atmospheresurrounding the Earth.

Fe/Mg−b
Fe−E

O2

H2O
O2

Solar Spectral Irradiance (airmass = 1.1)
5000

Fig. 2.

2.3.

Na−D

100

Fe/Ca−GHα10Spectral irradiance [ergs cm−2 s−2 Å−1]

Hβ

6000
Wavelength λ [Å]

7000

8000

Example of solar spectrum (2012/5/11 12:10).

THE SURFACE REFLECTANCE OF COMMON SATELLITE MATERIALSAs the articial satellites shine brightly by mainly reection of sunlight, it is important to know the spectral reectanceof typical materials of articial satellites. At rst, we obtained samples of Multi-Layer Insulation (MLI), monocrystalline silicon cells (solar panel), and Carbon Fiber Reinforced Plastic (CFRP), and then measured the spectral

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Table 2. Gunma LOW resolution Spectrograph and imager (GLOWS).
Item

Specication

Detector . . . . . . . . . . . . . . . . . . . . . . . .

Andor DW432(e2v CCD55-30 Back-illumination: 1250 × 1152)
0.6′′ / pixel → FOV: 10′
4, 000 ∼ 8, 000 Å
4 lter positions (+ hole) : B, V, R, I
Grism
400 ∼ 500
40′′ (length), 1.8′′ (width)
3 stage pertier
Fe, Ar, Ne
GENESIA Corp.

Coverage . . . . . . . . . . . . . . . . . . . . . . .
Imaging . . . . . . . . . . . . . . . . . . . . . . . .
Disperser . . . . . . . . . . . . . . . . . . . . . . .
Resolution . . . . . . . . . . . . . . . . . . . . . .
Slit . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cooler . . . . . . . . . . . . . . . . . . . . . . . . .
Comparison . . . . . . . . . . . . . . . . . . . . .
Manufactuerer . . . . . . . . . . . . . . . . . .

reectances [4]. The measured samples are listed in Table 3.
Table 3. Sample list [4].
SampleSurface characteristics

Multi layer Insulation (MLI) . . . . . . . . . . . . . . . . . . . . . .
Mono-crystalline Silicon Cells (solar panel) . . . . . . . .
Carbon Fiber Reinforced Plastic (CFRP) . . . . . . . . . . .

Gold & silver, smooth surface
Black, smooth surface
Black, rough surface

In Figure 3, we plot the logarithm of the spectral reectivity against wave length for the samples in Table 3. The
incident angle to the normal of sample plane is set to 15◦ . The broken lines, dot-dashed lines and solid lines show
the s-polarized, p-polarized and averaged light, respectively. The passbands of the Johnson's UBVRI photometry areplotted as dotted lines. And yellow lines, blue lines and black lines show the reectance of MLI, solar panel and CFRP,
respectively.
From the Figure 3, we can see that the reectance of MLI is in proportion to the wave length from B band to V band.
The solar panel, on the other hand, is inverse proportion to the wave length in the B-V bands. The data of solar panel
are intentionally hidden in R band because characteristic features are seen in this sample. This is probably due to thesurface material of the multilayer coatings.

3.
3.1.

OBSERVATIONSTHE OBSERVATION JOURNAL

First of all, the observation journal of GEO satellite targets obtained with GLOWS are listed in Table 4. Note that wechose these targets based on their location, as they were located within the longitude range ±60◦ from +135◦ of east
longitude, and whose orbital inclination were smaller than 1◦ . These spectroscopic observations were carried out from
April through June 2016. For each target, ten single frames with an exposure time of 120 seconds were obtained.
In order to compare the observed spectra with others, we also observed the standard stars and the Moon spectra. The

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

100

U

B

V

R

I

Efficiency [%]10

MLI (gold)
MLI (silver)
Solar panel
CFRP

1

S−pol.
P−pol.
Average

0.1

4000

Fig. 3.

5000

6000
Wave length λ [Å]

7000

8000

Spectral reectance of typical materials.

observation journal both of the standard stars used for calibrations and the Moon whose spectra is similar to the Sun,are also listed in Table 4.

3.2.

