The Operational Land Imager (OLI) and the Thermal Infrared Sensor (TIRS) on the Landsat Data Continuity Mission (LDCM)

Abstract

Summary TextThe Thermal Infrared Sensor (TIRS) instrument, provided by NASA's Goddard Space Flight Center and the Operational Land Imager (OLI) provided by Ball Aerospace and Technology Corporation (BATC) will form the payload for the Landsat Data Continuity Mission (LDCM). This paper will describe the design, capabilities and status of both the OLI and the TIRS instrument. AbstractThe Landsat Data Continuity Mission (LDCM), a joint NASA and United States Geological Survey (USGS) mission, is scheduled for launch in December, 2012. The LDCM instrument payload will consist of the Operational Land Imager (OLI), provided by Ball Aerospace and Technology Corporation (BATC) under contract to NASA and the Thermal Infrared Sensor (TIRS), provided by NASA's Goddard Space Flight Center (GSFC). This paper will describe the design, capabilities and status of the OLI and TIRS instruments.

The Thermal Infrared Sensor (TIRS) on Landsat 8: Design Overview and Pre-Launch Characterization

“…The 100-m resolution reduces the number of cross-track pixels needed, which aided in meeting the pressing schedule and was determined to be sufficient for TIRS's primary applications, which include agricultural irrigation studies. As defined in [9,10] and shown in Table 1, the two spectral channels, centered near 10.9 and 12 microns, essentially double sample the single thermal band in the heritage TM/ETM+ systems. The two channels were chosen to allow the use of a "split-window" approach (see, e.g., [11] and the references therein) to compensate for the effects of the atmosphere in converting measured at-satellite radiances into surface temperatures.…”

“…The optics temperature directly affects the focus of the lens, because the Ge index of refraction is a strong function of temperature. The 10-degree temperature range of the optics provides a means of adjusting the focus [9,10]. Drawing of the optical system, including the SSM, the four lens elements and the focal plane assembly.…”

Landsat and Thermal Infrared Imaging

“…4. TIRS band definitions and maximum radiance error [Reuter et al, , 2011 The TIRS telescope uses a temperature-stabilized four-element refractive lens system-three germanium (Ge) elements and one zinc selenide element-to produce nearly diffraction-limited images at the focal plane ( Figure 6). A scene select mechanism (SSM) allows the field of regard to be pointed in the nadir direction for surface imaging, to a temperature-controlled on-board blackbody for radiometric calibration, and to a deep space view for thermal background subtraction.…”

“…To reduce the thermal background, the TIRS optics are cooled to 185 K and temperature-stabilized to ~0.1 K, using a radiative cooler and heaters controlled by the MEB. In addition, the first stage of the cryocooler is used to cool the focal plane enclosure to ~100 K. The optics temperature directly affects the focus of the Ge elements, because the Ge index of refraction is a strong function of temperature [Reuter et al, , 2011. This coupling provides a means of adjusting the focus.…”

“…There is a requirement for less than 0.7% drift between calibrations. As noted by Reuter et al [ , 2011, the QWIP array is in itself temporally stable, thus facilitating radiometric stability between calibrations. The normal calibration sequence described above is replaced on a periodic basis by two other calibration modes: 1) an integration time sweep calibration during the blackbody portion of the normal calibration, and 2) a series of normal calibrations during a blackbody temperature sweep.…”