Radio Methods for Observing Space

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Radio Methods for Observing Space Bo Thidé Swedish

LOIS Space Centre, Växjö, Sweden and the LOIS

Mohammadi, L. Daldorff, T. B. Leyser, L.

Ibragimov, R. Khamitova (BTH, Karlskrona), T.

Mendonca (Lisbon), W. Baan (Dwingeloo/Växjö), B.

1 Radio Methods for Observing Space Bo Thidé Swedish Institute of Space Physics, IRF, Uppsala, Sweden LOIS Space Centre, Växjö, Sweden and the LOIS OAM/radio topology collaboration J. Bergman, S. Mohammadi, L. Daldorff, T. B. Leyser, L. Norin (Uppsala), H. Lundstedt (Lund), N. Ibragimov, R. Khamitova (BTH, Karlskrona), T. Carozzi (Glasgow), R. Karlsson (Graz), H. Then (Oldenburg), Ya. N. Istomin (Lebedev Institute, Moscow), T. Mendonca (Lisbon), W. Baan (Dwingeloo/Växjö), B. Elmegreen, and O. Verscheure (IBM Research, NY) Physics in Space Programme LOFAR Outrigger in Scandinavia Presentation, Asiago Observatory, 24 October, 2008

2 The birth of radio astronomy Look for radio emissions from the Universe! Pioneers: Karl Jansky and Grote Reber. Intensity unit: 1 Jy = W/m 2 /Hz (very small!) 2

Radio signals from ET or Little Green Men? In 1967, Antony Hewish and Jocelyn Bell discovered the first radio pulsar (Nobel Prize later to Hewish only).

3 Radio signals from ET or Little Green Men? In 1967, Antony Hewish and Jocelyn Bell discovered the first radio pulsar (Nobel Prize later to Hewish only). A pulsar is an extremely compact neutron star (1.5 km across, same mass as our Sun!), that rotates rapidly and emits radio. The star s magnetic field is about times stronger than that of the Earth!! 3

4 Yesterday: Cosmic hydrogen radiates narrow band radio signals at MHz The 21 cm λ H hyperfine splitting line 4

5 Radio image of a nearby galaxy The array of fourteen 25 m dishes at Westerboork (NL), sees nearby objects emitting MHz (21 cm λ H hyperfine splitting) lines M31 (Andromeda, Local 5

6 Everything radiates electromagnetically! Maxwell: Light and radio are two different forms of electromagnetic radiation. All objects radiate, mostly in infrared (IR) 6

7 The Universe itself radiates Universe as a whole is C cold. Still it emits radio microwaves! 7

8 Big Bang really happened The predictions of the Big Bang and the microwave radio background radiation observations agree perfectly. 8

9 Challenge: How to observe cosmologically red-shifted 21 cm line radio emissions radiated already during the Epoch of Reionisation (EoR)? 9

Today: New-generation wide-area radio telescopes with improved sensitivity, resolution and flexibility LOFAR Low Frequency Array (10 240 MHz).

LOIS LOFAR In Scandinavia. Pathfinder station near Växjö operational 2004, fast fibre network, supercomputer 2005. Prototype station near Ronneby, 2008.

10 Today: New-generation wide-area radio telescopes with improved sensitivity, resolution and flexibility LOFAR Low Frequency Array ( MHz). Test station at Exloo operational 2004, full-scale deployment of antennas in progress. Must be able to handle data streams up to 23 Tbits/s. LOIS LOFAR In Scandinavia. Pathfinder station near Växjö operational 2004, fast fibre network, supercomputer Prototype station near Ronneby, Full-scale station in Poznan, Poland, in the timeframe. SKA Square Kilometre Array. Australia or South Africa, ~2020. Very sensitive ( antennas!). 10

11 LOIS physics idea: Space physics, space weather, solar radar, ionospheric turbulence... Download from 11

12 LOIS radio idea: Arrays of antennas to sample the entire EM field vectors both in time and space 12

13 Three orthogonal dipole antennas sample E(t,x) Three orthogonal loop antennas sample B(t,x) 13

14 LOIS prototype station under construction in Ronneby To be augmented by two outer, concentric rings, with 16 and 32 radio units, respectively, for a total of 56 units with three dipoles each (funding permitting) 14

15 Lorentz s microscopic Maxwell equations for the EM field (1903) Symmetric under inhomogeneous Lorentz transformations. The concomitant Lie group is the 10-dimensional Poincaré group P(10). According to Noether s theorem there therefore exist 10 conserved EM quantities. In fact there are 17 exact (in vacuo), [Ibragimov, 2008], plus an as yet unknown number of approximate, conservation laws. 15

