S. Somanath, Chairman of the Indian Space Research Organisation (ISRO), attributes the success of the Chandrayaan-3 mission to the moon to “the result of the hard work of thousands of people in ISRO”, the “rigour of the reviews”, and “corrective action taken meticulously.”

In an interview with T.S. Subramanian in Bengaluru, Dr. Somanath asserted that the launch of the LVM-3 rocket on July 14 from Sriharikota and its placing the Chandrayaan-3 spacecraft into its earth-bound orbit was the “most critical event” of the mission. He also spoke about the significance of the hop test conducted with the Vikram lander on the moon, said that “we are in the process of thinking about” a sample return mission from the moon, and shared his thoughts on the Aditya-L1 mission.

Question: How confident were you about the Chandrayaan-3 mission’s success? What were the contributing factors that led to the success – to the lander Vikram soft-landing on the moon and the rover Pragyan sliding down from Vikram?

Answer: There were many. The first and foremost is Chandrayaan-2’s unsuccessful attempt itself. When there is an unsuccessful attempt, it gives a lot of information. The analysis of that event gave us so [many] additional insights which were not available in the Chandrayaan-2 time frame itself. We understood the deficiencies very well. There were multiple deficiencies. It was a chain of events that caused the failure. In any rocket mission, we make sure that one event does not propagate. If one event propagates and results ultimately in failure, it means the protection mechanisms you had planned are not functioning.

There were at least five different events that culminated in the failure. There were windows left for the failure to propagate.  Once we understood them, we looked at what more could happen in similar lines. Once they were understood, we devised a set of tests that were much more rigorous and involved than what we did earlier. All these tests were done without a single item being dropped. All the tests’ results were reviewed and analysed, and corrective action taken meticulously. It took almost four years of work to be done. That is why there was such a long gap between Chandrayaan-2 and Chandrayaan-3.

You know every success comes not (repeat not) out of review or checks but it is the work of the people… So you have to challenge them. Unless you challenge them, unless they feel insecure, they will not do a great job. Complacency is dangerous. My job was to create an awareness about themselves… You have to stir them, challenge them. This is what we did.

Last time [during the Chandrayaan-2 mission], we had a problem with the software; we had problems with algorithms; we had problems with hardware; and we had problems with implementation. There was inadequacy of thrust.

Was the removal of the central, fifth engine in the lander a contributing factor to Chandrayaan-3’s success? Originally, there were only four engines in Chandrayaan-2 but a fifth engine was added. This additional fifth, middle engine in Chandrayaan-2 did not perform well. Time was running out. Fuel was running out.

No, no. I will explain. It had nothing to do with the failure or success of the fifth engine. The fifth engine was necessary in [the lander of] Chandrayaan-2 because only that much thrust was necessary. Only the central engine was used for the final landing. If you have four engines, a fifth engine is a possibility. A central engine was necessary in Chandrayaan-2 because the thrust of that engine matched with the thrust of the mass of the craft. But when it came to Chandrayaan-3, the mass of the craft was 250 kg more. A single engine would be unable to sustain such a mass. So you have to fire two engines.  When you have to fire two engines, four is a better configuration. The fifth engine was deleted in Chandrayaan-3 because the mass of the landing craft increased [and you needed two engines to fire]. The fifth engine in Chandrayaan-2 had nothing to do with the mission’s failure or success.

You had chosen a bigger area on the lunar surface to land now. Was it another contributing factor to Vikram’s successful landing?

Last time, we had an area of half a km by half a km to land. One of the biggest flaws last time was that we were trying to land exactly at a [particular] location. So the programme was trying to move the lander to that point and then land. Although it could have landed safely, it was not allowing. The software was trying to push it to that point. This was not really necessary.  We could have landed in a place away. We could have been left with no time to land.

We had a wider area this time. But a wider area was not possible last time because we did not have good images of the [lunar surface then]. We were actually imaging prior to the orbit and identifying the landing location from the previous orbit, sending it to the earth, and saying, “This is the location.”

This time, we already had the pictures from Chandrayaan-2. Using those pictures, we could choose a wider area. It was pre-planned.  This time, there was no taking pictures from the previous orbit and analysing them. So Chandrayaan-2 helped Chandrayaan-3 to land safely. A wider area of 4.5 km by 2.5 km was selected this time. We were supposed to land in the middle of it. We landed within 300 metres of it. 

You listed five “critical events” during the entire Chandrayaan-3 mission. They were the launch of the LVM3 (Launch Vehicle Mark 3) rocket and its putting Chandrayaan-3 first into earth-bound orbit; the propulsion module with the lander being put into trans-lunar orbit; the propulsion module being captured by the moon’s gravity; the separation of the lander from the propulsion module; and the lander Vikram soft-landing on the moon. In your estimate, which was the most critical of these five events?

Undoubtedly, it was the launch.

But the LVM-3 (Launch Vehicle Mark 3) rocket had had six successful flights in a row already.

