Effects of Climate Change on Earth’s Parameters
An Example of Exabyte-sized System
Giampiero Sindoni
1
, Erricos. C. Pavlis
2
, Claudio Paris
3,1
, Antonio Paolozzi
1,3
and Ignazio Ciufolini
4,3
1
Scuola di Ingegneria Aerospaziale, Sapienza University of Rome, Via Salaria 851, 00138 Rome, Italy
2
Joint Center for Earth Systems Technology (JCET/UMBC), University of Maryland,
Baltimore County and NASA Goddard, 1000 Hilltop Circle Baltimore, 21250 Maryland, U.S.A.
3
Museo Storico della Fisica e Centro Studi e Ricerce Enrico Fermi, Via Panisperna, 89, 00184 Rome, Italy
4
Dipartimento di Ingegneria dell’ Innovazione, Universit
`
a del Salento, Via per Monteroni, 73100 Lecce, Italy
Keywords:
Climate Change, Earth Orientation Parameters, Gravity Variations, Space Geodetic Techniques, Big Data,
ITRF.
Abstract:
Climate change at global scale affects Earth characteristics that can be detected by measuring global param-
eters such as Earth rotation and centre of mass variations. Similarly, changes in the harmonics of Earth’s
gravitational field model are an indication of environmental changes and provide a measure of the mass redis-
tributions causing these variations. There are four independent space geodetic techniques today that monitor
Earth’s geometric and dynamic parameters very accurately: Very Long Baseline Interferometry (VLBI), Satel-
lite/Lunar Laser Ranging (SLR/LLR), Global Navigation Satellite Systems (GNSS) and Doppler Orbitography
and Radiopositioning Integrated by Satellite (DORIS). These techniques have been operational for decades,
collecting a very large amount of data that after appropriate processing provide, among other things, the Earth
geometric and dynamic parameters used in global climate change monitoring. The same techniques are also
necessary for the establishment and maintenance of the International Terrestrial Reference Frame (ITRF). To
make the large amount of data more easily usable, scientists and engineers employ reduction techniques to
significantly reduce the amount of raw data with minimal loss of information. It will be shown that the total
amount of data available today is of the order of exabyte. Due to the complexity of data management and
processing several national and international bodies have been established.
1 INTRODUCTION
Very Long Baseline Interferometry (VLBI), Satel-
lite Laser Ranging (SLR), Global Navigation Satel-
lite Systems (GNSS) and Doppler Orbitography and
Radiopositioning Integrated by Satellite (DORIS) al-
though each can provide independent Earth parame-
ters, the combination of their data allows to negate
the weaknesses and complement the strengths of the
individual techniques. The first two techniques are
the oldest and the available data span over periods of
more than three decades. Processing is usually per-
formed using the longest time series constructed go-
ing back to the oldest acquisitions. This improves
confidence on the analysis that are substantially based
on fitting the models of the Earth parameters evolu-
tion with the data.
The complexity involved in integrating the four
techniques is very high. In fact the planning and oper-
ational management for the acquisition, storage, dis-
tribution, quality check, data formatting, and adher-
ence to standards is the task of international bodies
established as Services as will be described in detail
in section 3. While GNSS have a mass market the
other three techniques are more institutional oriented
and in particular SLR that is devoted mainly to studies
on geodesy but also to fundamental physics (Ciufolini
et al., 2013b) and gravitational physics (Bosco et al.,
2007). In particular the use of the orbital parame-
ters of the two LAGEOS satellites allowed an accurate
measurement of the Lense-Thirring effect, a manifes-
tation of frame-dragging (Ciufolini et al., 2012b; Ciu-
folini and Ricci, 2002) of the General Relativity the-
ory, with an accuracy of about 10% (Ciufolini et al.,
1998; Ciufolini and Pavlis, 2004). LARES is the lat-
est laser ranged satellite (Paolozzi et al., 2015), it has
been funded by the Italian Space Agency (ASI) and
launched on February 13, 2012 (Paolozzi et al., 2012;
Sindoni, G., Pavlis, E., Paris, C., Paolozzi, A. and Ciufolini, I.
Effects of Climate Change on Earth’s Parameters - An Example of Exabyte-sized System.
