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Landsat-7 ETM+ On-Orbit Radiometric CalibrationAs of July, 2000 the Enhanced Thematic Mapper Plus (ETM+) sensor on Landsat-7 has been operating on-orbit for about 15 months. The ETM+ images the Earth in has eight spectral bands in the visible, near-infrared (IR), short wavelength infrared (SWIR), and thermal portions of the spectrum. Three on-board calibration systems are available for the reflective bands: (1) the Internal Calibrator (IC), (2) the Partial Aperture Solar Calibrator (PASC), and (3) the Full Aperture Solar Calibrator (FASC). The Internal Calibrator also provides the thermal band calibration. Several investigators on the Landsat science team are also regularly performing vicarious calibrations. The internal calibrator, which during much of the pre-launch testing and early on-orbit check out period, showed up to 15% variability with time, has since stabilized as the instrument has assumed a regular schedule of operations and is now typically showing only a few percent variation with time, mostly associated with warm-up. The PASC has been the most variable of the sources: the response to the PASC has increased by as much as 50% is some bands and is oscillating with time, perhaps due to contamination. The FASC has been the most stable of the sources: mid scan response to the FASC diffuser have varied from -4%/yr for band 4 (0.83 microns) to -2%/yr for band 1 (0.49 microns) to +1%/yr for band 7 (2.2 microns). These decreases in response in bands 1-4 would have been about half as large if measured on the right (west) side of the panel and about twice as large if measured on the left side of the panel. The current interpretation is that the FASC diffuser panel is changing non-uniformly in its reflectance characteristics. Vicarious ground measurements have generally been consistent with the pre-launch measurements of the instrument responsivity and have not shown evidence of a change in responsivity with time. The FASC, IC, and vicarious results suggest the instrument has not changed by more than two percent in responsivity since launch and that the absolute calibration is good to the advertised five percent.
Document ID
20000119028
Acquisition Source
Goddard Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Markham, Brian L.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Kaita, Ed
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Miller, Jeff
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Barsi, Julia
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Smith, David E.
Date Acquired
August 19, 2013
Publication Date
January 1, 2000
Subject Category
Earth Resources And Remote Sensing
Meeting Information
Meeting: Characterization and Radiometric Calibration for Remote Sensing
Location: Logan, UT
Country: United States
Start Date: September 19, 2000
End Date: September 22, 2000
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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