ISRO’s VIEW TO THE INVISIBLE UNIVERSE:
“I am confident that when it comes to India's space programme, the best is yet to come.”
-Hon. PM Shree Narendra Modi
In this blog, we feel delighted to present you the insights from ISRO’s ASTROSAT MISSION, the first dedicated Indian astronomy mission aimed at studying celestial sources in X-ray, optical and UV spectral bands simultaneously launched in 2016.
The scientific objectives of AstroSat mission are:
1) To understand high energy processes in binary star systems containing neutron stars and black holes;
2) Estimate magnetic fields of neutron stars;
3) Study star birth regions and high energy processes in star systems lying beyond our galaxy;
4) Detect new briefly bright X-ray sources in the sky;
5) Perform a limited deep field survey of the Universe in the Ultraviolet region.
Mentioning the most unique features of this mission is that it enables simultaneous multi-wavelength observations of various astronomical objects with a single satellite.
This is a five years mission in which the satellite observes the universe in the optical, Ultraviolet, low and high energy X-ray regions of the electromagnetic spectrum.
ASTROSAT Configuration:
The cuboidal shaped AstroSat has two solar arrays consisting of Triple Junction solar cells that generate 2100 Watt power. Sun, star and gyroscope sensors have been used for orientation reference of the satellite. The Attitude and Orbit Control System [AOCS] of it accurately maintains the orientation by reaction wheels, magnetic torquers and thurtsers. Special thermal control schemes have been designed to manage typical payloads.
After successful injection into the orbit, the two solar panels of it are automatically deployed in quick session and the spacecraft control centre at Mission Operations Complex [MOX] of ISRO Telemetry, Tracking and Command Network [ISTRAC] at Bangalore manages the satellite during its mission life.
The science data gathered by FIVE Payloads of AstroSat are telemeterd to the ground station at MOX. The data is then processed, achieved and distributed by Indian Space Science Data Centre [ISSDC].
AstroSat Salient Features:
AstroSat Payloads:
1) Ultra- Violet Imaging Telescope (UVIT):
The Ultra-Violet Imaging Telescope, or the UVIT, is a remarkable 3-in-1 imaging telescope. Weighing all of 230 kg, the UVIT can simultaneously observe in the visible, the near-ultraviolet (NUV) and the far-ultraviolet (FUV). UVIT comprises of two separate telescopes. One of them works in the visible (320-550 nm) and the NUV (200-300 nm). The second works only in the FUV (130-180 nm). Remember that the famous Lyman-α line of Hydrogen is at 121.6 nm, at the far end of the FUV, and even beyond that is the X-ray band for which AstroSat has four different telescopes.
2) Soft X-rat Telescope (SXT):
SXT is an X-ray focusing telescope operating in the energy range 0.3-8.0 keV (X-rays are often again detected as individual photons. They are quantified in terms of their energy rather than their wavelength, purely due to initial development of X-ray detectors without optics. 1 keV photon is approximately 1.2 nm (for comparison, a blue light photon has an energy of about 3 eV).
3) Large Area X-ray Proportional Counters (LAXPC):
The special feature of the LAXPC instrument is its ability to measure X-ray spectra at very short time scales. Not only can these spectral measurements be made over periods as short as few milliseconds if the source is bright enough, up to few hundreds of seconds, but these spectra can extend over a large range of energies viz. 3-80 keV. The LAXPC can even look at how the brightness of a celestial source varies over tens of microseconds! Hence, this is the perfect instrument to study a wide variety of celestial objects that undergo sudden outbursts.
4) Cadmium- Zinc- Telluride Imager (CZTI):
Cadmium - Zinc - Telluride Imager (CZTI) is truly a hard X-ray imaging instrument in the energy range 10-100 keV with a collecting area of 976 cm2. This is a solid state detector and the entire detector assembly is divided into four identical and independent quadrants.The exact position of the source above the detector can be determined from the pattern of the shadow that it casts. CZT modules perform best in the temperature range 0-15 degree celsius and hence the heat generated by the detector assembly is drained out continuously by a radiator panel assembly.
5) Scanning Sky Monitor (SSM):
The Scanning Sky Monitor (SSM), as the name indicates, is to scan the portion of sky away from sun to look for any transient behaviour in X-ray sources. In any space mission such an instrument is mandatory because it can scan a large portion of the sky in a few hours. Hence, the SSM is good for detecting and locating any transient event in out bursting phase in the energy range 2.5-10 keV. Also, at the output of SSM, if some interesting source is found in a particular location, other instruments on-board AstroSat as well as ground based observatories can be alerted to conduct detailed observation towards that position. Hence SSM needs to have large field of view (FOV) and good angular resolution.
In addition to these, a Charged Particle Monitor (CPM) has also been used to detect charged particles.
This has been done because the satellite spends a considerable time (15-20 minutes) in South Atlantic Anomaly (SAA) Region, which has high fluxes of low energy photons and electrons.The high voltage will be lowered or put off using data from CPM when the satellite enters the SAA region to prevent damage to the detectors as well as to minimize ageing effect in the Proportional Counters.
AstroSat Observations:
1) Talking of WLM: Forming Stars efficiently in grand association, located in the constellation Cetus, 3 Million light years away, is a faint dwarf galaxy, Wolf-Lundmark-Melotte, or WLM for short. It is relatively isolated, lying in the outskirts of our Local Group of Galaxies. It has a mass that is thousands of times less than the Milky Way and a metallicity that is only 13% solar. Lower metallicity implies less heavy elements, which in turn hinders forming new stars. So why did AstroSat even look at this galaxy? WLM is a dwarf irregular galaxy with a low mass and metallicity and exists in solitude. Nevertheless, it manages to form new stars extremely efficiently. Adjusted for their respective masses, WLM forms stars at a rate that is 12 times higher than our own Milky Way! Astronomers are still not sure as to how WLM does this.
2) While the mission still continues, there are a lot of results yet to come. For more results and observations please keep visiting https://www.isro.gov.in/
AstroSat Self Model:
We can also make a self AstroSat model following this:
As ISRO completes 50 years, marking 50 years of India in Space and continuously making us proud, we at IEEE feel elated to celebrate National Space Day and mark this week of our activities dedicated to India in Space. A gentle reminder to all our readers, ANTARIKSHA 1.0 – An online quiz on ISRO and India’s achievements in Space to be conducted on May 1, 2020 at sharp 5:00 PM at our website http://ieee.nitp.ac.in/new/index.html
Forget not, winners get IEEE goodies such as T-shirts, stickers and pens!
A note for the readers:
You can find more details of the ASTROSAT Mission at ISRO’s official website, a book on AstroSat has also been released, with its e-copy available at the website and also a review article on "ASTROSAT -- Indian Multiwavelength Astronomy Satellite to View the Invisible Universe" by Prof. P.C.Agrawal has been published in Physics News, July -- December 2016 issue also available at ISRO’s website.
Further we really hope for the safety of our followers and their well-wishers. We all stand together in these tough times and stay home to stay safe.
Keep reading! Do drop your comments if you liked it and suggest more topics for upcoming Tech Thursdays.
NOTE: The entire source of this article is as per the information available at https://www.isro.gov.in/
Further attaching more pictures for reference.
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