Linear arrays of microbolometers for space applications

Space-grade linear arrays of microbolometers are a new class of sensors intended for pushbroom scanned remote sensing and atmospheric sounding with limited power and mass budgets. Such applications call for: (i) microbolometers with increased speed and detectivity; (ii) radiation hard CMOS circuits allowing for simultaneous data readout from all microbolometers; and (iii) robust radiometric packages. A series of single stage and double stage microbolometers with thermal conductances from 30 to 250 nW/K have been investigated. The time constants measured on single stage and double stage devices were in good agreement with the conductances, showing values as small as 6 ms. Low frequency detectivities were found to be in the range from 10⁸ to 10⁹ cm.Hz^1/2/W. Arrays of 512times3 microbolometers were monolithically built on CMOS circuits laid out such that all pixels can be read in parallel with their own signal chain. When integrated into a custom designed radiometric package, these arrays exhibit NETD values better than 80 mK to a 300 K scene using F/0.87 optics in the 8-12 um band and 50 ms integration time. The preliminary environmental tests performed on arrays integrated into a custom designed radiometric package indicated that they would meet the requirements for space operation.