In Proceedings of the 1st International Conference on Complex Information Systems (COMPLEXIS 2016), pages 131-138
ISBN: 978-989-758-181-6
Copyright
c
2016 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
131
Paolozzi and Ciufolini, 2013) by the VEGA launcher
provided by the European Space Agency (ESA). With
the addition of this new satellite the accuracy in the
measurement of the Lense-Thirring effect will be im-
proved by one order of magnitude as shown by a
Monte Carlo simulation (Ciufolini et al., 2013a), an
error analysis (Ciufolini et al., 2012a) and the results
of the preliminary orbital analysis (Ciufolini et al.,
2015). The ever increasing accuracy of the geodedic
techniques allow to detect very small variation of spin
axis, angular velocity and center of mass of the Earth.
Those small variations are related to several factors
among which the angular momentum exchange be-
tween the solid Earth and atmosphere which is not
perfectly co-rotating with the Earth because of winds,
air jets, tornadoes etc...(Kouba and Vondrk, 2005).
There have been also recent studies that found corre-
lation between Earth Rotation Parameters (ERP) vari-
ations and global climate change. (Lehmann et al.,
2009). Some more details on Earth global parameters
and climate change are reported in section 4.
2 EARTH’S MOVEMENT
In this section we will describe the Earth’s movements
since they are more complex than what usually taught
in non-specialized courses. In fact besides the well-
known revolution around the Sun, and the rotation
about its axis of maximum inertia, there are other mo-
tions, some of which are induced by external forces
and internal mass redistribution.
In the body reference frame (Terrestrial Refer-
ence Frame TRF) there is the polar motion and the
length-of-day variations, as well as variations of the
center of mass due to mass redistribution in the Earth
system (mostly seasonal), while in the Celestial Ref-
erence Frame (CRF), there are additional motions:
precession, nutation and free-core nutation. Usually
when referring to the body fixed reference frame, one
considers the Earth Rotation Parameters (ERP), be-
cause the EOP include also precession and nutation.
2.1 ITRF and EOP
Earth orientation parameters, center of mass varia-
tions and scale are the essential elements that define
the terrestrial reference frame that can have different
realizations based on each individual space geodetic
technique. The best realization of course is the one
obtained after the combination of the data from all
four techniques, since the combination benefits from
the information provided by each one and eliminates
the weaknesses of each technique. There is already a
large amount of data from each of the techniques used
in the development of these reference frames. The de-
velopment of the ITRF involves the data from all four
techniques, so a quadruple amount of data.
The current version of the ITRF, called ITRF2008,
has been obtained using data collected from 934 sta-
tions in 580 sites (463 of which in the northern hemi-
sphere) and distributed among the four techniques as
follows: 29 years of VLBI data, 26 years of SLR data,
12.5 years of GPS data, and 16 years of DORIS data.
84 sites have the co-location of at least two of the four
techniques.
3 GEODETIC TECHNIQUES
The huge amount of data and the complex relation
among the data and the owners made necessary the es-
tablishment of international bodies established as Ser-
vices under the International Association of Geodesy
(IAG) and comprising several working groups for
each individual technique. The coordination of activ-
ities of these Services is the task of their Governing
Boards and Central Bureaus, while high-level guid-
ance is provided by IAG. The operative part of IAG
is the Global Geodetic Observing System (GGOS)
that plans, designs, and advocates for the required
infrastructure of all observing techniques. The data
are available through the global data centers of each
Service, one of which is the Crustal Dynamics Data
Information System (CDDIS) located at the Goddard
Space Flight Center, and the only data center that
archives the data from all four Services. In particular
the CDDIS provides online access to the GNSS data
and products generated by the International GNSS
Service (IGS). The organizations that specifically deal
with the four techniques are listed in Table 1. The Ser-
vices are also devoted to data analysis and each one
has an analysis working group that coordinates these
activities.
Table 1: Organizations specifically devoted to the single
geodetic techniques.
