It's a Trap! Sensor Jamming Question

[The Bissler]

Hi all!

I'm putting together an adventure which will see the entire sector fleet for the Rebels subjected to a trap not dissimilar to the one we see with the Death Star II attack in RotJ.

The main question I have relates to that scene: the Rebels can't get any readings because they've been jammed, but on board the Mon Calamari ship, they pick up readings of enemy ships behind them. How is this possible? Has someone on board that ship picked up a visual of the Star Destroyers behind them (unlikely) or do they have more powerful sensors than the likes of the Falcon? In which case, isn't the Empire's jamming slightly redundant?

I do want them to have that same "how can they be jamming us if they don't know we're coming" moment in my game, but I'm wondering how, without doing a 180 turn on their ships, they'd detect enemy ships behind them...

If anyone is interested, I can set out the detail of the situation on this thread in greater detail!

[MrNexx]

This is entirely a layman's opinion.

To get a reading on the Death Star, the Rebels send out sensor waves. To jam them, the Death Star sends out counter-waves... ECM. However, those counter-waves only jam in the direction of the Death Star... they prevent the sensor waves from reaching the Death Star, and make sure that they return garbage noise. An analogy would be being in a dark room and turning on your flashlight to look in front of you... only for the place you're looking at to turn on flood lights. You can't see ANYTHING of the place your beam was going... there's too much overwhelming you.

But, if you look backwards, that light can help illuminate things behind you. You can shine your flashlight in the places it isn't an illuminate them better. You still don't know what's going on in front of you (towards the flood lights), but you can see things behind you OK, both because of the flood lights and because of your own efforts.
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[The Bissler]

Layman's or not, it's sound theory and makes perfect sense! I'm not sure why, but I'd always assumed that it was the Star Destroyers rather than the Death Star that was jamming them!

In my own scenario, the equivalent target of DSII, three Raiders and a refuelling station, have reason to want to jam because there's 5 Lambdas in close proximity running silent because they want the Rebels' capital ship to come in close. If they do the Lambdas will attempt to land in the docking bay and 100 veteran Stormtroopers (from the 501st) can board their vessel and take control. The pursuing Star Destroyers (one Imperial class and an Interdictor) behind the Rebels (and TIE swarms prevent fleeing on the flanks) would not care if the Rebels were aware of them so wouldn't bother with jamming.

Thanks Mr Nexx!

[garhkal]

So how's about the ships jamming, are the ones NOT wanting to be 'hidden, till the trap's sprung"..
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[Grimace]

I kind of always went with the idea that it was a matter of how much power the representative things were using for the task.

The fighters have power into sensors, but the power being used to jam them is GREATER than the power of the starfighter sensors. The Mon Cal ship, however, may have been initially taken by surprise, but as they put more power into sensors, they were able to "burn through" the interference and then detected the Imperial ships. Fighters just don't have the power to shunt into sensors to burn through the interference. Once the battle has begun, the interference is dropped because the trap is already sprung.

[The Bissler]

[The Bissler]

[CRMcNeill]

There’s a couple possibilities here.

The first is what’s known as Active Stealth, where a craft attempting to avoid active sensors broadcasts signals on an exactly opposed wavelength, thus canceling the original signal out. In the case of the Endor Shield, I would suggest that the Death Star itself was projecting the emission-canceling effect, likely with fine-tuning provided in advance by the Imperial Fleet before they hid behind Endor.

The other would be to allow ships to jam in deception mode, where a “lite” version uses active emissions to disguise the jamming ship as something else, by adding additional emissions or using the above “active stealth” method to cancel others out.

Of the two, the former application will be several orders of magnitude more difficult, both in complexity and power consumption, but considering the circumstances and resources available, the Empire likely wasn’t concerned with cost.

From what you’re describing, I’d suggest allowing most military ships to deceive sensors instead of only blocking them outright. That way, your Interdictor could be deliberately operating in stealth mode as part of an ambush.
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[garhkal]

[The Bissler]

Thanks for this, I think I'll adjust the set up then with the Lambdas perhaps hidden behind the rebel ships with the Interdictor and the Star Destroyer. My only concern is that the PCs won't think to do a sensors sweep behind them, only discovering when they try to jump, in which case they're likely doomed.

There's a Retired (Star Destroyer) Captain in the team now so perhaps a Tactics roll would allow him to identify what is going on.

To help illustrate the scenario, here's the image, first with the original set up with colour coded highlight key:

Green: Nowhere & Rebel squadrons of X-Wings and Y-Wings
Red: Star Destroyer
Orange: Interdictor
Cyan: 3 Raiders, 12 TIEs, 5 Lambdas and Refuelling Station (which will be able to heavily damage the Raiders if a 2 metre fuel regulator can be hit)

[The Bissler]

Set up 2. Same colour code as before, only Lambdas are with the Interdictor in the orange box

[Raven Redstar]

Very cool! Look forward to reading about this!
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[garhkal]

[The Bissler]

[The Bissler]