1. A reflect-array based threat detection system ( 100 ) employing compressive sensing to effectively determine whether or not an object ( 600 ) is a threat, the system ( 100 ) comprising: (a) a first processor ( 950 ) executing a first optimization algorithm using a plurality of samples ( 320 ) to generate a plurality of optimized projections ( 300 ); (b) a library ( 200 ) operatively coupled to the first processor ( 950 ), wherein the plurality of optimized projections ( 300 ) and the plurality of samples ( 320 ) are stored in the library ( 200 ), wherein the library ( 200 ) is capable of adaptively increasing an amount of samples by adding a plurality of new measurement results to improve accuracy of threat determination accuracy; (c) a reflect-array panel ( 400 ) emitting a synthesized radiation ( 500 ) in a plurality of directions to scan the object ( 600 ), wherein the reflect-array panel ( 400 ) comprises a first set of reflect-array elements ( 410 ), wherein each reflect-array element emits the plurality of optimized projections ( 300 ) as a radiation pattern in one of the plurality of directions, wherein the synthesized radiation ( 500 ) is a collective radiation comprising each radiation pattern emitted by each reflect-array element, wherein an illumination pattern results from the synthesized radiation ( 500 ) reflecting off of the object; (d) one or more detectors ( 150 ) configured to collect a plurality of measurements ( 800 ) of the illumination pattern; and (e) a compressive sensing unit ( 700 ), operatively coupled to the one or more detectors ( 150 ), having a second processor ( 960 ) configured to execute a compressive sensing optimization algorithm, herein referred to as a second optimization algorithm, wherein the second optimization algorithm processes the plurality of measurements ( 800 ) and determines whether the object ( 600 ) poses a threat using the plurality of optimized projections ( 300 ) as bases of measurement.