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GMRT : New Results & Future Plans

GMRT : New Results & Future Plans. Yashwant Gupta NCRA. CASPER 2011 Pune, October 12 2011. 1 km x 1 km. 14 km. The GMRT : A Quick Overview.

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GMRT : New Results & Future Plans

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  1. GMRT : New Results & Future Plans Yashwant Gupta NCRA CASPER 2011 Pune, October 12 2011

  2. 1 km x 1 km 14 km The GMRT : A Quick Overview • 30 dishes, 45 m diameter each • 12 dishes in a central 1 km x 1 km region (central square) • remaining along 3 arms of Y-shaped array • baselines : ~ 200 m (shortest); • ~ 30 km (longest) • Frequency range : • 130-170 MHz • 225-245 MHz • 300-360 MHz • 580-660 MHz • 1000-1450 MHz • max instantaneous BW = 32 MHz • Effective collecting area : • 30,000 sq m at lower frequencies • 20,000 sq m at highest frequencies • Supports 2 modes of operation : • Interferometry, aperture synthesis • Array mode (incoherent & coherent)

  3. GMRT Performance Figures

  4. GMRT : Usage Statistics • The GMRT is open to international participation via a formal proposal system • Proposals are invited twice a year and reviewed by the GMRT Time Allocation Committee • Observations are scheduled for 2 cycles of 5 months each • The GMRT is presently oversubscribed by a factor of 2.5 • Distribution of Indian vs Foreign users : close to 50:50

  5. GMRT : Results • Total of more than 250 refereed papers to date, based on GMRT data • At present, about 30 refereed journal papers per year • Some recent new improvements and results…

  6. The GMRT Software Back-end (GSB) • Software based back-ends : • Few made to order hardware components ; mostly off-the-shelf items • Easier to program ; more flexible • The GMRT Software Back-end (GSB) : • 32 antennas • 32 MHz bandwidth, dual pol • Net input data rate : 2 Gsamples/sec • FX correlator + beam former + pulsar receiver • Uses off-the-shelf ADC cards, CPUs & switches to implement a fully real-time back-end • Raw voltage mode : record raw data to disks, for all antennas; off-line read back & analysis • Current status : now working as the observatory back-end Jayanta Roy et al (2010)

  7. GSB Test Results : Imaging • J1609+266 calibrator field at 1280 MHz • 8.5 hrs synthesis image • Central source : 4.83 Jy • Noise level at HPBW : • 34 microJy • Dynamic range achieved : ~ 1.5 x105 [data analysis by Shubhashis Roy, NCRA]

  8. New capabilities : raw voltage mode • The GSB also supports a raw dump mode : can record raw voltages from 32 stations (dual poln.) for ~ 12 hrs (sustained) • Data is transferred from the 16 acquisition nodes to 16 recording nodes. Each node records data for 4 antennas (1 polarisation) as 4 raw data files. • Offline analysis code for producing visibility data • For VLBI : Data conversion to LBA format and subsequent analysis in DiFX (courtesy : colleagues from Curtin)

  9. New capabilities : finding RFI sources • Imaging RFI sources on the ground, using SVD to separate sources on the ground and the sky -- work done by the GMRT EoR group (Ue-Li Pen et al) Paciga et al, 2011

  10. Sample results : Polarization EN1DEEP06 : GMRT Deep Polarization Field 610 MHz, 30 hrs, 15 microJy RMS courtesy : Russ Taylor & team , July 2011 Total Intensity Polarized Intensity

  11. Sample Results : EoR • EoR project at the GMRT led by Ue-Li Pen (CITA) • First published results establish interesting new limits on EoR signal strength Paciga et al, 2011

  12. Sample Results : TGSS • All sky survey at 150 MHz • Metrewave counterpart of NVSS • 20” resolution (5x better than NVSS) • 1 million sources expected • 2 data releases done (50,000 sources) TGSS team at NCRA : Sirothia, Ishwar-handra, Kantharia, Gopal-Krishna

  13. Sample Results : TGSS • Discovery of giant double radio relic source in the Planck ESZ Cluster (Bagchi et al, 2011)

  14. Sample Results : Fermi LAT Pulsars • Total of 4 new MSPs discovered in follow-up radio searches of Fermi LAT sources, using the GMRT, in the last 8 months Bhaswati Bhattacharyya et al

  15. Sample result : VLBI Cabability • VLBI run (Dec 2010) : • Mopra • ATCA • GMRT

  16. First VLBI fringes : December 2010 • Second VLBI run : 15 Dec 2010 : GMRT (4) + Mopra + ATCA • 1390 MHz ; 16 MHz BW ; J2253+1608 (3C454.3) (5 Jy at S-band)

  17. Looking ahead : The GMRT upgrade • A major upgrade is underway now at the GMRT, with focus on : • Seamless frequency coverage from~ 30 MHz to 1500 MHz, instead of the limited bands at present design of completely new feeds and receiver system. • Improved G/Tsys byreduced system temperature better technology receivers • Increased instantaneous bandwidth of 400 MHz (from the present maximum of 32 MHz) modern new digital back-end receiver • Revamped servo system for the antennas • Modern and more versatile control and monitor system • Matching improvements in offline computing facilities and other infrastructure

