In Return of the Jedi, upon jumping into the Endor system, this exchange happens on the Millennium Falcon:

Lando: We've got to be able to get some kind of a reading on that shield, up or down.

Nien Nunb: [incomprehensible]

Lando: Well, how could they be jamming us... if they don't know if we're coming...

Lando (over com): Break off the attack! The shield is still up.

Wedge: I get no reading. Are you sure?

Lando: Pull up! All craft pull up!

You can view the exchange here:

It's clear that the Empire is using some kind of signal jamming to prevent them from taking any reading on whether the shield (projected from Endor) is active or not. But a little while later, immediately following the ground force team's success, all that's said in the space battle is:

Ackbar: The shield is down! Commence attack on the Death Star's main reactor!

Lando: We're on our way. Red group, Gold group, all fighters follow me. [laughs] I told you they'd do it!

But if the Imperial forces were jamming their sensor readings, how did they know the shield had come down? Was the Empire no longer broadcasting a jamming signal at this point? Why did they stop, if so?

I'm interested in both Canon and Legends, even if Canon overrides Legends.

  • 2
    Conceivably, either the jamming was coming from the same shield projection station, or the change from shielded to not shielded was detectable as a notable change in sensor readings?
    – user16696
    May 28, 2015 at 5:35
  • 2
    @cde - There's no indication where the jamming was coming from in the script, film or novels.
    – Valorum
    May 28, 2015 at 7:32

4 Answers 4


According to the ROTJ junior novelisation, it appears that it was because the Rebel Fleet saw the explosion of the shield generator on the surface of the planet:

Han Solo ran out of the Imperial bunker shouting, “Move! Move! Move!” Chewbacca and the other Rebels ran away and dived for cover. A moment later, the bunker exploded, followed by the turbine generator and the reactor core. The generator tower was suddenly consumed by a series of explosions, and the enormous dish-shaped shield projector array came crashing down to the ground.

The destruction of the moon-based Imperial outpost was immediately acknowledged by the space cruiser New Home’s Mon Calmari crew. Admiral Ackbar announced, “The shield is down! Commence attack on the Death Star’s main reactor.”

Interestingly, the official novelisation seems to conflict with this; that Admiral Ackbar was able to see the shield on his scanner and that when the shield came down, there was a scanner confirmation:

On the Rebel command ship bridge, smoke and shouts filled the air.

Ackbar reached Calrissian on the comlink. ‘The jamming has stopped. We have a reading on the shield.’

... [Shortly afterwards]

A captain ran up to Admiral Ackbar, his voice tremulous. ‘Sir, the shield around the Death Star has lost its power.’

Ackbar looked at the viewscreen; the electronically generated web was gone. The moon, and the Death Star, now floated in black, empty, unprotected space.

  • 1
    In the novelization, does the jamming stop before the Endor base is destroyed or after? After would support cde's suggestion that the base was doing the jamming. That might also be a way of reconciling the junior version with the official.
    – jpmc26
    May 28, 2015 at 6:41
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    @jpmc26 - It's substantially before. The jamming stops shortly after the rebels discover that the shield is still active in the first place.
    – Valorum
    May 28, 2015 at 7:30
  • 3
    That would lead me to suspect that the jamming process has drawbacks - energy usage that would be better suited to running ship's engines, weapons and shields, or restricting their own communications - so once the cat is out of the bag, there was no further need for the jamming, so it only made sense to take it down.
    – Baldrickk
    Jan 7, 2020 at 13:55

The official comic book adaptation gave a different answer—that the jamming had stopped, before the rebels' victory down on the moon. Why that happened, however, is unexplained.

Comic Book

This is Admiral Ackbar, General! The jamming has stopped. We have a reading on the shield. It's still up!


There was no direct evidence from Ackbar's instrument panel that I saw alerting him Death Star protective screen was down. In my estimation, the explosion of the moon based shield generator would be easy recognizable by pilots on other rebel ships and then Ackbar announced to his fleet that the jamming had stopped. He had no way of knowing that maybe the stopped jamming was just a temporary outage and could possibly start up again?

It was the huge explosion seen from the moon of Endor that would be the true evidence and confirmation to the rebel fleet that yes, finally the shield was down for the count.


I don't have any references or supporting documentation. However, by pure reason we can deduce an answer:

One of the Rebel ships could have taken the occasional pot shot at the Death Star until they detected the shield down.

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