ELECTRICAL POWER AND SOLAR PANEL SPAN

Table 5 shows the electrical power and the solar panel span of observed GEO satellites [5]. Note that the electrical
power used by optical satellites is generally smaller than that of communications and broadcasting satellites. In Table 5,
the electrical power used by weather satellites is smaller than that of communications and broadcasting satellites. In
practice, the weather satellites MTSAT2 (HIMAWARI-7) and HIMAWARI-8 have only 3 (not larger than 10 m) and 2(2.8 m × 2) solar panels on one side of their satellite bus, respectively.

4.
4.1.

SPECTRAL ANALYSISSPECROSCOPIC DATA REDUCTION

We have carried out standard data reductions using the bias, dark and at eld frames. In order to obtain the ux
calibrated spectrum, we have observed the spectroscopic standard stars HR4468 and HR5501 as well at almost thesame elevation angles where the observations of the target satellites were made. The spectrum of these standard stars
are well-known based on standard star database. By comparing with the spectra of standard stars, the ux calibrated
spectra of target satellites are calculated.
In order to evaluate the systematic error of these correction, we calculate the spectrum normalized by the averaged
intensity in the spectral range of 5, 000 ∼ 7, 000 Å. The normalized spectra of standard stars are plotted against the
wavelength in Figure 4. Except for the spectral range of < 4, 500 Å and around well-known absorption lines, thesystematic deviations of the data from the average are less than 10 % as shown in Figure 5. Hereafter, we estimate thesystematic error of these spectral correction is kept less than 10 %.

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Table 4. The observation journal.
Category

Exposure [s]Elevation [◦ ]2006-004A
2014-060A
2000-012A

weather
weather
communication
standard star
standard star

1,200
1,200
1,200
50
50

47.2
47.6
41.1
42.9
42.8

HIMAWARI-8
SUPEBIRD-C2
HR5501
HR5501
N-SAT-110
JCSAT-2AJCSAT-5A
JCSAT-3A
JCSAT-RA
JCSAT-4B

2014-060A
2008-038A

2000-060A
2002-015A
2006-010A
2006-033A
2009-044A
2012-023A

weather
communication
standard star
standard starbroadcastcommunication
communication
broadcastbroadcastbroadcast

1,200
1,200
100
100
1,200
1,200
1,200
1,200
1,200
1,200

47.6
47.3
54.1
54.1
33.8
44.7
46.9
46.0
46.0
44.7

2016/5/23 21:20  21:23
2016/5/23 21:46  22:16
2016/5/23 22:49  22:51

HR5501HIMAWARI-8
Moon

2014-060A


standard star
weatherreference

50
1,200
3

51.1
47.6
26.0

19 .
20 .
21 .

2016/6/2
2016/6/2
2016/6/2

22:05  22:10
22:16  22:46
22:51  23:20

HR5501
BSAT-3C
HIMAWARI-8


2011-041B
2014-060A

standard starbroadcastweather

100
1,200
1,200

53.8
37.7
47.5

22 .
23 .

2016/6/5
2016/6/5

22:35  22:41
22:46  23:15

HR5501HIMAWARI-8


2014-060A

standard star
weather

100
1,200

51.3
47.5

I.D.

Observation time (JST)

1 ..
2 ..
3 ..
4 ..
5 ..

2016/4/26 20:15  20:45
2016/4/26 20:52  21:28
2016/4/26 21:47  22:46
2016/4/26 21:32  21:34
2016/4/26 21:37  21:39

MTSAT-2
HIMAWARI-8
SUPEBIRD-B2
HR4468
HR4468

6 ..
7 ..
8 ..
9 ..
10 .
11 .
12 .
13 .
14 .
15 .

2016/5/18 21:21  21:50
2016/5/18 21:59  22:28
2016/5/18 22:35  22:39
2016/5/18 22:40  22:45
2016/5/18 22:52  23:20
2016/5/18 23:33  24:04
2016/5/18 24:08  24:38
2016/5/18 24:43  25:12
2016/5/18 25:24  25:51
2016/5/18 26:01  26:29

16 .
17 .
18 .

4.2.

