Author(s): Steven Bernstein, Lorraine Prior, James Calvin, and Vineet Mehta
Submitter's e-mail: email@example.com
Affiliation: M.I.T. Lincoln Laboratory
Title: Glownet and Bossnet Gigabit Network Infrastructure for e-VLBI
Abstract: Glownet (Gigabit Lincoln Optical WDM Network) and Bossnet (Boston South optical Network) are providing
metropolitan and wide-area gigabit/sec network connectivity respectively for real-time e-VLBI. Each network
operates over "dark fiber" leased from commercial providers. Glownet networking equipment uses off-the-shelf
hardware to connect Haystack Observatory, MIT Lincoln Laboratory, the MIT campus and the Bossnet terminus
in Boston. Whereas Bossnet, reaching about 1000 km from Boston to Washington DC without data regeneration,
requires the use of custom designed optical transmission techniques and components. Each network conveys
data in standardized gigabit Ethernet and/or SONET OC-48 formats. The technology is scalable to multiple
e-VLBI gigabit/sec sites spanning the globe. Experiments with Bossnet have shown TCP throughputs of a
gigabit/sec between Boston and Washington.
Abstract: Since 1995, NTT Laboratories have been conducting a joint research project on ultra speed networking
with national research institutes including Communications Research Laboratory (CRL), National Astronomical
Observatory of Japan (NAOJ) and Institute of Space and Astronautical Science (ISAS). Among many
applications tried in the project, the real-time VLBI (very long baseline interferometry) has proved to be benefited
greatly from the high performance communications technologies. With the real-time data transmission using high
speed communications network, the bottleneck resulted from the limited data rates in the conventional magnetic
tape based VLBI system can be removed. Thus, by utilizing the ultra wide bandwidths of the communications
network, the performance of the observation system can be upgraded significantly in terms of sensitivity. The
dedicated experimental network connects the NTT R&D centers and participating research organizations with
2.4Gb/s circuits, repeaters, ATM (Asynchronous Transfer Mode) Switches and high-performance IP routers.
The first real-time VLBI observations system KSP (Key Stone Project) using very high speed ATM technology
was achieved in collaboration with the CRL in 1996. Many antennas belonging to our partner organizations are
also connected to the network including Nobeyama 45m, Usuda 64m, Kashima 34m antennas in addition to
KSPÕs 11m antennas. Extensive research items regarding the real-time VLBI technology are also being
conducted on this experimental network, together with the scientific observations. So far, through the
experiments using the developed real-time VLBI system, great improvement in observation performance
has been achieved. In addition to ATM technology, we've started to use the Internet technologies for sending
VLBI data, and successfully conducted a real-time VLBI observation between Usuda 64m and Kashima 34m
antennas using our IP transmission system. The transmission speed of the developed system can be easily
upgraded because of its modular architecture that splits a high speed data stream into multiple IP sub-streams
to be sent in parallel in the network. This will open up a possibility of connecting antennas abroad to our network.
Future research plans include distributed data processing using a number of PCs connected to the network, huge
data storage for the raw data and international collaborations with other research organizations abroad.
Abstract: The Internet VLBI system developed at CRL is dedicated to taking over
current geodetic VLBI system. A geodetic VLBI system usually receives 14 to 16
frequency channels at S and X bands. Each channel data are transmitted
independently by using the IP (Internet protocol) technology. Thus, only
establishing the system for one channel, we can easily expand it to the
multi-channel system, i.e., geodetic VLBI system. We have been developing the
system as a PC-based system consisting of a PCI-bus sampler board and PC
softwares to make real-time data transmission, reception and correlation.
Current status will be presented at the meeting.
Abstract: It is anticipated that efficient e-VLBI data transmission systems (DTSs) will
connect directly to the synchronous telecommunication network. A SONET/SDH
frame payload format for astronomy data is proposed at the OC-12/STM-4 level
but may be adapted to other levels. It supports but is not restricted to
VSI-H DTS operations. The format is designed for efficient implementation in
FPGA hardware and may find additional application in wideband DASs and
correlators for internal data transmission.
Abstract: Since its first success in 1997, more than 700 realtime VLBI sessions were
carried out with the Key Stone Project stations at Kashima, Koganei, Miura
and Tateyama. The introduction of the realtime VLBI system enabled us to
perform continuous unattended observations at remote stations and minimized
the turn around time from the observations to the final release of the data
analysis results. Current efforts of our system developments are focused on
the use of Internet Protocol and higher data rate. Especially, the PC based
realtime correlation system currently under developments will eliminate
barriers among different observation hardware systems. To establish an open
platform to which many institutes can contribute for the system developments,
we consider it is essential to define a minimal set of standards and
requirements for the data stream.
Abstract: The VLBI group at JPL has used e-VLBI to track the Mars 2001 Odyssey
spacecraft. This effort was motivated by a desire to improve angular tracking
accuracy. A total of 47 tracking passes were attempted with 100% success.
The data were digitized at the antenna site. Typically we recorded 16
Msamples/s of 2 bit/sample data covering roughly 75 MHz spanned bandwidth.