People take it for granted that the launch is just a routine affair. But the launch is much more complex than even the Chandrayaan-3 satellite which is such a simple, upper stage of the PSLV only. But it has a little more sensors and software. That is all. But a rocket is much more complex. It has to go through the atmosphere, do the turning, do the work under severe conditions, experience stress and strain, and reach the correct orbit. The number of systems [working in a rocket] is ten times more than that of Chandrayaan-3 craft. The propulsion, algorithms, gyros, mechanisms, sensors and so many complex events are taking place. Yet the rocket has to be successful. But people take it for granted. “It is all child’s play” [people think]. The good part is that we are doing the launch multiple times. If we do it again and again, we have the confidence. That is all the result of the work of thousands of people. Chandrayaan-3 is also such a result.

I consider the launch [to have been] the most critical event because there is no intervention in that. It is fully autonomous. There is no human intervention.

It is totally autonomous…

From lift off, you give the command, up to the injection of the satellite into orbit, there is no human intervention. But manoeuvres of Chandrayaan-3 spacecraft such as its trans-lunar injection, its being captured by the moon, Vikram landing on the moon, everything is with our intervention. All of these, we can intervene at any point. We can change the software. We can change the parameters. We can land appropriately. All these are possible except in the launch. That is why the launch is more critical.

Can you explain the expected behaviour and the actual behaviour of Vikram during the landing process?

Actually, the landing process is a very complex process. It is the reverse of the rocket taking off. The rocket takes off vertically and finally becomes horizontal.

It will become tangential to the earth. It will continuously take an arc from the lift-off to the injection of the satellite into orbit. 

During the landing process, the lander has to come down from a high velocity to low velocity. In this case, the lander could have come down straight away. But we did not plan it like that. In this mission, in-between, we introduced a lot of check-points. From 30 km, it will come down to 7.80 km, then it will come down to 150 metres. It will then do certain checks. The lander will hover at these points. This hovering was necessary to do certain instruments’ verification. [For instance) Altimeter. In the general soft-landing, all these are not necessary. It made the whole landing process a little more complex. It is longer than needed. It will consume more fuel.

After the confidence building resulting from Chandrayaan-3, the landing process in the future missions will be smoother and without break. It will be continuously coming down from one point to another. It will be more fuel-efficient and faster.

One of the problems during the Chandrayaan-2 landing was the way of landing. We had one section called the rough braking phase, then the camera coasting phase, the fine braking phase and the terminal descent phase. Conversion into four different phases is not really necessary. It can seamlessly continue.

We did a scenario of continuous landing in case of some emergency where the sensors need not come into picture. In future missions, we will do [it] like that. This landing in Chandrayaan-3 followed exactly what we had planned. The velocity reduction, orientation changes etc. happened perfectly. It did the hovering exactly. In the last 150 metres, we had some time to study the lunar surface and see whether there were any boulders. The lander moved a little bit. We identified that it moved a little bit to see whether it was clear of rocks. It landed very safely. Almost all the sensors worked… So I must say it was a perfect landing.

What is the significance of the hop test done by the Vikram lander? It hopped 50 cm and it rose a little bit in the air.

In any mission, the craft which goes to the moon or Mars should come back. Otherwise, it will be a one-way mission. The vehicle is supposed to do a two-way mission. If you do a two-way mission, the vehicle will take off from the moon’s surface and come back to the earth. When you take off from the moon’s surface, it is a different algorithm. It is not a landing algorithm. It is a rocket algorithm. It has to go into orbit. From the orbit, it has to restart and come back to the earth. If you do it, the cycle is complete

When human beings go to the moon, all these have to be achieved. We have to learn all these in steps. I thought that after this primary mission goes off well, why don’t we start trying it out [the hop test]. It is new thinking. A week after the landing, we mooted this idea. Once all the mission’s objectives were met, why can’t we do some trials … to see whether it is possible. But we could not do it fully. If you take off, it can actually take off. There was no issue. But people were scared. The lander can fail. It can topple. It should not jeopardise the mission. After a week, the daylight will come. So we decided that we will do a short pulse.

A short jump?

Yes, a short jump. If you don’t stop, it will continue. The hopping is to show it rises to a certain height, it can land and to see whether our control systems, propulsion systems and sensors have worked well. This is the trial here. It worked reasonably well.

Is it a trial for the sample-return mission?

Chandrayaan-3 configuration cannot work for a sample return mission. You have to design a new craft, a new approach. It requires more mass, a higher payload. Then a sample return mission is possible. The travel for coming back from the moon to the earth requires energy. We have to plan for that. We are in the process of thinking about it.

You have sent Aditya-L1 to study the sun’s corona, the solar flares, the solar winds etc. What made you choose the sun for study? Is it because “Without the sun, you cannot study the earth”?

The study of the sun is not a new thing. We have the Physical Research Laboratory (PRL) in Ahmedabad. It has a research group which is focused on the study of the sun. We have a solar observatory at Udaipur. It is under the PRL. There are ground-based observations of the sun happening regularly. There are multiple institutions such as the Indian Institute of Astrophysics (IIA), the Inter-University Centre for Astronomy and Astrophysics (IUCAA) and others concentrating on sun-related studies.