ObjectENERGY SPECTRA OF THE GEO SATELLITES

After the correction described in section 4.1, we compare the ux calibrated spectra of GEO satellites. Figures 6  8compare the energy spectra of GEO satellites observed with GLOWS in the visible spectral range. The source uxesof communications satellites are plotted against the wavelength in Figure 6. In the same way, the Figure 7 and Figure 8
show the spectra of broadcasting and weather satellites, respectively. Especially, the weather satellite HIMAWARI-8
was observed with GLOWS ve times in the period from April through June.
For all spectra of GEO satellites obtained from GLOWS, the well-known absorption lines such as Hα, H β, Na-D, water
vapor and oxygen are clearly seen. Compared with the solar radiation spectrum as shown in Figure 2, the spectral
distribution of GEO satellites is also very similar to that of the solar spectrum.
Next, we compare with the spectra of the same satellite target obtained at another day observations as shown in Figure 8.
Although the strength of atmospheric absorption varies day by day, there is no signicant spectral dierence in thevisible wavelength range. Any systematic deviations of atmospheric correction can be negligible.

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Table 5. Electrical power and solar panel span.
Satellite nameBus

Size [m]Electrical power [kW]Solar panel span [m]JCSAT-2A . . . . . . . . . .
JCSAT-5A . . . . . . . . . .
Superbird-B2 . . . . . . . .
Superbird-C2 . . . . . . . .

Boeing 601
A2100AX
Boeing 601 HP
DS2000

2.7 × 3.6 × 4.3
2.7 × 3.6 × 4.0
6.3 × 3.7 × 3.0

3.7
4
5.5
8.0

26.9
26
31.6

N-SAT-110 . . . . . . . . . .
JCSAT-3A . . . . . . . . . .
JCSAT-RA . . . . . . . . . .
JCSAT-4B . . . . . . . . . .
BSAT-3C . . . . . . . . . . .

A2100AX
A2100AX
A2100AX
A2100AX
A2100A

-

8.3
4
4
7.5

26
26.9
26.9
-

MTSAT-2 . . . . . . . . . . .
HIMAWARI-8 . . . . . . .

DS2000DS2000

2.4 × 2.6 × 2.6
2.2 × 2.1 × 2.0

3.4
2.6

(∼ 10)(2.8 × 2)

A spectrum of the Moon observed by GLOWS is presented in Figure 9, which is almost the same as the solar spectrum
since the Moon shines reecting the sunshine.

5.

DISCUSSIONAs described in section 4.2, the obtained spectrum of both GEO satellites and the Moon are similar to the solar
spectrum. We introduce a spectrum ratio between the GEO satellites and the Moon. Figures 10  13 show the spectrum
ratios of communications satellites, broadcasting satellites, and weather satellites, respectively. In these spectrum
ratios, absorption features such as Hα, H β and Na-D lines cannot be seen. Since both the satellites and Moon areshining by reecting solar light which contains those spectral features originated in the solar surface, they are canceledby dividing the satellite spectrum by the spectrum of the Moon. This result indicates that the spectrum ratio is usefulenough to investigate the material properties of the GEO satellites.
On the other hand, since the strength of atmospheric absorption is dierent in each observation, residuals of theabsorption features such as water vapor and oxygen originated by the Earth's atmosphere are remained even in the
spectrum ratios. No other characteristic absorption features are found.
In addition, by excluding the data aected by the large atmospheric absorption at wavelengths shorter than 4, 500 Å, theslope of spectrum ratios shown in Figures 10  13 are generally decreasing, or at against the wavelength. It means thatthe spectral reectance of satellite materials is bluer than that of the Moon. In the spectrum ratios of HIMAWARI-8
as shown in Figure 12, we can clearly see the characteristic dip around 4,800 Å. However, we couldn't detect such acharacteristic dip found in HIMAWARI-8 in the spectrum ratios of communications satellites, broadcasting satellites
and MTSAT-2 as shown in Figures 10, 11 and 13, respectively.
In order to convert sunlight into electricity, solar panels of GEO satellite are extended and oriented towards the Sun.
Depending on the phase angle dened as the angle between the ray from the Sun to the satellite and the line of sight tosatellite, the projected area of solar panels are generally expected to be larger than that of the satellite body. Therefore,
it is assumed that the amount of reected light from solar panels is signicantly larger than that from the satellite bus.
Since the reectivity of solar panels decreases against the wavelength as shown in Figure 3, we thus consider that the

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Standard stars
5
5000

Fig. 4.

6000
Wave length λ[Å]7000

Energy spectra of standard stars.

