QWIP-based thermal infrared sensor for the Landsat Data Continuity Mission

The thermal infrared sensor (TIRS) is a QWIP based instrument intended to supplement the Operational Land Imager (OLI) for the Landsat Data Continuity Mission (LDCM) [See Landsat project description at: http://landsathandbook.gsfc.nasa.gov/handbook/handbook_htmls/chapter1/chapter1.html, [1]. The LDCM is planned to be launched in late 2012 and will continue the 35 year legacy of the Landsat program as Landsat 7 degrades. The LDCM is a joint NASA–US Geological Survey (USGS) mission. The TIRS instrument is a far infrared imager operating in the push broom mode with two IR channels: 10.8 μm and 12 μm. The focal plane will contain three 640 × 512 QWIP arrays mounted on a silicon substrate. The readout integrated circuit (ROIC) is intended to be the Indigo 9803. The focal plane operating temperature will be 43 K (nominally). Bandpass filters will define the precise spectral response of the focal plane. Two QWIP designs will be pursued, the corrugated structure and the grating structure. NASA/Goddard, the Army Research Lab and QmagiQ will work closely together to obtain the suite of arrays that will best meet the mission requirements (primarily adequate conversion efficiency at the required wavelengths). This paper will describe the design and fabrication of the TIRS instrument with particular emphasis on the QWIP detectors. The QWIP parameters that are driving the mission requirements include spectral response, dark current, conversion efficiency, read noise, temperature stability, pixel uniformity and pixel yield. Additional mechanical constraints such as co-registration between the three arrays, filter design and assembly and testing will also be discussed.