• A. N. RAMAPRAKASH

      Articles written in Journal of Astrophysics and Astronomy

    • Generation of a Near Infra-Red Guide Star Catalog for Thirty-Meter Telescope Observations

      Smitha Subramanian Annapurni Subramaniam Luc Simard Kim Gillies A. N. Ramaprakash G. C. Anupama C. S. Stalin Swara Ravindranath B. Eswar Reddy

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      The requirements for the production of a near Infra-Red Guide Star Catalog (IRGSC) for Thirty Meter Telescope (TMT) observations are identified and presented. A methodology to compute the expected J band magnitude of stellar sources from their optical (𝑔, 𝑟 , 𝑖 ) magnitudes is developed. The computed and observed J magnitudes of sources in three test fields are compared and the methodology developed is found to be satisfactory for the magnitude range, JVega = 16–22 mag. From this analysis, we found that for the production of final TMT IRGSC (with a limiting magnitude of JVega = 22 mag), we need 𝑔, 𝑟, 𝑖 bands optical data which go up to 𝑖AB ∼ 23 mag. Fine tuning of the methodology developed, such as using Spectral Energy Distribution (SED) template fitting for optimal classification of stars in the fainter end, incorporating spectral libraries in the model, to reduce the scatter, and modification of the existing colour–temperature relation to increase the source density are planned for the subsequent phase of this work.

    • A Road Map for the Generation of a Near-Infrared Guide Star Catalog for Thirty Meter Telescope Observations

      Smitha Subramanian Annapurni Subramaniam T Sivarani Luc Simard G. C. Anupama Kim Gillies A. N. Ramaprakash B. Eswar Reddy

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      The near-infrared instruments in the upcoming Thirty Meter Telescope (TMT) will be assisted by a multi conjugate Adaptive Optics (AO) system. For the efficient operation of the AO system, during observations, a near-infrared guide star catalog which goes as faint as 22 mag in ${\rm J}_{{\rm Vega}}$ band is essential and such a catalog does not exist. A methodology, based on stellar atmospheric models, to compute the expected near-infrared magnitudes of stellar sources from their optical magnitudes is developed. The method is applied and validated in JHKs bands for a magnitude range of ${\rm J}_{\rm{Vega}}$ 16--22 mag. The methodology is also applied and validated using the reference catalog of PAN STARRS. We verified that the properties of the final PAN STARRS optical catalog will satisfy the requirements of TMT IRGSC and will be one of the potential sources for the generation of the final catalog. In a broader context, this methodology is applicable for the generation of a guide star catalog for any existing/upcoming near-infrared telescopes.

    • A near-infrared camera for iRobo-AO on the IUCAA 2-m telescope

      JYOTIRMAY PAUL A. N. RAMAPRAKASH HILLOL K. DAS MAHESH BURSE RANI BHANDARE PRAVIN CHORDIA KALPESH CHILLAL PRAVIN KHODADE ABHAY KOHOK VILAS MESTRY DEEPA MODI SUJIT PUNNADI CHAITANYA RAJARSHI SINHA SAKYA

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      The effect of atmospheric turbulence is gentler at infrared wavelengths than in visible regime. Hence adaptive optics (AO) delivers better performance in the infrared regime. Robotic Adaptive Optics (Robo-AO) is an AO system for medium-sized telescopes jointly built by Caltech, USA and IUCAA, India. It works with minimal overheads and provides good sky coverage in both visible and infrared regime. The first version of Robo-AO does not have a high-quality NIR camera. For the second version called iRobo-AO, an NIR camera was developed at IUCAA to accommodate AO-corrected 1.0$^{\prime}$ field-of-view in near-infrared bands. It can be used as a science camera as well as a tip-tilt camera. Here we describe the salient features of the NIR camera like optics, optomechanical design, detector control system etc.

    • India-TMT project—science instrumentation program

      THIRUPATHI SIVARANI RAMYA SETHURAM S. SRIRAM DEVIKA DIVAKAR ARUN SURYA HARI MOHAN VARSHNEY SUDARSHAN KAMBALA AMIRUL HASAN AJIN PRAKASH K. V. GOVINDA VISWANATHA G. C. ANUPAMA G. MAHESWAR D. OJHA S. B. PANDEY J. PANDEY M. PURAVANKARA A. N. RAMAPRAKASH B. E. REDDY SARANG S. SHAH R. SRIANAND A. SUBRAMANIAM S. SUBRAMANIAN

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      The future of astronomy in the coming decades will be shaped by the upcoming three extremely large optical telescopes, the Thirty Meter Telescope (TMT), the Giant Magellan Telescope (GMT) and the European Large Telescope (ELT). The USA astronomy and astrophysics 2020 decadal survey and the Canadian long-range plan for astronomy have recently recommended these large observatories as a top priority for ground-based astronomy for the upcoming decade. India is a 10% partner in one of these large observatories, the TMT, which is jointly funded by the Department of Science and Technology (DST) and Department of Atomic Energy (DAE). Here, we highlight India’s contributions to the development of the telescope and science instruments. The size of back-end science instruments scale with telescope aperture, hence, science instruments for TMT will be the biggest ever built for any telescope. Designing and building them requires broad collaboration within India, across TMT partnership and industries. India contributes >30% of the work share towards the development of wide field optical spectrometer (WFOS). India is part of the development of other first-light instruments, the infrared imaging spectrograph (IRIS) and multi-object diffraction-limited high-resolution infrared spectrograph (MODHIS). Infrared guide star catalog is an important contribution from India to these adaptive optics (AO)-assisted instruments. India leads the development of high-resolution optical spectrograph (HROS), a major workhorse among the first decade instruments of TMT. India is also part of the instrument development team of other first-decade instruments. Concerted efforts have been made to contribute to some of the TMT precursor instruments that will help us to maximize the scientific productivity when TMT is operational, especially in the area of exoplanet science and observations that require AO. India-TMT is part of the science team for the Keck high-resolution infrared spectrograph for exoplanet characterization (HISPEC), a precursor instrument to TMT-MODHIS. In addition, Indian Institute of Astrophysics (IIA) is participating in the science and development of Santa Cruz array of lenslets for exoplanet spectroscopy (SCALES) project for Keck, which is a direct imaging spectrograph for exoplanet studies and a precursor to the TMT planetary system imager.

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      Posted on January 27, 2016

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      Posted on July 25, 2019

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