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  1. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (1 of 16) Further Reading: Chapter 04 of the text book Outline - satellite orbits - satellite sensor measurements - remote sensing of land, atmosphere and oceans

  2. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Remote Sensing: Remote observations of electro-magnetic radiation arriving from the earth system with sensors onboard satellites, aircrafts, etc. Reflection and emission Land, Oceans, Snow, Ice, and Atmosphere Currently there are about 4000-5000 active satellites orbiting the earth; the US has about 1000 Not all of these are scientific Defense Communications Global Positioning System (GPS) Advantages Cheapest way to repeatedly view the entire Earth Digital data (easy to manipulate) Disadvantages High initial cost (100-500 million dollars to build and launch) High-tech Myneni Lecture 09:Remote Sensing Feb-05-07 (2 of 16) Introduction

  3. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (3 of 16) Geo-stationary Orbit • Geo-stationary: • Orbits over the equator • Goes through one orbit every 24 hours • Hence, it rotates at the same speed as the earth - “sits” over the same spot the entire time • Approximately 22,000 miles above earth • Takes 5 satellites to cover the entire disk

  4. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (4 of 16) Geo-stationary Satellites: Example

  5. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (5 of 16) Polar Orbit • Orbits over the poles • Takes approximately 100 minutes to complete an orbit • Can view the entire earth’s surface in approximately 2-6 days • Approximately 470 miles above the earth • Also called “Sun synchronous” Example: Polar Orbiting NASA’s Terra Platform Flying at an altitude of 705 km, Terra orbits the Earth once every 98 minutes in a near-polar orbit. The spacecraft descends southward across the equator at 10:30 a.m., when cloud cover is minimal and its view of the surface is least obstructed. As Terra orbits, notice that the Earth is also spinning, so that adjacent orbits are offset somewhat at the equator and there is a small gap between the MODIS instrument's viewing swaths. It will take a little more than 1 day for these gaps to be filled on subsequent overpasses, so that MODIS will provide us snapshots of the entire surface of the Earth within every 2 days.

  6. Most satellite sensors measure radiation This radiation can either be sunlight reflected from some surface Land Atmosphere Oceans Sea Icea Can also measure (emitted) longwave radiation coming from the earth system Different sensors are designed to detect different types of radiation “Images” can be simple pictures, typically high resolution sensors - (Pentagon, San Francisco, Costa del Sol) Multi-spectral sensors measure reflected solar radiation at different wavelengths Moderate Resolution Imaging Spectroradiometer (MODIS) Multi-angle sensors measure reflected solar radiation at different directions Multi-angle Imaging Spectroradiometer (MISR) Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (6 of 16) Remote Measurements

  7. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (7 of 16) Remote Sensing of Land Deforestation: Amazon

  8. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (8 of 16) Remote Sensing of Land Deforestation Detail: Amazon

  9. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (9 of 16) Remote Sensing of Land Deforestation Stats: Amazon

  10. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (10 of 16) Remote Sensing of Land boreal forests grasslands savannas tropical forests Mapping land covers from satellite data – an example

  11. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (11 of 16) Remote Sensing of Land Monitoring global vegetation greenness from satellite data

  12. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (12 of 16) Remote Sensing of the Atmosphere Example atmospheric products from MODIS http://modis-atmos.gsfc.nasa.gov/IMAGES/mod08m_menu.html

  13. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (13 of 16) Remote Sensing of Oceans MODIS Sea Surface Temperature (SST) MODIS Ocean Color

  14. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (14 of 16) Remote Sensing of Oceans

  15. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (15 of 16) Remote Sensing of the Cryosphere 1999 seasonal sea ice concentrations in the Antarctic at the approximate seasonal maximum and minimum.

  16. Natural Environments: The Atmosphere GE 101 – Spring 2007 Boston University Myneni Lecture 09:Remote Sensing Feb-05-07 (16 of 16) Remote Sensing of the Cryosphere Model Simulations of Artic Sea Ice