Update on LBA Technical Developments CASS Chris Phillips 11 October 2013

Linear to Circular conversion

Linear Polarizations While VLBI standard is to use circular polarizations, linear polarizations are “better”: Easier to make wideband receivers Better separation between polarizations Need to convert linear to circular for compatibility with other antennas and calibration and analysis software RF and IF hybrids typically narrow band VLBI TECHNOLOGY KOREA - Chris Phillips 3 |

Digital Polarization Conversion Digital polarization conversion can overcome wideband problem Has worked very well with ATCA for 20 years Conceptually easy: Align amplitude, phase and delay between two polarizations Rotate phase of one polarization by 90 degrees Simply add and subtract two linear polarizations Essentially same as hybrids Ideally added to VLBI DAS firmware but never implemented VLBI TECHNOLOGY KOREA - Chris Phillips 4 |

L2C in DiFX Can we do circular conversion within DIFX Very “cheap” to do conversion after FFT in correlator Biggest DIFX change is to get calibration values into correlator Side benefit is polarization dependent delay offset VLBI TECHNOLOGY KOREA - Chris Phillips 5 |

VLBI TECHNOLOGY KOREA - Chris Phillips 6 | FFT Xmult Amplitude & Phase Correction Amplitude & Phase Correction Add and subtract FFT Xmult

Status One session at ASKAP, new receiver installed with linear rather than circular polarizations (no hybrid) ASKAP no noisecal to aid calibration Also very good isolation between polarizations Need to use VLBI cross correlations for calibration Delays well calibrated but problem getting phase difference Seeking help to work out calibration problem VLBI TECHNOLOGY KOREA - Chris Phillips 7 |

Xcube Wideband VLBI Backend

X-cube Data Logger 100% COTS hardware recorder Proprietary software 16 Gbps capability External replaceable storage modules –Up to 32 TB packs Management of slow or broken disks Standard file-systems

Back View of Chassis © 2010 XCube R&D Ethernet (2 x 10Gb/s) SAS Disk Cables (16 x 300MB/s) Self Contained Disk Pack Cooling and Power

Xcube Internals “Mix and Match” approach to plug in devices 1 or 2 dual 10 Gbps Ethernet –Intel SPP+ Optical module needed Can support up to 4 disk modules GPU for number crunching Other options available –However may run out of slots…. VLBI TECHNOLOGY KOREA - Chris Phillips 11 |

Xcube tests Seems to run fine up to around 8 Gbps/diskpack (as advertised) Basic Ethernet recorder, similar to Mark5C However this is NOT a feature Records full Ethernet frame – allows post recording filtering Simple easy to use control program Can control remotely via XML messages Does not allow simultaneous recording and reading Have not started using for operations yet VLBI TECHNOLOGY KOREA - Chris Phillips 12 |

Data access Data cannot be accessed directly Cannot directly use standard transfer software such as ftp, gridftp, tsunami-udp etc Supplied with easy to use library to read data from diskpack Can copy “raw” files and decode on a different system Easy to write code to copy off disk Time filtering etc available not tested VLBI TECHNOLOGY KOREA - Chris Phillips 13 |

Xcube sampler 4 Channel 1 Gsample/sec 4x512 MHz IFs For each IF 16 channel polyphase filterbank 32 MHz channels, complex “double sideband” sampling Re-quantization to 2 bit 8 Gbps VLBI VLBI TECHNOLOGY KOREA - Chris Phillips 14 |

Xcube Issues Only 8 or 4 Gbps modes No channel sub-selection Clumsy quantization threshold setting No automatic gain adjustment No total power monitoring No eVLBI option Initial firmware version had synchronization issues… Fixed now and “zero baseline” fringes to existing LBA DAS VLBI TECHNOLOGY KOREA - Chris Phillips 15 |

VLBI TECHNOLOGY KOREA - Chris Phillips 16 |

Next Steps Working with Xcube to transition to “production” suitable operation Probably combination of Firmware and software changes Roll out at Parkes and ASKAP Mopra when satisfied system is usable ATCA Xcube recorder All digital system VLBI TECHNOLOGY KOREA - Chris Phillips 17 |

ATCA CABB ATCA correlator is now 2x2 GHz (dual pol) 32 Gbps 2 bit capable 10 Gbps (x16) Ethernet output available Engineer assigned to implement 10 GbE output of tied array But wrong clock on board…. Requires “full board” heat sink to be removed from every board VLBI TECHNOLOGY KOREA - Chris Phillips 18 |

Oz eVLBI No major changes recently 1 Gbps between ATNF observatories 1 Gbps shared routed to elsewhere 10 Gbps routed connection “soon” 40 Gbps test circuit between Parkes and ATCA 10 Gbps upgrade to observatories cheap but no funding and VLBI only user VLBI TECHNOLOGY KOREA - Chris Phillips 19 |

AARnet4 80x100 Gbps from Adelaide to ASKAP (MRO) 80x100 Gbps wavelengths on East coast by middle x40 Gbps Sydney to USA Upgraded to 100 Gbps VLBI TECHNOLOGY KOREA - Chris Phillips 20 |

Mopra Mopra operational again after fires which devastated control room Equipment room survived with relatively little damage VLBI TECHNOLOGY KOREA - Chris Phillips 21 |

Astronomy and Space Science Chris Phillips t wwww.csiro.au/atnf ASTRONOMY AND SPACE SCIENCE Thank you