Indian Space Program: News & Discussions

Gautam

Team StratFront
Feb 16, 2019
11,642
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Tripura, NE, India
Question? : This OCT - will this be encrypted? - How does one encrypt Optical communications?
Let me go through the whole cycle of encryption as is used with communication systems today.

Data is quantifiable by energy. That is the very basis of computers. All data can be expressed in terms of the binary( 0 & 1 ). Thus information flowing between two nodes, say satellite and a ground terminal, if properly tapped can be completely accessible. That's the problem with RF based communications. The energy from the antennas are radiated in all directions equally. Thus making it possible for multiple users to access it as long as you are in range. To ensure information stays private it needs to be encrypted. Encryption is essentially jumbling up the 0s and 1s in a very specific manner. The end result is still 0s and 1s, but everything is out of order.

Lets take an example, if I say :

1=A
2=B
then 3= ??

You can easily identify the pattern and say 3=C. This is what encryption does, its just the maths is a lot more complex with multiple exceptions built in. Thus it take a long time to solve the problem and even if solved some data remains out of reach. You will hear encryption systems described as 8 bit, 16 bit, 32 bit, 64 bit etc. What this means is that the key to solving the encryption has 8 digits of 0s and 1s, 16 digits etc etc.

The longer the key the more difficult it is break. But not impossible. With the advent of quantum computers these encryptions will be broken in no time. To counter this proble QKD are being developed. India is in a pretty advanced state with this development. Go through this thread :


Any kind of optical communication will use quantum bits for communications. This will render the entire data stream un-tapable. The GSAT-29's OCT is essentially a laser and sensor combined together. Now to tap in to the OCT you need to have your tapping equipment exactly where the laser is targeting. The target ground terminal is probably going to be some highly secure ISRO ground facility. Remote tapping is not an option. This will make the communication virtually impossible to break into.

There are problems too. Optical communications tend to be more energy consuming than their RF counter part. Bad weather, receiver mis-alignment etc can be problems too. The OCT is still very much experimental and for the foreseeable future a bulk of our data comms will continue to be RF based. However the RF comms can adopt QKDs to make it more secure.

Sorry for the long rant !:p
 

GuardianRED

Call Sign "RED"
Dec 2, 2017
503
394
Let me go through the whole cycle of encryption as is used with communication systems today.

Data is quantifiable by energy. That is the very basis of computers. All data can be expressed in terms of the binary( 0 & 1 ). Thus information flowing between two nodes, say satellite and a ground terminal, if properly tapped can be completely accessible. That's the problem with RF based communications. The energy from the antennas are radiated in all directions equally. Thus making it possible for multiple users to access it as long as you are in range. To ensure information stays private it needs to be encrypted. Encryption is essentially jumbling up the 0s and 1s in a very specific manner. The end result is still 0s and 1s, but everything is out of order.

Lets take an example, if I say :

1=A
2=B
then 3= ??

You can easily identify the pattern and say 3=C. This is what encryption does, its just the maths is a lot more complex with multiple exceptions built in. Thus it take a long time to solve the problem and even if solved some data remains out of reach. You will hear encryption systems described as 8 bit, 16 bit, 32 bit, 64 bit etc. What this means is that the key to solving the encryption has 8 digits of 0s and 1s, 16 digits etc etc.

The longer the key the more difficult it is break. But not impossible. With the advent of quantum computers these encryptions will be broken in no time. To counter this proble QKD are being developed. India is in a pretty advanced state with this development. Go through this thread :


Any kind of optical communication will use quantum bits for communications. This will render the entire data stream un-tapable. The GSAT-29's OCT is essentially a laser and sensor combined together. Now to tap in to the OCT you need to have your tapping equipment exactly where the laser is targeting. The target ground terminal is probably going to be some highly secure ISRO ground facility. Remote tapping is not an option. This will make the communication virtually impossible to break into.

There are problems too. Optical communications tend to be more energy consuming than their RF counter part. Bad weather, receiver mis-alignment etc can be problems too. The OCT is still very much experimental and for the foreseeable future a bulk of our data comms will continue to be RF based. However the RF comms can adopt QKDs to make it more secure.

Sorry for the long rant !:p
Excellent Write up - Very Informative - Definitely not a rant!

So to sum it all - OCT - is essentially - Line of Sight. - A development to look forward to (y):giggle:
 
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Nikhil

nik141993
Dec 1, 2017
474
268
India
I read somewhere that 50 to 60 % of Indian sattlite components are just imported from abroad & screw drive here.....for strategic sector it's even higher. how much truth in that @Gautam ? & What's the update with SCE 200 engine
 

Gautam

Team StratFront
Feb 16, 2019
11,642
7,079
Tripura, NE, India
I read somewhere that 50 to 60 % of Indian sattlite components are just imported from abroad & screw drive here.....for strategic sector it's even higher. how much truth in that @Gautam ?
Not true at all. In fact ISRO is insists on indigenous design & manufacture even in not so high tech areas like satellite buses. ISRO does import stuff that's not available in India. Like processors.

Until recently we used to import processors from Intel for our satellites and launch vehicles. ISRO has recently stopped using Intel processors for launch vehicles and have replaced them with the VIKRAM-1601 processors. At a future date, ISRO plans to use an upgraded version of the VIKRAM or the upcoming C-DAC processors for satellites. Whichever provides better performance.

What's the update with SCE 200 engine
Component testing was supposed to end this year. COVID has played spoilsport. From sat pics the test stand at LPSC, Mahendragiri seems to have been completed. No official announcements yet. The next phase is hot test of the engine at that test stand. ISRO has called for tender to augment the SLP to house Kerosene for fueling purposes. SCE-200 is the only engine with ISRO that uses Kerosene as fuel.

