India’s space programme began with one of the great visionaries of India, Vikram Sarabhai. Encouraged by Homi Bhabha who initiated India’s nuclear programme and supported by India’s first Prime Minister Jawaharlal Nehru, Sarabhai laid the foundation of the programme. Begun originally with US assistance in sending up sounding rockets that barely went about 100 km up, Sarabhai soon realised the need for complete indigenisation of the programme. Today, India’s programme owes no credit to any other nation.
The finest designers of rockets and satellites
In this highly secretive and competitive human endeavour, Indian programme has made its mark with by far the most reliable launch vehicle called PSLV (Polar Satellite Launch Vehicle), and as the finest designers of satellites.
A space programme has two components, rocket, the vehicle that takes the object into space, and the satellite or the payload that goes into space. Rockets are tricky since they have to accelerate an object from rest to about 11 km/s in a matter of a few minutes. Few rocket engines can do it single-handed. So typically, the rocket that we see as a rocket, is typically 3 or 4 rockets sitting on top of each other. The lowest most rocket carries the upper rockets to a certain height and then disengages so that the second rocket can be ignited (switched on) to take the payload further into the space and so on, until the payload or payloads that the rocket may carry, are put into their desired orbit.
Similarly, satellites present a distinct challenge of their own. A satellite must withstand being accelerated from 0 km/s to 11 km/s in a matter of few minutes. It must be packed into an extremely small volume – typically a payload bay is a couple of meters in diameter and height. Once in space, it must generate its own power through solar panels, and withstand the harsh environment of outer space. Once launched, a satellite, in general, cannot be repaired. So it must also be extremely reliable.
Amongst the rockets, India’s work horse, the PSLV, can take a payload into an orbit up to 800 km. Originally designed to put payloads into polar orbit (rotating from North pole to South Pole), it has now been modified for a variety of uses. However, the rocket is not very large and can take a maximum of 2000 kg objects into space. India is now in the final stages of testing and approving a far bigger GSLV (Mark 3) which will carry about 5000 kg into space. We will then be able to launch our own communication satellites, which we currently launch using foreign rockets.
Payloads may be satellites that revolve around the earth or interplanetary missions. They may be used for observing the earth or observing the space, free from interference of the atmosphere. When the satellites observe the earth, it is preferable that they are kept in an orbit that goes from pole to pole so that as they complete their revolution, the Earth, spinning under them, will allow the satellite to see the whole earth with minimal effort. The communications satellites on the Earth should move with the Earth so that they complete one rotation per day, and are also at the Equator so that they appear stationary to us. These are called geostationary satellites and are used for communication. These satellites need to be at an altitude of about 36,000 km so that their revolution period is 24 hours. Such satellites can be used for communication, weather monitoring etc.
Nearly self-reliant
The Indian space programme has made India nearly self-reliant in the exploration of space. We not only make and operate our own communication and Earth observing satellites, we also participate in space programmes to explore other worlds. India now also has two kinds of global positioning systems, namely GAGAN, which is used for civilian purposes to help guide aircrafts and ships in their navigation, and a system for Navigation with Indian Constellation (NAVIC) also called Indian Regional Navigation Satellite System (IRNSS). GAGAN sits on the American GPS satellites and improves its accuracy from ten meters to three meters using a series of ground stations and three geostationary satellites (GSAT 8, GSAT 10 and GSAT 15).
NAVIC is entirely indigenous and uses a combination of five of our geostationary satellites (IRNSS 1A to 1G). Out of these, IRNSS 1C is geostationary, while others are Geosynchronous, that is, they go around the earth once in 24 hours but are at an inclination to the equator, giving them a slight vertical motion. Using these it can provide highly accurate positioning system for all Indian needs in civilian and defence arena. India also has a vibrant space exploration programme. We have sent one mission each to the Moon and Mars, flown astronomy payloads on several satellites and now have a completely dedicated astronomy satellite. More missions are in the pipeline.
The Moon mission
Our Chandrayaan-1 Mission was the first satellite of the Moon to provide unequivocal evidence that there is water on moon – soaked in its soil – like water in a sponge. During its nine months of operation, it demonstrated India’s ability to use Earth’s gravity as an effective sling shot, allowing us to send a mission to the Moon with much less fuel than other missions. Mangalyaan-1, a technology demonstration mission established our ability to send a mission that far, again using Earth gravity as a sling shot. Reaching Mars is like hitting a Re. 1 coin, 1 km away, with a grain of sand moving at 24 km/s. We achieved it in our first try. We are now looking forward to Chandrayaan-2 which will allow us to drive a car on the Moon, an Aditya mission to the Sun, as well as Mangalyaan-2. ISRO is providing excellent opportunities to Indian space explorers to explore the universe.
India also has a unique programme called ‘Student Sat’. These are small payloads, typically one meter cubes and 10 watt power, which can be designed by students from universities with the help of ISRO. These help students learn the complexities of space programmes.