India's Space based Telescopes and Astronomical spacecraft

Karthi

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panoramic view of the Devasthal Observatory . The larger white dome.jpg



Panoramic view of the DOT. The larger white dome houses 3.6-m DOT and the smaller enclosure houses a 1.3-m wide-field optical telescope.

Picture of the fully assembled telescope.jpg


Picture of the fully assembled telescope

The adaptor rotatir instrument.jpg




The Adapter Rotator Instrument Support Structure (ARISS) with main instrument envelope (a), side-port instrument envelope (b), rotator bearing (c), pick-off mirror (e), adaptor bearing (f), turn table (g), and optical bench with guider camera and wavefront sensor (h).
 

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A picture of the 3.6-m telescope pier. The pier is a hollow cylinder with an inner.jpg


A picture of the 3.6-m telescope pier. The pier is a hollow cylinder with an inner diameter of 5 m, an outer diameter of 7 m, and a top slab with a thickness of 1 m. The height of the pier from the ground is 8.26 m. Right: A picture of the dome overhead cranes.


The instrument envelope for side ports and main port instruments is shown.jpg



The instrument envelope for side ports and main port instruments is shown
 

Karthi

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NISAR instrument physical layout..jpg

NISAR instrument physical layout2.jpg


NISAR physical layout



Spacecraft in stowed configuration.jpg



Spacecraft in stowed configuration.Spacecraft in stowed configuration..jpg


Spacecraft in stowed configuration.



NISAR will image Earth’s dynamic surface over time. NISAR will provide information on changes in ice sheets and glaciers, the evolution of natural and managed ecosystems, earthquake and volcano deformation, subsidence from groundwater and oil pumping, and the human impact of these and other phenomena.

Anticipated scientific results over the course of the mission include:

Comprehensive assessment of motion along plate boundaries that are on land, identifying areas of increasing strain, and capturing signatures of several hundred earthquakes that will contribute to our understanding of fault systems;

Comprehensive inventories of global volcanoes, their state of activity and associated risks;

Comprehensive biomass assessment in low biomass areas where dynamics are greatest, and global disturbance assessments, agricultural change, and wetlands dynamics, informing carbon flux models at the most critical spatial and temporal scales;

In combination with GEDI and other missions, comprehensive global biomass to set the decadal boundary conditions for carbon flux models;

Complete assessments of the velocity state of Greenland’s and Antarctica’s ice sheets, each month over the mission life, as a key boundary condition for ice sheet models;


Regular monitoring of the world’s most dynamic mountain glaciers; • Comprehensive mapping of sea ice motion and deformation, improving our understanding of ocean-atmosphere interaction at the poles;


A rich data set for exploring a broad range of applications that benefit from fast, reliable, and regular sampling of virtually any areas of interest on land or ice. These include infrastructure monitoring, agriculture and forestry, disaster response, aquifer utilization, and ship navigability.
 

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Figure 3-1. .jpg


InSAR measures surface deformation by measuring the difference in the phase of the radar wave between the two passes if a point on the ground moves and the spacecraft is in the same position for both passes (zero baseline). InSAR deformation geometry is demonstrated in these figures at the left and right. On Pass #1, a surface of interest is imaged and the radar satellite measures the phase φ1 (x,y) between the satellite and the ground along the line-of-sight (LOS) direction. Later at Pass #2, the satellite makes another measurement φ2 (x,y) between the satellite and the ground. If the ground moves between passes, the phase difference Δφ (x,y) is proportional to the ground deformation between passes along the LOS direction.





Figure 4.10.jpg



Sweep-SAR Technique Illustration of enabling “SweepSAR” concept, which allows full-resolution, multi-polarimetric observations across an extended swath (> 240 km). By transmitting energy across the full feed aperture, a wide swath is illuminated on the ground. Each patch element on the feed can receive independently, allowing localization in time, hence space, of the return echo scattered from the ground. Note: Transmit and Scanning Receive events overlap in time and space.


