Outline Further Reading: Chapter 04 of the text book - satellite orbits - satellite sensor measurements - remote sensing of land, atmosphere and oceans Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (1 of 12)

Introduction Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (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 ( million dollars to build and launch) High-tech

Geo-stationary Orbit Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (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 Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (4 of 12) Geostationary System The 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 Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (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 PlatformTerra 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)PentagonSan FranciscoCosta del Sol Multi-spectral sensors measure reflected solar radiation at different wavelengths –Moderate Resolution Imaging Spectroradiometer (MODIS)MODIS Multi-angle sensors measure reflected solar radiation at different directions –Multi-angle Imaging Spectroradiometer (MISR)MISR Remote Measurements Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (6 of 12)

Remote Sensing of Land Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (7 of 12) Deforestation: Amazon

Remote Sensing of Land Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (8 of 12) Mapping land covers from satellite data – an example

Remote Sensing of Land Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (9 of 12) Monitoring global vegetation greenness from satellite data

Remote Sensing of the Atmosphere Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (10 of 12) Example atmospheric products from MODIS

Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (11 of 12) Remote Sensing of Oceans MODIS Sea Surface Temperature (SST) MODIS Ocean Color

Natural Environments: The Atmosphere GG 101 – Spring 2005 Boston University Myneni Lecture 09:Remote Sensing Feb (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.