evsc494: Introduction

LA NINA 1998 (after the EL NINO 1997).....MAJOR WINTER SNOW PILES UP OVER MIDWEST ......DEADLY TORNADOES RIP THROUGH TENNESSEE.....DEVASTATING HURRICANE MITCH STRIKES CENTRAL AMERICA....EXTENSIVE FIRES IN FLORIDA.....What do these current issues you have read about in the newspaper (or on the net!) or seen on TV during 1999 and 1998 have in common? Yes, they are all problems in which remote sensing plays a significant role in their detection. The purpose of this course is to introduce you to the basics of remote sensing. All of you have used remote sensing devices, you are using them right now-our eyes, evolved to respond to light in the "visible" portion of the electromagnetic spectrum, are our own precious remote-sensing equipment. In this course we will be focussed on learning how satellites and their payloads operate as eyes in space giving us a wealth of information about our planet (and other planets) from a range of perspectives. The number of applications of remote sensing in environmental sciences is quite remarkable, and these should only increase with time as more sophisticated instruments are designed, and we learn how to make better use of multi-spectral data we are currently collecting.

Remote sensing, which we can think of as reconnaissance at a distance, is generally based on the principal that we can identify surrogates which provide us with information about something that we actually want to know. For example, if we want to know the height of clouds from a meteorological satellite, we don't actually measure the height, but we derive information about the temperature of cloud tops, and through our understanding of the atmosphere, and other in situ observations (like rawinsondes), we can relate temperature to height In general what is remotely sensed is always radiant energy, electromagnetic radiation in a number of different spectral regions, with this radiation either being reflected or emitted from some part of the atmosphere/earth/ocean system. The remarkable number of applications is based on the fact that we have this ability to view the earth from different "perspectives" making use of many different spectral regions.

Pre- 1925 Early photographs were taken over Paris from cameras strapped to pigeons (Harris, 1987). Aerial photography from balloons and from aircraft during World War I illustrated the value of this kind of information

1925-1945- Aerial photography became widespread during World War II, with improved lenses and platform stability, enemy positions and military installations could be identified from aircraft.

1945-1960- Cameras were launched on rockets as this science expanded in the post-World War II era, giving rise to the idea that we might be able to observe weather from space. On October 4, 1957 the Russians launched the first successful Earth satellite, Sputnik 1 (thereby labelling an era, and launching an emphasis on science education in the United States). A swift 123 days later, the US launched its first satellite, Explorer 1 on January 31, 1958. The first satellite with a meteorological instrument (Vanguard 2) was launched February 17, 1959, the first successful meteorological instrument (Suomi radiometer) was launched October 13, 1959. One of the first satellite images ever made of the earth comes from the TIROS 1 (Television and Infrared Observational Satellite) which was launched April 1, 1960. It was taken by a vidicon camera, an adaptation of the standard television camera. Compare this with a relatively recent visible image of Hurricane Fran (which you may recall tore through Virginia at the beginning of the fall semester in 1996 )and you will see that we have indeed come a long way in 38 years!

1960-1972- This was the age of instrument development, particularly for meteorological satellites which expanded to provide global coverage on an operational basis by the end of this period. The Nimbus satellite series of experimental meteorological remote sensing was initiated in 1964. It introduced two new concepts, one was three-axis stabilization control allowing instruments to constantly view the earth, and the other was sunsynchronous orbits, which meant that satellites saw the same locations at approximately the same time each day. By 1966, meteorological satellites moved from being experimental to being operational with the introduction of the ESSA series of satellites which included Automatic Picture Transmission to surface receivers. ESSA (Environmental Science Service Administration) was the national predecessor of NOAA (National Oceanic and Atmospheric Administration). The Defense Meteorological Satellite Program (DMSP) was started by the U.S. Air Force in 1966, and the first geostationary satellite (ATS-1, Applications Technology Satellite) was launched the same year. Image color filters and multi-spectral scanning as well as sounding instruments were being developed and tested during this phase of satellite remote sensing history. At the very end of this period, the first satellite designed for high-resolution land surface sensing was launched July 23, 1972, Landsat 1 (also referred to as Earth Resources Technology Satellite.

