The Imager for the All-Sky One-Second Survey

Pim Schellart
LOFAR TKP Meeting, Amsterdam, June 2011

Transcript

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