Abstract
The Thermal Infrared Sensor (TIRS) for the Landsat 8 platform was designed and built at NASA Goddard Space Flight Center (GSFC). TIRS data will extend the data record for thermal observations from the heritage Landsat sensors, dating back to the launch of Landsat 4 in 1982. The two-band (10.9 and 12.0 μm) pushbroom sensor with a 185 km-wide swath uses a staggered arrangement of quantum well infrared photodetector (QWIPs) arrays. The required spatial resolution is 100 m for TIRS, with the assessment of crop moisture and water resources being science drivers for that resolution. The evaluation of spatial resolution typically relies on a straight knife-edge technique to determine the spatial edge response of a detector system, and such an approach was implemented for TIRS. Flexibility in the ground calibration equipment used for TIRS thermal-vacuum chamber testing also made possible an alternate strategy that implemented a circular target moved in precise sub-pixel increments across the detectors to derive the edge response. On-orbit, coastline targets were developed to evaluate the spatial response performance. Multiple targets were identified that produced similar results to one another. Even though there may be a slight bias in the point spread function (PSF)/modulation transfer function (MTF) estimates towards poorer performance using this approach, it does have the ability to track relative changes for monitoring long-term instrument status. The results for both pre- and post-launch response analysis show general good agreement and consistency with edge slope along-track values of 0.53 and 0.58 pre- and post-launch and across-track values 0f 0.59 and 0.55 pre- and post-launch.
Highlights
Landsat 8 was launched on 11 February 2013, with a mission to continue into a fifth decade the measurements of the heritage Landsat sensors
Thermal Infrared Sensor (TIRS) is a two-band sensor (10.9 and 12.0 μm) with 100-m spatial resolution that was built by NASA Goddard Space Flight Center
Because edge spread function (ESF) and the line spread function (LSF) are often more intuitive than modulation transfer function (MTF), the results developed in this paper will focus largely on the ESF measurement and its derivative, LSF, as an assessment of the spatial quality of the TIRS instrument
Summary
Landsat 8 was launched on 11 February 2013, with a mission to continue into a fifth decade the measurements of the heritage Landsat sensors. This dataset is critical for the understanding of land use changes and resource management [1]. Landsat 8 is a two-sensor platform comprised of the Operational. Land Imager (OLI) and the Thermal Infrared Sensor (TIRS), with OLI operating in concert with, but independent of, TIRS. Both instruments are push-broom sensors with a roughly 185 km-wide swath. TIRS is a two-band sensor (10.9 and 12.0 μm) with 100-m spatial resolution that was built by NASA Goddard Space Flight Center
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