Figure 4-8.png


Locations of NISAR Ka-band ground stations (NASA stations in Alaska, Svalbard and Punta Arenas, and ISRO stations in Shadnagar and Antarctica are shown
 

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jaduguda-underground-lab_650x400_41504605740.jpg



Indias Dark Matter operating research centre

Jaduguda Underground Science Laboratory a 21st century underground lab in a quest to find the dark matter.A lab buried about 1,800 feet (550m) below the Earth’s surface in an abandoned uranium mine in Jaduguda in the eastern Indian state of Jharkhand is the first of its kind in India that aims to find dark matter.

This was established and inaugurated in September 2017. More specifically, the first phase of the laboratory covered under this proposal, is set up to determine the gamma ray and neutron background from the radiogenic and the cosmogenic sources, radon level, vibration level at the underground lab location, etc. The research work to be done at the underground laboratory will be supported by adequate theoretical endeavor and simulations, as well as developmental aspects involving radiation detectors and related electronics aimed at high sensitivity under very low radiation and noise background levels. The experiments to be carried during this phase and the resulting data will be useful for the upcoming major underground laboratory facilities and experiments to be conducted therein. The work will be supported by multi-institutional collaborative efforts involving major research institutes, apart from SINP which is taking the lead role in establishing the laboratory, like BARC, NISER, TIFR, and VECC, etc.

There was another Research facility at Kolar . In 1992, after four decades of conducting pioneering experiments, the 2.3 km-deep research facility at Kolar Gold Field was shut down cos of the mine’s vast network of tunnels had flooded due to disuse (as the gold reserves had dwindled, the mining operations had stopped).
 

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L Band Active Phased Array Antenna. motr.jpg


L Band Active Phased Array Antenna of ISRO MOTR, out of curiosity I have calculated the Detection range of MOTR against F22 got 140 Km against frontal RCS of 0.0001 certainly the Detection range is greater cos F22 side and Rear RCS is greater
 

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real time ground trace plot of PS4 stage of PSLV-C29 mission debris.jpg


real time ground trace plot of PS4 stage of PSLV-C29 mission debris using MOTR
 

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View attachment 49908

L Band Active Phased Array Antenna of ISRO MOTR, out of curiosity I have calculated the Detection range of MOTR against F22 got 140 Km against frontal RCS of 0.0001 certainly the Detection range is greater cos F22 side and Rear RCS is greater
I think 0.0001 frontal RCS value for F22 which the Americans are claiming is for X-band (8-12 GHz) (which is also greatly exaggarated), not L band (1-2 Ghz). Also the RCS figures varies for monostatic or bistatic configuration of the radar.

Source:
 
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NICSPol is a near infrared imaging polarimeter developed for the Near Infrared Camera and Spectrograph
(NICS), one of the back end instruments of the 1.2 m Cassegrain telescope at the Mount Abu Infrared Observatory.
The polarimeter consists of a rotating wire grid polarizer (WGP)which is mounted between the telescope
optics and NICS.

NICSPol unit with the 25 x 25 cm WGP.jpg
NICSPol unit with the 25 x 25 cm WGP.jpg


NICSPol unit with the 25 x 25 cm WGP



The second WGP mounted in NICSPol to polarize the incoming light to achieve 100% polarized rad...jpg
The second WGP mounted in NICSPol to polarize the incoming light to achieve 100% polarized rad...jpg


The second WGP mounted in NICSPol to polarize the incoming light to achieve 100% polarized radiation.
 

