US satellite jammer is set for delivery as flaws are fixed | Hacker News Reader

US satellite jammer is set for delivery as flaws are fixed

bloomberg.com

Is there some more info on what exactly this system is jamming? Radar satellites? It probably can’t prevent optical images and downlinking of collected data to enemy ground stations.

Edit: according to this ( https://www.dailymail.co.uk/sciencetech/article-14001079/amp... ), it jams enemy communication which is relayed over satellites. I imagine this only works if the receiving antenna on the satellite isn’t highly directional enough to only pick up signals where enemy troops are known to be. If the satellite has a phased array, the origin of the signal could be filtered very fine grained as far as I know and this kind of jamming could be removed (unless it is so strong that it completely saturates the amplifiers of the receiver?).

I bet it would jam synthetic aperture radars

A phased array can have its phase altered to be steerable. That doesn't work if you overwhelm the receiver to the point it becomes a non-linear device.

Yeah, but it does take a lot more power as you point out. Just like you can use the phased array to form a beam toward a particular location of a particular size, you can also do the opposite and create deliberately low gain toward the jammer. So then you need enough jammer power to overwhelm the LNAs on the individual elements, each of which have relatively low gain.

no, it doesn't work that way at all. The receive side of a communication satellite would be multiple antennas each connected to its own receivers. The receiver all use a common clock source to perform demodulation (which is a bunch of steps usually, but whatever). The result of each receiver is summed, the result signal is transmitted by another transmitter connected to a different antenna on a different frequency. Phase difference between the receivers is used to steer the array. How the phase difference is created varies. But if you overwhelm just one receiver it basically just injects noise into the entire process. So you wind up summing noise with all the other signals, which destroys the signal to noise ratio of the transmitted signal

now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful. Whether or not military comm satellites can do that is most definitely classified.

>now if the control station can switch one receiver off to a dummy load, instead of to an antenna that might be useful.

That wouldn't do anything, would it? A phased array antenna is relatively small enough that a jamming signal from the ground would jam all antennas, not just one or a few.

depends on the arrangement of the antennas. When it comes to phased arrays you can basically use any arrangement you want within reason

I was assuming the receive antenna is also a phased array and the first thing after each element has to be a passband filter and an LNA for reasons of G/T. That happens before all the demodulation per element. You said the approach was to "overwhelm the receiver to the point it becomes a non-linear device", and pushing that LNA past P1dB will start to do just that. If the LNA remains linear, a countermeasure to the process you're talking about would be for its user to lower the symbol rate and number of carriers per channel to increase the C/N of the desired signal in an effort to punch through the jamming, albeit with less capacity.

Having said all that, not sure which of the two effects is at play here.

Communication satellites generally need to have multiple antennas to provide spanning coverage over large geographic areas, which are divided up into coverage cells; some of the antennas may be phased array antennas; antennas and their associated coverage "beams" are generally steerable to some degree, electronically for phased array, and/or mechanically via physical gimbal mechanisms. In some or most cases, communication signals are non-viable without focused coverage because the signal strength would otherwise be insufficient.

Received signal strength, from the point of view of a terrestrial satellite communications terminal on the ground/airborne/maritime can also vary based on where the terminal is located within the footprint of a communication satellite's coverage beam; it's typically strongest at the center of a beam.

The most primitive conceptual model for a communications satellite is often described as a "bent pipe," where signals transmitted up to a satellite from the ground are relayed as-received by the satellite back down to terrestrial receivers. In the linked article, the diagram reflects a concept such that: if a "jammer" can interfere with the transmitted signal to the satellite in a manner that the satellite cannot discern the true signal from noise contributed by the "jammer," what is relayed back down to terrestrial receivers by the satellite is "drowned out" because the relayed signal is now a combination of the true signal and sufficiently more noise contributed by the jammer rendering the communications channel and any signals over that channel non-viable (i.e. "jammed").

Noob antenna question: in a phased array is most transmit energy lost to destructive interference?

I thought that the beam was just the region where the waves didn't destructively interfere

> in a phased array is most transmit energy lost to destructive interference?

No. Phased-array antennae can be up to 90% efficient [1]. You aren't losing energy to destructive interference so much as channeling it to the constructive modes. (Totally physically inaccurate, but I think analogously correct.)

[1] https://www.mwrf.com/technologies/embedded/systems/article/2...

