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One of the major objectives of the optomechanics is to support large optics required for the purpose and also to maintain high dynamic stability in operation. This requirement calls for more number of supports, to support large optics. While addressing this issue, the mounting system tends to become non-kinematic and distorts the optical surface and leads to poor image quality. The distorted optical surfaces bring in increased RMS surface wavefront errors which will result in poor image quality. In this context, a new concept is proposed in our previous publication (Nagabhushana et al., 2021) which involves introduction of deformable bushes at the optomechanical interfaces. These are deformed by applied clamping forces and also enabling all degrees of freedom (DOF) to be arrested. This also ensures that the clamping force in axial DOF is limited to a minimal value. This technique enables to arrest of axial DOF without exerting the clamping force on the optomechanical assembly there by reduces optical aberrations and improves the mounting system's dynamic stability. This is because deformable bushes absorb all the clamping forces and the strain has no impact on the mount and therefore does not lead deformation of the optical surface. The clamping forces are simulated by Finite Element (FE) methods. Further, in this paper, the concept is verified and validated by experiments. The simulation results are observed to be in close correlation with experiment results. Improved stability is also observed by additional constraints introduced to optomechanical mounts with no compromise in wavefront errors. [ABSTRACT FROM AUTHOR]

There is a continuous need to enhance the aperture size of telescopes by astronomers to explore the space much deeper by getting better resolutions and high image quality. Supporting large optics and maintaining high dynamic stability involves more number of constraints. This renders optical surface more distorted and results in poor image quality, since the image quality deteriorates with increase in RMS surface error. A new approach is proposed to introduce deformable bushes at the interfaces. These are tuned to deform under specific clamping force and thus arrests all Degrees of Freedom (DOF). This limits the clamping force exerted by an axial DOF ( U z ) to an insignificant value. This approach helps to arrest U z without imposing clamping stress on the opto-mechanical mount and brings down optical aberrations and enhances dynamic stability of the mounting system. This due to the fact that all clamping forces are taken by deformable bushes and the stress is not transferred to mount and thus does not contribute to non-uniformity of the optical surface. The non-uniformity of the optical surfaces influenced by clamping forces is simulated by Finite Element (FE) techniques. The use of deformable bush approach in minimizing optical aberrations and stability enhanced by additional constraints to opto-mechanical mounts are demonstrated by simulations. [ABSTRACT FROM AUTHOR]

The activity of radium (226Ra), radon (222Rn) and physicochemical parameters in ground water around study area were estimated by standard techniques. The average values of activity of 226Ra, 222Rn in the study area are higher than the global average but physicochemical parameter are within the safe level. The total dose and ELCR to the workers and publics of the study area are less than the prescribed and accepted level. The industrial activity influences the activity of radionuclides and physicochemical parameter in ground water. The correlation was observed between radium with fluoride, chloride and nitrate. The obtained data are discussed in this paper. [ABSTRACT FROM AUTHOR]

ADITYA-L1 is India's first dedicated mission to observe the Sun and its atmosphere from a halo orbit around L1 point. Visible emission line coronagraph (VELC) is the primary payload on board Aditya-L1 to observe the Sun's corona. VELC is designed as an internally occulted reflective coronagraph to meet the observational requirements of wide wavelength band and the field of view close to the solar limb (1.05 R Sun ). Images of the solar corona in continuum and spectra in three emission lines 5303 Å [Fe xiv], 7892 Å [Fe xi] and 10747 Å [Fe xiii] obtained with high cadence are to be analyzed using software algorithms automatically. A reasonable part of these observations will be made in a synoptic mode in which the data are processed through a standard pipeline and the resulting products will be made available for public use. The procedure involves the calibration of instrument and detectors, converting the images into the FITS format, correcting the images and spectra for the instrumental effects, and aligning the images (in terms of position angles and image scales) etc. Then, develop image processing algorithms to detect the occurrence of energetic events using continuum images. Also derive physical parameters, such as temperature and velocity structure of solar corona using emission line observations. Here, we describe the calibration of detectors and the development of software algorithms to detect the occurrence of CMEs and analyze the spectroscopic data. [ABSTRACT FROM AUTHOR]

Over the last 5 years, UVIT has completed observations of more than 500 proposals with ∼ 800 unique pointings. In addition, regular planned monitoring observations have been made and from their analysis various key parameters related to in orbit performance of UVIT have been quantified. The sensitivities of the UV channels have remained steady indicating no effect of potential molecular contamination confirming the adequacy of all the protocols implemented for avoiding contamination. The quality of the PSF through the years confirms adequacy of thermal control measures. The early calibrations obtained during the Performance Verification (PV) phase have been further revised for more subtle effects. These include flat fields and detector distortions with greater precision. The operations of UVIT have also evolved through in orbit experience, e.g. tweaking of operational sequencing, protocol for recovery from bright object detection (BOD) shutdowns, parameters for BOD thresholds, etc. Finally, some effects of charged particle hits on electronics led to opimised strategy for regular resetting. The Near-UV channel was lost in one of such operations. All the above in-orbit experiences are presented here. [ABSTRACT FROM AUTHOR]