Organization Acronym Technique
International VLBI
Service for Geodesy
and Astrometry
IVS VLBI
International GNSS
Service
IGS GNSS
International Laser
Ranging Service
ILRS SLR/LRR
International DORIS
Service
IDS DORIS
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132
IVS is a service of the International Association
of Geodesy (IAG) and of the International Astro-
nomical Union (IAU). VLBI has been exclusively
ground based (the attempt to increase the baseline
performed with the Japanese HALCA space borne
radio-telescope provided limited results and the cur-
rently operating Russian Radioastron spacecraft has
been used for astrometric observations only), while
SLR/LLR, GNSS and DORIS need necessarily an op-
erating space segment, besides the ground-based in-
struments. In the case of SLR/LLR the space seg-
ment can be purely passive. GNSS has an active space
and ground segments. The GNSS constellations are
continuously increasing due to the massive market of
applications in navigators and to the will of Europe,
China, India and Japan (the last two with two regional
systems) to be independent of the GPS (USA) and/or
GLONASS (Russia) systems.
In this section the four techniques, including an esti-
mate of size of data, are described.
3.1 VLBI
VLBI is a measuring technique that uses radio-
telescopes located on the Earth surface to observe ra-
dio signals from extragalactic sources (quasars) which
are at practically infinite distance from Earth (Figure
1). The difference in arrival times of the same signal
at two telescopes carries information about the length
of the baseline between the two telescopes. By ob-
serving several quasars in different directions from a
pair of telescopes, we can infer the length and abso-
lute direction of the baseline between the two tele-
scopes. Doing so from a global network of such tele-
scopes allows to determine the shape and size of the
network very accurately. Because the observations do
not depend on the absolute location of the network
in space (due to the infinite distance of the sources,
VLBI does not sense the location of the geocenter,
nor its variations. On the other hand, since the quasars
form a quasi-inertial frame, VLBI can observe preces-
sion, nutation and free-core nutation, and determine
the absolute orientation of Earth in space that are the
primary contributions of VLBI in the development of
the ITRF and the associated EOP series.
VLBI is the geodetic technique that collects the
largest amount of raw data to deliver its products. The
amount that it collects at present on a yearly basis for
the entire network is about 0.3 EB, and one could es-
timate that over its 30 yrs of existence, it has collected
well over 3 EB of data alone (the network was a lot
smaller in the early years).
IVS coordinates VLBI observing programs, sets
performance standards for VLBI stations, establishes
conventions for VLBI data formats and data products,
issues recommendations for VLBI data analysis soft-
ware, sets standards for VLBI analysis documenta-
tion, and institutes appropriate VLBI product deliv-
ery methods to ensure suitable product quality and
timeliness. IVS also coordinates its activities with the
astronomical community because of the dual use of
many VLBI facilities and technologies for both radio
astronomy and geodesy/astrometry.
3.2 SLR
Satellite Laser Ranging (SLR) and Lunar Laser Rang-
ing (LLR) use short-pulse lasers and state-of-the-art
optical receivers and timing electronics to measure
the two-way time of flight (and hence distance) from
ground stations to retroreflector arrays on Earth or-
biting satellites and the Moon. Scientific products
derived using SLR and LLR data include precise
geocentric positions and motions of ground stations,
satellite orbits, components of Earths gravity field and
their temporal variations, Earth Orientation Parame-
ters (EOP), precise lunar ephemerides and informa-
tion about the internal structure of the Moon. Laser
ranging systems are already measuring the one-way
distance to remote optical receivers in space and can
perform very accurate time transfer between sites far
apart.
The ILRS network (Figure 2) collects today
roughly 110 TB per year, and with some averaging
and considering the significantly smaller network and
fewer number of target satellites, one can estimate
that over its 30 year existence, SLR has collected
about 1 PB or 10
3
EB raw data. SLR is thus a much
more efficient system, producing its products on the
basis of significantly less raw information than VLBI.
Laser ranging activities are organized under the
International Laser Ranging Service (ILRS) which
provides global satellite and lunar laser ranging data
and their derived data products to support research in
geodesy, geophysics, Lunar science, and fundamen-
tal constants (Pearlman et al., 2002). This includes
data products that are fundamental to the International
Terrestrial Reference Frame (ITRF), which is estab-
lished and maintained by the International Earth Ro-
tation and Reference Systems Service (IERS). SLR
is the only technique that can determine accurately
and in an absolute sense the origin of the ITRF, i.e.
the geocenter, and along with VLBI, the scale of the
ITRF network of stations. These are the primary con-
tributions of SLR in the development of the ITRF,
with minor contributions in the determination of the
associated ERP series, especially as far as the long
wavelength signals. The ILRS develops the neces-
Effects of Climate Change on Earth’s Parameters - An Example of Exabyte-sized System
133
Figure 1: VLBI sites, the global IVS network.
