The design, manufacture and characterization of the SWIR channel detector for the Proba-V mission

Proba-V is a Belgian mini-satellite, designed to bridge the gap between the present Spot-Vegetation Mission and the future GMES Sentinel missions. In order to continue the information gathering the earth surface shall be scanned in 3 Vis/NIR bands and 1 SWIR band. In this paper we will mainly focus on the development of the SWIR band FPA, whereas other contributors will discuss more in detail the mission and the overall optical concept. The SWIR FPA is a long linear array of 68 mm, as long as the visual detector array; due to the fact that the SWIR FPA is a hybrid one with a detector array and a silicon readout circuit, the resolution of the SWIR array is halved wrt the visible array. InGaAs, grown lattice matched on an InP substrate and operated at room temperature, is selected as the baseline detector material. Due to the length of the linear array w.r.t. the InGaAs wafer size; it was decided to compose the overall FPA of several subparts. During the architecture study, it was decided to aim for a mechanically butted array with 3 staggered sensors lines, which are separated by 1.5 mm. App 140 pixels are foreseen in the overlap in order to realign the ground information. The pixel alignment over the full array can be maintained within the following error margins: in plane (X- and Yorientation) : ≤ 25 μm and out of plane (Z-direction): &≤ 100 μm. The detectors are wire bonded to the Silicon readout circuit. The detector interface is a CTIA with selectable gain or sensitivity. The nominal Feedback capacitor is 600 fF, resulting in a sensitivity of 270 nV/e-. The analog signal path is further equipped with a CDS stage and a S&H bank. The power dissipation of the array in slow scan mode is below 300 mW per module or < 900 mW for the FPA. The noise of the array is measured to be below 1 mVrms on a signal swing of 2 Vptp , resulting in a circuit dynamic range of >2000:1..