Indian Space Program: News & Discussion

[chetak]

“Nonsense” is dismissing the basics. A degraded NavIC isn’t “useless”—loss of navigation ≠ loss of function; satellites can still provide timing and messaging, which are operationally relevant. And no, the Agni series isn’t a plug-and-play satellite launcher. Push back is fine—but it should be grounded in how the system actually works, not in caricatures.

These kinds of posts are why you appear to miss the point, either unintentionally or deliberately

NavIC is dead, or at least crippled. Its useless for missile navigation. Its shameful that we let it come to this

This is the simple truth. No amount of 1000 word explanations are going to change this basic fact

Prem Kumar ji,

single point of failure, the design disaster that one is always taught to guard against

[Tanaji]

Chetakji,

Most likely what happened was this: ISRO came up with a resilient design that would cater for 2-3 failures of satellites without loss of performance. The DoS babooze would have pushed back saying “no need for resiliency, unnecessary expense , remove the extra sats” given their superior intelligence in all matters due to their success at UPS exam. ISRO designer would have then pushed back asking for funds for reserve sats., which would have been canned by babooze as well.

Here is where bad PM kicks in and a good PM would have made this non negotiable…. We had worse luck as all the clocks failed…

[Amber G.]

<img]https://pbs.twimg.com/media/G70zRrwasAA ... ame=medium[/img>

FOBS ?
Dedicated launcher for spy sats ?

Yes, FOB, ASAT ... As said before this is about small, rapid LEO launches—not NavIC-class satellites; completely different mission and precision requirements.

(Hint typical NaviC sat are about 36,000 Km high -- When fully ready in future - can launch small LEO satellites quickly but cannot replace navigation satellites (NavIC class) which are heavy, require precise GEO/IGSO insertion, and need high-accuracy orbital placement)

[Tanaji]

Is there an estimate on how many satellites in LEO orbit would be required to have at least 5 satellites overhead the Indian landmass at any given time?

It would be interesting to see how the economics stacks up this way as opposed to geosats.

[drnayar]

Just putting things in perspective

https://petapixel.com/2026/03/21/as-spa ... night-sky/

This week SpaceX passed an eye-watering milestone: it launched its 10,000th satellite into low-Earth orbit

[Amber G.]

Is there an estimate on how many satellites in LEO orbit would be required to have at least 5 satellites overhead the Indian landmass at any given time?

It would be interesting to see how the economics stacks up this way as opposed to geosats.

FWIW My take (Assuming the question is serious:- please read on)

Good question—but it’s not a simple apples-to-apples swap.
You can absolutely build a LEO-based regional system—but it trades:

Fewer, expensive, long-lived GEO sats
for
many, cheaper, short-lived LEO sats + higher operational complexity

That’s why most GNSS (and NavIC) chose the high-orbit route—not because LEO is impossible, but because the total system economics and stability tend to favor fewer satellites at higher altitude.

Basics:
For continuous coverage over India with ≥5 satellites visible at all times, a rough order-of-magnitude is :
~ 50 LEO satellites (depending on altitude, inclination, and elevation mask)

Why so many? LEO sats (~500–1000 km) move fast → each is visible only 5–10 minutes per pass
You need multiple orbital planes + phasing to maintain continuous overlap
And you need margin for GDOP, not just visibility.. (If you want, I can sketch a quick back-of-the-envelope constellation (planes, inclination, revisit time) to show where this about 50 number comes from )

GEO is ~40× higher orbit and much stricter insertion precision.

Economics vs GEO (like NavIC)

LEO approach:

Lower per-satellite cost, Easier launches (smaller rockets), Many more satellites (~50 vs ~7), Continuous replenishment every ~5 years -- MUCH larger ground/control complexity

GEO/IGSO (NavIC):

Very few satellites (~7), Continuous coverage over India, Long lifetimes (~10–12 years), Higher per-satellite cost, Demanding launch precision

[Tanaji]

Why wouldnt it be a serious question?

Access to space is getting easier and cost per kg is falling year on year. However, this is for lower orbits where there are lots of players. At LEO we can benefit from a smaller size satellite hopefully as power requirements are lesser for transmitted power due to closer distance, which means a smaller solar panel, antenna etc. This would translate to smaller payload. I have no idea what weight would be but perhaps PSLV could launch 2 at a time?

Although the 50 number was more than I expected, I sort of thought it to be closer to 30 for no reason. The economics wont work out in that case I would guess. If we have 3 geosats working, perhaps some sort of coverage could be worked out with lesser number of LEO satellites