Polarimetric observations of the Galilean satellites near opposition in 2011
We present results of the new polarimetric observations of the Galilean satellites Io, Ganymede, Europe, and Callisto carried out on October 21 - November 1, 2011. We used 1.25m telescope equipped with the UBVRI double image chopping photoelectric polarimeter, 2.6m Shain telescope equipped with a on...
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| Zitieren: | Polarimetric observations of the Galilean satellites near opposition in 2011 / S.V. Zaitsev, N.N. Kiselev, V.K. Rosenbush, F.P. Velichko, S.V. Kolesnikov, K.A. Antonyuk, V.N. Psarev // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 2. — С. 177-179. — Бібліогр.: 14 назв. — англ. |
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irk-123456789-1193952017-06-07T03:05:47Z Polarimetric observations of the Galilean satellites near opposition in 2011 Zaitsev, S.V. Kiselev, N.N. Rosenbush, V.K. Velichko, F.P. Kolesnikov, S.V. Antonyuk, K.A. Psarev, V.N. We present results of the new polarimetric observations of the Galilean satellites Io, Ganymede, Europe, and Callisto carried out on October 21 - November 1, 2011. We used 1.25m telescope equipped with the UBVRI double image chopping photoelectric polarimeter, 2.6m Shain telescope equipped with a one-channel photoelectric photometer-polarimeter, 1m RCC telescope equipped with a one-channel photoelectric photometer-polarimeter (Crimean Astrophysical Observatory, Ukraine), and 0.7m telescope equipped with a one-channel photoelectric photometer-polarimeter (Chuguev Observational Station of Astronomical Institute of Karazin Kharkiv National University, Ukraine). The measurements were performed at phase angles ranging from 0.34° to 2.12°. Our new observations fully confirmed the presence of the polarization opposition effect for high-albedo satellites Io, Europa, and Ganymede at phase angles less than 2° . Within the accuracy of the measurements we did not detect the polarization opposition effect for moderate-albedo satellite Callisto. 2012 Article Polarimetric observations of the Galilean satellites near opposition in 2011 / S.V. Zaitsev, N.N. Kiselev, V.K. Rosenbush, F.P. Velichko, S.V. Kolesnikov, K.A. Antonyuk, V.N. Psarev // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 2. — С. 177-179. — Бібліогр.: 14 назв. — англ. 2227-1481 http://dspace.nbuv.gov.ua/handle/123456789/119395 en Advances in Astronomy and Space Physics Головна астрономічна обсерваторія НАН України |
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We present results of the new polarimetric observations of the Galilean satellites Io, Ganymede, Europe, and Callisto carried out on October 21 - November 1, 2011. We used 1.25m telescope equipped with the UBVRI double image chopping photoelectric polarimeter, 2.6m Shain telescope equipped with a one-channel photoelectric photometer-polarimeter, 1m RCC telescope equipped with a one-channel photoelectric photometer-polarimeter (Crimean Astrophysical Observatory, Ukraine), and 0.7m telescope equipped with a one-channel photoelectric photometer-polarimeter (Chuguev Observational Station of Astronomical Institute of Karazin Kharkiv National University, Ukraine). The measurements were performed at phase angles ranging from 0.34° to 2.12°. Our new observations fully confirmed the presence of the polarization opposition effect for high-albedo satellites Io, Europa, and Ganymede at phase angles less than 2° . Within the accuracy of the measurements we did not detect the polarization opposition effect for moderate-albedo satellite Callisto. |
