Environmental Engineering Reference
In-Depth Information
3.1
Introduction
The Moderate Resolution Imaging Spectroradiometer (MODIS) is an instrument
designed for comprehensive studies of land, ocean, and atmosphere processes and
trends (Esaias 1986 ; Salomonson et al. 1989 ). It was launched on the Terra and
Aqua spacecrafts that represent key missions of the NASA Earth Observing System
(EOS) conceived originally as “System Z” in the 1970s and implemented progres-
sively through launch of several, coordinated missions formally starting from 1997
to the present (Salomonson et al. 2011 ; Parkinson et al. 2006 ; http://eospso.gsfc.
nasa.gov/eos_homepage/mission_profiles/index.php ) . The Terra spacecraft was
launched in December 1999 into a sun-synchronous orbit with equator crossing
time nominally at 10:30 a.m., and the first observations became available in
February 2000. The Aqua spacecraft was launched in May 2002 into a sun-
synchronous orbit with an equator crossing time nominally at 1:30 p.m., and the
first observations became available in June 2002.
This chapter will describe characteristics of the total MODIS effort with empha-
sis on aspects that relate to the use of the MODIS instrument and attendant data
products for studies of the climate of the Earth. The principal emphasis will be on
describing procedures and results that have so far (as of early 2012) led to the data
being calibrated and characterized so as to yield consistent Level 1B observations
that subsequently can be reliably and confidently used to produce climate-related
products. First, the characteristics of the MODIS instrument will be described along
with the extensive efforts to calibrate the instrument and characterize its perfor-
mance over more than a decade. In later sections, the availability of data products
will provided along with examples illustrating the present and future potential for
climate studies. Next, a brief description of the operational environmental follow-
on instrument similar to MODIS called the Visible Infrared Imager Radiometer
Suite (VIIRS) will be described. Lastly, concluding remarks describe some of the
challenges foreseen as data from MODIS and VIIRS are acquired, checked, and
studied for their integrity and continued use for climate studies.
3.2 MODIS Instrument Characterization and Performance
The MODIS instrument was developed with improvements over heritage sensors in
terms of its spectral, spatial, and temporal resolutions and with rigorous, stringent
calibration requirements. The heritage sensors include the Advanced Very High
Resolution Radiometer (AVHRR) and the High Resolution Infrared Radiation
Sounder (HIRS) that fly on National Oceanic and Atmospheric Administration
(NOAA) environmental satellites, the Landsat Thematic Mapper (TM), the Coastal
Zone Color Scanner (CZCS), and the Sea-viewing Wide Field-of-view Sensor
(SeaWiFS). Band selection for the MODIS instrument was guided by the bands
existing on all these sensors. The MODIS instrument, in particular, and in terms
related to global, daily coverage, complements and enhances observations from the
AVHRR (still operating) and the CZCS that dated back to 1978 and was followed
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