Current LBA Developments

Chris PhillipsCSIRO ATNF

13/7/2005

Disk Based Recording

• Thanks to initial work by Uni of Tasmania and Swinburn Uni, the LBA has disk based recorders at all Australian stations & NZ

• Based on Metsähovi “VSIB” digital input card– “PCEVN”

• Have just ordered 10 systems for uniformity across LBA

System Setup

• LBA DAS for sampling and digital filtering– Produces up to two 16 MHz bands for 2 IFs– 256 Mbps data rate– Parkes, Mopra and ATCA have 2 DAS (512

Mbps)

• MRO “VSIC” converts S2 input data into VSI-H format

• MRO “VSIB” PCI card used for data input into standard PC

• Data recorded onto disk using normal Linux filesystem

Recorder PC setup• Dual processor (AMD64 )Tyan motherboard• Dual onboard gigabit Ethernet• Primary disk recording into Apple Xserve

RAID– 14 400 GB disks in RAID5 configuration

• 4 400 GB removable IDE (PATA) disks in software RAID configuration for compatibility– Running on Promise Ultra133 TX2

• Also 2 400 GB internal SATA disks– 4 onboard SATA-II connectors

Recorder Costs

• PC with 800 GB disk space– €2410 ($A3890)

• VSIB+VSIC input cards– €1090

• Apple Xserve RAID with 5.6 TB disk space– €9900 ($A1600)

• 4x400 GB IDE PATA disks– €1014 ($A1640)

Why Not Mark5?

• Mark 5a not compatible with LBA DAS– MRO systems engineered to work with S2

data format

• MRO system better suited to software correlation– Data recorded using normal Linux

filesystems

• Cost is similar to Mark5– Apple Xserve RAID is major component

Huygens VLBI Experiment

• Intended to be Mark5– Not compatible with LBA (Parkes, ATCA,

Mopra, Ceduna)

• Installed second DAS for experiment• Produced special cable to record data

from 2 DAS onto one disk recorder

Real Time Fringe Testing

• Suite of networked Perl scripts allow almost realtime interactive fringe testing

• 0.5-1 seconds of data transferred to Swinburne to correlate in software– Limited by slow networks,

• 512 kbps for ATCA, Parkes• 33kbps modem for Hobart!

• Can get fringes within 30sec– Usually a couple of minutes

• Routinely run for all LBA experiments

Observations to Date

• First full LBA test experiment in April04– Including Hart, VLBA, Kashima (Mk5, K5)

• Also Nov04, May05• Tests to NZ • Huygens experiment and Huygens tests• High spectral resolution of OH masers

– 4 MHz, 16000 channels

Disk VLBI Availability

• Disk based recording added as option for OCT05 observing session– Shared risk basis

• Data recorded at rates up to 512 Mbps– Possibly up to 1 Gbps

• Will be correlated using Swinburne software correlator

• Suitable for sensitive observations, high spectral resolution, pulsar coherence dedispersion etc

Future Developments

• MRO systems are not compatible with ATNF S2 correlator– Delay tracking performed by S2 playbacks

• All disk & eVLBI correlation using Swinburne software correlator– May be able to do disk S2 copying

• On-going project to record 2x64 MHz bands from DAS (512 Mbps)– Currently problem with clocking

• 2x16 MHz 8bit (or 10bit)

eVLBI

• Recorders equipped with dual onboard gigabit Ethernet

• Suitable for 512 Mbps transfer• Initially record and transmit, then

remote recording• Will experiment with realtime software

correlation– Initially single baseline– Possibly to Uni of Western Australia

Long Term Plan

• New correlator being developed for ATCA– Based on FPGA digital filterbanks

• Plan to use as VLBI correlator– Should handle data rates up to 64 Gbps

• 2 GHz, 2 Pol, 8 bit