CT How did the Rebels know the Death Star’s shields went down?

Ackbar seems to know almost immediately that the shields are down after the generator is destroyed on Endor, even though when the fleet first arrived they note that they can’t tell anything about the shields one way or another because they’re being jammed. What’s the most logical explanation for this? Possible theories I’ve come up with so far:
1) the explosion of the shield generator is visible from space.
2) there’s some sort of cost associated with jamming the Rebels’ sensors that leads to the Empire dropping the effort when it becomes clear that the Rebels have figured out that the shields are still up. (Originally they were being jammed in the hopes that some number of the attacking ships would crash into the shield on the assumption that it was no longer there)
3) the strike team is able to contact them and inform them that they were successful somehow. This one doesn’t really make sense because of there was some reason they couldn’t reach the fleet prior to completing their mission, then just the absence of hearing from them should tip off the fleet that they had not yet been successful.

What explanation do you prefer? Is there anything I’m missing? General thoughts?

 

I would say #3. If not, I'd go on a limb and say that Ackbar (or one of this subordinates) knew how to hack into a Star Destroyer's computer to learn about that through a transmission.

 

#2 with a twist. Jamming the Rebel's sensors would also jam the Imperial Fleet's sensors. The hope was to get some Rebels to crash into the shield. But mostly it was to draw in the entire Rebel Force closer to the Death Star and trap them between the fleet and the shield. Once the trap is sprung the Death Star stops the sensor jamming so their fleet can see what is going on.

#1 is also plausible.

#4 The way the shield generator is blown up creates tell tale signs the shield is down.

#5 The jamming comes from the same place as the shield, so when one went down they both went down.

 

I actually considered a version of #5 but I was thinking about it more from the viewpoint of #3, as in the strike team’s communications with the fleet were being jammed by the same place they blew up.

 

The Imperial jamming doesn't stop the fleet and fighters communicating with each other, It seems to only be stopping the sensors ability to detect the shield.

 

There's a subtle difference between the novel (Lucas' thinking in February 1982) and the theatrical script. Novel says: 'A captain ran up to Admiral Ackbar, his voice tremulous. “Sir, the shield around the Death Star has lost its power.”' Theatrical is merely, "The shield is down! Commence attack on the Death Star's main reactor." So the novel has a strange way of saying 'We saw a large explosion on Endor, therefore, QED, shield is down.' At least as of February 1982, it was not obviously or apparently or reasonably Lucas' thinking that a visible explosion is what led to the conclusion that the shield has lost its power.

Jamming is the one factor that survived to theatrical so that we got that nice out of the frying pan moment with Lando. Theatrical Lando said, "We've got to be able to get some kind of a reading on that shield, up or down. Well, how could they be jamming us if they don't know if we're coming." It cannot be the case that all sensors available at the start of this are no longer functioning. It cannot be the case that all ships that have the necessary sensors have been eliminated. Someone, somewhere, needs to still have the ability to get "some kind of reading on that shield, up or down." It should be foolish to think or believe that Home One was dependent upon the sensors of the MF. It should be foolish to think that any ship larger than the MF was dependent on the sensors of the MF. All ships or all sizes, from small to large, did the evasive maneuver. Since Mon Montha had said the death star was not yet operational, and still the largest cruisers turned to avoid the shield, the shield presents the same danger to large vessels as to small vessels. Therefore the foolishness of thinking that the largest vessels did not have their own capability to detect the shield, up or down, is doubled.

^^^ That does not address the jamming. FOR any vessel to get a reading on the shield, up or down, and there are many vessels that can get that reading, the jamming has to have stopped.

If the jamming came from the death star, and it still had power of its own, it is disappointingly infantile just-so story, to armor the plot of our twelve-year-old facing fairy tale, to assign that the Imperials decided to cease using one method of deterrent that was working - electronic countermeasure of camouflaging their state. Such a capability was worth many minutes or hours of tactical time. It would require a random rebel ships straying too close to the shield, and then NOT being destroyed, to realize that the shield had actually come down and it was safe to attack. The idea that the death star itself was the source of the jamming, sought after to increase the resolution of the battle of Endor experience, creates stupidity where one was hoping for... higher resolution with (suspended disbelief in) credibility.

The novel does not put any emphasis on the Empire's "main communications ship" as being a source or conduit to the jamming. Theatrical has no contiguous remaining presence of the Empire's "main communications ship". The Imperial fleet is out of sight, presumably on the far side of Endor, during the moments when MF and fleet approach Endor moon and then death star. So, the jamming occurs prior to seeing the fleet.