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Mystery of a peculiar star SU Lyn resolved by PRL scientists using AstroSat
In a breakthrough, a team of astronomers from the Physical Research Laboratory (PRL), Ahmedabad used the data from Ultra-Violet imaging telescope (UVIT) onboard India’s Astrosat space observatory to resolve the nature of a peculiar star named SU Lyn. They have utilized, for the first time, the UV spectroscopy capability of UVIT and in the process, have thrown new light on the class of stellar objects known as symbiotic stars.
SU Lyn had long been known as an ostensibly unremarkable red giant star – a class of very large and cool stars, which form at the final stages of stellar evolution. However, it was noticed in 2016 that hard X-ray emission was emanating from SU Lyn. This raised the suspicion that the star harboured a hidden, hot companion assumed to be a white dwarf – an end-product when stars of intermediate-mass die. White dwarfs can be as massive as the Sun, yet they have a size similar to the size of the Earth.
The suggestion that SU Lyn could likely host a white dwarf posed a challenge for our understanding of such systems. Binary stellar systems consisting of a white dwarf and a red giant are known as symbiotic systems. In a symbiotic system, the white dwarf and red giant's interaction gives rise to several complex physical phenomena such as an accretion disk, jets, ionized symbiotic nebula, interaction of stellar winds to name a few. Due to this, Symbiotics are considered as one of the most intriguing astrophysical laboratories. A schematic picture of a typical symbiotic system and its various constituents are shown in Figure-1. These symbiotic systems have traditionally been identified and characterized by the presence of intense emission lines of several high ionization species observed in their optical spectra using ground-based telescopes. However, the optical spectrum of SU Lyn was devoid of these lines, raising a question mark on its symbiotic nature.
A schematic diagram showing various components of a symbiotic system
A more definite way to establish the presence of a white dwarf is through ultra-violet (UV) observations since white dwarfs are hot and emit radiation mostly in the UV range. UV radiation, however, cannot penetrate the Earth’s atmosphere and can only be detected using space-based UV telescopes and instruments. But at present, there are few UV telescopes in space and UV telescopes with spectroscopic capability are even rarer.
This is where India’s Astrosat space observatory and one of its payloads UVIT – the Ultra-Violet Imaging Telescope – played a crucial role. Instruments onboard the observatory are capable of recording the UV spectrum of stars, a feature that proved extremely useful. The PRL team had been observing SU Lyn since 2016 with various Indian observing facilities and a suite of instruments, most notably with the UVIT. From the ground, the star was observed with the HESP instrument on the IIA-HCT telescope, with the indigenous in-house developed MFOSC-P spectrograph and with the Near-Infrared Camera and Spectrometer on the PRL 1.2 m telescope at Mount Abu.

The Astrosat-UVIT spectrum of SU Lyn with the emission lines identified. Archival spectra of three other symbiotic systems (ER Del, SY Mus and AS 210) are also shown for comparison.
The Far-UV (1300-1800 Angstroms) spectrum of SU Lyn, obtained with the Astrosat-UVIT instrument, showed emission lines of silicon (Si IV), carbon (C IV), oxygen (OIII), and nitrogen (N III) in a spectrum typical of symbiotic stars (figure-2). The high-resolution optical spectrum also shows the weak presence of few emission lines, which are typically seen in the optical spectrum of symbiotic stars. The UV spectrum, complemented by optical and NIR spectra, thus, confirms the symbiotic nature of SU Lyn. Using a simple theoretical model to fit the UV observations, it was further shown that the white dwarf in SU Lyn is orders of magnitude less luminous (0.16 solar luminosity) compared to a white dwarf in a traditional symbiotic system (~100-1000 solar luminosity). Instead, the symbiotic phenomenon is predominantly powered by the relatively weaker UV radiation from the accretion disk (0.66 solar luminosity) around the white dwarf. This is the reason that the emission lines are weak in the optical spectrum and why the symbiotic nature of SU Lyn could not be established from ground-based observations earlier.
The resolution of the nature of SU Lyn is a significant result for stellar astronomy. There are only a few hundred symbiotic systems known in our Galaxy. This is in contrast with their predicted population of several hundred thousand. The presence of intense emission lines in low-resolution optical spectra has always been the traditional way to identify and discover symbiotic stars. However, these traditional methods would fail to detect the SU Lyn type of Symbiotics. These recent results by the PRL team have firmly established the existence of SU Lyn type symbiotic systems. It is highly probable that many more symbiotic stars like SU Lyn can exist which have so far evaded the detection by conventional methods. And this could be a reason why a smaller than expected number of symbiotic systems have been discovered so far.
It is equally important to note that these results are derived from a lesser-known spectroscopic capability of the UVIT instrument, which is preliminarily designed as an imaging instrument.
Reference :
Vipin Kumar, Mudit K Srivastava, Dipankar P K Banerjee, Vishal Joshi, UV spectroscopy confirms SU Lyn to be a symbiotic star, Monthly Notices of the Royal Astronomical Society: Letters, Volume 500, Issue 1, January 2021, Pages L12–L16; https://doi.org/10.1093/mnrasl/slaa159
 

