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Proceedings Paper • Open Access

TDI CMOS image sensor for Earth Observation
Author(s): Jérôme Pratlong; Paul Jerram; Georgios Tsiolis; Vincent Arkesteijn; Paul Donegan; Laurens Korthout

Paper Abstract

The first Earth Observation satellites used linear sensors, which have a significant limitation in the signal that can be gathered in each pixel resulting in a limited ground sampling distance (GSD) in order to achieve the required signal to noise ratio (SNR). The solution to this was to use TDI (Time delay integration) detectors. The first generations of TDI detectors were based on CCDs, which can intrinsically operate in a TDI mode by moving charge within the detector at a rate corresponding to the movement of the satellite over the ground. The CCD technology used relatively large pixels (typically 10-13μm) with low line rate of typically around 10kHz achieving a ground resolution of down to 0.5m with very high SNR. More recent CCD TDI sensors can achieve line rates of up to 30kHz with pixels as small as 7μm but the interfaces become extremely complex and power dissipation is high. Improvements to satellite technology means that a higher resolution is now achievable and this requires higher line rates, over 30kHz and pixel sizes significantly below 7μm as well as more complex sensors with higher numbers of multispectral lines to give improved spectral data. In order to achieve all of these requirements the use of a CMOS sensor with on chip digitization become essential.

The first CMOS approach was to carry the TDI functionality using digital summation. This approach quickly demonstrated limitations in terms of line rate and power consumption as the entire sensor has to be read for every line on the ground that is sampled. More recently CMOS technology has matured the charge domain CCD approach with comparable electro-optical performance to CCDs while offering higher speed, smaller pixel pitch and high level of integration.

This latest technology step has also considerably eased the integration of the sensor into the satellite, opening new opportunities to produce focal planes at significantly lower cost with much reduced power dissipation, size and weight. The challenge has been to establish a CCD on CMOS technology that can obtain a similar full well capacity and charge transfer efficiency (CTE) performance to CCDs. This CCD on CMOS technology has now reached the point where the performance is comparable to CCDs but with very much lower operating voltages.

This paper will present the evolution of earth scanning image sensors with a focus on the latest TDI CMOS technology including the recent results obtained with the latest CMOS technology using TDI in charge domain approach. These results will include FWC, CTE, radiation performance as well as results from very high speed, up to 3.6Gbps output stream, and highly integrated readout circuitry.

Finally we will provide details of new devices that will provide performance that would not have been possible with CCDs.

Paper Details

Date Published: 12 July 2019
PDF: 12 pages
Proc. SPIE 11180, International Conference on Space Optics — ICSO 2018, 111806H (12 July 2019); doi: 10.1117/12.2536152
Show Author Affiliations
Jérôme Pratlong, Teledyne e2v UK Ltd. (United Kingdom)
Paul Jerram, Teledyne e2v UK Ltd. (United Kingdom)
Georgios Tsiolis, Teledyne-e2v (United Kingdom)
Vincent Arkesteijn, Teledyne-e2v (United Kingdom)
Paul Donegan, Teledyne-e2v (Canada)
Laurens Korthout, High Tech Campus (Netherlands)

Published in SPIE Proceedings Vol. 11180:
International Conference on Space Optics — ICSO 2018
Zoran Sodnik; Nikos Karafolas; Bruno Cugny, Editor(s)

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