2

HR4468 4/26
HR5501 5/18
HR5501 5/23
HR5501 6/2
HR5501 6/5
HR5501 6/17

1

Ratio (/Average)
8000

0.5

1

HR4468 4/26
HR5501 5/18
HR5501 5/23
HR5501 6/2
HR5501 6/5
HR5501 6/17
Average

0.1

Normalized flux

10Standard stars

Fig. 5.

5000

6000
Wave length λ[Å]

7000

8000

The deviations of the standard star spectra.

observed spectrum ratios of GEO satellites in Figures 10  13, except for the characteristic dip as discussed later, arealso generally decreasing or at against wavelength.
The characteristic dip around 4,800 Å can be clearly seen in every spectrum ratio of the HIMAWARI-8 (Figure 12),
whereas such a feature cannot be found for any other communications satellites and broadcasting satellites as shownin Figures 10 and 11, respectively. In fact, the areas of solar panels of the weather satellites are smaller than thoseof communications and broadcasting satellites as listed in Table 5. It is suggested that the characteristic dip around
4,800 Å is more prominent in the spectrum ratios of HIMAWARI-8 because the amount of light reected by the solar
panels is relatively smaller.
In case of the MTSAT-2 satellite, the number of solar panels are larger than that of the HIMAWARI-8 satellite as also
listed in Table 5. Such a dierence may make the spectral ratio of the MTSAT-2 rather similar to the communications
and broadcasting satellites.

6.

CONCLUSION

In order to characterize and classify the articial satellites based on the optical characteristics, we have observed anumber of GEO satellites with the using the GLOWS on the 1.5 m reector at GAO in Japan.
Our target sample of the GEO satellites consists of two weather satellites, ve broadcasting satellites, and fourcommunications satellites as listed in Table 4. These targets are located within the longitude range ±60◦ from +135◦ ofeast longitude, and the orbital inclination smaller than 1◦ . These spectroscopic observations were performed for several
days between 26th April 2016 and 5th June 2016. We rst review the results obtained from GLOWS observations as
described below:All the GEO satellites in our observation sample show the optical spectra resemble to the solar spectrum, which
the well-known absorption features such as Hα, H β, Na-D, water vapor and oxygen molecule are clearly seen
(Figures 6  8).

There is no signicant spectral variation in the visible wavelength range during the observation period from
April to June (see Figure 8), while atmospheric absorption features varies day by day due to the dierenceof atmospheric condition of the Earth. The systematic error caused by the atmospheric correction could be
negligible (Section 4.2).

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Geostationary satellites
10−12

10−12

Geostationary satellites

HαFe/Ca−G

H2O

Fig. 6.

6000
Wave length λ[Å]

7000

5000

Fig. 7.

H2O
O2

O2

6000
Wave length λ[Å]

7000

8000

Moon
Energy spectra ofbroadcasting satellites.

10−8

10−12

Na−D

N−SAT−110
JCSAT−3A
JCSAT−RA
JCSAT−4B
BSAT−3C

8000

Weathersatellites
Energy spectraof communications
satellites.
HαFe/Ca−G

H2O
O2

10−14

MTSAT−2
5000

Fig. 8.

7000

Energy spectra of weather satellites.

HαFe/Mg−b
Fe−E

HIMAWARI−8
2016/4/26
2016/6/2
2016/5/18
2016/6/5
2016/5/23
6000
Wave length λ[Å]

Hβ

O2

Na−D

H2O
O2

O2

10−9

Na−D

10−13

Fe/Mg−b
Fe−E

Moon
10−10

Hβ

Source flux [ergs cm−2 s−1 Å−1]

Fe/Ca−G

Source flux [ergs cm−2 s−1 Å−1]

HαFe/Mg−b
Fe−E

10−13

5000

Hβ

O2

O2

10−13

Na−D

Superbird−B2
Superbird−C2
JCSAT−2A
JCSAT−5A

10−14

Source flux [ergs cm−2 s−1 Å−1]

Fe/Mg−b
Fe−E

10−14

Hβ

Source flux [ergs cm−2 s−1 Å−1]

Fe/Ca−G

8000

5000

Fig. 9.

6000
Wave length λ[Å]

7000

8000

Energy spectrum of the Moon.