Low gain where there is destructive interference and high gain where there is constructive interference. That is the feature. Same amount of energy is radiated, it is just amplified in the high-gain main lobe.

A low gain direction is not the same as no signal though. With enough power you can overpower the main lobe signal.

https://en.wikipedia.org/wiki/Gain_(antenna)

> Received signal strength, from the point of view of a terrestrial satellite communications terminal on the ground/airborne/maritime can also vary based on where the terminal is located within the footprint of a communication satellite's coverage beam; it's typically strongest at the center of a beam.

That’s why I was asking, the jammer would have to be very strong to overwhelm a „real“ signal which is located in the main lobe when the jammer is outside.

>That’s why I was asking, the jammer would have to be very strong to overwhelm a "real“ signal which is located in the main lobe when the jammer is outside.

The mobile jammer in the article's scenario is transmitting toward the satellite, not the terrestrial terminals on the ground.

Imagine in the primitive example case that the "real" signal transmission must also be coming from a terrestrial terminal as well. The real terrestrial terminal is likely be similar in size to the mobile jammer, and subject to the same kinds of constraints as the jammer. However, the jammer doesn't have to consider much about the quality of its radiated energy at the target frequencies. Let's also assume that that both the real transmission terminal and the jammer can emit the same amount of energy.

The distance between both the real transmission terminal(s) and the jammer to the communications satellite, for all practical purposes, is roughly the same.

From the primitive example communications satellite's perspective, it will see/hear both the real signal and an equally "loud" signal (noise) at the same frequencies. When the communications satellite relays or retransmits what it hears to the receiving terrestrial terminals, it will be the combination of what the satellite saw/heard.

Instead of the "bent pipe" imagine another primitive example where the communications satellite is an optical mirror, and the "real" signal comes from a light source on the ground pointed at the satellite. The "real" signal could be represented using different modulations of that light in brightness, frequency/wavelength, as well as temporal pulses. Terrestrial receivers decode the "real" signal based on the flashes of light it observes from the mirror. The jammer in this scenario is another light source pointed at the same mirror.

Terrestrial, ground-based jammers are not the only type of potential jammer in a satellite communications system's operational scenarios. In the prior example ground-based jammers look upward to jam the satellite. You can also imagine scenarios where airborne jammers are possible, which look downward to jam receiving terrestrial terminals.

A ground-based jammer versus an airborne jammer would have a few differences. The ground-based jammer mostly needs to consider a fairly well-known location of the communications satellite, as the satellite can be easily observed, and its future positions can be calculated using ephemeris data, for targeting. An airborne jammer would have to deal with the issue that it has a lower field of view than the satellite beam's footprint and needs to have more specification information about the location of terrestrial receiving terminals to apply its own area of effect, which would be smaller than the satellite's beam. However, the effective distance between the airborne jammer and terrestrial terminals will be orders of magnitude lower than the communications satellite and terrestrial terminals. Power transmission capacity is a constraint for all terminals, satellites, etc, and an airborne jammer's ability to apply power will be more effective than satellites due to distance, but the airborne jammer must be more selective on where to apply (i.e. target) that power.

One jammer could be used to affect the transmission signal, but it would likely take many jammers to target receiving terminals when there are many geographically dispersed terminals.

I am assuming a directional receiving antenna on the satellite. If a highly directional antenna is pointed at the location where the signal is expected to come from, a jammer on the other side of the frontline 100 km away should be attenuated a lot, if the antenna is directional enough.

Most modern command/control systems are what is called 'frequency agile' https://en.wikipedia.org/wiki/Frequency_agility#:~:text=Freq.... and so a C&C system operates cross a wide band, and each system has a series of one time tables that says 'next hop' and the transmit and receive communications - or it random hops, with each one telling 'next'. Small drones can not carry the computational power to do this. Often the higher power base does all this and tells the drone/missile 'next' Frequency agility, coupled with directional agility(phased array) make it harder. Drone systems usually depend on higher power frequency hopping to saturate a range of frequencies and hope for the duration of the desensitising effect where the lower power and computational power of the drone to insert ambiguity into the bidirectional C&C signals and hope the drone settles down or goes home. It is complex, but as the drone get further away from the C&C it becomes easier to disrupt. A drone can fly in a cruise mode and when it detected interference - often with sync bars on the screen, instruct the drone to switch into a less jammable frequency (but uses more battery power- the scarce resource in a drone) as it gets closer to the target where more jamming power is expended. I expect low power ARM systems will help in this.

