Indian Space Program: News & Discussion

[Amber G.]

..as someone said., the US optical spy sats [ KeyHole 11 or KH11 ] are similar to Hubble satellites , have mirrors comparable in size to Hubble's (2.4 meters) and utilize similar electro-optical digital imaging, KH11s are bigger as well..looking in the other direction .. and there are quite a few of them.. one can just imagine how much each would cost!

Yes, Thanks for binging that up!

It’s well-known (though not officially confirmed by the U.S. government ) that the KH-11 series, especially the later “CRYSTAL” have mirror sizes around 2.4 meters, just like Hubble... same designs as Hubble’s Ritchey–Chrétien telescope, but pointed down at Earth instead of out into space!

Electro-optical imaging sensors for real-time or near-real-time digital imagery.. (as opposed to old film-return satellites as it was common in 1970''s).

Fun fact: in 2012, two spare Hubble-class telescopes were donated by the NRO (National Reconnaissance Office) to NASA—proof that these spy satellites are indeed Hubble’s secret twins.

Later KH-11s are thought to have longer focal lengths, enabling ultra-high resolution (estimates range from 10–15 cm GSD—ground sample distance).

Yes we can imagine cost is astronomical..
These systems form the backbone of U.S. strategic intelligence gathering ..

In some ways, the U.S. has had “Google Earth-level” resolution (and far better) decades before it became public tech.

(Added: Per Google: KH-11 satellites have been launched regularly since 1976, with the most recent ones in 2021 and 2022, as part of the Evolved Enhanced CRYSTAL class under the NROL (National Reconnaissance Office Launch) missions. They represent the U.S.’s most advanced optical reconnaissance capability.

[Amber G.]

Sharing some news : The IIT Kanpur inaugurated a course on “Space Mission Design, Analysis, and Operations” from 28 July to 9 August 2025, as part of the Indian Technical and Economic Cooperation (ITEC) initiative of the Ministry of External Affairs, Government of India.

[A_Gupta]

https://english.gujaratsamachar.com/new ... ch-failure
PSLV-C61 failure: "The National Failure Analysis Committee, reportedly composed of top scientists – more than half of whom are from premier institutions such as the Indian Institute of Science (IISc) and the Indian Institutes of Technology (IITs)—has been tasked with conducting a detailed review. The panel is expected to submit its report by mid-June."

Was anything made public?

[Prem Kumar]

NISAR launch successful, per TOI

Kudos to ISRO & NASA!

[SSridhar]

Very accurate orbital injection.
2 Kms dispersion in apogee, 3 Kms in perigee, 0.2 deg in inclination.
Attitude changes done, solar panels deployed & power generation started etc.

[bala]

For those wanting to see the launch, watch the historic launch of GSLV-F16 carrying the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite, a joint Earth observation mission by ISRO and NASA.

GSLV-F16 Launch with NASA-ISRO NISAR Earth Observation Satellite
https://www.youtube.com/watch?v=OgC1MxtCwq4

[drnayar]

For those wanting to see the launch, watch the historic launch of GSLV-F16 carrying the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite, a joint Earth observation mission by ISRO and NASA.

GSLV-F16 Launch with NASA-ISRO NISAR Earth Observation Satellite
https://www.youtube.com/watch?v=OgC1MxtCwq4

no hitch at all .. compare to how the spy satellite launches failed ..

[SSridhar]

'The most sophisticated radar we've ever built': US-Indian NISAR satellite launches to track tiny changes on Earth's surface

[Amber G.]

^^^ Congratulations!
( I have made about 5-6 long detail posts about NISAR - starting my first one more than 3 years ago .. when NISAR was scheduled to in 2023 or so - see my next post)

For BRF, some observations/points (as has been made several times here) without exaggeration -

NISAR s a BIG milestone for both NASA and ISRO. It’s the first satellite in the world to use dual-frequency radar—L-band from NASA and S-band from ISRO—on the same platform. That means it can track even tiny changes on Earth’s surface, like shifting glaciers, landslides, or underground water changes, with accuracy down to about a centimeter. It carries a huge 12-meter antenna (NASA’s biggest ever in space), giving it wide coverage and sharp detail in every pass, day or night, rain or shine.