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Article |
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Zaitsev, S.V. Kiselev, N.N. Rosenbush, V.K. Velichko, F.P. Kolesnikov, S.V. Antonyuk, K.A. Psarev, V.N. |
| spellingShingle |
Zaitsev, S.V. Kiselev, N.N. Rosenbush, V.K. Velichko, F.P. Kolesnikov, S.V. Antonyuk, K.A. Psarev, V.N. Polarimetric observations of the Galilean satellites near opposition in 2011 Advances in Astronomy and Space Physics |
| author_facet |
Zaitsev, S.V. Kiselev, N.N. Rosenbush, V.K. Velichko, F.P. Kolesnikov, S.V. Antonyuk, K.A. Psarev, V.N. |
| author_sort |
Zaitsev, S.V. |
| title |
Polarimetric observations of the Galilean satellites near opposition in 2011 |
| title_short |
Polarimetric observations of the Galilean satellites near opposition in 2011 |
| title_full |
Polarimetric observations of the Galilean satellites near opposition in 2011 |
| title_fullStr |
Polarimetric observations of the Galilean satellites near opposition in 2011 |
| title_full_unstemmed |
Polarimetric observations of the Galilean satellites near opposition in 2011 |
| title_sort |
polarimetric observations of the galilean satellites near opposition in 2011 |
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Головна астрономічна обсерваторія НАН України |
| publishDate |
2012 |
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http://dspace.nbuv.gov.ua/handle/123456789/119395 |
| citation_txt |
Polarimetric observations of the Galilean satellites near opposition in 2011 / S.V. Zaitsev, N.N. Kiselev, V.K. Rosenbush, F.P. Velichko, S.V. Kolesnikov, K.A. Antonyuk, V.N. Psarev // Advances in Astronomy and Space Physics. — 2012. — Т. 2., вип. 2. — С. 177-179. — Бібліогр.: 14 назв. — англ. |
| series |
Advances in Astronomy and Space Physics |
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| fulltext |
Polarimetric observations of the Galilean satellites
near opposition in 2011
S.V. Zaitsev1∗, N.N.Kiselev1, V.K.Rosenbush1, F. P.Velichko2, S. V.Kolesnikov3,
K.A.Antonyuk4, V.N. Psarev2
Advances in Astronomy and Space Physics, 2, 177-179 (2012)
© S.V. Zaitsev, N.N.Kiselev, V.K.Rosenbush, F. P.Velichko, S.V.Kolesnikov, K.A.Antonyuk, V.N.Psarev
1Main Astronomical Observatory of the National Academy of Sciences of Ukraine, Zabolotnoho 27, 03680, Kyiv, Ukraine
2Institute of Astronomy of Karazin Kharkiv National University, Sumskaya Str., 35, 61022, Kharkiv, Ukraine
3Astronomical Observatory of Odessa National University, T.G. Shevchenko Park, 65014, Odessa, Ukraine
4Crimean Astrophysical Observatory, 98409, Nauchny, Crimea, Ukraine
We present results of the new polarimetric observations of the Galilean satellites Io, Ganymede, Europe, and
Callisto carried out on October 21 � November 1, 2011. We used 1.25m telescope equipped with the UBVRI
double image chopping photoelectric polarimeter, 2.6m Shain telescope equipped with a one-channel photoelectric
photometer-polarimeter, 1m RCC telescope equipped with a one-channel photoelectric photometer-polarimeter
(Crimean Astrophysical Observatory, Ukraine), and 0.7m telescope equipped with a one-channel photoelectric
photometer-polarimeter (Chuguev Observational Station of Astronomical Institute of Karazin Kharkiv National
University, Ukraine). The measurements were performed at phase angles ranging from 0.34◦ to 2.12◦. Our new
observations fully con�rmed the presence of the polarization opposition e�ect for high-albedo satellites Io, Europa,
and Ganymede at phase angles less than 2◦. Within the accuracy of the measurements we did not detect the
polarization opposition e�ect for moderate-albedo satellite Callisto.
