The activities of the six-station IAA RAS correlator include regular processing of national geodetic VLBI programs Ru-E, Ru-U, and Ru-F. The Ru-U sessions have been transferred in e-VLBI mode and correlated in the IAA Correlator Center automatically since 2011. The DiFX software correlator is used at the IAA in some astrophysical experiments

Ken, Voitsekh

Melnikov, Alexey

Mishin, Vladimir

Shantyr, Violet

Sokolova, Nadezda

Surkis, Igor

Zimovsky, Vladimir

NASA Technical Reports Server

IAA RAS IAA Correlator Center
IAA Correlator Center
Igor Surkis, Voitsekh Ken, Alexey Melnikov, Vladimir Mishin, Nadezda Sokolova,
Violet Shantyr, Vladimir Zimovsky
Abstract
The activities of the six-station IAA RAS correlator include regular processing of national geodetic
VLBI programs Ru-E, Ru-U, and Ru-F. The Ru-U sessions have been transferred in e-VLBI mode and
correlated in the IAA Correlator Center automatically since 2011.
The DiFX software correlator is used at the IAA in some astrophysical experiments.
1. Introduction
The IAA Correlator Center is located at and staffed by the Institute of Applied Astronomy in
St. Petersburg, Russia.
The IAA Correlator Center is devoted to processing geodetic, astrometric, and astrophysical
observations made with the Russian national VLBI network Quasar.
Figure 1. View of the six-station ARC correlator, showing four racks containing (left to right) signal
distribution and synchronization system (SDSS) and three Mark 5B playback units, two correlator crates
and KVM, three correlator crates, and one more cabinet with SDSS and three Mark 5B playback units.
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https://ntrs.nasa.gov/search.jsp?R=20150003887 2019-08-31T11:13:31+00:00Z
IAA Correlator Center IAA RAS
2. Component Description
The ARC (Astrometric Radiointerferometric Correlator) (Figure 1) was the main data pro-
cessing device in the IAA Correlator Center in 2012. The ARC was designed and built in the IAA
RAS in 2007 - 2009. The correlator has an XF design and is based on FPGA technology.
The ARC is a six-station, 15-baseline correlator. It is able to process up to 16 frequency
channels on each baseline, for a total of 240 channels. The correlator accesses two-bit VLBI
signals with 32 MHz maximal clock frequency. The maximal data range from each station is
1 Gbit per second. The correlator requires VSI-H input VLBI signals, and it is equipped with
Mark 5B playback terminals.
Since 2011 the DiFX software correlator has been used in some astrophysical experiments. The
DiFX is installed at the IAA on a Sun Fire X4450 Server as a virtual machine under the VMware.
3. Staff
• Voitsekh Ken — GPU software developer;
• Alexey Melnikov — software developer, DiFX processing, scheduler of the Ru-sessions;
• Vladimir Mishin — software developer, data processing;
• Nadezda Sokolova — software developer;
• Violet Shantyr — software developer, post processing;
• Igor Surkis — leading investigator, software developer;
• Vladimir Zimovsky — leading data processing;
• Ekaterina Medvedeva — data processing;
• Alexander Salnikov — leading e-VLBI data transfer;
• Ilya Bezrukov — e-VLBI data transfer;
4. Current Status and Activities
The ARC correlator was used for processing all of the national geodetic VLBI observations in
the IAA Correlator Center in 2012. The RUE and RUU geodetic VLBI sessions were observed in
IAA RAS.
The three-station 24-hour RUE sessions for EOP determination were observed one time per
week, as in 2011.
The two-station one-hour sessions for UT1-UTC determination in e-VLBI mode were carried
out one time per week up to June 2012 and one time per day starting in July 2012. The RUU
sessions were executed on cold station receivers, with a frequency channel bandwidth of 8 MHz
and a total bitrate of 256 Mbps, and on warm receivers, with a frequency channel bandwidth of
16 MHz and a total bitrate of 512 Mbps. The data transfer speed from station to correlator was
improved in 2012, and near to realtime correlation processing with a data bitrate of 256 Mbps was
achieved.
In 2012, the DiFX software correlator became the main tool for a spectral radio source obser-
vation processing routine. We have started regular observing program Ru-P in 1.35 cm band and
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18 cm band. Target sources are Orion KL, W49N, W3OH, and W75, and the experiment bitrate
is 32 Mbps. The processing time for one second of real data is about eight seconds with DiFX
using current facilities on a Sun Fire X4450 Server and its virtual machines under the VMware.
The output data has a resolution from 1024 to 4096 spectral channels. Several experiments were
observed with station Simeiz: RU0069, RU0083, RU0084, RU0087, and RU0088. These were 1.35
cm band sessions. Data from the Simeiz station were transferred via Internet directly to IAA’s
server, then processed with DiFX. We also used DiFX in test experiments of a new wideband DAS:
a single IF channel of 512 MHz width with 2 Gbps total bitrate was successfully processed using
DiFX.
5. Future Plans
The design of a new FX software correlator intended for the new small antenna VLBI network
in comformance with VLBI2010 was started in 2012 at IAA RAS. The correlator design is supposed
to process up to 16 Gb/s data stream from each of up to six observatories. VLBI data are recorded
from four frequency bands with bandwidth up to 1024 MHz in one circular polarization or up to
512 MHz in two linear polarizations using 2-bit sampling. The input data format is VDIF. The
correlator computes cross-spectra with a resolution up to 4096 spectral channels, and it extracts
up to 16 phase calibration tones in each frequency band of each station. The correlator’s hardware
is based on hybrid blade server technology. Blade server contains two Intel CPU and two Nvidia
Tesla GPUs. All critical computing such as Fourier transform, spectra multiplication and addition,
and phase cal extraction will be perfomed using GPU; other tasks (data stream synchronization
and distribution) will be provided by CPU. By a preliminary estimate, the hardware will contain
up to 20 blade servers.
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