Several aircraft sensors were developed by NASA
in the mid 1980's to verify data from new satellite sensors and
to collect unique datasets which would serve to justify future
space-based instruments on low-Earth and geostationary observation
platforms. In 1985, the Multispectral Atmospheric Mapping Sensor
(MAMS) was developed and flown to verify small-scale water vapor
features observed in Visible Infrared Spin Scan Radiometer (VISSR)
Atmospheric Sounder (VAS) imagery aboard the Geosynchronous
Operational Environmental Satellites (GOES). This aircraft
sensor provided an opportunity to independently verify single-pixel
variations observed in the VAS channels.
This verification continued for several years providing useful
correlative measurements. More recently, NASA developed the Moderate
Resolution Imaging Spectrometer (MODIS) Airborne Simulator (MAS)
to provide preliminary data and to underfly the EOS (Earth Observing
System) MODIS instrument to be launched in the late 1990's. While
MAS provides unique spectral channels in which to study atmospheric
moisture variations, MAMS also provides significant moisture
data, particularly in the upper troposphere. Because of this
MAMS will continue to play an important role in the study of
atmospheric moisture variability.
MAMS is a multispectral
scanner which measures reflected radiation from the Earth's surface
and clouds in eight visible/near-infrared bands,
and thermal emission from the Earth's surface, clouds, and atmospheric
constituents (primarily water vapor) in four infrared bands.
The 5.0 mRa aperture of MAMS produces an instantaneous field-of-view
(IFOV) resolution of 100 m at nadir from the nominal ER-2 altitude
of 20 km. The width of the entire cross path field-of-view scanned
by the sensor is 37 km, thereby providing detailed resolution
of atmospheric and surface features across the swath width and
along the aircraft flight track. For clouds and thunderstorm
features the IFOV decreases with increasing cloud height by a
factor of (Z-20)/20, where Z is the cloud height in kilometers.
The MAMS 6.5 micrometer channel has been used
to map variations in upper tropospheric water vapor associated
with a variety of atmospheric disturbances. The upper tropospheric
water vapor imagery from VAS and the new GOES imager and sounder
is very useful in the study of upper-level dynamics of mid-latitude
weather systems. This is readily apparent in video "loops"
of this from the satellite channel, which show smooth flowing
patterns associated with large-scale weather disturbances. Changes
in the brightness of the water vapor features are related to
the vertical distribution of water vapor in the middle and upper
troposphere, the integrated water vapor amount, and to a lesser
degree the temperature profile. In addition, water vapor imagery
can be used to discern small-scale variability of high clouds
(particularly cirrus) and clear air atmospheric water vapor fields.
In particular, MAMS water vapor imagery has been used to map
clear air moisture variations in a number of different applications
including lee wave situations.
The split-window channels
from MAMS are similar to those from the Advanced Very High Resolution
Radiometer (AVHRR), VAS, and GOES-8/9/10 imager
and sounder. The 11 micrometer
channels of MAMS and VAS are very similar, while those of AVHRR
and the GOES-8/9/10 imager and sounder are narrower and shifted
toward shorter wavelengths. The 12 micrometer channel of AVHRR
is positioned near 11.8 micrometer with a bandwidth about twice
that of MAMS and VAS (which are centered at longer wavelengths).
The GOES-8/9/10 imager and sounder 12 micrometer channels are
also narrow when compared to AVHRR. One of the sounder 12 micrometer
channels and the imager 12 micrometer channel are centered near
12.0 micrometer, while the other sounder channel is near 12.7
micrometers. These 12 micrometer channels measure upwelling radiation
where water vapor and other constituent absorption (particularly,
by the Q-branch of CO2 at 12.63 micrometers) are more significant.
The spectral differences of the 12 micrometer channels produce
small differences in brightness temperatures for VAS and MAMS,
but somewhat larger differences between AVHRR and MAMS (or VAS).
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Technical Contact: Dr. Gary J. Jedlovec (firstname.lastname@example.org)
Responsible Official: Dr. James L. Smoot (James.L.Smoot@nasa.gov)
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Last updated on: November 2, 1999