ASTER, MOPITT, and CERES - Remote Sensing Application - Completely Remote Sensing, GPS, and GPS Tutorial

ASTER produces images over a range of wavelengths. This plot compares the ASTER bands with those on the Landsat Thematic Mapper; the two sensors are similar but ASTER has multispectral capability by having 5 thermal bands:

Comparison of ASTER and TM band.

The first image we look at is a black and white view covering part of the Visible-Near IR spectrum which depicts a segment of the San Francisco River in Brazil. Note its similarity to Landsat images but at 15-m resolution

An ASTER daytime Visible image of the San Francisco River in the jungle of  Brazil; 15 m resolution.

Look next at an ASTER thermal IR image taken at night, showing (in light tones signifying warmer temperatures) the Red Sea and a small land area (dark; cooler) in Eritrea in eastern Africa. This is similar to HCMM images examined on page 9-8 but the image area is just 60 x 60 km and the ground resolution is 90 meters.

An ASTER nighttime thermal IR image, 90 m resolution, of the Red Sea off the coast of Eritrea.

ASTER contains enough wavebands to choose several to make false color composites that appear almost identical to those characteristc of both early and later Landsats. Here is Calcutta, India produced in this mode:

Calcutta in the standard false color rendition, produced from ASTER data.

The fourth image is also a false color composite made from three of the Visible-Near IR bands merged wth the higher resolution panchromatic camera image.. The 15-meter resolution is capable of picking out many of the larger buildings in Reno, Nevada.

False color composite of Reno, NV, made from 3 of the Vis-NIR bands on ASTER.

Since ASTER has channels (bands) in both the Visible and Near Infrared (also designated SWIR for Short Wave Infrared), it can produce color composites from both reflected and thermal multispectral radiation. Look first at this image showing the summit and eastern flank of the huge Mauna Loa volcano on the Big Island of Hawaii. This false color composite singles out a dark black (recent) lava flow emanating from a fissure that sends tongues out against an older, more weathered lava surface.

False color composite made from ASTER bands, displaying the lava flows on the east flank of Mauna Loa on the Island of Hawaii.

The companion ASTER scene is a multispectral thermal image made from bands at 10, 12, and 14 µm (rendered in blue, green, and red respectively). Note the resemblance to images produced by the TIMS airborne system (page 9-7). The sharp contrast of the black flow, seen above, with neighboring lava is now obscured as the two areas are more uniformly purple, indicating a similarity of composition. The aqua areas beyond are previous (older) flows.

 Same Hawaiian scene, now showing the volcanic surface using three thermal bands combined into a color image.

The ASTER thermal bands can actually indicate something of the chemical composition of materials, including gases. A fire near Mosul in the postwar period in Iraq produced smoke that was enriched in noxious SO2. This takes on a distinctive color (pinkish-purple) in the false color composite shown here:

Smoke plume in Iraq, in late June 2003, containing sulphur dioxide fumes, given this diagnostic color in an ASTER image which includes a thermal channel that is affected by an absorption band due to this substance.

The next three ASTER images display the now familiar San Francisco Bay area. The top image is made from SWIR bands. The middle image is a composite using thermal data with visible bands: the warmest temperatures (red and straw yellow) are found in San Francisco and across the Bay in the Oakland group of cities (more industry). The bottom image blacks out the land and uses thermal data to depict temperature variations in the water, with the usual convention of reds being warmest and blue coolest.

 The San Francisco Bay area depicted in a false color image using SWIR bands on Aster.
 Same Bay Area scene, but with ASTER thermal bands combined with a visible band to make color composite in which reds indicate warmer areas.
The waters around San Francisco, with temperature variations (red = warmest) determined with ASTER thermal bands.

ASTER data are acquired in stereo mode. The Japanese space program has had the task of producing a low resolution global map of the Earth's land topography. Results were released in June, 2009 in two versions, both of which are shown below (Greenland and the Antarctic are shown as high because the thickness of the ice is considered part of the topography):

ASTER-derived map of the Earth's land topography, shown in the customary green and brown tones used in geography.
The same data now rendered in a sequence of colors ranging from blue as low through the color spectrum to red as high.

MOPITT's prime task is to measure concentrations of CO (carbon monoxide) (using the 4.3 µm channel) and methane (CH4) (using the 2,4 µm channel) in a vertical column through the atmosphere. The image below shows radiance variations measured by Channel 1 within a series of strips covering part of the Earth's globe but the black areas represent regions still to be traversed. Reds and yellows are high and blues low quantities of radiance.

 Radiance values determined from a channel on Terra�s MOPITT, arranged in strips representing orbital path coverage (incomplete) for the Earth; carbon monoxide (CO) variations can be derived from MOPITT band data.

