Gary Johnstone (Branch Head Geodesy Geoscience Australia)
Abstract
Michael R. Pearlman1, Graham M Appleby2, Giuseppe Bianco3, Carey Noll4, Erricos Pavlis5
(1 Harvard-Smithsonian Center for Astrophysics, Cambridge MA, United
States, 2 NERC Space Geodesy Facility, Herstmonceux, UK, 3 Centro di Geodesia
Spaziale "G. Colombo", Agenzia Spaziale Italiana, Matera, Italy, 4 NASA Goddard
Space Flight Center, Greenbelt MD, United States, 5 University of Maryland,
Baltimore MD, United States)
Satellite Laser Ranging (SLR) is one of the fundamental Space Geodesy techniques,
along with VLBI, GNSS and DORIS, that we use to maintain and improve the
reference frame, which is the basis for all of our metric measurements over space,
time, and evolving technology. The primary data products of SLR are Precision
Orbit Determination (POD) and Time History of Station Positions and Motions for
altimetry, gravity field modeling, Earth rotation, fundamental constants and many
other applications that are of interest to the Global Geodetic Observing Systems
(GGOS). It also supports space engineering applications, accurate time transfer,
lunar science, and tracking of space debris. SLR is unique among the space geodesy
techniques since it is the only one that operates in the optical region and the only
one that measures the range to satellites directly. The integration of new
technologies and procedures and the fielding of new SLR sites is improving SLR
data and data products; new stations in process and planned for implementation
over the next several years will significantly enhance the measurement capability.
On the other hand, serious voids in global distribution and the present mix of new
and old technologies and operating conditions oppose challenges.
In this talk we will review the SLR Technique, its coordination by the International
Laser Ranging Service and its role within GGOS. We will also discuss some of the
new emerging technologies, the expanding constellations of satellites, and the
projected expansion of the network of co-located space geodesy sites.
Abstract
Toshimichi Otsubo1, Barasa Miyahara2 and GGOS Working Group of Japan (1
Hitotsubashi University, 2 Geospatial Information Authority of Japan)
The "GGOS Working Group" was formed in Japan in 2013. Helped by a number
of institutes and organizations, we organised the Geodetic Site List where 7
geodetic sites in Japan and Antarctica were included. Each site has at least one
VLBI or SLR station, all collocated with a GNSS station. One of them has a
DORIS antenna and some have a gravimeter. The list was submitted to the GGOS
bureau and all sites were approved as GGOS sites. It should be noted that 6
different institutes own and operate these sites. Each of them has its own
backgrounds and missions but all of them have worked in collaboration. The
GGOS WG of Japan, as the first GGOS Affiliate, strives to improve the quality and
productivity of our geodetic stations, to encourage the collaboration beyond each
technique, and to make/help strategic projects for the future.
Abstract
Ryan Ruddick (Geoscience Australia)
The integrity and strength of multi-technique terrestrial reference frames, such as
realisations of the International Terrestrial Reference Frame, depend on the
precisely measured and expressed local-tie connections between space geodetic
observing systems at co-located observatories. Australia has several
observatories which together host the full variety of space geodetic observation
techniques. The observational reference point of large geodetic observing systems,
such as SLR and VLBI, are generally inaccessible. Therefore, Geoscience Australia
developed an indirect measurement approach, using terrestrial observations, to
precisely determine the invariant reference point (IVP) of SLR and VLBI telescopes.
The indirect IVP determination technique involves a rigorous process of threedimensional
circle fitting to the coordinates of targets observed on the structure
during rotational sequences about each of the systems’ independent axes (e.g.
azimuth and elevation). Geoscience Australia routinely measures millimetre
accurate connections between survey monuments and geodetic observing systems
at co-located observatories across Australia. The IVP derivation technique
continues to be refined, looking to account for further un-modelled systematic
errors.
Abstract
Sergei Gulyaev (Auckland University of Technology)
Current activities in New Zealand's Warkworth Radio Astronomical Observatory
will be outlined along with plans for future developments with particular emphasis
on the AOV support and operations.
Abstract
Oleg Titov (Geoscience Australia)
A short report on scientific results from 12 AOV sessions (six sessions in 2017, and
six sessions in first half of 2018) is presented.
Abstract
Masafumi Ishigaki (Geospatial Information Authority of Japan)
The Geospatial Information Authority of Japan (GSI) has actively been involved in
the Asia-Oceania VLBI Group for Geodesy and Astrometry (AOV) since its
establishment. The Ishioka VLBI station has performed international observations
including AOV sessions since 2015. GSI also makes schedules, carries out
correlation and analysis, and provides feedback to participating stations in AOV
sessions a few times a year in cooperation with Shanghai Astronomical
Observatory (SHAO) and University of Tasmania (UTAS). In June 2018, Ishioka
changed the regular S/X feed to the broadband feed and participated in broadband
observations from June to September including AOV broadband experiments with
the Hobart station. We report on the current status of the Ishioka station and its
future plan.
Abstract
Takaaki Jike (National Astronomical Observatory of Japan)
In order to open the geodetic VLBI data of VERA geodetic VLBI, status and
characterristics of VERA geodetic VLBI analysis system are explained. This system
is constructed for estimation of geodetic parameter from the correlation data of the
the Mitaka FX correlator. To suit to time system used in existing geodetic VLBI
estimation system, time system convertor is installed to the analysis system.
