Remotely Observing the Earth-Atmosphere System

Dr. Owen E. Thompson
University of Maryland College Park
Copyright, 1996, 97
 TEXT:
Our Changing Planet, There is not a substantial amount of material on remote sensing and inference in this text. Students are advised to study carefully the materials provided in, and linked to, this outline.

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1. WHAT DID YOU THINK YOU MEANT BY REMOTE SENSING?

The term "remote sensing" has come to mean different things to different people. For example, a lot of folks point to the example below as the best example of ...
"Real Remote Sensing"
Most college students have never lived in a time when there were no environmental satellites in earth orbit. But, in the "good old days", the term "remote sensing of the environment" refered exclusively to weather radar tracking storm systems.
Weather Radar (Image & MPEG Movie) (Embedded MPEG Movie)
Current Composite Weather Radar

2. THE DIFFERENCE BETWEEN REMOTE SENSING AND INFERENCE

Remote Sensing and Remote Inference

3. WHAT IS IT THAT REMOTE SENSORS SENSE?

Passive satellite remote sensing involves the measurement of electromagnetic radiation (i.e. light, heat, etc.) upwelling to a satellite instrument. By examining the electromagnetic spectrum of radiation emitted from the sun, or emitted from the Earth system, as it interacts with the Earth system, one may discover signal information for "things" in the atmosphere, oceans, or on Earth's surface.

Remote Sensing Signals in Space

4. WHAT IS THE SATELLITE REMOTE SENSING STRATEGY?

A. What types of measuring devices to install ...
Examples of Passive Radiometers

B. What types orbiting strategy ...
Examples of Satellite Orbits

C. What types of viewing strategy ...
Examples of Scanning Strategies

5. SORTING OUT VARIABLES FROM REMOTE SENSING DATA

Remote sensing scientists do not have the luxury of controlling the properties of the vast environmental system under observation from orbiting satellites. Upwelling electromagnetic radiation at satellite orbit is a remarkably complex mixture of signals about the composition and thermal nature of the three dimensional field of view. Scientists must carefully analyze this signal information in order to sort out the environmental variables of interest.

Sorting Out Atmospheric Variables

6. REMOTE SOUNDING OF THE ATMOSPHERE FROM SPACE

While viewing cloud cover from space may be an example of a remote sensing enterprise which is intuitive, the "sounding" of, say, the vertical variations of temperature, moisture, or ozone through the atmosphere is not obvious or intuitive at all. The signals (infrared radiation measured in very narrow wavelength intervals in the absorption bands of carbon dioxide, water vapor, and ozone) which relate to vertical temperature, moisture and ozone variability must be carefully sorted out, and then subjected to a class of mathematical problems called "inverse integral problems". Unfortunately, these mathematical problems are not at all well behaved nor easy to solve. We review this "inverse inference" atmospheric sounding problem from a conceptual point of view in order to appreciate the care that must be taken in building inference algorithms for transforming space data into reliable information about atmospheric behavior.

7. Earth Observing System, and the Future

The EOS era, incorporating the knowledge gained over the past 35 years of remote sensing science, will be fully underway before many of the students have purchased their first Porsche. In this closing section, we take a brief look into the future to get a feeling for what it may be like to live in the EOS era.

"Mission to Planet Earth" (NASA)

"Earth Observing System" (NASA)

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