The data were networked back to JPL from the three Deep Space Network sites
in Goldstone, CA, Canberra Australia, and Madrid Spain at data rates of about
The data were correlated using a software correlator running
on a Sun workstation, thus eliminating the need for interfacing with a custom
hardware correlator as was our practice in the past. The results contributed
significantly to the successful navigation of the Mars Odyssey spacecraft.
In 2002, we plan to use e-VLBI to measure the Mars ephemeris in the
quasi-inertial frame defined by quasars. Our goal is to improve our knowledge
of the position of Mars by a factor of 2-5 down to about 1 nrad (0.2 mas).
Other near term applications may include the determination of Earth
Abstract: Following the success of the VLBI Space Observatory Programme (VSOP), a next
generation space VLBI mission (VSOP-2) is currently being planned. We expect
to have wider bandwidth (at least 1 Gbps) than that of VSOP satellite, to get
more sensitivity. We will have 3 observing band, 5-8, 22, and 43 GHz with the
dual polarization, the 10 m antenna, and the apogee height of 30,000 km in
the current baseline design. We also consider the upgrade options relative to
the baseline design. It is no need to say that the ground VLBI is
indispensable for the space VLBI mission, as we do in the VSOP mission,
and the e-VLBI system will highly affect on the space VLBI mission.
Abstract: Real time VLBI, is of interest to the NRAO for two reasons.
First, if the recording system could be replaced with a
real time system on the VLBA, some of the major expenses
and constraints involved in the operation of the instrument
would eliminated. Of course, this would trade against the
cost of access to the links, which is currently a big
unknown. The second reason is that similar technology will
be needed for the second phase of the EVLA project. That
phase will include the New Mexico Array (NMA) that will
extend the resolution of the VLA by a factor of 10 and fill
the UV gap between the VLA and the VLBA. Links of up to
several hundred km, with the EVLA bit rate of 96 Gbps, will
be required. It will also become possible to integrate the
EVLA and VLBA, including using the same correlator for the
whole instrument. The fullest integration would require
eVLBI links with bandwidths well beyond what is being
considered in most current discussions.
Abstract: We are going to present NTTÕs IP data transfer system for real-time VLBI. The
system is based on a parallel IP transfer scheme, where single input ID1
stream is divided and converted to multiple IP streams, transmitted over IP
network. At the other end of the network, each IP stream is received and
serialized to a single ID1 stream as an output. We implemented the system by
using multi-purpose PCs for transmitting and receiving IP data. In addition,
to handle ID1 stream, we developed a pair of equipment: one for parallelizing
and the other for serializing, each of which is connected to multiple PCs via
IEEE1394 interfaces. Our system features low cost and transfer rate
scalability up to 256 Mbits/sec, by using parallel transfer with PCs. Using
the system, we conducted an experiment of real-time VLBI observation with
Kashima antenna (Communications Research Laboratory) and Usuda antenna
(Institute of Space and Astronautical Science). In the experiment, observed
data was transferred with IP at the data rate of 128 Mbits/sec
(32 Mbits/sec x 4 streams) from Usuda to Musashino (NTT Research and Development Center)
where a cross correlator was installed. From Kashima, observed data was transmitted by asynchronous transfer mode.
We successfully detected a fringe. This experiment is the first IP-based
real-time VLBI in the world.
Abstract: Historically, VLBI signals have been correlated using custom designed
hardware in order to achieve the desired throughput rates. Continued rapid
advances in general purpose computing have brought workstation performance to
the point where it is now practical for some applications to correlate VLBI
data using general purpose workstations.
This poster will report on a software correlator which has been in use at JPL
in support of differential VLBI measurements of spacecraft position.
Abstract: The EVN data processor at JIVE will shortly be connected directly to the Amsterdam Internet Exchange at the Amsterdam Science and Technology Centre (WCTW), via a 2-colour, 2Gb/s optical-fibre link. The connection contract will be placed by SURFnet who are also negotiating a connection from the Westerbork array to JIVE/ASTRON. Co-located at WCTW are computer-scientists and particle physicists who are engaged in various international projects to develop research networks and computational Grids. These projects need bandwidth-hungry applications to act as test-beds for next-generation network infrastructure. VLBI is recognised as an interesting and suitable case which has unique requirements for network loading and Quality of Service. In the UK similar contacts between astronomers, particle physicists and grid/network developers have succeeded in placing VLBI on the agenda of various network development fora. The idea of creating a real-time interferometer between Jodrell Bank and Westerbork using the JIVE data processor to correlate the data is now receiving serious attention. I will talk about the current status of this initiative.
Abstract: The Mark 5 VLBI data system has been designed to support e-VLBI in several modes at data rates up to 1 Gbps. For example, data may be transferred in real-time from antenna to correlator, or may be disc-buffered at either antenna or correlator or both. A demonstration of 1 Gbps real-time and near-real-time e-VLBI data transfer is being prepared using antennas at Westford, MA and NASA/GSFC in MD, a distance of ~700 km, with data being transmitted to the Mark 4 correlator at Haystack Observatory for processing. The data connection utilizes a combination of dedicated and shared networks including Bossnet, Supernet,MAX and GSFC/HNET. Early results of tests over portions of the network have achieved sustained transfer rates of ~990 Mbps using standard Gigabit Ethernet. This work will be described and results to date presented. We plan to build on this demonstration to extend high-speed data connections to both Europe and Japan in the near future.
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