Key words: polarization, planets and satellites: surfaces
introduction
Polarimetry is a very powerful method for study-
ing distant atmosphereless Solar System Bodies
(ASSBs), such as asteroids, planetary satellites,
planetary rings. The characteristics of phase-angle
dependence of polarization for these bodies are very
sensitive to the mechanisms of the light scattering
as well as to the albedo, composition, and structure
of the particular surface. The phase-angle depen-
dence of polarization near the opposition for di�er-
ent ASSBs is still in the focus of attention because
the behaviour of polarization at small phase angles
is a key test for alternative models of light scatter-
ing by regolith surfaces [13]. High-albedo Jovian
satellites Io, Europa, and Ganymede are among the
ASSBs exhibiting narrow, asymmetric spike of neg-
ative polarization at small phase angles, namely, a
secondary minimum superimposed upon the nega-
tive polarization branch (the so-called polarization
opposition e�ect) [11]. Its appearance was theoreti-
cally predicted by Mishchenko [5] as manifestation
of coherent backscattering as the primary mecha-
nism to explain the observed opposition e�ects for
high-albedo ASSBs. Measurements of the degree of
linear polarization of the Galilean satellites at di�er-
ent phase angles were started in 1960s [2], but so far
the available polarimetric data are still not enough to
trace the behaviour of polarization at small phase an-
gles in details. Moreover, according to Chigladze [1]
for Jupiter satellites there are the secondary points of
inversion at phase angles about 0.5◦. We present re-
sults of new polarimetric observations of the Galilean
satellites at small phase angles in 2011 as well as the
results of observations obtained in 1988 � 2010.
observations
Polarimetric observations of the Galilean satel-
lites Io, Ganymede, Europa, and Callisto were
carried out on October 21 � November 1, 2011.
We used 1.25m telescope equipped with the UB-
VRI double image chopping photoelectric polarime-
ter [7], 2.6m Shain telescope equipped with a
one-channel photoelectric photometer-polarimeter,
1m RCC telescope equipped with a one-channel
photoelectric photometer-polarimeter [14] (Crimean
Astrophysical Observatory, Ukraine), and 0.7m
telescope equipped with a one-channel photoelec-
tric photometer-polarimeter [14] (Chuguev Observa-
tional Station of Astronomical Institute of Karazin
Kharkiv National University, Ukraine). Observa-
tions were carried out in the U, B, V, R, I bands.
The measurements were performed at phase angles
ranging from 0.34◦ to 2.12◦.
The data of the highest accuracy were obtained
∗hastkes@yahoo.com
177
Advances in Astronomy and Space Physics S.V. Zaitsev, N.N.Kiselev, V.K.Rosenbush et al.
in the V and R spectral bands. Fig. 1 shows the
phase-angle dependencies of linear polarization for
the Galilean satellites in the V and R bands at phase
angles less than 7◦ according to this work (�lled sym-
bols) and previous studies (open symbols) � Rosen-
bush et al. [8], Rosenbush and Kiselev [9], Kiselev et
al. [4], Zaitsev et al. (unpublished). Circles repre-
sent the data for leading hemispheres, and diamonds
for trailing hemispheres. For Europa and Ganymede
solid lines show the regular negative branches of po-
larization. For Io and Callisto solid and dashed lines
correspond to the regular negative branches of po-
larization for the leading and trailing hemispheres,
respectively [9].
The Stokes parameters u and q were determined
from observations, and then the degree of linear po-
larization P and the position angle of the polariza-
tion plane θ were calculated, using the following ex-
pressions:
P =
√
u2 + q2, (1)
θ =
1
2
arctan
(
u
q
)
. (2)
The random errors σp were calculated in two ways.
The �rst one uses the statistics of recorded photons
from the object no and from the sky background ns
according to the expression
σp =
√
1
no
(
1 +
1 + τ
R
)
, (3)
where τ is a ratio of the measurement durations for
object and the sky background, and R is a ratio of
the recorded photons no and ns for the same period
[12]. Another method lies in using the expression
σp =
√
1
2
(
σ2
u + σ2
q
)
, (4)
where σu and σq are the mean square root errors
of the individual measurements of parameters u and
q, respectively [12]. The larger of these two errors
σp was adopted as a measurement accuracy of the
weighted mean values of polarization parameters P
for night. The errors σθ in the position angle mea-
surements were determined using the standard rela-
tion
σθ = 28.65
σp
P
. (5)
Instrumental polarization u and q in the V and
R spectral bands determined from the observations
of unpolarized standard stars do not exceed 0.4% for
1.25m telescope, 0.2% for 1m RCC telescope, 0.06%
for 2.6m Shain telescope (Crimean Astrophysical Ob-
servatory), and 0.1% for 0.7m telescope (Chuguev
Observational Station of Astronomical Institute of
Karazin Kharkiv National University, Ukraine) with
errors of about 0.02%. This was carefully taken into
Fig. 1: Phase-angle dependencies of polarization for the
Galilean satellites in the V and R bands.
