Indian Space activities have been started around 1962-63 under the depart-ment of atomic energy. The government of India set the Space Applications Center & a Department Of Space with a view to promote the development & application of Space Technology & space Sciences for socio-economic benefits of the nation.

Main objectives of ISRO

1. Long distance telecommunication, diffusion of T.V. signals using satellite.
2. Remote sensing of natural renewable parameters from satellite.

To realize the above objectives ISRO activities are oriented predominantly towards: -

1. Design & development of application sensing, TV broadcasting & meteorology.
2. Establishment of ground station facilities for using these satellites for launching.

INDIAN SPACE RESEARCH ORGANISATIO (ISRO) is an important participant of policies formed by the space commission. Space research activities in India can be broadly classified into three main areas:

• Space Sciences
• Space Technology
• Space Applications

Mainly using ground-based instruments at a number of locations was pursuing space science research.

Space Applications Centre, Ahmedabad

Since 1972, SAC, constituent of ISRO, is a premier institution in the country responsible for experimentation & evaluation of the applications of space technology.

SAC has carried out several remote-sensing experiments for agriculture, forestry, water resources & television broadcasting & reception via satellite is carried out. Work is also being conducted in the field of satellite meteorology & geodesy. Satellite geodesy can help us in fixing the position of any place on earth to a high degree of accuracy.

A number of departments are in SAC, AHMEDABAD to achieve the requisite objectives.

Some of technical one’s are :-

1. Ahmedabad Earth Station (AES)
2. Data Communications Division (DCD)
3. Data Communication Test Facility (DCTL)
4. Signal & Image Processing Group (SIPG)
5. Satellite Photogrametry & Digital Cartography Division (SPDD)
6. Thermo Vaccume Test Facility (TTF)

Image Processing

Image processing is a powerful group of techniques for uncovering information in a digital set of data. Some of these techniques are comparable to photographic darkroom processes, but much more is involved. The principal idea behind image processing is to make an image more informative.

Image processing is a special form of 2D signal processing. Digital image processing like other glamorous fields, suffer from myths, micro conceptions, misunderstanding & misinformation. It is a vast umbrella under which fall diverse aspects of optics, electronics, mathematics, photography & computer technology.

In the past, images were sent in analog form, which suffered from too much noise and quality of image wad poor. If image remained in analog firm, processing will be more difficult. So it is better to convert image in digital form and use computer for processing. This eliminated most of noise. Normally images have the following problems.

1. Geometric distortion resulting in picture being distorted.
2. Photometric non-linearity, which resulted in image tending to be darker at edges and brighter towards the center.
3. Bleeding of oscillation in camera into the video signal resulting in a rug-like pattern.

Once image is in computer, these three problems are resolved by image processing algorithms.

First problem that is geometric distortion was solved by literally "stretching" the image to standard calibration pattern for the camera. All stretching is done by software.

Isolating a section of image with noise, computing its Fourier Transform and using this as a filter to be subtracted from the rest of image solve second problem, of photometric non-linearity.

These techniques resulted in dramatic improvement of image.

Scene are developed from a camera like sensors, either a conventional film based system or a scanner & manipulated so that they provide more information. An image is produced by radar detector or by an electro-mechanical scanner or by a digital x-ray machine.

Image consisting of tiny equal areas or picture elements arranged in regular rows & columns. Pixel position is determined on xy co-ordinate system. Each pixel also has a numeric value called gray level that records the intensity of electromagnetic energy for the ground resolution cell represented by that pixel.

Image may be described in strictly numerical terms in 3 co-ordinate system with x and y locating each pixel and z giving the digital number, which is displayed as a gray scale intensity value.

Indian Remote Sensing Satellite (IRS)

The launch of first operational Indian Remote Sensing satellite, IRS-1A, on March 17, 1988, on board a Soviet Vostok rocket, ushered in a new era in the country’s resources survey & management system. The second satellite in this series, IRS-1B, identical to IRS-1A, was launches on August 29, 1991. IRS-1B has become the mainstay of National Natural Resources Management System (NNRMS) for effectively managing the country’s resources.

Data from the IRS satellite are used for several applications such as agricultural crop acreage & yield estimation, drought monitoring & assessment management, ocean/marine resources survey, urban planning, mineral prospecting, forest survey etc.

In order to provide the user community with improved remote sensing data, the next generational satellites, IRS-1C/TD have been taken up. These satellites will have better spectral & spatial resolutions, more frequent revisits, stereo viewing & onboard recording capabilities. It incorporates three cameras: -

1. A multi spectral camera LISS-III
2. A panchromatic camera
3. A CAMERA WITH Wide Field Sensor (WiFS)

IRS_1C satellite when launched in Dec. 1995. Will be one of the best remote sensing satellite systems available compared to any other civilian operational remote sensing satellite systems.

IRS_1D,IRS p4, IRS p5

Introduction to SPDD (Satellite Photogrammetry & Digital Cartographic Division)

SPDD is a division of SIPG (Signal and Image Processing Group), which in turn comes under SIIPA (Signal, Image and Information Processing Area).

SIPG is responsible for the design and development of Data Product Systems in close interaction with other ISRO/DOS centers (NRSA, ISAC) to meet the Indian and International Ground Stations’ requirements and the development of advanced technologies in the field of image processing.

SPDD is responsible for the design and development of cartographic quality data products, simulation studies for satellite based topographic mapping, R & D of digital mapping systems, development of value added services and R & D on integration of aerial and satellite photogrammetry.

SPDD designs and develops software for Satellite Image Data Processing, which is implemented in NRSA (National Remote Sensing Agency), Hyderabad.

SPDD provides the users with different types of data products.