Figure 2: Stations of the International Laser Ranging Service (ILRS) global network.
sary global standards/specifications for laser ranging
activities and encourages international adherence to
its conventions.
3.3 GNSS
The Global Navigation Satellite Systems are constel-
lations of satellites (identical or very similar), that
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Figure 3: Stations of the IGS global network.
emit radio signals with encoded information, that can
be tracked by receivers located practically anywhere
(ground, sea, air, on static or moving platforms), in
order to determine their position, velocity and time.
In simple terms, the technique used is based on solv-
ing a point-positioning problem from the measure-
ment of at least four simultaneous pseudorange (bi-
ased range) measurements to four different satellites
from the same receiver. These allow for the de-
termination of the observer’s position and the time-
difference between the receiver’s clock and the time
kept by the satellites atomic clocks. For higher accu-
racy, scientific receivers collect also phase measure-
ments for each signal and at two different frequencies,
so that ionospheric delay effects can be calibrated out.
Further modeling or estimation of the tropospheric
delay in the observed signals allows to reach ultra pre-
cise levels, delivering geodetic products with an accu-
racy of a few millimetres.
Since 1994 the International GNSS service (IGS)
provides GNSS products that are used for many ap-
plications including the realization of the ITRF. The
number of stations has continuously increased reach-
ing today 500 units (Figure 3). The IGS supports
research for the continuous development of new ap-
plications and products through Working Groups and
Pilot Projects supporting geodetic research and schol-
arly publications. Using average data collection esti-
mates, we can infer that the GNSS network collects
some 25 TB of raw data per year in the current state.
The network and the available satellites were signif-
icantly smaller in size/number in the early years, so
taking that into account, the entire lot of data collected
since the early 90s is roughly 0.5 PB or 0.5 ×10
3
EB
raw data, again, similar in order of magnitude to the
SLR raw data set.
3.4 DORIS
The Doppler Orbitography and Radiopositioning In-
tegrated by SatelliteDORIS system is a French civil
precise orbit determination and positioning system
(Figure 4). It is based on the principle of the Doppler
effect with a network of transmitting terrestrial bea-
cons and on-board instruments on the satellite’s pay-
load (antenna, radio receiver and ultra-stable oscilla-
torUSO).
DORIS is one of three systems used for precise
determination of the Jason-1 satellite’s orbit. Several
of these techniques are sometimes onboard the same
satellite: Jason-1 satellite includes three tracking sys-
tems, DORIS, GPS and SLR array. The DORIS sys-
tem perfectly corresponds to the specifications re-
quired for the ocean’s topography observations and
the amplitude of the observed phenomena: it now
enables to measure the satellite position on its orbit
close to 1 cm. It is interesting to compare this pre-
cision with the precision obtained at the beginning of
the space age, where the satellite position was esti-
mated close to 20 km, then close to 20 meters in the
80’s. Since 1998, the Diode navigator has added real-
time measurement processing capability for satellite
navigation.
The DORIS system was designed by CNES, the
Effects of Climate Change on Earth’s Parameters - An Example of Exabyte-sized System
135
Figure 4: DORIS stations co-located with other IERS techniques (VLBI, SLR or GNSS).
French space agency, in partnership with France’s
mapping and survey agency IGN and the space
geodesy research institute GRGS. The successive
missions since Spot 2 and Topex/Poseidon have truly
demonstrated its performance. It is currently on-
board the Cryosat-2, Jason-2, HY-2A and SARAL
altimetric satellites and the remote sensing satellite
SPOT-5. It also flew with SPOT-2, SPOT-3, SPOT-
4, TOPEX/POSEIDON, ENVISAT and Jason-1.
Since 2003, IDS is an international service that
supports science through DORIS data and products
for geodetic, geophysical, and other research and op-
erational activities. IDS contributes its products for
the development of the ITRF and with the newest
systems in orbit it can determine near-real time or-
bits onboard the platform carrying the system, thence
allowing the geolocation of the collected data (e.g.
sea-surface heights) in near-real time. The DORIS
system collects the raw data on-board the satellites
that carry DORIS receivers and subsequently down-
loads that data to the appropriate master stations of
the network for further processing and archiving. The
amount of collected data over the period of its exis-
tence is at the same order of magnitude as the GNSS,
perhaps a little lower, but in any event, by far less than
the dominating VLBI data set that defines the order of
magnitude and complexity of this observing system.
