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January 24, 2012

Raytheon has quantum dot system that mimics the radiation profile of a satellite as an anti-missile decoy

US Patent - Raytheon has a countermeasure system for protecting a satellite from a missile attack, the system comprising:

* a decoy comprising a plurality of quantum dots,
* the quantum dots being selected, responsive to excitation radiation, to emit radiation having an emission profile similar to a profile of a blackbody radiation signature of the satellite in space,
* the emitted radiation diverting the missile attack from the satellite onto the decoy.




The researchers propose that such a mixture of quantum dots, when dispersed like a cloud in space, may act as an efficient decoy, making even the advanced sensor devices unable to differentiate between the target and the decoy. The cloud of quantum dots can be created either by exploding a small pack of quantum dots suspended in an inert gas (Argon/Helium) or by just spraying them from a storage tank.

Previous generation of disposable. IR countermeasures (flares used as decoys) relied on either the emission peaks of specific chemical agents or on the high level blackbody radiation of pyrophoric sources. However, as stated above these systems offer limited utility in a space environment since many consume oxygen in the reaction. Furthermore, since a high signal-to-noise ratio (SNR) is required to spoof a missile seeker, these systems are required to have a high temperature, shifting the intensity peak towards the visible. This make this type of countermeasure easily foiled by advanced sensors using two color filters or other means which discriminate between the hot decoy and the hot target against the backdrop of space.

A quantum dot cloud may be able to simulate the radiation signature of a protected asset (e.g., satellite) by reproducing an accurate infrared spectrum that would have a general profile as the radiation emission profile of the protected asset. The amount of quantum dot material needed to achieve an adequate SNR (e.g., a SNR between about 10:1 and about 1000:1) is relatively small. For example, the amount of quantum dot material needed to achieve a SNR of 1000:1 to simulate a satellite having the size of the Hubble telescope is relatively small. FIG. 7 is plot of the weight of quantum dots material (in grams) as a function of desired emission wavelength required to replicate a 1000:1. SNR for a satellite having a size of Hubble telescope. For example, to obtain an emission peak centered around 8 .mu.m with a SNR equal to 1000:1, it is sufficient to use 0.008 g (8 mg) of quantum dot material, with an appropriate dispersion of the quantum dots and when the quantum dots are properly excited with a pump source of radiation. As shown in FIG. 7, the greater the wavelength desired to replicate a radiation signature of the asset (satellite) the greater is the amount of quantum dot material that may be needed to achieve a same SNR.


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