Quality of MISR Radiometric Calibration February 5, 2009

Calibration Process

MISR has challenging radiometric specifications of 3% absolute, and 1% band and camera-relative calibration. The radiometric calibration is facilitated by use of an on-orbit calibrator (OBC) experiment, which is utilized at bi-monthly intervals. During these experiments a diffuse panel reflects solar light into the cameras. The intensity of this light is measured with on-board photodiode "detector standards." With the measured incident radiance and output DN, radiometric calibration coefficients are computed. Following each experiment the coefficients are packaged into a file called the Ancillary Radiometric Product (ARP). This new ARP file is used for the next two months to produce the MISR Level 1B1 radiance product, and in turn the Level 1B2 geo-located product.

Because of the challenging radiometric requirements, the calibration team at JPL has been researching various procedures for reducing the calibration data and producing coefficients. Calibration-algorithm changes have occurred over time, and thus the initial ARP time-series files have not been produced using a common algorithm. The full history of this activity is reported in Table 2 below.

It is desirable to generate all reprocessed data at a uniform quality level which reflects the most current and accurate approach available to calibrating the instrument. To this end, the ARP time-series files have been regenerated twice during the mission with fixed algorithms. The first regeneration effort, conducted in January of 2004, and described in Table 3 below, was used to produce reprocessing Collection 4 data. The second and final ARP regeneration effort, described in Table 1 below, was conducted in November of 2004. The user must pay attention to the version number portion of the ARP_INFLTCAL Filename in order to determine the uncertainty of the resulting data. Users are advised to obtain data products generated with the ARP file version specified in table 1.

Table 3 below describes ARPs that were used to create MISR reprocessing collection 4. These products were widely distributed. Collection 4 products will eventually be replaced by another reprocessing collection. This set of ARPs was generated with uniform quality in January, 2004, before the camera-by-camera adjustment was available.

Warning: Do not use MISR Level 1 radiance products with the version number F03_0021. Products with this version number were generated with ARP files containing an error in the band-to-band calibration. This error resulted in Red band radiances that were 6% too high and Near-Infrared band radiances that were 2% high. All data products containing this error have been removed from the Langley DAAC archive. The first ARP to include the erroneous correction was T024_F02_0001, but T017-T023 were redelivered with the error at the same time. The Langley DAAC used these bad ARPs between December 5, 2003 and January 23, 2004.

Further information may be found in the following papers:

• Bruegge, Carol J., Wedad A. Abdou, David J. Diner, Barbara J. Gaitley, Mark C. Helmlinger, Ralph A. Kahn, and John V. Martonchik (2004). Validating the MISR radiometric scale for the ocean aerosol science communities. In Post-launch calibration of satellite sensors, Stanley A. Morain and Amelia M. Budge, editors. A.A. Balkema Publishers, Leiden, Netherlands, pp.103-115.
• Kahn, R., W-H. Li, J. Martonchik, C. Bruegge, D. Diner, B. Gaitley, W.Abdou, O. Dubovik, B. Holben, S. Smirnov, Z. Jin, and D. Clark, 2005. MISR low-light-level calibration, and implications for aerosol retrieval over dark water, J. Atmosph, Sci., in press.
• Diner, D.J., R.A. Kahn, C.J. Bruegge, J.V. Martonchik, W.A. Abdou, B.J. Gaitley, M.C. Helmlinger, O.V. Kalashnikova, and W-H. Li (2004). Refinements to MISR's radiometric calibration and implications for establishing a climate-quality aerosol observing system. Proc. SPIE 5652, 57-65.
• Bruegge, Carol J., Nadine L. Chrien, Robert R. Ando, David J. Diner, Wedad A. Abdou , Mark C. Helmlinger, Kurtis Thome. Validation of Multi-angle Imaging SpectroRadiometer (MISR) radiometric data products IEEE Trans. Geosci. Remote Sens., 40 (7), pp. 1477-1492, July 2002.
• Chrien, Nadine, L, Carol J. Bruegge, and Robert R. Ando (2001). Multi-angle Imaging SpectroRadiometer (MISR) On-Board Calibrator (OBC) In-flight Performance Studies. IEEE Trans. Geosci. Remote Sens., 40 (7), pp. 1493-1499, July 2002.
• Abdou, Wedad A., Carol J. Bruegge, Mark C. Helmlinger, James E. Conel, Stuart H. Pilorz, William Ledeboer, Barbara J. Gaitley, and Kurtis J. Thome. Vicarious calibration experiment in support of the Multi-angle Imaging SpectroRadiometer. IEEE Trans. Geosci. Remote Sens., 40 (7), pp. 1500-1511, July 2002.

The MISR Access Data Table contains a link to the MISR Validation website for those who desire more details.