The Imager for the All-Sky One-Second Survey

The Imager for the All-Sky One-Second Survey

Pim Schellart
LOFAR TKP Meeting, Amsterdam, June 2011



June 17, 2012


  1. The LOFAR TBB imager Pim Schellart M. v.d. Akker, A.

    Corstanje, H. Falcke, A. Horneffer, J. R. Hörandel, C. W. James, S. Thoudam, S. ter Veen Cosmic Rays Key Science Project
  2. TBB imaging pipeline • Python based • Low level functions

    implemented in C++ • Imaging optimized for multicore systems • In the near future distributed memory clusters and possibly GPU hardware acceleration. Tcomputing ∝ N−1 Cores if NPixel > NCores
  3. Imaging by tied array beamforming CHAPTER 3. THE LOPES ANALYSIS

    SOFTWAR Source Antenna 1 B C Antenna 2 Center A Image from: PhD thesis A. Horneffer
  4. P(￿ ρ)[ω] = |S(￿ ρ)[ω]|2 = ￿ ￿ ￿ ￿

    ￿ NAnt ￿ i=1 ωi(￿ ρ)[ω]si[ω] ￿ ￿ ￿ ￿ ￿ 2 Two methods P(￿ ρ)[ω] = ￿|S(￿ ρ)[ω]|2￿ = 1 NBlocks NBlocks ￿ k |Sk(￿ ρ)[ω]|2 ⇒ Tcomputing ∝ NPixel ∗ NBlock ∗ NAnt = ￿|S(￿ ρ)[ω]|2￿ = N Ant2 ￿ i,j Wij(￿ ρ)[ω] ∗ ￿Cij[ω]￿ ⇒ Tcomputing ∝ NPixel ∗ N2 Ant + NBlock ∗ N2 Ant Equations from: Ph.D. thesis A. Horneffer
  5. Advantages of imaging through beamforming • Keep full time resolution

    • Faster for short integration times • All-sky images (curved images in general) which are not directly possible through visibility function
  6. Currently implemented

  7. Imaging with incoherent dedispersion Crab giant pulse imaged from LOFAR

    CS002 TBB data
  8. Multi-station imaging Crab giant pulse imaged with TBB data from

    two and four LOFAR core stations respectively
  9. Maximum time resolution imaging Single pulse from airplane imaged at

    5ns time resolution
  10. All sky imaging Localizing single pulses And finding RFI sources

  11. • Support for any WCS specified coordinate system and projection

    • Multi station imaging • Maximum time resolution (5ns) imaging • Optional frequency or time integration • Incoherent dedispersion • Optimized for multicore shared memory systems What we have now
  12. What remains to be done • Speed, speed and more

    speed (cluster implementation and possibly GPU acceleration) • 3D imaging • Image cleaning
  13. Conclusion • Can make images of LOFAR TBB data •

    Maximum flexibility, including generating all sky images to exclude pulsed RFI sources • High time resolution to capture Fast Radio Transients