16 Conserved quantities in a closed electromechanical system (matter + EM fields) [Boyer, 2005] (1) Homogeneity in time => conservation of system energy (no EMF, no radiation; cf. Poynting s theorem): Homogeneity in space => conservation of system linear momentum (gives, e.g., rise to EM Doppler shift): Foundation of conventional linear momentum radio. 16

17 Conserved quantities in a closed electromechanical system (matter + EM fields) [Boyer, 2005] (2) Invariance under proper Lorentz transformations => conservation of system centre of energy: Isotropy in space => conservation of system angular momentum (gives rise to azimuthal Doppler shift): Foundation of angular momentum radio or dual radio. 17

18 Total EM field angular momentum For radiation beams, the EM field angular momentum J EM can be separated into two parts [van Enk & Nienhuis, 1992]: The first part is the EM orbital angular momentum (OAM) L EM, and the second part is the EM spin angular momentum (SAM) S EM, a.k.a. wave polarisation. NB: In general, both EM linear momentum p EM, and EM angular momentum J EM = L EM + S EM are radiated all the way out to the far zone! 18

19 Standard textbooks show that classical EM angular momentum is radiated all the way to infinity 19

20 That far-zone POAM is generated by near-zone longitudinal E fields is well known since

21 Micromechanical action of SAM and OAM Particles of sizes 1 3 μm irradiated by SAM/OAM laser beams Spin angular momentum s = 1 Bo Thidé Asiago, 24October, 2008 Orbital angular momentum l = 8 21

22 Comment on the use of POAM 22

23 EM beam with circular polarisation S but no orbital angular momentum (POAM) L Phase fronts (loci of constant phase) Optics (LG) Radio M. J. Padgett, J. Leach et al., U. Glasgow, UK; Royal Society Sjöholm and Palmer,

24 Instantaneous field vectors across an antenna array for a radio beam with circular SAM Phase 0 Phase 45 24

25 EM beams on the same frequency but with different OAM would be orthogonal and not interfere with each other Spiraling Poynting/linear momentum (and OAM) vectors! l=+1 l=+3 l= -4 25

26 Instantaneous field vectors in a cross section of a radio beam carrying both SAM and OAM Phase 0 Phase 45 26

27 Radio POAM can be observed with distributed telescopes. Optimally with vector sensing antennas Thidé et al., Phys. Rev. Lett., 99, ,

28 Field vector sensing means total configurability 28

29 Radio beam topology degrees of freedom Conventional linear momentum (Poynting) flux and E 29

30 An electromagnetically and acoustically quiet POAM radio chamber just readied at the Ångström Laboratory, Uppsala Bo Thidé Asiago, 24October,

simulation for s=1 and l=1 without any simplifying

31 Spin momentum ( photon spin current ) V and separation of SAM and OAM in a radio beam Full numerical simulation for s=1 and l=1 without any simplifying assumptions such as paraxial geometry, multipolar expansion etc. 31

Challenge: Ionospheric and atmospheric turbulence distort low-frequency radio signals from outer space Today it is possible to compensate ( self-calibrate ) for

32 Challenge: Ionospheric and atmospheric turbulence distort low-frequency radio signals from outer space Today it is possible to compensate ( self-calibrate ) for amplitude and nonsingular phase distortion of signals propagation through the ionosphere. Data from observations at VLA (Very Large Array, NM, USA) at 74 MHz. 32

33 Phase singularities (dislocations) are to be expected in radio beams propagating through space 33

34 First OAM/vorticity radio experiment in the ionospheric plasma (HAARP, Alaska, 27 Feb, 2008) 34

35 Hyperentangled SAM and OAM photon states break the linear-optics channel capacity threshold 35

36 Shannon s law revisited 36

37 Recent initiatives for POAM in space Prepare for the building of a radio telescope on the far side of the Moon Radio-on-chip, mm 2, 4 grams Bare die components on silicon 37

38 Spin-off LOIS developments for space physics, astroparticle physics, and space communications Vector sensing radio on a chip, mm 2 at 4 grammes based on bare die components on silicon Vector radio system for detection of UHE neutrino induced radio pulses in the Antarctic ice 38

ET, we may wish to reconfigure our radio telescopes to look for encoding of the message via such subtle

39 New ideas new audiences. SETI? The investigation of new transmission modes by Thidé and Bergman hints that if we do find a signal from ET, we may wish to reconfigure our radio telescopes to look for encoding of the message via such subtle effects as orbital angular momentum. A simple signal may only be a cipher for a more complex message, and there may be more things in heaven and earth than even Maxwell had dreamt of 39

40 Thank you for your attention...there may be more things in heaven and earth than even Maxwell had dreamt of 40

Introduction to Radio Astronomy

Introduction to Radio Astronomy The Visible Sky, Sagittarius Region 2 The Radio Sky 3 4 Optical and Radio can be done from the ground! 5 Outline The Discovery of Radio Waves Maxwell, Hertz and Marconi