178
Advances in Astronomy and Space Physics S.V. Zaitsev, N.N.Kiselev, V.K.Rosenbush et al.
account. The calibration of the position angle of the
polarization plane was made using the observations
of stars with well-known large interstellar polariza-
tion [3]. The angle θr between the polarization plane
and the plane perpendicular to the scattering plane
ϕ was calculated according to the expression:
θr = θ − (ϕ± 90◦). (6)
In all cases, the angle θr is close to 90◦, i. e., the
degree of polarization is negative, as it is generally
agreed.
discussion
Our new observations fully con�rmed the pres-
ence of asymmetric secondary minimum of polar-
ization (the polarization opposition e�ect) super-
imposed upon the negative polarization branch for
high-albedo satellites Io, Europa, and Ganymede
[4, 8, 9] at phase angles less than 2◦. The shape and
amplitude of the polarization opposition e�ect are
slightly di�erent for di�erent satellites. For Europa
and Ganymede the polarization peaks are slightly
deeper then for previous observations, that con�rms
that the amplitudes of the polarization peaks are
slightly di�erent for di�erent apparitions (the same
e�ect was observed for high-albedo asteroid 64 An-
gelina [10]). The di�erence in polarization from
apparition to apparition possibly can be explained
by longitude dependence of polarization, which is
caused by di�erence in physical properties of the
surface layer (surface roughness and single-particle
geometrical and optical properties), by systematic
errors of the measurements in di�erent sets of ob-
servations, and di�erences in aspects in di�erent ap-
paritions. The signi�cant scatter of polarization data
points is mainly the result of local inhomogeneities of
the satellites surface, which is superimposed on the
global di�erences of polarimetric properties of the
leading and trailing hemispheres. We did not de-
tect the polarization opposition e�ect for moderate-
albedo satellite Callisto. New data for this satellite
con�rm distinctions of polarimetric properties of the
leading and trailing hemispheres [10].
For all Galilean satellites Chigladze [1] found that
there are the second inversion points at phase angles
about 0.5◦. Non-zero degree of polarization (about
0.3%) of the satellites at phase angle about 0.5◦ was
observed by Morozhenko [6]. In addition the angle
between the plane of polarization and the scatter-
ing plane was close to 45◦. The Chigladze's and
Morozhenko's data are inconsistent with our present
and previous results. Our observations have not re-
vealed the presence of the second points of inversion,
and the plane of polarization was always parallel to
the scattering plane. The reasons for these di�er-
ences have been analysed by Kiselev et al. [4]. After
correction of Chigladze's and Morozhenko's data the
contradiction in results disappears.
conclusion
New polarimetric observations of the Galilean
satellites of Jupiter in 2011 are in a good agreement
with our previous observations and con�rm the pres-
ence of the polarization opposition e�ect for Io, Eu-
ropa, and Ganymede in the range of phase angles
smaller than 2◦. Within the accuracy of the measure-
ments we did not detect any polarization opposition
e�ect for the moderate-albedo satellite Callisto.
references
[1] ChigladzeR.A. 1989, Ph.D. Thesis, Abastumani Astro-
physical Observatory
[2] DollfusA. 1975, Icarus, 25, 416
[3] HeilesC. 2000, AJ, 119, 923
[4] KiselevN., RosenbushV., VelichkoF. & Zaitsev S. 2009,
J. Quant. Spec. Radiat. Transf., 110, 1713
[5] MishchenkoM. I. 1993, ApJ, 411, 351
[6] MorozhenkoA.V. 2001, Kinematika i Fizika Nebesnykh
Tel, 17, 6, 549
[7] PiirolaV. 1973, A&A, 27, 383
[8] RosenbushV.K., AvramchukV.V., RosenbushA.E. &
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