Generally, higher concentrations of CO are associated with either smoke or pollution, or a combination of both. When agricultural burning (a practice common in Africa and South America) on a grand scale occurs, the smoke plumes combine and extend over large areas. Below is a MODIS image of such a plume on February 17, 2004 and a map of CO concentration in parts per billion (ppb) derived from MOPITT data. The levels shown can have adverse health effects:

MODIS image of smoke plume in West Africa.
MOPITT data indicating carbon monoxide levels integrated over most of February, 2004.

Carbon Monoxide (CO) concentration values are derived from radiance differences with measurements taken at different times by the several channels in this instrument; other ancillary data are then added to determine amounts. The amount of variations can then be converted into maps by assigning colors to the determined ranges. In the next image, the data show CO distribution over large regions of North America; yellows and browns are higher and greens and blues lower CO readings.

Carbon monoxide variations in the atmosphere over the U.S. and adjacent oceans, as measured by MOPITT; reds, yellows, browns = higher concentrations.

A different rendition indicates variations in CO along strips that pass over southern Asia and India:

Differences in CO distribution in southern Asia.

And, over time the CO measurements allow plots of variations over the entire globe, as indicated in this series of 4 seasonal (3 months) maps. Note that the highest concentrations in the temperate latitudes of the northern hemisphere are in the winter months

Global maps of CO concentrations (in parts per billion) in the atmosphere fo</div>r 4 three month periods as acquired by the MOPITT sensor on Terra.
Source: Cathy Clerbaux; NCAR

There is a close correlation between aerosol distribution and increases in CO, as seen in this pair of Terra images:

MOPITT maps showing aerosol and CO distribution.

Global studies of CO distribution are leading to a better understanding of why certain areas show higher concentrations. The next two maps taken at different times in the year 2000 show the influence of burning forests and grasslands (especially in the lower image where the orange colors are found mainly in the Amazon and the tropical forests of west central Africa).

April and October 2000 maps of CO distribution determined by MOPITT.

MOPITT can follow over short time spans specific plumes of CO gas that exhibits notably high concentrations. In the sequence below, an elongated plume begins off the coast of Asia and moves across the Pacific, reaching the west coast of North America. The dates of observation are: Upper left = March 10, 2000; Upper right = March 12, 2000; Lower left = March 13, 2000; Lower right = March 15, 2000.

CO plume, March 10, 2000. Co plume, March 12.
CO plume, March 13, 2000. CO plume, March 15.

Monitoring of CO from space took on a sense of urgency in July and August of 2010. Large areas in both western and eastern Russia experience, in places, the hottest summers on record. Temperatures in Moscow reached 100 F. and above on several days - almost unheard of historically. The heat led to drought which in turn dried out forest trees and grasslands. Hundreds of individual brush and forest fires caused smoke to spread over wide expanses. As a result CO levels rose to dangerous levels, so that many citizens used masks when outdoors. The next suite of photos summarizes the story of these Russian fires; read each caption for description and details.

Temperatures in Russia (dark red-black is hottest) as measured by MODIS.
CO in Russia as measured by MOPITT.
Woodland fires.
Brush fires within Moscow.
MODIS image of fires in western Russia.
MODIS image of fires in central Russia.
MODIS image of fires in Siberia.

CERES measures both reflected and emitted radiation attributed to the Sun's irradiance. The image below is a map of emitted radiation from the surface and atmosphere, caused by solar heating, for the United States in early April. Reds and yellows are warm; blues and grays cool.

Emitted (long wavelength) radiation from the surface and atmosphere for the United States, representing response to incoming solar rays; CERES measurement in April 2000.

Part of the eastern hemisphere of Earth is shown in this later summer CERES map. The blue areas are primarily caused by large cloud banks, whose temperatures register as cool relative to the much warmer land surfaces.

CERES map of parts of Asia and Africa.

The final pair of images in this initial data set from Terra's first days of measurements shows, on top, a global map of reflected solar radiation at the top of the atmosphere as sensed by the CERES instrument for a 24-hour period and on the bottom emitted thermal radiation from both the atmosphere and land surfaces (with color assignments of red/yellow to warm and green/blue to cooler).

CERES-determined variations in reflected solar radiation over the land and sea as plotted on a global scale map.

 The long wavelength emitted (thermal) radiation for the entire Earth, due almost entirely to solar heating, as measured by CERES.

The next logical step in the EOS series would be to fly a satellite with similar sensors to Terra that passes over the globe in the afternoon. This is the mission of EOS-PM, or Aqua, described next.