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AstroSat’s Ultraviolet Imaging Telescope spots rare ultraviolet-bright stars in a massive intriguing cosmic dinosaur in the Milky Way
Posted On: 21 JAN 2021 3:42PM by PIB Delhi



Astronomers exploring the massive intriguing globular cluster in our Galaxy called NGC 2808 that is said to have at least five generations of stars have spotted rare hot UV-bright stars in it. These stars whose inner core is almost exposed, making them very hot, exist in the late stages of evolution of a Sun-like star. It is not clear how these stars end their lives as not many of them are detected in these fast-evolving phases, making their study crucial.


Motivated by the fact that old globular clusters referred to as dinosaurs of the universe present excellent laboratories where astronomers can understand how stars evolve through various phases between their birth and death, scientists at the Indian Institute of Astrophysics (IIA) an autonomous institute of the Department of Science & Technology, Government of India, looked out for NGC 2808.


With spectacular ultraviolet images of the cluster from Ultraviolet Imaging Telescope (UVIT) onboard India’s first multi-wavelength space satellite, AstroSat, they distinguished the hot UV-bright stars from the relatively cooler red giant and main-sequence stars which appear dim in these images. The findings of this study have been accepted for publication in the journal ‘The Astrophysical Journal’.


The team of scientists comprising Deepthi S. Prabhu, Annapurni Subramaniam and Snehalata Sahu from IIA combined the UVIT data with observations made using other space missions such as the Hubble Space Telescope and the Gaia telescope along with ground-based optical observations. About 34 UV-bright stars were found to be members of the globular cluster. From the data, the team derived the properties of these stars such as their surface temperatures, luminosities and radii.


One of the UV-bright stars was found to be about 3000 times brighter than the Sun with a surface temperature of about 100,000 K. The properties of these stars were then used to place them on what astronomers call the Hertzsprung-Russel (HR) diagram along with theoretical models to throw light on the characteristics of their parent stars and to predict their future evolution. Most of the stars were found to have evolved from a solar stage called the horizontal branch stars with hardly any outer envelope. Thus they were bound to skip the last major phase of life called the asymptotic giant phase and directly become dead remnants or white dwarfs.


Such UV-bright stars are speculated to be the reason for the ultraviolet radiation coming from old stellar systems such as elliptical galaxies which are devoid of young blue stars. Hence, it is all the more important to observe more such stars to understand their properties.





Figure 1: A false colour image of the globular cluster NGC 2808 obtained using AstroSat/UVIT. The stars as seen using far-UV (FUV) filter are shown in blue colour, and the yellow colour is used to show the stars observed in near-UV (NUV).
 

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Apr 20, 2021
Announcement of Opportunity (AO) for Utilizing AstroSat archival data (3rd Batch)
AstroSat

AstroSat is India's first multi-wavelength observatory class mission. Data from AstroSat was opened to public on 28th September 2018
(https://www.isro.gov.in/update/26-sep-2018/archival-data-of-astrosat-released) and archived at ISSDC (https://astrobrowse.issdc.gov.in/astro.html).
Proposals are hereby invited from Astronomy community of the nation for utilizing AstroSat archival data. This announcement of opportunity (AO) is open to Indian scientific community for submitting research proposals towards utilisation of data from any and/or all the experiments for limited financial assistance.
For a detailed information on the AO please refer to AstroSat_AO
The completely filled-in application has to reach [email protected] on or before 31-05-2021.
 

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‘India’s first solar mission likely to launch next year’: ISRO


3-4 minutes


India’s first solar mission, which was pushed from early 2020 due to the Covid-19 pandemic, is likely to be launched in the third quarter of 2022, when the country’s second space observatory Xposat, aimed at helping astronomers study cosmic sources such as pulsars and supernova, will also be launched, senior officials from the Indian Space Research Organisation (ISRO) said.

 

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