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WHAT IS PROPOSED ?

Design, development and use of a broad-band Sky Watch Array Network across India are proposed with the following objectives.

1) To facilitate and conduct searches and studies of fast (typically of sub-second duration) and slow transient radio radiation originating from astronomical sources.

2) To facilitate and conduct high angular resolution imaging of discrete galactic and extragalactic sources at low radio frequencies.

3) To train, involve and provide hands-on experience to a large number of undergraduate and postgraduate students in all aspects of the SWAN, through their direct and active participation starting from the design stage to research using the array network

WHY ?

Over the past several decades (since the beginning of radio astronomy), most of the measurements with big arrays/apertures have corresponded to the “steady” component of the radio radiation from the sky, with the exception of the observations of Jupiter, flare stars, solar bursts, scintillations, pulsars, supernovae and GRBs. There is growing realization about the need to learn about the transient sky, which would open up an entirely new dimension of astronomical exploration with a huge potential (which is presently difficult to quantify) for yet unanticipated discoveries of astronomical objects and phenomena. This has naturally prompted astronomers to revisit archival data, as well as to conduct new surveys to search for radio transient signals. Similar initiatives at optical wavelengths have yielded exciting results, but corresponding view at radio range is lacked. There have been recent reports of detection of fast radio bursts, believed to be of extragalactic origin, but with little possibility of confirming them or studying their origin. The reported detection imply a high rate of such events, but no optimized setup exists yet anywhere in the world to search for a large volume of the space with required sensitivity to detect such signals routinely, enabling a proper study. The proposed Indian-SWAN (Sky-Watch Array Network) will fill this gap by providing capabilities that are carefully optimized together for extensive search, reliable detection and localization of energetic radio transients (including the ones that do not recur), and for their possible follow-up.

While cm and mm wave studies of radio sources have been possible at angular resolutions of even sub-arc-second level, meter-wave studies have not yet been possible at any comparable resolution. There is a need thus for such a very long baseline array, particularly in India, complementing the capabilities of the GMRT at the low radio frequencies. The proposed Indian-SWAN will extend our capabilities for studies at these frequencies in both sensitivity and angular resolution, by significant factors.

Despite the several student internship programs offered by the various Indian research institutes providing useful research experience to typically a few hundred students each year, an overwhelming majority of the bright and motivated students still remain unexposed to the exciting developments and research opportunities in radio astronomy. Due to the lack of exposure at an early stage, much of the talent is missed to be attracted to graduate studies and research in astronomy. The proposed initiative aims to provide extensive opportunities to a large number of undergraduate and post-graduate students at the Indian technology and science institutes, as well as at some universities to be directly involved in the realization of the SWAN, including in the design, and also in the operation/usage of the setup for astronomical observations, as well as the follow-up/research. These opportunities have the potential to seed significant growth of future generations of Indian radio astronomers pursuing active research, including with the future large telescopes (e.g. SKAs).

HOW ?

The proposed competitive coordinated network (with nominally 1000 sq. m array area at each location and operation spanning a decade in frequency; 50-500 MHz) will be developed. In the beginning phase, a moderate setup will be attempted for realizing and demonstrating the essential features. In the coming months, the focus will be on realizing a setup with 8 independent stations operating over a common narrow band, using most of the available hardware (e.g. GBT receiver, MWA tiles and beamformers). After such a setup is fully developed and tested at Gauribidanur, relocation of the system at 8 different sites will be considered. Test observations will include targeted searches for radio transients in a few select directions of specific astronomical interest, and coordinated observations with the GMRT.
In the second phase, the aperture size and spectral coverage will be increased. Hardware/Digital receivers required for this will be developed in parallel with the first phase activities. An 8-station setup, now with the final spectral coverage and the aimed aperture size per station, will be developed providing most of the observational modes. This setup will be subjected to extensive tests, also including fruitful test observations.
On successful completion of this crucial second phase, the network will be swiftly expanded in a timely manner to the full set of locations and array configurations to reach with the aimed watch (or survey) sensitivity and volume coverage, etc., for the transient search. The scope of routine operations and modalities will be assessed carefully before this expansion.
The implicit aim is to initiate a collective effort to develop the SWAN with as many of the 40+ technology and science institutes i.e. the (IIT, NIT, IISER & NISER)s, as well as some universities across India. The prospective institutes, particularly motivated people in these, will be approached for partnership. To prepare for student involvement, appropriate schools/workshops (in co-ordination with existing programs) are to be arranged to formally introduce under-grad and masters students to radio astronomy, basic concepts and advance topics/techniques, over a few weeks each year, along with hands-on experience with instrumentation. Active participation from the students in all aspects of the SWAN, including studies of astronomical sources, will be sought and explicitly encouraged/supported. A suitable core team at RRI has been formed.

Indian SWAN (Sky Watch Array Network) : A strategic Initiative.