4 EXAMPLE OF EARTH
PARAMETER INFLUENCED BY
THE GLOBAL WARMING
Global warming is believed to occur faster than in the
recent past. This will cause an anomalous ice melt-
ing on polar ice caps and on Greenland. As a con-
sequence the rotation axis of the Earth will show an
anomalous drift. In Figure 5 are reported real data of
polar motion, i.e. the intersection of the Earth rotation
axis with the Earth surface as seen from an observer
fixed with the Earth. The graph has been obtained also
using about two years of LARES data. The circular
path is the Chandler wobble that can be qualitatively
explained by solving the rigid body Euler equations
in the torque free case. The variation in diameter of
the polar motion is due to a beating phenomenon with
an annual forcing component. The slow drift of the
center is mainly attributed to the post glacial rebound
(the slow recovery of the ground after the release of
the weight after the glacial era). The change in direc-
tion of this drift that occurred in 2005 is attributed to
accelerated ice melting in polar ice caps and Green-
land (Chen et al., 2013). Besides polar motion also
gravitational harmonics of the Earth gravity field and
position of the center of mass are affected by global
changes (Pavlis et al., 2015a; Pavlis et al., 2015b; Sin-
doni et al., ). We report for the sake of clarity the dis-
placement of the center of mass of the Earth (Figure
6). The analysis was performed using SLR data of
the last 25 years. The results, taken from (Pavlis et
al., 2015a), show clearly the accuracy that is below 1
mm. We observe predominantly annual oscillations
with an amplitude of 3 mm in X and Y, and 5
mm in Z. These are caused by the redistribution of
mass during the year between the northern and south-
ern hemispheres, thence the larger Z-component am-
plitude.
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136
Figure 5: Polar motion from 1962 (Pavlis et al., 2015b).
Figure 6: Components of the center of mass obtained ana-
lyzing SLR data from 1990 to 2015 including the last two
years of LARES data (Pavlis et al., 2015a).
5 CONCLUSIONS
The four geodetic techniques described constitute an
exabyte size system. The data analysis provides,
among other things, Earth global parameters such as
spin axis and center of mass of the Earth. The accu-
racy of the combined techniques allow to reach mil-
limiter accuracy that are capable to signal events such
as accelerating ice melting in Greenland or sea level
rise in part of the globe due to global climate change.
When we add up all the data collected by all four
space geodetic techniques, VLBI, SLR, GNSS and
DORIS, the amount of data products that they deliver
to IERS/ITRS for the development of the ITRF and
its associated EOP series, reaches the level of about
3.5 EB, dominated by the VLBI data. As the net-
works of all techniques expand to meet the goals of
the next generation networks as outlined by GGOS
and considering the exponentially increasing number
of satellite targets due to the proliferation of naviga-
tion constellations (Galileo, BeiDou and IRNSS are
all launching new satellites with a fully operational
state by 2020 or so), we can easily predict that this
global geodetic observing system will surpass the cur-
rent 3.5 EB of data and perhaps reach the 5 EB level
by 2020.
ACKNOWLEDGEMENTS
The authors acknowledge the supported by the Ital-
ian Space Agency under contract 2015-021-R.0. E.C.
Pavlis acknowledges the support of NASA Grants
NNX09AU86G and NNX14AN50G. The authors
thanks the International Laser Ranging Service for
tracking LARES and providing the laser ranging data.
REFERENCES
Bosco, A., Cantone, C., Dell’Agnello, S., Delle Monache,
G. O., Franceschi, M. A., and Garattini, M. a. a.
(2007). Probing gravity in NEO with high-accuracy
laser-ranged test masses. International Journal of
Modern Physics D, 16(12a):2271–2285.
Chen, J. L., Wilson, C. R., Ries, J. C., and Tapley, B. D.
(2013). Rapid ice melting drives earth’s pole to the
east. Geophysical Research Letters, 40(11):2625–
2630.
Ciufolini, I., Monge, B. M., Paolozzi, A., Koenig, R., Sin-
doni, G., Michalak, G., and Pavlis, E. (2013a). Monte
carlo simulations of the LARES space experiment to
test general relativity and fundamental physics. Clas-
sical and Quantum Gravity, 30.
