Rafale DH/EH of Indian Air Force : News and Discussions

[randomradio]

Yeah and there's a reason why they carry their own power supply. Which is what I said:

"An LBJ that small can't probably transmit the kind of power needed to deal with long wavelength radars. You're gonna need more than that for effective jamming."

Without a large dedicated RAT (which it's obvious that the small housing doesn't have) you cannot hope to overwhelm the kind of radars that use long-wavelengths (typically ground-based types powered by their own generator sets on trucks).

Which is why it makes no sense for it to be an LBJ. It would make sense for it to be a HBJ however. As the kind of sensors those jammers are meant to go up against typically require far less power to successfully jam, like AAM/SAM seekers.

Don't need it. An L band jammer TRM is just 50-100W, only a few of those are necessary for its task. The Rafale generates far more power than what's possible from a podded RAT.

NGJ is a standoff jammer meant to jam over a much wider area, versus a Rafale that's gonna go in low and fast and requires it only for self-protection.

Considering it's in the rear, it's very likely gonna be used in the mountains, where penetration missions will require protection from the rear as well. Separately, a Rafale will also have to use a standard LBJ pod for other missions.

In any case, it's too big for Ku band alone. Anyway, for now let's go with the theory that it's only Ku band. It's necessary anyway.

I doubt depot-level periodic maintenance needs would have necessitated inclusion of new hatches, especially if no new LRUs are present. You don't drill holes in the airframe (and all the structural testing & certification that would necessitate) to save a few minutes of time in an MRO job that takes weeks/months to complete anyway.

You only need extra access points either if you have new LRUs that cannot be reached/serviced from existing panels, or if the existing panel positions make post-flight checks and/or LRU hot-swapping difficult or time consuming.

The only India-specific need would be geography. Anyway, let's hope we get to know more eventually.

 

[Picdelamirand-oil]

Isn't time in your control? In the case of passive TDOA localization, time isn't in your control, but in case of radar, you know the timestamp and the signal is in your own database. So, in principle, the receiver radars are acting as semi-active seekers. And all the transmitter has to do is transmit the signal name, PRN , PRF data, and timestamp to the receivers. Processed data can also be transmitted via SDR. And directional signals are possible with SDR too.

The idea is simple, if constant, uninterrupted connectivity is necessary for multistatic radar, then yeah, a patrol link is necessary. But if only a simple burst of information does the trick, then SDR in a secretive mode is more than enough. Everything is AESA now.

When using multistatic radar, the transmitter and receiver are the foci of an ellipse that the receiver must be able to calculate. An ellipse is the location of points such that the sum of the distances to the two foci is constant, so all we need to know is this sum, which is measured by the time taken for the signal to leave the transmitter, reflect on the target and reach the receiver. To do this, the receiver has to measure the date of arrival of the signal, which is standard for a radar, then it can compare this date of arrival with the time stamp of the transmission as you suggest, but the measurement will only be accurate if the transmitter and receiver have the same time base.

 

[randomradio]

When using multistatic radar, the transmitter and receiver are the foci of an ellipse that the receiver must be able to calculate. An ellipse is the location of points such that the sum of the distances to the two foci is constant, so all we need to know is this sum, which is measured by the time taken for the signal to leave the transmitter, reflect on the target and reach the receiver. To do this, the receiver has to measure the date of arrival of the signal, which is standard for a radar, then it can compare this date of arrival with the time stamp of the transmission as you suggest, but the measurement will only be accurate if the transmitter and receiver have the same time base.

Yep. So the question is if constant connectivity is necessary to ensure both antennas are operating on the same time base. 'Cause I believe it's much more like sending a text message rather than maintaining a voice call.

 

[Picdelamirand-oil]

Yep. So the question is if constant connectivity is necessary to ensure both antennas are operating on the same time base. 'Cause I believe it's much more like sending a text message rather than maintaining a voice call.

There are three main ways of achieving this result: embedding an atomic clock, but this is very expensive, using the time base of a constellation of navigation satellites by regularly recalibrating the local time base, and doing the same with the time base of a low-latency link.

 

[randomradio]

There are three main ways of achieving this result: embedding an atomic clock, but this is very expensive, using the time base of a constellation of navigation satellites by regularly recalibrating the local time base, and doing the same with the time base of a low-latency link.

My understanding is for a multistatic radar, you only need frequency coherence only for coherent integration, whereas only passive localization requires coherence across the entire time domain. So the former doesn't require constant connectivity, while only the latter requires a patrol link.

And recaliberating to the local time base also doesn't require constant connectivity. Radar operation is also very short, relatively speaking.

 

[Amarante]

RB007

 

[Picdelamirand-oil]

My understanding is for a multistatic radar, you only need frequency coherence only for coherent integration, whereas only passive localization requires coherence across the entire time domain. So the former doesn't require constant connectivity, while only the latter requires a patrol link.

And recaliberating to the local time base also doesn't require constant connectivity. Radar operation is also very short, relatively speaking.

One second of error is 300,000 km in distance, one millisecond is still 300 km, one macrosecond is 300 m and if we want the synchronisation error to add no more than 3 m to the other errors, we need synchronisation to within 10 nanoseconds. This is feasible between two fixed sites and with a fibre optic link that has been characterised, but it is not so obvious between two highly manoeuvrable mobiles with an estimated position.