FITSIO is I/O tool of correlatio raw data and the observed-delay data set.
Abstract
Mamoru Sekido
(National Institute of Information and Communications Technology)
NICT/KASHIMA VLBI Group is participating to IVS and AOV observations with
Kashima 34m, Kashima 11m, and Koganei 11m VLBI stations. In addition to the
regular geodetic VLBI experiments, we have been engaged in VLBI technology
development as a IVS Technology Development Center. Our current target of
development is broadband VLBI system for application to long distant precise
frequency transfer. That system named GALA-V is broadband VLBI system
composed of small (2.4m diameter) broadband VLBI station (MBL) as the node
and joint observation with high sensitivity antenna for boosting SNR of the
network observation. After a series of domestic experiment until 2018, we have
exported one small VLBI station to Italy to examine the system for intercontinental
VLBI experiment. This presentation will report about current activity of our group.
Abstract
Bo Xia (Shanghai Astronomical Observatory)
The Shanghai Astronomical Observatory (SHAO) has been involved in the AOV
activities by contributing observing time of Tianma65 and Seshan25, and sharing
scheduling and correlation load. This report will outline recent geodetic activities
conducted at SHAO and report our plans in the near future, with emphasis on the
AOV activities.
Abstract
Warren Hankey (University of Tasmania)
With the permanent installation of the wideband receiver of the Hobart12
telescope last year, we have made a major change to our capabilities with the
AuScope array. Despite some setbacks and difficulties, we have made significant
progress in developing towards VGOS, assisted by our collaborations with the
Ishioka and Kashima observatories.
While our main focus has been on bringing the Hobart12 system into operation as
a VGOS station, we have also been investigating the inter-operability of our new
system with the "legacy" S/X system. In this talk we present the current status of the AuScope array and the results of
our "mixed-mode" observations using both the S/X and wideband systems.
Shinji Horiuchi
Abstract
Phurdth Jaroenjittichai (National Astronomical Research Institute of Thailand)
National Astronomical Research Institute of Thailand (NARIT) has embarked on
another challenging mission to establish research and development in radio
astronomy and VLBI geodesy via the umbrella project, "Radio Astronomy Network
and Geodesy for Development" (RANGD). For phase I (2017-2021), the project
includes the constructions of the 40-m Thai National Radio Telescope (TNRT) and
a 13-m VGOS antenna, electronics and RF labs and the visitor and education centre
for the public. Both co-located telescopes will form a VLBI observatory which will
allow significant contributions to astronomy and geodesy community and VLBI
networks. Astronomical receivers at L- and K-band wavelengths, ku-band
microwave holography receiver and state-of-the-art software backend are being
developed and will be installed and commissioned together with the TNRT later in
2019. The 13-m VGOS telescope will come on-line in the early 2020. Electronics
and RF labs and equipment are being deployed for maintenance and to
accommodate future self-sustained technological development. Receivers for
TNRT at C-, Q- and W-band wavelength are also being planned.
Abstract
Simin Salarpour (University of Tasmania)
To determine accurate celestial and terrestrial reference frames, next-generation
VLBI observations will face a very important issue which is called source structure.
Quasar structure is a highly dependent variable to frequency and time. This issue
is a big challenge for observing over a wide range of 2-14 GHz which is one of VGOS'
aims. For the same source, structure effects can be distinct at different frequencies.
So far, research on source structure effect in VGOS has been sparse.
During my PhD, I intend to investigate source structure, both theoretically and
observationally. Using automatically extracted information from source images,
we can calculate visibility phase changes over the broadband frequency range. On
the example of J0136+4751, we can then calculate the source structure effects as a
function of frequency and time for varying geometries. Using simulated global or
regional VGOS networks, this approach allows us to give estimates about the
number of observations within a session that may be affected by source structure,
in dependence of the source’s activity cycle as well as baseline length and observing
geometry.
We will also briefly discuss opportunities within the AOV to further support
research on source structure and for the success of VGOS observations.
Abstract
Fengchun Shu (Shanghai Astronomical Observatory)
The AOV network is unique to astrometry of radio sources in the middle southern
hemisphere and the ecliptic plane. In the first 3 years of AOV observing sessions,
we have observed more than 200 target sources. 194 sources have been included
in the ICRF3 catalog released in August 2018. We find there are 145 sources
matching with Gaia DR2 objects within 0.1 arc second. Compared with the ICRF2,
the ICRF3 has 1122 new sources. Among them, 149 sources (13.3%) were observed
by the AOV sessions, and 132 sources have been firstly observed by the AOV. In
order to observe more sources and reduce their positional uncertainties, we need
to continue AOV astrometric sessions.
Abstract
Chris Phillips (CSIRO Astronomy and Space Science)
Abstract
Gabor Orosz (University of Tasmania)
Observations at low VLBI frequencies are dominated by direction-dependent
ionospheric propagation errors, which place a tight limit on the angular separation
of suitable phase referencing calibrators for relative astrometry. MultiView is a
multi-calibrator phase-referencing solution that can help compensate for
atmospheric spatial-structure errors by characterizing the two-dimensional phase
screen around the target, which results in increased astrometric accuracy and more
relaxed constraints on the angular separation of calibrators. In my talk, I will
introduce VLBI tests of MultiView and discuss the applicability of directiondependent
phase calibration for various topics in astrophysics.
Oleg Titov (Geoscience Australia)