An ideal solution is that the fleet could jam from around the limb of Endor moon. It is ideal because it distributes the ability of electronic countermeasures away from a single failure mode. That strains suspended disbelief in terms of physics plausible in GFFA. An alternative is that the shield emitter is itself, simultaneously, emitting the jamming signal. This requires the conception that the power required to jam the sensors of the entire rebel fleet could not have come from an emitter of less size than the shield emitter. This preserves the fact that the Imperial fleet is nowhere to be seen when Lando realizes they are being jammed. This allows the novel's "main communications ship" to remain unconnected to the jamming idea. This idea doesn't address how the primary dish emitting the shield towards the death star manages to jam the fleet at great distance, but, you can make arguments that those tiny dishes around the rim are the jamming emitters.

A hybrid micronarrative might be that the shield emitter did most of the jamming work and the main communications ship was also doing some of the jamming work. That would preserve some importance to the early Lucas conceptions of the main communications ship, and would not require suspended disbelief that the jamming signal can go around Endor moon's limb.

 

Right which made me consider that if the communications in space still worked but the surface to space transmissions were being blocked then most likely the source of this jamming would be on the moon itself and possibly destroyed along with the generator. Then even if the sensor jamming is still in effect it doesn’t matter if the strike team reports the destruction to the fleet directly. However this would require a bit of a coincidence because the Rebels are planning on the generator already having been destroyed but don’t seem to plan on being able to get confirmation from the strike team so they must not suspect that the two are related.

 

That's what I'm thinking too. Cell phones and other communication devices we use work thanks to a network of broadcast towers and orbital satellites. It's possible the strike team couldn't dependably contact the fleet.

The movie seems to make it clear that an 'all clear' signal from the strike team was never part of the plan.

 

While some plausible scenario could be cobbled out of jamming as an inconvenience and the Empire’s history of hubris, I do tend to agree that “the Empire voluntarily dropped the sensor jam at some point” is an unsatisfying explanation. That leaves only 2 possibilities: the Rebels somehow thwarted the ability of the Empire to continue an effective jam, or the event of the shield transitioning from up to down was observable by some means other than looking at a readout that says “Death Star: shields=none.” The first category rules out that the generic fleet or Death Star is doing the jamming, as they are still intact at this point, unless there exists some sort of counter-jamming technology the Rebels can employ. Perhaps this “communications ship” is responsible and has been destroyed at this point but you’re correct that it would have to be capable of such a thing from its original hiding position. This leaves either the shield generator as the culprit or we must turn to option two. Previously stated candidates for an explanation along these lines would be a visual or audio cue that the generator had been destroyed being detectable by the fleet from the surface of Endor. However the more I think about it I’m starting to become partial to the idea that the very act of the shield dissipating bombards the surrounding area with particles in such a way that it is either “louder” or of a “different frequency” than whatever interference prevents the ships from detecting a static shield. It’s possible that a ship can detect these types of particles hitting its hull or it’s own shields in a different way than whatever sensor is being jammed.

(to your point about which Rebel ships are capable of shield detection, both Lando and Wedge imply that they’ve attempted it, which suggests that it’s a standard feature aboard combat vessels)

 

This topic is more intriguing than I initially believed it to be.

 

Here's a pretty good logic puzzle on the expense of the Empire's jamming signal. The Emperor allowed it to be leaked that the death star was under construction and not yet operational. We cannot know that he designed that Madine design to knock out the shield generator and then Ackbar design to send one man fighters into the superstructure to knock out the main reactor. The Emperor might have designed that Ackbar attempt to neutralize the death star with the cruiser's weapons. The Emperor did design that Luke seek out Vader, but we cannot assert that he designed that Luke do so as part of what turned out to be Madine's design to infiltrate the shield. What is applicable is that the Emperor did rely upon force of arms with respect to the shield generator. In a hierarchy of value, the legion of his best troops was subordinate to the shield generator, and the shield generator was subordinate to the continued existence of the death star. While the Emperor was on the death star, he made pointed comment that "We are quite safe from your friends here", meaning, the Emperor well knew that the death star left to its own devices and its own defenses was not as quite safe as it was quite safe with the generated shield still intact. If the Emperor depended upon the shield for the peace of mind that he was quite safe, and at certain extents of eventualities his life depended upon that shield, then, to an equivalent extent the Emperor's (peace of mind and) life depended upon any surrogate for the shield remaining in existence. That includes jamming. It is immaterial how expensive it was to maintain the jamming signal, whether the shield was up or not. The empire would spare as much expense to maintain the jamming as the Empire spared expense to get another death star up an running inside six years since the last one. None expense. The Emperor *hoped some of the fleet would crash into it, but he is satisfied that the fleet in the aggregate fell into a pincer movement. But he *designs that the fleet not gain confidence, whether the shield is up or down, to commence an attack. He knows, by design, what Lando intuits, that, the Rebellion won't get another chance like this. If the shield fails and jamming is the only thing standing between him and the rebel fleet, why, that jamming is going to be maintained. It is as critical as anything else, and as worth the exorbitant cost as anything else, in his grand scheme. As a source of the jamming signal, I am put in mind of Disaster Area of Hitchhiker's Guide.

