Looking at Atmospheric Gasses from Space: Analysis of Atmospheric CO,
CH4, and Aerosols using Satellite Remote Sensing
A Summary of the Presentation given to the Remote Sensing Seminar class (ASEN 6210) on
April 28, 2004. By Thomas Kampe of Ball Aerospace and Technologies Corp.
By Jasper Hammond
On April 28th, 2004, Thomas Kampe
provided us with a report on the importance of
CO, CH4 and Aerosols in the atmosphere, and
about some of the various methods we can
employ to measure their quantities in the
atmosphere. He continued to describe some of
the sensors used in this study, and to show how the data can be analyzed to provide, at
times, three-dimensional gas and aerosol data. Mr. Kampe finalized his lecture by
displaying some of his work to us, and by
describing future sensors, and how they are
going to help us come to a more complete
picture of the presence, creation, and
movement of these gases and particles
throughout the atmosphere.
Why is CO important? Carbon
Monoxide, or CO, is a very important component of the atmosphere due to its effects on
air pollution and atmospheric chemistry. Aerosols, while also playing an important part in
the aforementioned processes, are also one of the key components of atmospheric
radiative forcing. Radiative forcing is the balance of radiation coming in the atmosphere
and radiation going out (www.grida.no/climate/vital/04.htm). One question that is being
explored through the use of remote sensing is whether aerosols (as pictured above) cause
warming (positive radiative forcing) or cooling (negative radiative forcing) of the
atmosphere. To answer this, scientists must determine if the aerosols reflect incident short
wave radiation or absorb it. Continuous observation of atmospheric gas and temperature
interactions by multiple instrument platforms may be the way to answer this question.
Mr. Kampe continued to describe carbon monoxide’s importance in the cycling of
OH in the atmosphere. CO has an average lifetime in the atmosphere of 1 – 3 months.
This makes it an excellent tracer substance for atmospheric gas transport studies. The
measurement of CO from space can also provide us details about CO sources and sinks
across the globe, as a monitor for global air pollution,
The next portion of Mr. Kampe’s presentation introduced the instruments that are
being used to study atmospheric CO and methane, and aerosols from space.
MODIS, is a Moderate resolution Imaging Spectrometer. It covers 36 bands, from
0.412 to 14.3 micrometers in
wavelength. It was first
launched on the Terra
Satellite. It was then launched
aboard the AQUA satellite as
well. MODIS has multiple
channels that help it to
distinguish between fine-
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grained aerosols, and heavier
dust and sea salt particles.
The coarse mode can pick up
airborne particles such as dust,
and sea salt, while the fine
mode picks up important finegrained pollutants, including
manmade pollutants, and smoke from the burning of biomass.
TOMS, or as it is otherwise known as: “Total Ozone Mapping Spectrometer”.
This instrument can create an average daily aerosol measurement of the Earth, and also
(as its moniker implies) can be used to monitor the ozone layer.
The third instrument that was covered in Mr.
Kampe’s lecture is the MOPITT sensor. MOPITT stands
for Measurement Of Pollution In The Troposphere. It
was designed to collect and retrieve detailed data on CO
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and CH4 in the atmosphere. MOPITT was launched in
December, 1999. The satellite produced vertically
layered data for CO and CH4 concentration studies for
about 14 months, until the Cryo-Cooler part of the
instrument began to malfunction. This malfunction greatly reduced the satellite’s
capability to acquire data. It now can only record total atmospheric column data for CO.
Another limitation of MOPITT is the fact that it only covers a small amount of land day .
Its swath path covers 22 km by 22 km.
The next instrument
described to us by Mr. Kampe was
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the AIRS instrument. The AIRS
instrument is also being flown on the
AQUA platform (like the MODIS
instrument). The AIRS instrument is
also known as the Atmospheric InfraRed Sounder. It has 248 spectral bands. It can make
highly accurate measurements of air temperature, humidity, clouds and surface
temperature. AIRS can also map silicate aerosols at a resolution of approximately 13.5
km. Additionally, AIRS covers about 82% of the globe per day. Mr. Kampe suggested
that a comparison of CO and aerosols could help to distinguish between pollution being
generated by automobiles and pollution being generated by burning of other materials.
This figure illustrates the AIRS instrument and its general operation.
The high spectral resolution of the AIRS instrument gives it the additional ability to
retrieve information about trace gasses in the atmosphere with its sensors.
Through the use of these instrument platforms, much can be determined about the
quantity, character and movement of trace gasses and aerosols through the Earth’s
atmosphere. Learning more about intercontinental transport of aerosols and trace gasses
may lead us to a greater understanding of global air pollution and how it affects the
world. Mr. Kampe continued his lecture to explain the ways in which different processes
produce different types of air pollution and in different ratios. Here are a few examples
taken directly from his presentation:
Mr. Kampe then showed us how comparisons of total atmospheric column CO vs.
Aerosol Optical Depth measurements correlate to these different types of particulateproducing events. These explanations were pretty technical for description here, and are
treated quite beautifully in the original PowerPoint presentation.
Mr. Kampe ended his presentation with the discussion of new instruments that are
still being developed, and may prove to be the future direction of the remote sensing of
aerosols and trace gasses in the atmosphere.
The first was “SIRAS-G” , or Spaceborne Infrared Atmospheric Sounder for
Geosynchronous orbit. It is a small package instrument bundle that aspires to a spectral
resolution “/” of 800 – 1000; a unit of which I am not very familiar with.
This is a diagram of the SIRAS-G instrument bundle.
The SIRAS-G is being designed as a follow-up to AIRS, with efficiency in mind. It
weighs in at a whopping 50 kg (which is much smaller than most instruments, which are
similar to it.
Another instrument of the future as described by Mr. Kampe was the IMOFPS
instrument. It is a high spectral resolution (0.1 1/cm) spectrometer tuned to sample the
absorption spectra of important trace gasses. The unique design of its correlation filter
allows it to provide excellent matching of non-periodic gas absorption features.
Mr. Thomas Kampe concludes that combined measurements from current and
future high spectral resolution IR sensors will be an important source of data to aid our
understanding of global air pollution transport, and possibly to help us come up with
better long-term air pollution policies which may help to create a brighter, fresher world.