Ciufolini, I., Paolozzi, A., Koenig, R., Pavlis, E. C., Ries, J.,
Matzner, R., Gurzadyan, V., Penrose, R., Sindoni, G.,
and Paris, C. (2013b). Fundamental physics and gen-
eral relativity with the LARES and LAGEOS satel-
lites. Nuclear Physics B - Proceedings Supplements,
243-244:180–193.
Ciufolini, I., Paolozzi, A., and Paris, C. (2012a). Overview
of the LARES mission: orbit, error analysis and tech-
nological aspects. Journal of Physics. Conference Se-
ries, 354. conference 1.
Effects of Climate Change on Earth’s Parameters - An Example of Exabyte-sized System
137
Ciufolini, I., Paolozzi, A., Pavlis, E., Koenig, R., Ries, J.,
Gurzadyan, V., Matzner, R., Penrose, R., Sindoni, G.,
and Paris, C. (2015). Preliminary orbital analysis of
the lares space experiment. The European Physical
Journal Plus, 130(7).
Ciufolini, I. and Pavlis, E. C. (2004). A confirmation of the
general relativistic prediction of the Lense-Thirring
effect. Nature, 431:958–960.
Ciufolini, I., Pavlis, E. C., Chieppa, F., Fernandes-Vieira,
E., and Mercader, J. P. (1998). Test of general relativ-
ity and measurement of the Lense-Thirring effect with
two earth satellites. Science, 279:2100–2103.
Ciufolini, I., Pavlis, E. C., Paolozzi, A., Ries, J., Koenig, R.,
Matzner, R., Sindoni, G., and Neumayer, H. (2012b).
Phenomenology of the Lense-Thirring effect in the so-
lar system: measurement of frame-dragging with laser
ranged satellites. New Astronomy, 17:341–346.
Ciufolini, I. and Ricci, F. (2002). Time delay due to spin in-
side a rotating shell. Classical and Quantum Gravity,
19(15):3875.
Kouba, J. and Vondrk, J. (2005). Comparison of length of
day with oceanic and atmospheric angular momentum
series. J. Geod, 79:256–268.
Lehmann, E., Grtzsch, A., Ulbrich, U., Leckebusch, G.,
Nevir, P., and Thomas, M. (2009). Long-term erp
time series as indicators for global climate variability
and climate change. Geophysical Research Abstracts,
11:EGU2009–9084–1.
Paolozzi, A. and Ciufolini, I. (2013). LARES succesfully
launched in orbit: satellite and mission description.
Acta Astronautica, 91:313–321.
Paolozzi, A., Ciufolini, I., Flamini, E., Gabrielli, A., and
Mangraviti, E. (2012). LARES is in orbit! some as-
pects of the mission. In 63rd International Astronau-
tical Congress IAC 2012. IAF.
Paolozzi, A., Ciufolini, I., Paris, C., and Sindoni, G.
(2015). LARES, a new satellite specifically designed
for testing general relativity. International Journal of
Aerospace Engineering, Volume 2015:9 pages. Arti-
cle ID 341384.
Pavlis, E., Sindoni, G., Paolozzi, A., and Ciufolini, I.
(2015a). Contribution of LARES and geodetic satel-
lites on environmental monitoring. In 2015 IEEE 15th
International Conference on Environment and Electri-
cal Engineering (EEEIC), pages 1989–1994. IEEE.
Pavlis, E. C., Paolozzi, A., Ciufolini, I., Paris, C., Sindoni,
G., and Gabrielli, A. (2015b). Use of LARES satellite
data for earth science. In Proceedings of XXIII AIDAA
Conference. AIDAA.
Pearlman, M., Degnan, J., and Bosworth, J. (2002). The
international laser ranging service. Advances in Space
Research, 30:135–143.
Sindoni, G., Paris, C., Vendittozzi, C., Pavlis, E., Ciufolini,
I., and Paolozzi, A. The contribution of LARES to
global climate change studies with geodetic satellites.
In Proceedings of ASME Conference on Smart Ma-
terials, Adaptive Structures and Intelligent Systems
(SMASIS2015).
COMPLEXIS 2016 - 1st International Conference on Complex Information Systems
138