  18. Frequency Band (MHz) 125-250 250-500 550-900 1000-1450 Max Bandwidth (MHz) 125 250 350 400 Incoherent Array Beam FoV (deg) 3.2 1.4 0.8 0.4 Incoherent Array search sensitivity for 10 min (uJy) 2500 350 250 200 Phased Array Beam FoV (arcsec) 20 9 5 2 Phased Array search sensitivity for 10 min (uJy) 400 60 40 35 Expected Performance Figures (for array mode)

  19. Proposed configuration of feeds and receivers and their current status : 1000 – 1450 MHz : wideband feed + improved receivers available on all antennas 550 – 900 MHz : prototype feed + receiver tested on 2 antennas; getting ready for mass production 250 – 500 MHz : prototype feed + receiver in last stages of development and testing 125 – 250 MHz : will be a scaled version of 250 – 500 MHz feed 30 – 80 MHz : prototype system (in collaboration with RRI, Bangalore) installed & tested on 4 antennas; awaiting decision for mass production 1553.32 nm (193.0 THz) 1553.32 nm 30 – 80 MHz Feed 1551.72 nm (193.2 THz) 1551.72 nm Fiber link 22.9 km OTX 1550.11 nm (193.4 THz) ORX 1550.11 nm OTX 1548.51 nm (193.6 THz) ORX 1548.51 nm 550 – 900 MHz feed DWDM Multiplexer At ANTENNA Base DWDM de-Multiplexer at CEB GMRT Upgrade : New Wideband Systems • Modification of optical fibre signal transport to support broadband signals : prototype developed & installed on 6 antennas; mass production underway • Wideband back-ends : prototypes under development…

  20. Development of new back-ends for the GMRT For existing 32 MHz system • The GMRT Software Back-end (GSB) -- with CITA • GMRT Transient Analysis Pipeline : GSB + GPUs -- with Swinburne • 300 MHz Wideband Pocket Correlator on the Roach -- CASPER • PacketisedCorrelator for 400 MHz, 4 antennas, dual pol -- with CASPER + SKA-SA • GPU based hybrid correlator -- with Swinburne For 400 MHz GMRT upgrade system

  21. First Results from 400 MHz Correlator at the GMRT • 4 antenna, dual pol, 400 MHz packetised correlator • 2 F engine Roach boards • 4 X engine Roach boards • Delay correction tested • Fringe correction tested Collaboration with SKA-SA team & CASPER

  22. PacketisedCorrelator Design (collaboration with SKA-SA + CASPER) ADC (2 channels) ADC (2 channels) Switch (10 Gbe) Roach (X engine) Roach (X engine) Antenna 1 (400 MHz 2 pols) ADC (2 channels) Data Acquisition and Control Roach (X engine) Antenna 32 (400 MHz 2 pols) Antenna 2 (400 MHz 2 pols) Roach (F engine) Roach (X engine) Roach (X engine) Roach (F engine) Roach (X engine) Roach (F engine)

  23. Antenna 32 (400 MHz 2 pols) Antenna 1 (400 MHz 2 pols) ADC (2 channels) CPU + GPU (correlator) ADC (2 channels) Switch (10 Gbe) Antenna 2 (400 MHz 2 pols) ADC (2 channels) Data Acquisition and Control CPU + GPU (correlator) CPU + GPU (correlator) Roach (packetizer) CPU + GPU (correlator) CPU + GPU (correlator) Roach 2 (packetizer) CPU + GPU (correlator) Roach (packetizer) Hybrid Correlator Design (collaboration with Swinburne)

  24. First Results from GPU Correlator at the GMRT • 2 antenna, 200 MHz design • iADC + iBoB sending data at 800 Mbytes/sec to a Nehelam CPU • Data written to shared memory ring buffer after on-the-fly delay correction • Data read from shared memory and sent to GPU for FFT + MAC operations Collaboration with Swinburne team

  25. GMRT-NCRA and CASPER : the road thus far • The NCRA as been involved in an active manner in CASPER since 2008. • Combination of CASPER technology and past experience of the NCRA members has proved very useful for us for the GMRT upgrade. • The GMRT has proved an excellent test bed for the CASPER designs. • The NCRA team is making useful contributions to CASPER designs & tools : e.g. delay & fringe blocks, digital noise source for FPGAs, pocket beamformer, SFP+ adaptor board for Roach-I, CPU & GPU based techniques … • Look forward to further cooperation and growth.

  26. Summary • The GMRT is a versatile, multi-element low frequency instrument, producing excellent quality science. • The GMRT is undergoing a major upgrade that will improve its sensitivity for pulsar and transient work by upto a factor of 5. • There is a significant synergy between CASPER and the upgrade of the GMRT digital back-ends – you will hear more on this in the next few talks !

  27. Thank You

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