Some standouts

- First-of-its-kind with both L- and S-band SAR onboard

- Massive 12 m radar dish on a 9 m boom—deployed in space

- Churns out ~35 TB of data daily, one of the highest for Earth missions

- Tracks surface shifts as small as 1 cm—ideal for disaster and climate monitoring

- Helps map carbon, biomass, and land use changes

- Works in any weather, 24/7, through clouds, smoke, and forest cover

- A real co-build effort—NASA made the L-band radar; ISRO built the S-band and satellite bus

- In a 90-day commissioning phase now, full science ops expected by late October

- Will release most data openly, with quick turnaround in emergencies

In short, NISAR is like giving Earth an ultra-precise radar eye—hugely useful for scientists, disaster response teams, and climate researchers around the world!

[Vayutuvan]

( I have made about 5-6 long detail posts about NISAR - starting my first one more than 3 years ago .. when NISAR was scheduled to in 2023 or so - see my next post)

Wow, well done sir jee. I, for one, am very grateful for your service. I hope that much of sabhashi is enough. If not, don't be shy and tell me. I will give more praise. I will have to ask my IAS friends for more superlative words than I can muster.

[Amber G.]

NISAR – A Joint Journey in Science
- Amber G. (For BRF)

- From someone who’s been following this closely — a scientist-teacher, and a quiet admirer of both nations’ space efforts.

Now that NISAR has successfully launched — a major milestone in US–India cooperation in space science — I thought it might be useful (and a bit satisfying!) to look back at some key moments from its journey.

What follows is a quick recap of updates and reflections I’ve shared in the US–India thread over the last few years. . Please see the detail post(s) under each heading.

Not official press releases — just a collection of informal posts from yours truly, a scientist and teacher who’s been quietly proud of this unique collaboration and what it stands for.

- April 2022 – Diplomatic Spotlight

In the official India–US joint statement, NISAR was mentioned prominently — a sign of how important this scientific mission was to both governments.

It wasn’t just about satellites — it showed how Earth observation and climate science had entered the strategic partnership space.

February 2023 – Nearing the Finish Line
(February 2023 – Nearing the Finish LineII )
1. At-a-glance update:

Shared this brief note:

The NASA-ISRO Synthetic Aperture Radar (NISAR) mission was moving toward a 2024 launch.

It would use dual-frequency radar (L-band and S-band) to systematically track changes in forests, water, agriculture, and crustal deformation — all with open-access data.

2. Big move – Payload ships to India:

“Scientific heart of NISAR leaves JPL in style!”

In early Feb 2023, NASA’s radar payload was prepped and officially sent to India after a public rollout.

NASA’s Laurie Leshin and ISRO’s S. Somanath jointly highlighted how this mission could monitor everything from glacier motion to soil moisture.

Posted photos of the equipment inside JPL’s clean room — looked stunning.

August 2023 – Reflections Amid Big Announcements

Around the time news of the Biden-Modi State Visit broke, I re-shared the NISAR post in the context of growing trust and cooperation between the two nations.

Also said this:

I was particularly happy when S. Somanath became ISRO Chairman — he’s respected by both scientists and the public, and also has a solid reputation in NASA and US circles.

Felt like a moment worth acknowledging — one where science, leadership, and diplomacy all aligned.

June 2025 – The Launch
Finally, the big news:

NISAR planed to be launched in 2025

I shared a summary of what makes this mission special:

What NISAR does:

Uses synthetic aperture radar to detect minute Earth changes (down to centimeters)

Works day or night, in all weather

Data is freely available — supporting:

Disaster response (e.g., floods, landslides, oil spills)

Climate monitoring (e.g., ice sheets, land deformation)

Agriculture (e.g., soil moisture estimation)

Features include:

Scans land and ice surfaces twice every 12 days

Tracks flooded vegetation, wetlands

Observes glacier motion, coastal erosion

Total cost: approx $1.5 billion

It's a triumph of open science, international trust, and engineering.

