Landsat 7 Sensor ( ETM+)

 The Band 6 on Landsat 7 is divided into two bands, high and low gain, Images in two modes

         • Panchromatic Image : operating in visible & near infra red region.(15m Resolution) TM band 1 for 

            Bathymetry ,Solid vegetation, Different forest types identification.

          • Multispectral Images: obtain image data in 7 bands of visible, Near IR & Middle IR region. (30 m

            Resolution)

Two mid IR bands on TM are useful for vegetation and soil moisture status, discriminating soil and rock 

Far IF band for soil mapping, soil moisture and vegetation study.This system currently operated by US Geo survey. As result of this image capturing techniques image cost dropped down. They have seven LANDSAT satellites, the first launched in 1972. Landsat 5 and Landsat7 are in operational. Land sat has multispectral sensors Multi spectral Scanner(MSS) and Thematic Mapper(TM). MSS has 80m and TM has 30m resolution.  

Spectral Resolution (µm)    Band   Spatial Resolution(m)

      Band  1   0.450 – 0.515  

      Band  2   0.525 – 0.605  

      Band 3    0.630 – 0.690 

      Band 4    0.760 – 0.900  

      Band 5    1.550 – 1.750  

      Band 6†  10.40 – 12.5  

      Band 7     2.080 – 2.35  

      Band 8     0.52 – 0.92  

     Blue -Green  30

     Green           30

     Red              30

     Near IR        30

     Mid IR         30

     ThermaL IR  60

     Mid IR         30

     Pan              15

SPOT 2.5m

        This is main earth observation satellites operated by French since 1985. This system has two sensors, Multispectral or panchromatic mode. Multispectral image have 20m and panchromatic mode has 10m resolution. It has three multi spectral bands, Green, Red and Infrared. It aunched in 1998. SPOT is the only satellite system acquire stereo satellite imagery.

ISR

        This is Indian Remote Sensing Satellite has 5 satellites system, Launch in 1995 to 2004. This is main earth observation satellite. Spatial resolution 5.8m to 23.8m

FCC – 3,2,1 PNCC – 2,3,1

QuickBird 0.6m

       Canyon Lands, UT (0.6 m resolution) April 20, 2003.  Launched in 18 OCT,2001, operated by DIGITALGLOBE, 450 km orbit, sun-synchronous, 1-3.5 day revisit period, 0.61 m- 0.72 panchromatic, 2.44 m-2.88M multispectral. Spectral Pan – 1, MS – 4. Radimetric 11bit

Band 1 – Blue 0.45-0.52, Band 2 – Green 0.52-0.6, Band 3 – Red 0.631 – 0.691, Band 4 – NTR 0.76 – 0.9

IKONOS (4 m Multispectral)

       Launched by Space Imaging in 1999, 1 m panchromatic and 4 m multispectral resolution, 681 km orbit, crosses equator between 10 and 11 am daily, revisit 1.5-3 days.

RADAR (Radio Detection and Ranging)

       SLAR (Side looking Airborne Radar) developed by military in 1950’s, and SAR (Synthetic aperture radar), Image is NASA TOPSAR of Pasadena valley, CA.

LIDAR (Light Detection and Ranging) 

      Image: Bainbridge Island, WA courtesy Pudget Sound LIDAR Consortium, 2005

ALOS 

        Advanced Land Observation Satellite system. ALOS launch in 2006. This is an Earth observation satellite. Spatial resolution 10m

Pre-image Procession

       Prior to data analysis, initial processing on the raw data is usually carried out to correct for any distortion due to the characteristics of the imaging system and imaging conditions. Its depend on the user's. These procedures include radiometric correction and field of view of the sensor. 

Eclipses.

Considering two solid opaque objects, Moon and Earth, arranged according to the picture and illuminated by a large source of light Sun. Earth is Eliminated by the rays from Sun which reach it, but owing to the presence of Moon between Sun and Earth, shadows are obtained on parts of Earth. By drawing the extreme rays from Sun it can seen that the region a on Earth receives no light, and this region, known as the umbra, is therefore in total darkness. The region on Earth between a, b, and a, d receives light from only part of Sun, and is hence in partial shadow; such a region is known as a penumbra. Beyond b to c, and beyond d to e, the region is illuminated by rays from the whole of Sun, and is therefore bright. 

Illustrates the eclipse of the sun

At some stage in their movement round the sun, S, the moon M comes between it and the earth E. A total eclipse is observed at the region a on the earth, and a partial eclipse is observed at the regions b and d. Observers at c and e on the earth receive rays from the whole of the sun, so that no eclipse is seen. The sun’s appearance at different points on the earth is illustrated by small circles below the main figure.

                The moon is not a Iuminous object; it merely reflects light from the sun. An eclipse of the moon happens when the earth comes between it and the sun, since the moon is then in the shadow of the earth and is no longer illuminated by the sun.

Summary:

Eclipses of the sun are due to the shadow formed when the moon passes between the sun and earth. An umbra is a region of total shadow; a penumbra is a region of partial shadow.    

REFERENCE
M. Nelkon M.Sc.(Lond.), A.K.C