Ultra Violet Imaging Telescope (UVIT) is one of the 5 instruments on AstroSat satellite, which was launched on September 28, 2015. UVIT was designed to make images with a resolution of < 1. 8 ′ ′ , simultaneously in two ultraviolet channels: Far Ultraviolet (130–180 nm) and Near Ultraviolet (200–300 nm). Images are also made in visible region (320–550 nm) for tracking drifts in pointing. The shortest wavelengths to be observed with UVIT can be heavily absorbed by mono-molecular deposits/contamination on the optical surfaces. Keeping contamination under control in UVIT was a major challenge and it required a variety of actions: (i) strict control of the payload materials and process, (ii) mechanical configuration, (iii) baking of all the parts to release all the adsorbed molecules etc., (iv) assembly in ultra cleanrooms, (v) pre-inspection and auditing of all the areas, in which UVIT was placed, for any potential for contamination, (vi) continuous purging, with ultra-pure nitrogen gas, till a few days before the launch, etc. In order to minimise any possible cross contaminations from the other payloads/satellite, the doors of UVIT were opened 2 months after the launch. The high performance in the orbit and high stability of the sensitivity over 4 years in the orbit shows that the contamination was negligible. This paper presents the processes and protocols followed during the integration and testing phase to minimise the contamination in order to prevent any performance degradation. [ABSTRACT FROM AUTHOR]

The Ultra Violet Imaging Telescope (UVIT) is one of the major scientific instruments on the proposed ASTROSAT mission of the Indian Space Research Organisation. The design of a telescope to meet the scientific requirements within the weight and volume constraints of the satellite bus has been a major challenge. The design has also to meet the qualification levels for launch into orbit as well as the thermal environment in orbit. Here we present the overall design of the UVIT mechanical structure with details of some critical aspects. [ABSTRACT FROM AUTHOR]

In the present paper, the radon concentration in drinking water samples of the Hassan city, Karnataka state, India, was analyzed using the radon emanometry technique. The measured radon concentrations ranged from 19.5 ± 1.5 to 121.8 ± 5.6 Bq/L with an average value of 61.4 ± 3.3 Bq/L. This study reveals that all the drinking water samples have radon concentration levels higher than the maximum contaminant level of 11 Bq/L as suggested by the Environmental Protection Agency, and 75% of the recorded radon concentration values were found to be well below the action level of 100 Bq/L recommended by the World Health Organization. The average annual effective dose to the population of the studied area was found to be slightly greater than the safe limit of 100 μSv/y recommended by the World Health Organization. [ABSTRACT FROM AUTHOR]

The performance of the ultraviolet telescope (UVIT) on-board AstroSat is reported. The performance in orbit is also compared with estimates made from the calibrations done on the ground. The sensitivity is found to be within $$\sim $$ 15% of the estimates, and the spatial resolution in the NUV is found to exceed significantly the design value of $$1.8^{\prime \prime }$$ and it is marginally better in the FUV. Images obtained from UVIT are presented to illustrate the details revealed by the high spatial resolution. The potential of multi-band observations in the ultraviolet with high spatial resolution is illustrated by some results. [ABSTRACT FROM AUTHOR]

Solar coronagraph mimics total solar eclipse by blocking the solar disk and enabling the observation of extended coronal atmosphere of the Sun. Visible Emission Line Coronagraph (VELC), on-board Aditya-L1 space mission, is an internally occulted solar coronagraph capable of simultaneous imaging, spectroscopy and spectro-polarimetry close to the solar limb. This payload is designed to study the coronal plasma and heating of the solar corona. Studying development, dynamics and origin of coronal mass ejections and measurement of coronal magnetic fields over active regions are other important science goals. VELC is designed to image the solar corona at 500 nm with an angular resolution of 5" over a field of view (FOV) of 1.05-3 Ro. It also facilitates simultaneous multi-slit spectroscopy at three emission lines, viz. Fe XIV (530.3 nm), Fe XI (789.2 nm) and Fe XIII (1074.7 nm) with a spectral resolution of 28, 31 and 202 mÅ/pixel respectively, over an FOV of 1.05-1.5 Ro. The payload has a dual-beam spectro-polarimetry channel for magnetic field measurements at 1074.7 nm. [ABSTRACT FROM AUTHOR]

The outer atmosphere of the sun - called the corona - has been observed during total solar eclipse for short periods (typically < 6 min), from as early as the eighteenth century. In the recent past, space-based instruments have permitted us to study the corona uninterruptedly. In spite of these developments, the dynamic corona and its high temperature (1-2 million K) are yet to be fully understood. It is conjectured that their dynamic nature and associated energetic events are possible reasons behind the high temperature. In order to study these in detail, a visible emission line space solar coronagraph is being proposed as a payload under the small-satellite programme of the Indian Space Research Organisation. The satellite is named as Aditya-1 and the scientific objectives of this payload are to study: (i) the existence of intensity oscillations for the study of wavedriven coronal heating; (ii) the dynamics and formation of coronal loops and temperature structure of the coronal features; (iii) the origin, cause and acceleration of coronal mass ejections (CMEs) and other solar active features, and (iv) coronal magnetic field topology and three-dimensional structures of CMEs using polarization information. The uniqueness of this payload compared to previously flown space instruments is as follows: (a) observations in the visible wavelength closer to the disk (down to 1.05 solar radii); (b) high time cadence capability (better than two-images per second), and (c) simultaneous observations of at least two spectral windows all the time and three spectral windows for short durations. [ABSTRACT FROM AUTHOR]