 

I think Lando is saying there should be some sort of trace of the dropped shield but the sensor input is too clean. Whatever the jamming signal does to counterbalance their reading, even if it adjusts to the change when the shield goes down, Lando and the rebels can detect some sort of "event." There is a blip that happens, or the jamming signal becomes loud because it's not canceled by the emanations from the active shield.

 

That would make sense. Lando and the Rebels have to wear more than one hat, since they have to be tech-savvy, good fighters, and adept at espionage. The 2015 novel about Luke depicted him as being as much a Rebel fighter and spy as he as an aspiring Jedi.

 

My interpretation has always been that the Rebels have a line on their displays that reads something along the lines of “shields=present/not present/some specific measurement of strength”. However what it says when they arrive on Endor is “shields= ”. (Or for fun we can imagine it’s the GFFA equivalent of the infinite loading circle or 404 error). The most obvious explanation for this is that their sensors are being jammed but they don’t consider that a possibility because it apparently requires some amount of set up, and the Empire would have had to have initiated the process prior to their arrival. Lando realizes “they can’t be jamming us if they don’t know that we’re coming” implies “they can be jamming us if they do know that we’re coming”. Thus the answer to the question “is our surprise attack clear to engage or are we going to crash into a shield?” goes from “I don’t know” to “I don’t know about the shield but it turns out that our attack is the opposite of a surprise”. With this information Lando makes the executive decision that assuming the deflector shields are still quite operational is a much safer bet than not. The sudden appearance of the Imperial fleet confirms that the Empire was expecting them and set a trap.

 

When they arrive and the shield is up but the Rebels don't suspect can be explained that because they believed they'd surprised the Empire and that having a communications black out, they expected the shield to be deactivated. Wrongly as it turns out. but they fail to scan the area around the DS and the Forest Moon. So knowing that they then put their sensors to scan for a shield, they then have their scanners on when the shield loses its power source.

Just an alternative theory...

I think the reality is it's almost certainly it's a plot hole, it only really serves the purpose of a shock moment but you get that with the superlaser firing. May be Lucas and Kasdan didn't think there was enough suspense, but the audience already knew as we'd seen Han's failures on the Forest Moon. Or may be, using how confusion was a factor in the then recent war in Vietnam, they intended confusion to be running rife between the two elements of the attack.

 

No seriously, the jamming would have to come from a signal, and once the shield goes down there should be a spike in that signal even if it gets corrected to match the residual electromagnetic fluctuations of a deactivated shield. or whatever fluctuations. We don't necessarily know how a jamming signal works, but an easy guess is that it's a kind of noise cancellation thing that is meant to keep the active shield's emanations from being detectable. Such a system would suddenly look like the opposite of an active shield (rather than no shield) once the shield went down. If it were adjusted to the new condition, there would be fluctuation in the brief interim that would be noticeable.

 

Just to be clear, I think that’s a very plausible theory and I wasn’t necessarily disagreeing with you.

 

Someone on the ground team might’ve contacted home one and informed him of the shields destruction or maybe home one had a scanner that could detect if the shield was up or not.

 

I guess maybe they saw the explosion on Endor's surface? For good measure, they could've fired a few shots towards the shield to make sure it was down.

 

They knew because Ackbar had one of these on his ship

 

Seeing as that the Rebels had control of the situation to the point of being able to blow up the generator, it's highly feasible they had the time to communicate with the fleet to tell them it's down. Once it blows up, they're not doing much except maybe chasing down any Imperial remnants still on the forest moon.

My other thought on this, once the shield goes down, having a signal blocked or not, the Rebels will be able to detect the change in the electrical field created. Especially when it's a field the size of what is protecting the Death Star. They're not detecting the electrical field itself, or lack there of. They're detecting the change.

 

They were told about it by the Endor ground troops, and perhaps felt the shield pull had disappeared.