I also made it clear I wouldn’t waste time with online trolls — science like this deserves better.

----
Some personal refrection:

Flashy deep-space missions are fun — but missions like NISAR are where real-world impact and international cooperation shine brightest.

From California’s JPL to ISRO’s Satish Dhawan Space Centre, from radar arrays to rice paddies, from glacial flow to groundwater maps — this mission speaks to the planet’s needs.

It’s a proud moment — for science, for diplomacy, and for the many teams across two continents who made it happen.

– Amber G.

[SriKumar]

^^^Does the satellite pick a reference point on the earth to measure movements upto a cm accuracy? The earth is spinning, and the satellite is moving in LEO at a fast speed. Where is the origin of the spatial reference point on earth? Is there an earth-centric coordinate system? And how does the satellite keep a 'lock' on it, with all the relative movements.

[Amber G.]

^^^Does the satellite pick a reference point on the earth to measure movements upto a cm accuracy? The earth is spinning, and the satellite is moving in LEO at a fast speed. Where is the origin of the spatial reference point on earth? Is there an earth-centric coordinate system? And how does the satellite keep a 'lock' on it, with all the relative movements.

Great Question!
Short Answer

NISAR doesn’t “lock” onto a single point — it uses:
- The ITRF Earth-fixed coordinate system
- Extremely accurate orbit tracking
-InSAR phase comparison over time

...to measure relative surface motion with centimeter or better precision.
---
(Little More explanation - Physics main points)

NISAR uses InSAR (Interferometric Synthetic Aperture Radar), which compares the phase of radar signals reflected from the ground over repeated passes. By analyzing the phase difference between two observations, it can detect surface movement as small as a few centimeters or even millimeters.

To achieve this:

1. Precise Earth-Centered Coordinate System (ITRF):
NISAR uses the International Terrestrial Reference Frame, a global 3D coordinate system anchored by GPS and ground stations worldwide.

It provides a stable, Earth-fixed reference to measure changes against.

2. Highly Accurate Satellite Positioning:
NISAR’s orbit is known to centimeter-level precision using onboard GPS and possibly laser retroreflectors.


3. Relative Motion Detection via InSAR:
The satellite compares radar phase from the same ground location across different orbits (~every 12 days).

Any ground shift changes the path length, which alters the radar phase — allowing detection of motion.

Thus

NISAR detects surface changes by comparing radar phase over time, using a stable Earth-fixed coordinate system (ITRF) and precise satellite positioning. No single fixed ground point is needed — it’s all relative motion.

(Yes, the Earth rotates — but that’s predictable and modeled.
-Yes, tectonic plates shift — but again, that's what NISAR is meant to measure.
-The key is to calibrate out known motions, so that what’s left is the change you care about: landslides, earthquakes, glacier movement, etc.)

[nits]

Can Nisar tech can act as base for our future spy satelites

[SriKumar]

NISAR detects surface changes by comparing radar phase over time, using a stable Earth-fixed coordinate system (ITRF) and precise satellite positioning. No single fixed ground point is needed — it’s all relative motion.

(Yes, the Earth rotates — but that’s predictable and modeled.
-Yes, tectonic plates shift — but again, that's what NISAR is meant to measure.
-The key is to calibrate out known motions, so that what’s left is the change you care about: landslides, earthquakes, glacier movement, etc.)

Interesting, thanks. Since the phase difference is being measured, does the satellite compute the velocity of the target (e.g. a glacier) i.e. via Doppler effect? How do they account for scatter of signal and accompanying loss of strength, which is to be expected from a lot of earth surfaces e.g. forests, and water even.
The ITRF system sounds very interesting. It seems like it is a computational model to account for mass flows within earth and on surface as well (including plate movements). It seems like everything is moving, and corrections based on new observations and new computations are applied periodically, to establish a newer reference point and frame. Any comment on how many GPS stations are needed on earth surface to achieve a reasonable level of positional accuracy?

I recall your mentioning that relativity was used to adjust the timing calculations since the time duration of received/reflected signals is so low. To what extent are regular Newtonian equations of motion are used in velocity and distance calculations. Thanks