3000 In Ga As Photodiode Multiplexed Linear Array For The Spot 4 S.W.I.R. Channel
Jean‐Pierre Moy, Xavier Hugon, Jean Chabbal, J. de Cachard, C. Lenoble, D. Mollaret, Marc‐André Villard, B. Villotitch · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 1989
SPOT 4 will be an improved version of the SPOT 1,2 and 3 earth remonte sensing satellites ; a SWIR channel is added for agriculture monitoring, and the lifetime is entended to 4 years. The SWIR sensor was designed to be fully compatible with the visible and near IR silicon CCD : - the 3000 30 μm x 30 μm pixels can be registred to the visible detectors with an accuracy better than =/= 2 μm ; - the radiometric performance (uniformity of response, dynamic range, linearity,...) is imilar to that of the visible-channel CCD ; - the operating temperature is + 5°C. The 3000-pixel sensor consists of an ultra-precise assembly of ten elementary modules comprising 300 InGaAs photodiodes and two associated CCD multiplexers on both side. One single pixel is destroyed at the splice between two adjacent modules; The ten modules are read out in sequence. The reading sequence last 3 ms. Quantum efficiency of the photodiodes is typically 65%. Noise equivalent power is 10-13 W. A dynamic range of better than 4000 is obtained at the output of the multiplexer. The histogram of output noise voltages will be presented. A map of the relative sensitivity along the array will be displayed. The cut--off wave-length depends on the In/Ga ratio in the active layer, and the operating temperature. It is 1.690 0.005 μm at +5°C. Several detectors are presently undergoing re liability tests ; no significant alteration in performance has been noticed after aging at 125°C (operating).