further reading: chapter 04 of the text book outline...

Outline

Further Reading: Chapter 04 of the text book

- satellite orbits

- satellite sensor measurements

- remote sensing of land, atmosphere and oceans

Natural Environments: The AtmosphereGG 101 – Spring 2005

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MyneniLecture 09:Remote Sensing

Feb-09-05(1 of 12)

Introduction


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Feb-09-05(2 of 12)

• Remote Sensing:Remote observations of electro-magnetic radiation arriving from the earth system with sensors onboard satellites, aircrafts, etc.

• Reflection and emission• Land, Oceans, and Atmosphere

• Currently there are about 4000 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)

• Dis-advantages• High initial cost (100-500 million dollars to build and launch)• High-tech

Geo-stationary Orbit


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Feb-09-05(3 of 12)

Geo-stationary:

• Orbits over the equator• Goes through one orbit every 24 hours• Hence, it rotates at the same speed as the earth and “sits” over the same spot the entire time• Approximately 22,000 miles above earth• Takes 5 satellites to cover the entire disk

Geo-stationary Satellites: Example


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Feb-09-05(4 of 12)

Geostationary SystemThe objective of the geostationary operational environmental satellite (GOES) system is to maintain a continuous data stream from a two-GOES system, primarily to support the National Weather Service requirements. The program objective is to meet requirements by procuring, through the GOES Acquisition Manager (NOAA/SAO) and NASA/GSFC, spacecraft, instruments, launch services, and ground equipment. The GOES program also invests in new product development and assists with implementing the approved products into operations.

Polar Orbit


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Feb-09-05(5 of 12)

• 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.

• Most satellite sensors measure radiation• This radiation can either be sunlight reflected from some surface

– Land– Atmosphere– Oceans

• 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)

Remote Measurements


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Feb-09-05(6 of 12)

Remote Sensing of Land


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Feb-09-05(7 of 12)

Deforestation: Amazon



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Feb-09-05(8 of 12)

Mapping land covers from satellite data – an example



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Feb-09-05(9 of 12)

Monitoring global vegetation greenness from satellite data

Remote Sensing of the Atmosphere


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Feb-09-05(10 of 12)

Example atmospheric products from MODIS


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Feb-09-05(11 of 12)

Remote Sensing of Oceans

MODIS Sea Surface Temperature (SST)

MODIS Ocean Color


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Feb-09-05(12 of 12)

Remote Sensing of the Cryosphere

1999 seasonal sea ice concentrations in the Arctic and Antarctic at the approximate seasonal maximum and minimum. Images courtesy of the National Snow and Ice Data Center, University of Colorado.

further reading: chapter 04 of the text book outline...

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