 

[randomradio]

One second of error is 300,000 km in distance, one millisecond is still 300 km, one macrosecond is 300 m and if we want the synchronisation error to add no more than 3 m to the other errors, we need synchronisation to within 10 nanoseconds. This is feasible between two fixed sites and with a fibre optic link that has been characterised, but it is not so obvious between two highly manoeuvrable mobiles with an estimated position.

Yes. They have to automate flight profiles and synchronise the aircraft itself. I had touched upon the subject a few years ago, compared it to synchronized swimming. The transmitter can also predict where the receiver aircraft will be at a later point of time as long as the flight profiles of all aircraft are pre-planned.

Once the fighting begins, flight profiles will become far too aggressive for such synchronization to matter. In fact, even a 100-300m accuracy at that point will become important, enough for other sensors to compensate. It's considered enough for VHF/UHF radars.

What do you think about synchronization for accuracy within 100 to 1000 nanosecond? I'd assume 30 to 300m is more than enough to accurately cue IRST.

And if the requirement is just 1 to 0.1 microseconds, that's just 4x10^10 to 4x10^9 au. So is an atomic clock of this level affordable? Let's also not forget that synchronization is necessary only for 30 min to an hour per flight so any fractional error is marginal to the point of irrelevance.

Originally, the patrol link should have been available by now. But if what you say is what's gonna happen, an SDR is not enough, then Rafale cannot defeat stealth targets with its radar until the patrol link is available, and that's 2031-35.

 

[Picdelamirand-oil]

Originally, the patrol link should have been available by now. But if what you say is what's gonna happen, an SDR is not enough, then Rafale cannot defeat stealth targets with its radar until the patrol link is available, and that's 2031-35.

No, you can do it with Galileo or any other satellite navigation system: when you calculate the coordinates in this type of system, you calculate X, Y, Z, T and T has the precision of an atomic clock, but you need a military signal to resist jamming and not be spoofed.

 

[randomradio]

No, you can do it with Galileo or any other satellite navigation system: when you calculate the coordinates in this type of system, you calculate X, Y, Z, T and T has the precision of an atomic clock, but you need a military signal to resist jamming and not be spoofed.

So doesn't that mean SDR is enough? Assuming the comm signal cannot be interfered with.

You only need to synchronize the start time, post which predictive algorithms can take over.

If there's a flight of 4 Rafales, then all you have to do is downlink GPS information of all aircraft. The transmitter aircraft then only has to transmit the signal name, PRN sequence and time base of the pulse train. And autopilot can ensure that for the next 10-15 minutes, all 4 aircraft are equidistant from each other, following a predictive path, this tech already exists. And if the time base is based on a GPS clock, then any fractional error is practically non-existent for 15 mins. If necessary, resynchronization can be done once every 5 minutes, which I think is necessary only if there's disruption in navigation.

In fact, if the GPS satellite resynchronizes the Rafale's clock every 5 or 10 min, then the Rafale only needs a basic quartz clock. Even that may not be necessary for just 1 sortie with a quartz clock.

This tactic can be repeated for passive localisation as well, but this definitely needs a patrol link.

 

[Picdelamirand-oil]

This tactic can be repeated for passive localisation as well, but this definitely needs a patrol link.

And yet the passive localisation of aerial tracks is still planned with F4.2 !

 

[randomradio]

And yet the passive localisation of aerial tracks is still planned with F4.2 !

Then, if multilateration is possible without the need for a patrol link, then shouldn't the same be possible for multistatic radar too?

My understanding is SPECTRA's correlators are synchronized to a global clock. Which means the radar's receivers can also have its correlators synchronized to the same clock, which is in turn synchronized with GPS.

 

[Picdelamirand-oil]

We will see !

 

[marich01]

Hoping its done in due course, and also on the mirages too

 

[Picdelamirand-oil]

 

[Amarante]

https://twitter.com/x/status/1708053633529713042

 

[Ashwin]

 

[Fatalis]

https://twitter.com/x/status/1711656907122028954

Is this legit or is there some new stuff in market?

 

[randomradio]

https://twitter.com/x/status/1711656907122028954

Is this legit or is there some new stuff in market?

The original posts from 2019, that was somewhat the plan, until the IAF killed it and decided on a tender. IN wasn't part of the deal back then, they had to evaluate the jets after all.

The new post, yeah, that's the plan. IN gets its own deal, 26 is the initial numbers, they obviously need 2 squadrons at the minimum. And IAF gets MRFA, but it's a full-fledged tender. No clue about the tranche purchases, best case we get all F5+.

No clue about export orders yet, but some will definitely happen. Qatar, Indonesia and UAE are natural partners.

 

[vstol Jockey]

The original posts from 2019, that was somewhat the plan, until the IAF killed it and decided on a tender. IN wasn't part of the deal back then, they had to evaluate the jets after all.

The new post, yeah, that's the plan. IN gets its own deal, 26 is the initial numbers, they obviously need 2 squadrons at the minimum. And IAF gets MRFA, but it's a full-fledged tender. No clue about the tranche purchases, best case we get all F5+.

No clue about export orders yet, but some will definitely happen. Qatar, Indonesia and UAE are natural partners.

If you may recall, way back in 2016 itself I had predicted a total of over 250 Rafale for IAF+IN. I still maintain this figure. The final figure for IN itself could easily cross 100.