1972-present- This defines what we currently think of as the "mature" phase of satellite meteorology (However, I shouldn't need to remind you that one generations mature phase is another's infancy!). The first Geostationary Operation Environmental Satellite (GOES 1) was launched October 16, 1975. During this period we have seen rapid advances in image resolution, new sensors providing imagery in many wavebands, operational data collection (and most recently, operational data dissemination), and a burgeoning in applications and research making ever greater use of remotely sensed information.

I encourage you to take the following introductory tour of some historical images put together by Nick Short from Goddard Space Flight Center, who has developed an excellent on-line tutorial on Remote Sensing (listed under EVSC 494 course links). We will visit this site in periodic assignments.

The History of Satellite Meteorology (Chapter 1 of Kidder and Vonder Haar, see Sources link.) includes a remarkable table of all the satellites that have made measurements of the earth. As of 1994 it had over 360 entries. With the exception of its exclusion of very recent satellites (including systems we will study such as GOES-9, SeaWifs, etc.), this table is an excellent reference, providing satellite name, ID, date, payload mass, orbital data, and comments regarding instrumentation. For satellites we study in greater detail during this course, this kind of information will be provided in lectures as we proceed.

We live in an information age. The amount of information available is staggering. It is my hope to leave you impressed, but not overwhelmed. We are presently receiving several hundred megabytes of real-time data daily, making routine use of imagery from multi-spectral imagers on GOES 8 and 9 in my research group (see UVA weather page). But this is an almost infinitesimally small portion of the data which is flowing in continuously from satellites. As a class, we will make use of both archived and near real-time images which are routinely available to the remote-sensing literate, which will soon include you.

The future of remote sensing in environmental sciences is extremely bright and promising. NASA and NOAA have planned the launch of a number of new platforms, with advanced sensors, and more involvement from applications scientists, the "end users" of satellite "data". There is currently an effort to merge the oversight structure and platforms for civilian and military satellite programs operated by the government. While I think it is important that part of your education in this course will include having you critically assess the limitations of remote sensing data for specific applications, I personally dislike the skeptical view in which remote sensing data are referred to disparagingly as "remotely sensible" data. The future of environmental science, as envisioned by large agencies such as NASA will surely be shaped by major programs like the Earth Sciences Enterprise.

The following text is quoted from Section I of NASA's Strategic Plan for the Earth Sciences Enterprise:

"The Challenge to Earth System Science:To develop the capability to predict those changes that will occur in the next decade to century, both naturally and in response to human activity.

Some Science Questions:	Some Practical Implications:
Can climate variation be predicted a season or year in advance? Can long-term climate variation be detected and drivers identified? What are the impacts of climate change on marine ecosystems? How do terrestrial ecosystems respond to land cover change? How do sudden solid Earth changes affect the land surface?	Agricultural activity and drought or flood preparation could be adjusted. Investments in chemical and aerospace technologies might be guided. Productivity of fisheries could be better restored or maintained. Forestry and watershed management practices would be improved. Earthquake and flood development and aftermath could be better understood and mitigation strategies devised.

Some Science Questions:

Some Practical Implications:

Can climate variation be predicted a season or year in advance?

Can long-term climate variation be detected and drivers identified?

What are the impacts of climate change on marine ecosystems?

How do terrestrial ecosystems respond to land cover change?

How do sudden solid Earth changes affect the land surface?

Agricultural activity and drought or flood preparation could be adjusted.

Investments in chemical and aerospace technologies might be guided.

Productivity of fisheries could be better restored or maintained.

Forestry and watershed management practices would be improved.

Earthquake and flood development and aftermath could be better understood and mitigation strategies devised.

A central program of ESE is the Earth Observing System (EOS), a set of polar orbiting satellites designed for long-term global observations of the atmosphere, oceans, land surface and biosphere. As an example, you can check out a list of earth science plans and plenty of links to more information from the main ESE web site. This list should make it clear, the world needs educated individuals who are prepared to consider ever more complex issues of global importance. Welcome to EVSC 494.