ISRO has also called tenders for a truck based transport system for a SC160 stage. By ISRO's naming system SC160 means Semi Cryogenic stage with 160 tons of propellant. If they are drawing plans for stages already I would say they are fairly confident on the completion of the engine.

The original timeline for readying a SCE-200 based stage was set at 2021. COVID will delay it no doubt. But we should get to see the first hot test of the SCE-200 in Mahendragiri by 2021.
 
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RISING SUN

Senior member
Dec 3, 2017
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Global team of scientists discovers one of the earliest galaxies using India’s AstroSat
In a major breakthrough, a global team led by scientists of the Inter University Centre for Astronomy and Astrophysics (IUCAA) has discovered one of the earliest galaxies in extreme ultraviolet light. AstroSat, India’s first multi-wavelength satellite that has five unique X-ray and ultraviolet telescopes working in tandem, has detected extreme UV light from a galaxy called AUDFs01, 9.3 billion light-years away from Earth.

The discovery was made by an international team of astronomers led by Dr Kanak Saha, associate professor of astronomy at IUCAA, and was published on August 24 by Nature Astronomy. The team comprises scientists from India, Switzerland, France, USA, Japan and Netherlands.

Dr Saha told The Indian Express that the team observed the galaxy, which is located in the Extreme Deep field, through AstroSat. These observations lasted for more than 28 hours in October 2016. But it took nearly two years since then to carefully analyse the data to ascertain that the emission is indeed from the galaxy.

This is a very important clue to how the dark ages of the Universe ended and there was light in the Universe, said Dr Somak Raychaudhury, director of IUCAA. “We need to know when this started, but it has been very hard to find the earliest sources of light,” he said.

Since UV radiation is absorbed by Earth’s atmosphere, it has to be observed from space. Earlier, NASA’s Hubble Space Telescope (HST), which is significantly larger than the Ultra Violet Imaging Telescope (UVIT) on Astrosat, did not detect any UV emission (with energy greater than 13.6 eV) from this galaxy because it is too faint.

“AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVIT detector is much less than the ones on HST,” said Dr Saha.

He added, “We knew it would be an uphill task to convince the international community that UVIT has recorded extreme-UV emission from this galaxy when the more powerful HST has not… this discovery of AUDFs01 by AstroSat establishes that there is hope and perhaps, this is the beginning”.

A statement issued by IUCAA explained that after the Big Bang, the Universe was a hot soup of particles (i.e.,protons, neutrons, and electrons). As the universe started to cool, the protons and neutrons began combining into ionized atoms of hydrogen (and eventually some helium). These ionized atoms of hydrogen and helium attracted electrons, turning them into neutral atoms — which allowed light to travel freely for the first time, since this light was no longer scattering off free electrons. The universe was no longer opaque. But there were no stars, and no galaxies, and the Universe was dark.

A while after this, maybe a few hundred million years after the Big Bang, the dark ages ended when the first stars and galaxies formed and the energy pouring out from them ionized the hydrogen and helium, splitting the atoms back again in protons and electrons, — this is the epoch of reionization.

Astronomers have been looking for sources that reionized the early universe. The usual suspects have been the first astronomical objects, especially the newborn small galaxies. But observing ionizing radiation from these sources is next to impossible. The probability that a fraction of extreme-UV photons escape the host galaxy and are caught by a telescope on Earth is practically zero, because these photons will be absorbed by the gas in the galaxy or the gas surrounding the galaxy or the matter between the galaxy and us.

How some of these high-energy photons manage to cross all the barriers and reach Earth is a mystery. The absorption in the intergalactic medium is so severe that it is impossible to observe ionizing photons in the reionization epoch directly.

“In the later epoch, the intergalactic absorbers decrease and we have a chance to detect such photons, but it is still like a lottery,” said co-author Dr Akio Inoue, professor of Waseda University in Japan.
 

RISING SUN

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Dec 3, 2017
6,143
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Indian satellite AstroSat detects UV light from galaxy 9.3 billion light-years away from Earth
India's first multi-wavelength satellite, AstroSat, has detected an extreme ultraviolet (UV) light from a galaxy which is 9.3 billion light-years away from Earth, the Inter-University Centre for Astronomy and Astrophysics (IUCAA) said on Monday.

A release from the Pune-based Inter-University Centre for Astronomy and Astrophysics said a global team led by IUCAA scientists have achieved the major breakthrough.

The discovery was made by an international team of astronomers led by Dr Kanak Saha, associate professor of astronomy at the IUCAA, and published on August 24 by 'Nature Astronomy', the release said. This team comprised scientists from India, France, Switzerland, the USA, Japan and the Netherlands.

Saha and his team observed the galaxy, which is located in the Hubble Extreme Deep field, through AstroSat. These observations lasted for more than 28 hours in October 2016, the release stated.

But it took nearly two years since then to carefully analyse the data to ascertain that the emission is indeed from the galaxy. Since UV radiation is absorbed by Earths atmosphere, it has to be observed from space, it said.

Earlier, NASAs Hubble Space Telescope (HST), a significantly larger than UVIT (UV imaging telescope), did not detect any UV emission (with energygreater than 13.6 eV) from this galaxy because it is too faint, it said.

AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVITdetector is much less than the ones on HST," said the release quoting Saha.

Saha said they knew it would be an uphill task to convince the international community that UVIT has recorded extreme-UV emission from this galaxy when more powerful HST has not.

Dr Somak Raychaudhury, Director of IUCAA, said, "This is a very important clue to how the dark ages of the universe ended and there was light in the universe.

"We need to know when this started, but it has been very hard to find the earliest sources of light. I am very proud that my colleagues have made such an important discovery."