– Avinash Deshpande

	WHAT IS PROPOSED ? WHY ? HOW ?
	WHAT IS PROPOSED ? Design, development and use of a broad-band Sky Watch Array Network across India are proposed with the following objectives. 1) To facilitate and conduct searches and studies of fast (typically of sub-second duration) and slow transient radio radiation originating from astronomical sources. 2) To facilitate and conduct high angular resolution imaging of discrete galactic and extragalactic sources at low radio frequencies. 3) To train, involve and provide hands-on experience to a large number of undergraduate and postgraduate students in all aspects of the SWAN, through their direct and active participation starting from the design stage to research using the array network

	WHY ? Over the past several decades (since the beginning of radio astronomy), most of the measurements with big arrays/apertures have corresponded to the “steady” component of the radio radiation from the sky, with the exception of the observations of Jupiter, flare stars, solar bursts, scintillations, pulsars, supernovae and GRBs. There is growing realization about the need to learn about the transient sky, which would open up an entirely new dimension of astronomical exploration with a huge potential (which is presently difficult to quantify) for yet unanticipated discoveries of astronomical objects and phenomena. This has naturally prompted astronomers to revisit archival data, as well as to conduct new surveys to search for radio transient signals. Similar initiatives at optical wavelengths have yielded exciting results, but corresponding view at radio range is lacked. There have been recent reports of detection of fast radio bursts, believed to be of extragalactic origin, but with little possibility of confirming them or studying their origin. The reported detection imply a high rate of such events, but no optimized setup exists yet anywhere in the world to search for a large volume of the space with required sensitivity to detect such signals routinely, enabling a proper study. The proposed Indian-SWAN (Sky-Watch Array Network) will fill this gap by providing capabilities that are carefully optimized together for extensive search, reliable detection and localization of energetic radio transients (including the ones that do not recur), and for their possible follow-up. While cm and mm wave studies of radio sources have been possible at angular resolutions of even sub-arc-second level, meter-wave studies have not yet been possible at any comparable resolution. There is a need thus for such a very long baseline array, particularly in India, complementing the capabilities of the GMRT at the low radio frequencies. The proposed Indian-SWAN will extend our capabilities for studies at these frequencies in both sensitivity and angular resolution, by significant factors. Despite the several student internship programs offered by the various Indian research institutes providing useful research experience to typically a few hundred students each year, an overwhelming majority of the bright and motivated students still remain unexposed to the exciting developments and research opportunities in radio astronomy. Due to the lack of exposure at an early stage, much of the talent is missed to be attracted to graduate studies and research in astronomy. The proposed initiative aims to provide extensive opportunities to a large number of undergraduate and post-graduate students at the Indian technology and science institutes, as well as at some universities to be directly involved in the realization of the SWAN, including in the design, and also in the operation/usage of the setup for astronomical observations, as well as the follow-up/research. These opportunities have the potential to seed significant growth of future generations of Indian radio astronomers pursuing active research, including with the future large telescopes (e.g. SKAs).

	HOW ? The proposed competitive coordinated network (with nominally 1000 sq. m array area at each location and operation spanning a decade in frequency; 50-500 MHz) will be developed. In the beginning phase, a moderate setup will be attempted for realizing and demonstrating the essential features. In the coming months, the focus will be on realizing a setup with 8 independent stations operating over a common narrow band, using most of the available hardware (e.g. GBT receiver, MWA tiles and beamformers). After such a setup is fully developed and tested at Gauribidanur, relocation of the system at 8 different sites will be considered. Test observations will include targeted searches for radio transients in a few select directions of specific astronomical interest, and coordinated observations with the GMRT. In the second phase, the aperture size and spectral coverage will be increased. Hardware/Digital receivers required for this will be developed in parallel with the first phase activities. An 8-station setup, now with the final spectral coverage and the aimed aperture size per station, will be developed providing most of the observational modes. This setup will be subjected to extensive tests, also including fruitful test observations. On successful completion of this crucial second phase, the network will be swiftly expanded in a timely manner to the full set of locations and array configurations to reach with the aimed watch (or survey) sensitivity and volume coverage, etc., for the transient search. The scope of routine operations and modalities will be assessed carefully before this expansion. The implicit aim is to initiate a collective effort to develop the SWAN with as many of the 40+ technology and science institutes i.e. the (IIT, NIT, IISER & NISER)s, as well as some universities across India. The prospective institutes, particularly motivated people in these, will be approached for partnership. To prepare for student involvement, appropriate schools/workshops (in co-ordination with existing programs) are to be arranged to formally introduce under-grad and masters students to radio astronomy, basic concepts and advance topics/techniques, over a few weeks each year, along with hands-on experience with instrumentation. Active participation from the students in all aspects of the SWAN, including studies of astronomical sources, will be sought and explicitly encouraged/supported. A suitable core team at RRI has been formed.