Spectral features coming from the solar spectrum such as Hα, H β and Na-D are canceled in the spectrum ratios
calculated by dividing the observed spectra of GEO satellites by a spectrum of Moon which represents the solar
spectrum. Any other characteristic features are not found in the spectrum ratios. It indicates that such spectrum
ratios are useful enough to investigate the material properties of GEO satellite (Section 5).

The spectrum ratios show a trend of decreasing as a function of wavelength or a at distribution for the optical
wavelength longer than 4, 500 Å, while they are much aected by atmospheric absorption at shorter wavelengths.
It means that the spectral reectance of satellite materials is bluer than that of the Moon (Section 5).

A characteristic dip around 4,800 Å is clearly seen only in the spectra of the HIMAWARI-8 (Figure 12). Such a
dip feature could not be found in the spectra of communications satellites and broadcasting satellites ( Figures 10
and 11), neither even in the spectrum of a weather satellite MTSAT-2 as seen in Figure 13 (Section 5).

Systematic errors in the analysis of the observed spectra are estimated to be less than 10 % for the wavelength
range of λ > 4, 500 Å (Section 4.1).

The reectivity of solar panels decreases as a function of wavelength as shown in Figure 3. Since the total amount oflight reected by the solar panels is much larger than the light reected by the bus for most satellites, it is natural that

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

Communication satellites
5

5

Broadcast satellites

O2
Hα
Na−D

H2O
O2

O2
Hα

5000

6000
Wave length λ[Å]

7000

8000

Fig. 11.

Spectrum ratios of communications satellites.

5000

8000

5

5

O2
Hα
Na−D

H2O
O2

2

O2
Hα
Na−D

H2O
O2

1

↓

Ratio (/Moon)

Characteristic
dip

5000

6000
Wave length λ[Å]

7000

8000

Spectrum ratios of the HIMAWARI-8 satellite.

0.5

2

7000

MTSAT−2

1

Ratio (/Moon)

6000
Wave length λ[Å]Weather satellites

HIMAWARI−8
2016/4/26
2016/6/2
2016/5/18
2016/6/5
2016/5/23

0.5

O2

Spectrum ratios of broadcasting satellites.

Weather satellites

Fig. 12.

H2O

1

Na−D

0.5

0.5

Fig. 10.

2

Ratio (/Moon)

2

N−SAT−110/JCSAT−110
JCSAT−3A/JCSAT−10
JCSAT−RA/JCSAT−12
JCSAT−4B/JCSAT−13
BSAT−3C/JCSAT−110R

1

Ratio (/Moon)

Superbird−B2
Superbird−C2
JCSAT−2A/JCSAT−8
JCSAT−5A/JCSAT−9

Fig. 13.

5000

6000
Wave length λ[Å]

7000

8000

Spectrum ratio of the MTSAT-2 satellite.

all the observed spectra of the GEO satellites show a decreasing or at trend against wavelength as seen Figures 10 
13.
In the case of the HIMAWARI-8, its solar panel area is relatively smaller than those of other satellites due to its smaller
energy consumption. It is likely that such a small size of the solar panels of the HIMAWARI-8 causes its uniquespectral feature of the dip around 4,800 Å.
As discussed above, we conclude that spectroscopic observation should be a powerful method for identifying andclassifying the GEO satellites by their spectroscopic characteristics.

7.

REFERENCES

1. Hashimoto, O. et al., Photometric and spectroscopic observations of geostationary satellites with the use of the
1.5 m telescope at Gunma Astronomical Observatory, Spaceguard Research, Vol. 8, 2015.
2. Takahashi, H., Hashimoto, O., Honda, S. and Taguchi, H., 150cm Reector & Incidental Instruments, ASJ autumn
annual meeting. A11c, 2008.

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com

3.

New Energy and Industrial Technology Development Organization, Solar radiation spectrum database,
http://app0_2.infoc.nedo.go.jp/.
4. Endo, T., Ono, H., Suzuki, J., Ando, T. and Takanezawa, T., Satellite Type Estimation from Ground-based
Photometric Observation, 17th AMOS Conference Proceedings, 922930, 2016.
5. The Society of Japanese Aerospace Companies., Space infrastructure data book: satellite edition, 2011.

Copyright © 2017 Advanced Maui Optical and Space Surveillance Technologies Conference (AMOS) – www.amostech.com