Engineers who pioneered India's race in space.
The Indian Space Research Organization aka ISRO rank 5th in worldwide space power. It was formed in 1969 and ever since been leading into betterment and development of it's Nation. This list has been made to give a significance importance to all those who have strive hard for their work. Their work must be recognized and given importance for it.
1. Dr.Vikram Sarabhai 
We cannot start this list without the Father of Indian Space program. With the help of his knowlege, India has started both space research as well as nuclear power technology. Dr Vikram Sarabhai helped Dr Homi Bhabha set up India's first rocket-launching station, which was built in St Mary Magdalene Church near Thiruvanathapuram. Dr Vikram Sarabhai fulfilled the promise the fabrication and launch of an Indian Satellite. Due to this promise the first Indian satellite, Aryabhata, was put in orbit in 1975 from a Russian Cosmodrome.
2. Satish Dhawan
If Dr. Sarabhai has started the Space program then it is definitely Satish Dhawan who had shaped the program. He was the one to develop and introduce about remote sensing and satellite communication for rural inhabitants. His efforts led to initiate
•INSAT- a communication satellite
•IRS- a remote sensing satellite •PSLV- a launch vehicle.
3.Dr.A.P.J Abdul Kalam.
As the trifecta, the third person has to Dr A.P.J Abdul Kalam. His title as Missile Man of India, no doubts comes from working decades on the missile department in Defence as well as the Space research centres. He was an important role in the first nuclear test by India - Pokhran-2 . He was also one of the pioneers of the SLV (Satellite Launch Vehicle)
4. Dr T.K.Alex
Dr. T.K.Alex is specialist in in electro-optic systems and satellite technology. Onwards with the first Indian satellite Aryabhata he has been responsible for the sensor systems in all the Indian satellites. Indo-soviet manned mission in which the first Indian astronaut, Rakesh Sharma, squadron leader, flew aboard Soyuz T-11,he was the project director of this remote sensing experiment.He contributed to India to the first Indian Moon mission, Chandrayaan-1 in 2008. He provided guidance to the inter-planetary mission, Mars Orbiter mission, Mangalyaan.
5. Nambi Narayanan
Nambi Naryanan is more known for his alleged espionage career than his hardwork.
He is an expert in the cryogenics department when india was still dependent on solid propellant, he introduced liquid propulsion.Narayanan's team developed the Vikas engine used by several ISRO rockets including the Polar Satellite Launch Vehicle(PSLV) that took Chandrayaan-1 to the moon in 2008. The Vikas engine is used in the second stage of PSLV and as the second and the four strap-on stages of Geosynchronus Satellite Launch Vehicle (GSLV).
Thealleged espionage case was that he had leaked important defense secrets to Maldivian intelligence. In the end all the allegations were cleared and he has reciever ₹1.3 crore from government of Kerala. His biographical movie called Rocketry: The Nambi Effect would be releasing in mid 2020.
6. K.Radhakrishnan
He started to show his talents in the national remote sensing application missions including the Integrated Mission for Sustainable Development (IMSD) aimed at generation of spatial database of natural resources and action plans for sustainable development of land and water.
Mars Orbit Mission (MOM; aka Mangalyaan) was conceived, planned and executed, within four years , establishing India as the first country to have successful mission to Mars in its maiden attempt and at significantly low cost (INR 4.5 Billion) way less than Interstellar.
7.George Joseph.
George Joseph is known for his contributions for remote sensing technology. He has been the main force of guidance in the design and development of all the earth observation cameras on board with Indian Remote Sensing Satellite and INSAT.
His initiative was to bring all the knowledge of space technology to common man.
I have to conclude here, even thgough their are loads of scientists who had helped in space technology. I believe that these scientists should recieve some kind of recognition in their hardwork.