Wouldn't such equipment attract anti-radiation weaponry very quickly? Combat practice with anti-aircraft battery is to light radar up for 30 seconds at most and then relocate immediately, because anything more will attract counter-battery fire.

What mechanism is this using?

I'd imagine a parabolic dish that points at the satellite, driven by something powerful like a klystron. With a highly directional antenna and high power one should be able to saturate the satellite receiver.

That's what L3's published images look like. A dish on a trailer that can be moved to wherever it's needed. It's an antenna that's producing (mostly) high-powered noise while pointed at a target satellite. Probably configurable like an ordinary antenna to make it mission specific and take advantage of known weaknesses in the target system.

https://en.wikipedia.org/wiki/Klystron

Early 1900s electronic devices/components have the best names.

I'll take "What are loitering munitions?" for $100, Alex

I feel like we're due for a proliferation of anti radiation munitions.

Uhm are they serious!? Jammers are forbidden by most countries and they find it okay to put that into space as a satellite. Honestly if the scenario they describe when it comes to use it will be a target immediately and shot down just causing more debris. Space should be kept weapon free for the sake of humanity.

> Jammers are forbidden by most countries and they find it okay to put that into space as a satellite.

You'll find such forbidding tends to exempt the countries themselves. Every military on the planet uses jammers.

I can't collect taxes, but they can. I can't put someone in jail, but they can. I can't negotiate with foreign powers, but they can.

> I can't negotiate with foreign powers

As an aside, I think this one is a maybe (in the US). Weirdly in over 200 years there's only been two indictments under the Logan Act and no convictions. [1]

[1] https://www.reuters.com/article/us-usa-trump-russia-un/flynn...

> shot down just causing more debris

Yes, wars create debris. In this case, on the ground.

Shooting other people is also forbidden in most countries, but militaries of said countries are still allowed to do it e.g. when they're at war. This is the same, but for satellite communications.

> Jammers are forbidden by most countries

Russia is jamming their Western neighbours' GPS. I can't wait for US microwave weapons that fry their satellites.

You can’t wait for escalation? Are you pro-war???

They're currently shipping North Korean soldiers in to assist their invasion of Ukraine. That's a rather significant "escalation".

no they are not thats dumb but what is most assuredly happening, useing the most correct military protocols,is that Russia is hosting military attaché's from China and many others ,ie non combatant oficers who can watch and learn how to combat western weapons and tactics and as its turned into drone war 1,everybody has to recalibrate,with the brick's block(heh heh) all realy realy glad it isnt them getting droned to bits Russia is training some north Korean troops,but its likely going to be realy basic stuff fof joint border patrols and all in all a pr stick in the eye for the collective west

In English, it's a convention to use a space after a comma.

Sure, they're just visiting. 18 NK soldiers were left in a wood in Kursk without food and instructions for days and Russian authorities arrested them 60 km from their positions. They were likely foraging for food.

https://www.kyivpost.com/post/40579

Are you pro-capitulation to authoritarian states?

The current slate of Russian GPS jamming is not being done by satellites.

Same with this system. It is terestrial with wheels.

They have satellites of their own. Since it's more expensive to launch, put them into orbit and operate them, I'm sure they'll reach some sort of "mutually beneficial" agreement, like we promise not to screw with yours if you won't mess with ours.

tit-for-tat means targeting ground equipment

attacking satellites is an escalation, and if they retaliate in-kind, we'll get mutually assured destruction of satellites and Kessler syndrome, and the size of the US economy means there's a lot more to lose in MAD compared to them

The jammer under discussion is not a satellite. It is a ground-based system that jams satellites. Did you read the article? There's even a photo of the system right at the top.

Damn I’m sorry.. the picture was blurry on the device I used since no JS and it was just the free part of the whole article. I was sloppy at the end of the workday and the weekend ahead.

Probably also biased towards a satellite with jammers.

Jammers are only illegal in the civilian legal context. I'm not aware of anything that makes jammers inherently illegal by broader law of armed conflict. Necessity and proportionality comes into play. Targeted jamming of military communications would certainly be allowed. Jamming of dual-use satellites becomes more nuanced.

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