Radio Astronomy Activities at RRI N. Udaya Shankar RRI Indo-SA Astronomy Workshop 7 August 2012

The economically important Silk Road (red) and spice trade routes (blue)

SALT Pepper: MWA Precursor SKA EOI in SKA Low Science Case for SKA MID Evolution of HI in the universe. SALT

world-wide collaborations. A&A group Theoretical astrophysics (5) Observational astronomy to (7) Builders: specialized instruments . Collaborations: Many body interactions Lead to joint pursuit of problems in Theory, Observations, Specialized instruments world-wide collaborations.

Present Focus: Low Frequency Radio Astronomy. Frequencies Below: 1 Present Focus: Low Frequency Radio Astronomy. Frequencies Below: 1.4 GHz. Developing interest in the freq range: 2 to 4 GHz.

Evolution of HI atom in the universe a. HI mass fluctuations using ORT; 327 MHz, z=3.3 b. EoR : I. Statistical Detection Our participation in MWA 80-300 MHz, z=4-16 ii. Global Signal Detection In-house Projects 87.5 – 175 MHz, z= 4-8 c. ERA : Epoch of Recombination array 2 – 4 GHz, z=1000 2.Transients and Pulsars, MWA and ORT

2.Transients and Pulsars, MWA and ORT 3. Halos and Relics in Galaxy Clusters GMRT and MWA 50 MHz system for GMRT 4. Multi-frequency observations of Compact objects , X-ray polarimeter.

2. Murchison Wide Field Array (MWA) MWA is a low-frequency imaging radio interferometer facility being built in the radio-quiet area of Western Australia

This is one exciting project … Scientifically rich EOR, Solar, Transients, Pulsars, RRLs, etc. Technologically innovative Leading the way in multiple simultaneous areas Trailblazing! Excellent partnership Common goals + motivations Abundance of talent and energy Enormous growth potential Inexpensive hardware, Moore’s law LFD/xNTD synergy, path to SKA Opportunities abound, for Australian, Indian, US, and Global community MWA-LFD Kick-Off June 2006

MWA Murchison

Antenna tile with 16 dipoles placed on a ground screen of 5 x 5 m

Physical Layout Antenna tile (~4m diam.) Cluster (50-100m diam.) clusters Array (~1.5km diam.) tile Cluster (50-100m diam.) node Coax out Tile beamformer Fiber out Central Processing

A digital receiver for MWA has been developed and built in the Radio Astronomy laboratory at RRI. RRI digital receivers operate between 80 and 300 MHz and are based on state-of- the-art Virtex-5 FPGA chips The receivers operate at 655 MHz sampling, include poly-phase digital filters and fiber optic links.

MWA Digital Receiver Each receiver receives outputs from 8 tiles , digitize them, do 512 CH PFB and send them through fiber links after serializing.

RRI contribution Development of i) A/D and Filter Bank (ADFB) Architecture ii) Firmware for ADFB board i) Backplane and ii) Clock for 32 T digital receiver i) Hardware and firmware architecture for AGFO ii) Design of Board and firmware development Development of Imaging Algorithms: Nithya’s Talk

Current status Actively involving in system testing under integrated environment Planning to mass produce 16 digital receivers for 128 tiles by mid 2012 Development of hardware and firmware to combine in the digital receiver the outputs of all 8 tiles to form one beam and use the entire bandwidth available

Challenges for MWA, LOFAR, GMRT, Global Signal Detection Experiments are same

Receiver is a 2 element interferometer with a space beam splitter Freq. range : 87.5 – 175 MHz The screen is made resistive to ensure required phase diff. between transmitted and reflected signals exists and has equal transmission and reflected signals

Receiver system for EoR detection Frequency Independent Antennas installed over absorber tiles Well matched receivers with low noise figure a digital receiver consisting of a high speed digitizers and a spectro-correlator

Take it to a radio quite zone Australia South Africa Current Status The Zero space interferometer has been completely characterized for all its properties and data acquired are being analyzed. Next Phase: Take it to a radio quite zone Australia South Africa

5. X-Ray Polarimeter X-ray polarimeter based on the principle of Thomson scattering is being developed at the Raman Research Institute (RRI) The experiment has been proposed to the Indian Space Research Organization for a small satellite mission.

Scientific Objective Polarisation measurement gives insight about The strength and the distribution of magnetic field in X-ray sources Geometric anisotropies in the source The nature of the accelerator responsible for energizing the electrons taking part in radiation and scattering. The instrument is suitable for X-ray polarisation measurement of hard X-ray sources like accretion powered pulsars, black hole candidates in low-hard states etc.

Instrument Specifications Energy band covered – 5-30keV Detectors – Proportional counters Photon collection area ~ 1018 cm2 Field of view - 33 degree with 0.5 degree flat response

Current Status The development of a Thomson polarimeter including proportional counter detectors, associated front-end electronics, event processing logic, data acquisition system, and test and calibration system have been completed successfully. Engineering Model is being developed For more details contact : bpaul@rri.res.in

Sub-mm telescope Balasubramanyam, R, 2004, MNRAS, 354, 1189 New Optics design has been developed for constructing large sub-millimeter radio telescope economically. Balasubramanyam, R, 2004, MNRAS, 354, 1189

Current Status At present a 3m Submillimeter-wave telescope prototype (3mSTeP) is being built The mechanical structure, design and optimization are completed Work on 8 GHz wide band spectrometer is under progress. For more details: contact : ramesh@rri.res.in

Possible Future Collaborations

Studies of galaxy populations in merging galaxy clusters using SALT and GMRT. Radio monitoring of transient X-ray sources, disk-jet connection. 3. Optical reprocessing of X-rays, simultaneous observations with ASTROSAT and SALT. 4. NIR-studies (in continuum and shocked molecular hydrogen @ 2.1/2.2 um) of chosen southern massive star forming regions. 5. Observing for Global EoR signal detection in SKA site in SA.

Gauribidanur T Array

GBD_image

MRT Aerial View

Human Resource Development: Hierarchical Interference mitigation. Imaging with a non-coplanar array. Imaging two steradinas of the sky. Human Resource Development: 8 Ph.D. students 1 MS student Several student projects

Major projects undertaken by RRI Aperture Array for Low Frequency Radio astronomy Development of Digital receivers for The Murchison Wide Field Array (MWA) Multiband receiver system at Green Bank Telescope Zero Spacing Interferometer to detect Cosmological Re-ionization Signatures Development of an X-ray polarimeter for small satellite mission Upgradation of Ooty Radio Telescope Development of a 3m Submillimeterwave telescope Prototype(3mSTeP)