IRS-1C Satellite
IRS-1C Satellite

This is one of the best satellites having highest spatial resolution of 5.8 m in Panchromatic and 23.5 m in multispectral.

Orbit Details

Launch date : Dec. 28, 1995 (Soviet Launcher Molniya used)
Altitude : 817 Kms.
Inclination : 99.049 degrees
Period : 101.35 minutes
Repetivity : 24 days (5 days - revisit)
Equatorial crossong time : 10.30 AM descending
Weight : 1250 Kg.
No. of Sensors : Three; 1) PAN, 2) LISS-III and 3) WiFS

Panchromatic Camera (PAN)

Parameters Specifications (PAN)
Band (microns) 0.50 - 0.75
Resolution (m) 5.8
Effective focal lenght 980 mm
Coding 6 bits (64 grey levels)
Camera SWR 0.2
SNR (at saturation radiance) >64
Data rate (MBPS) 84.903
Swath (km.) 1. Nadir
1. Off-nadir
Off-nadir viewing (deg) +/-26 for obtaining stereoscopic data and 5 day revisit
Steering step size (deg) 0.09

The data in the panchromatic region is useful in geological studies for mapping geological and geomorphological features. Higher spatial resolution will be useful for urban planning studies, detecting urban fringe growth, updating the urban transporation infrastructure etc. It is having off-nadir viewing capability and the view angle can be varied between +/- 26 deg. The advantages of off-nadir viewing are increased repetivity coverage and stereoscopy. Stereoscopic image pair obtainable by PAN can be used for topographic studies and generation of digital terrain models.

Imaging Sensor Characteristics ( LISS-III Sensor)

Parameters B2 B3 B4 B5
Spectral bands 0.52-0.59(green) 0.62-0.68(red) 0.77-0.86(NIR) 1.55-1.70 (MID)
Resolution (m) 23.5 (for bands B2,B3,B4) 70.5 (for b5)
CCD devices 6000 elements 2100
Swath (Kms) 141 148
Equi focal length (mm) 347.5 301.2
Number of grey levels 128 (7 bits) 128

The bands are similar to the IRS-1A, IRS-1B and IRS-P2 except blue band which is not included in IRS-1C.

Band 2 is centered around the first peak of the vegetation reflectance curve (refer to reflectance curves in standard books) and is useful for discrimination of vegetation. This band along with red and near IR regions forms the core data useful for discrimination of vegetation.

Band 3 is centered around the chlorophyll absorption region of vegetation. Strong correlation exists between spectral reflectance in this region and chlorophyll content. A reduction in the amount of chlorophyll can occur when the plant is stressed. This results in less chlorophyll absorption and an increase in red reflectance. This band along with the near IR band is used widely for deriving spectral indices like ratio and Normalised Difference Vegetation index (NDVI) which have been found to be very good indicators of crop vigour and biomass.

Band 4: The high reflectance plateau region of the vegetation reflectance is in this band. Plant reflectance in this region is highly governed by the internal structure of plant leaves. This band shows high reflectance for healthy vegetation and is useful for green biomass estimation and crop vigor.

Band 5: the middle infra-red region from 1.3-2.5 microns is sensitive to leaf water content. It has been shown that 1.55 - 1.70 is best suited in 0.7-2.5 region for monitoring plant canopy water status. Major applications of this band include discrimination of crop types, canopy water status, forest type separation and damage assessment. Crop classification accuracies can be improved by 1-15% when this band is included with other bands. Also useful snow-cloud discrimination. In geology, it will be useful for rock type discrimination.

Wide Field Sensor (WiFS)

Parameters Values
Spectral bands (microns) B3 - 0.62-0.68 (red)
B4 - 0.77-0.86 (near IR)
Resolution (m) 188
CCD devices 2048 elements
Swath (Kms) 810 (5 days repetivity)
Equivalent focal length (mm) 56.4
No. of grey levels 128 (7 bits)
SNR >128

This sensor is most useful for vegetation studies. With larger swath (770 Km), high repetivity ( 5 days) and operation in two vegetation specific bands, the sensor provide vegetation index at regional level, thus helping in assessment of crop condition and drought monitoring.