Surendra M Vaidya
Advisor – Technical, Godrej & Boyce Mfg. Co. Ltd.
Executive Vice President & Business Head, Godrej Aerospace – Retired
Today INDIA made another history of launching a mission to study Sun from a distance
where there are no disturbances and continuously we can watch sun rays in different
directions.
Such missions which are not in regular orbits of earth or where we go beyond influence of
earths gravitational force requires lot of study of various other forces those will impact on
satellites travel . In addition we need to study the best route that will take minimum fuel
while reaching final destination.
As we observed in Chandrayaan satellites after ejection from launch vehicles needs to be
raised away from earth in stages by spirally moving up. This is similar to climbing a ghat
portion by taking steps of hairpin bends. Even though we travel a longer distance we can
travel easily without burdening on our engine. Similarly, we are going to take baby steps to
move away from earth to reach a point where we can break gravitational tie between
satellite and earth. At this stage with minimum force will eject satellite from earths
gravitational force. This will take about 5-6 days. Once we are out of earth’s gravity, satellite
will travel about 11 lakh kilometres in next 110 days to reach a L1 point where gravitational
force between earth and sun will be almost equal. This will be a neutral point and satellite
then will not require to spend much of a fuel. This way Aditya will be orbiting for predicted
life of 5 years. Orbit selected is roughly perpendicular to line joining sun and earth.
Some important facts:
- There are 7 payloads mostly made in INDIA to study sun rays and various reactions
that are taking place on sun and able to maintain such a high temperature. - Even though we are travelling almost 11 lakhs kilo meters e we are just going 1% of
the distance between earth and sun. - Sun rays take little more than 8 min to reach earth. So any signal we are getting from
Aditya will also be delayed in similar percentage. - Temperature expected in sun facing side will be very high( +200 deg C) and hence
temperature Management is very critical and few of the payload sensors are directly
going to view rays where temp may go much higher. - Insertion in L1 orbit is PRE programmed and on board controls will operate.
- During launch we saw there were two or more patches in the journey where there
was no contact of launch vehicle with one of the antenna on earth. This calls for
precision up to milliseconds and during this blackout period vehicle has to travel in
prefixed trajectory. Such blackout periods are required to be identified based on
location of deep space network antennas established by various countries and have
tie ups for maximum coverage. - Such a precise calculation in space is possible after lot of simulations and in-depth
study of stars and planets and their movements and forces they apply on the objects
put in by mankind.
Now some thing on LAUNCHER: PSLV
- This is a fourth stage rocket used in Chandrayaan -1 and it was its 59th flight.
- This is one of the best and highly reliable rocket designed and developed by ISRO.
- After using first three stages of the rocket and detaching them in first 12 min, fourth
stage was used in two phases ( burn – Cruise-burn) to travelled for about an hour. - Such restarts in space is a big challenge and ISRO demonstrated it again. This has
saved lot of fuel on satellite and positioned it in the best trans orbit and with full
control.
About ISRO as a R&D organisation:
All these days ISRO was conducting very safe launches and satellites in a proven orbits. Now
that ISRO’s confidence is high, with learning’s from multiple missions it is ready to take
calculated risks. Such risks are well discussed across multiple committees and backed by
simulations by execution teams. I am sure this will accelerate our space exploration
in coming years and rather than catching up with other 5 nations we can start
leading the exploration.
Congratulations ISRO for one more success and making INDIA proud and bring us to position
of respect.
