e-VLBI “down-under”

Tasso Tzioumis

ATNF, CSIRO

July 2005

““Towards e-VLBI”Towards e-VLBI”

Outline

• Brief Overview - details in other presentations• The LBA• Current systems/developments

– Tapes– Disks– Correlators

• Plans– Networks– Correlators

LBA

x NTD

x New Norcia

Long baseline Array (LBA)

• Telescopes in Australia– ATNF, U.Tasmania, NASA– “core” Oz VLBI network

• + South Africa• + Telescopes in Asia Pacific region

– Japan, China, Hawaii, VLBA(west),…

Asia Pacific Telescope (APT)

LBA - S2 system• Canadian S2 VCR-based recorder

– 8 VCR recorders 128 Mbps max data rates

• 7-station LBA correlator at ATNF Sydney– XF architecture (ATCA correlator design)– Max 16 MHz channels (2-bit)– Spectral line system (2k+ channels)– Very configurable– (visits can be arranged during workshop)

• Remains the main production-VLBI system– No plans to upgrade correlator– S2 maintenance issues (no external support)

Phase-out within ~3-4 years?

LBA - DAS• DAS: Based on Digital Filters

– 2 input IFs @ 64 MHz BW (2 pols or 2 frequencies)– Sampling (10 bits) + Digital filters (ideal passbands)– Bands: 64MHz 125 KHz– S2 mode: 2 x 16 MHz ( 128 Mbps to match S2)– Huygens mode: 4 x 16 MHz (256 Mbps)– Maximum: 2 x 64 MHz (512 Mbps)– Multibit mode: 2 x 16 MHz x 8(10) bits 512 Mbps

• Interference excision?

• ATNF stations: 2 DAS units– 512 Mbps for Huygens– 1 Gbps with 64 MHz channels (under development)

• Remains the main DAS for LBA systems (tapes or disks)

LBA - Operations

• Open network EVN model of operation• Limited support - 1 correlator operator• Schedules via VLBA SCHED

• Information on systems and proposals: – http://www.atnf.csiro.au/observers/– http://www.atnf.csiro.au/vlbi

• New: Array sensitivity calculator

LBA - Disk recorders• (See C. Phillips talk for details)

• PCEVN-Metsahovi VSI interface system– VSIC (ECL-LVDS) & VSIB(computer)– Connects to LBA DAS– All LBA antennas equipped

• COTS server-class computers– Dell 1600SC servers (test systems)– New dual CPU machines ordered– X-RAID hardware RAID systems– IDE disks & software-RAID - PATA disks

Software correlators

• See talks by S. Tingay & A. Deller

• Swinburne Supercomputer– > 100 Dell computers in cluster– Much slower than real time?

• Cray XD-1 supercomputer in WA– Under development– Approach real-time operation?

• XF & FX software versions

• Only Oz correlators for disk systems

New LBA National Facility capability

• Limited National Facility observing offered in 2005OCTS with:– disk-based systems + software correlation

• Limits:– Disk availability– Software correlator time

• Technical details at:– http://www.atnf.csiro.au/vlbi/documentation/

VLBI_National_Facility_upgrade.html

LBA support for Huygens • See C. Phillips talk

• Spacecraft tracking of Huygens probe descent onto Titan (14 January 2005)

• LBA 512 Mbps disk system development• Software correlation underway at JIVE• Huge publicity for VLBI• Limited e-VLBI - delayed network transmission

ATNFJIVE• Demonstrated need for global e-VLBI connectivity

“Real-time” fringe testing• Disk-system runs parallel to S2 VCRs

– S2 C2 output port

• ~0.1 sec data acquired• Transfer to Swinburne - (slow) ftp• Correlate and post on web

– Within a few minutes– Record fringe in ~30secs

• Semi-automatic operation• Routine for all LBA observations

– Monitor fringes for all calibrators

Increased LBA reliability and robustness

The Future?

• e-VLBI– CABB Hardware Correlator

– Network Connectivity

CABB Correlator• See talk by w. Wilson

• Broadband upgrade of ATCA– VLBI capability added

• 4 Gsamples x (8) bits 32 Gbps streams– 4 IFs per antenna– 8 antennas

• Digital Polyphase filters

• ATCA operation in 2007 - VLBI?

2GHz

4k channels

4k channels

Multiple Zoom (>2 possible)

Multiple Zoom (>2 possible)

2GHz

4k channels

4k channels

Compound ZoomCompound Zoom

2GHz

4k channels

Simple Zoom

Simple Zoom

2GHz

4k channels

Basic Configuration

Basic Configuration

FFT

FFT

FIR

FIR

FilterbankFringe

Rotators CorrelatorsDMUX

A 2GHz bandwidth polyphase digital filterbank with 4096 channels ... ... will fit into four XC2V6000 FPGAs

FPGA hardware may be completely reprogrammed to

produce many different filterbank configurations, as

different observations may

require.

RF, IF and Baseband Signal Path

Filterbank Architecture

A Wideband Upgrade for the Australia Telescope Compact Array

Luneburg Lens Phased Array Luneburg Lens Phased Array6 * 22m antenna AT Compact Array

Network connectivity• See talks by K. Burston & G. McLaughlin

• AARNet3 Regional Network• Fibre tails to ATNF antennas in 2005

– $2M project, awaits final CSIRO approval

• 1 Gbps connectivity at start• 10 Gbps (x multiple wavelengths) backbone

Multiple 10 Gbps streams to CABB correlator

• Good international connectivity

• Future: -switching?

AARNet’s Regional Network

Summary

• Current work “towards e-VLBI”:– Disk-based developments – Software correlators– “real-time” fringe testing

• Future e-VLBI– Networks at 1 Gbps (2005)– 10 Gbps backbone– CABB correlator