Once a small team of scientists is there, it is good to look at the sun. Then the question of developing the instruments to study the sun came up. Three years ago, a discussion on how to develop these instruments began… From the time of U R Rao [former ISRO Chairman], discussions have been taking place. The idea is good but somebody has to develop the instruments.

Vikram Sarabhai was interested in the study of the sun.

Many missions to study the sun had already taken place. They were done the world-over by the Americans, the Europeans and others. We now have a little more understanding of the type of instruments needed to be built. We decided that our instruments must be unique in their ability to observe the sun. That is how the seven instruments were identified for Aditya L1. Solar coronagraph was developed by ISRO and the IIA. It looks at the solar corona, solar mass ejection etc. They help us in modelling the corona.

IUCAA’s instrument is for ultraviolet radiation. They have reasonable expertise in it. The VSSC, the PRL and others built the remaining instruments. The Space Physics Laboratory (SPL), Thiruvananthapuram, looks at the sun’s particles, its low-energy and high-energy X-rays, particle emissions, its magnetic influence and so on.

The importance of Aditya L1 is that it actually connects the solar emissions to particle emissions to X-ray emissions to magnetic influence. So there is a chain of connected events. In other missions, these types of [connected] measurements are not done. You measure coronal mass ejections and no other correlated measurements. If you do correlated measurements and there is a magnetic influence happening, I can relate to coronal mass ejections. This means these measurements are inter-related. They help in long-term predictions of the impact of such emissions on our sun.

What is the current status of the propulsion module of the Chandrayaan-3 mission? And what is its SHAPE (Spectro-polarimetry of Habitable Planet Earth) payload doing?

The propulsion module is going around the moon in a 100-km orbit. Its SHAPE payload is observing the earth… That data is being continuously collected.

With the success of the Mars orbiter, Chandrayaan-3, and Aditya L1 missions, will ISRO be concentrating more on interplanetary missions? Will you ask the private companies to build and launch application satellites?

Nothing like that. Scientific missions have been done by ISRO only. It may not have commercial value. If commercial values are there, industries will be interested. Otherwise, going to the moon and doing the sun mission, who will be interested? They are national missions with a certain objective of growing a scientific pool within the country and creating a certain capability. It has to be publicly funded. It cannot be private.

Of course, tomorrow, there is asteroid-mining and commercial opportunities are there, private companies will be interested. Private companies cannot work without profitability.

Another point you mentioned is whether all application-oriented satellites will be launched by private companies. That may not be possible because it goes with commercial viability. If they are not commercially viable, they will not implement some of the technologies. We have to build advanced communication satellites, with R&D components. We will be building hundreds of satellites. We will look at [satellites with] synthetic aperture radars, which are scientific in nature than observation. Such things as strategic satellites, we will continue to build.

How do you view in totality the three Chandrayaan, the Mars Orbiter, and the Aditya-L1 missions?

Space has always been an inspirational domain for scientists who want to pursue a career in science, engineering and technology. Every young boy and girl will say that he or she wants to become an astronomer, astrophysicist, and so on. Their career will take them to many places. They are fascinated by celestial bodies… Space technology is such an inspirational domain. We also know it is a complex domain. For countries like India, there are questions being asked even today about its relevance. During Sarabhai’s time, there were a lot of such questions. These types of missions [to the moon, Mars and so on] will reduce the number of such questions.

S. Somanath, Chairman of the Indian Space Research Organisation (ISRO), attributes the success of the Chandrayaan-3 mission to the moon to “the result of the hard work of thousands of people in ISRO”, the “rigour of the reviews”, and “corrective action taken meticulously.”

In an interview with T.S. Subramanian in Bengaluru, Dr. Somanath asserted that the launch of the LVM-3 rocket on July 14 from Sriharikota and its placing the Chandrayaan-3 spacecraft into its earth-bound orbit was the “most critical event” of the mission. He also spoke about the significance of the hop test conducted with the Vikram lander on the moon, said that “we are in the process of thinking about” a sample return mission from the moon, and shared his thoughts on the Aditya-L1 mission.

Question: How confident were you about the Chandrayaan-3 mission’s success? What were the contributing factors that led to the success – to the lander Vikram soft-landing on the moon and the rover Pragyan sliding down from Vikram?

Answer: There were many. The first and foremost is Chandrayaan-2’s unsuccessful attempt itself. When there is an unsuccessful attempt, it gives a lot of information. The analysis of that event gave us so [many] additional insights which were not available in the Chandrayaan-2 time frame itself. We understood the deficiencies very well. There were multiple deficiencies. It was a chain of events that caused the failure. In any rocket mission, we make sure that one event does not propagate. If one event propagates and results ultimately in failure, it means the protection mechanisms you had planned are not functioning.

There were at least five different events that culminated in the failure. There were windows left for the failure to propagate.  Once we understood them, we looked at what more could happen in similar lines. Once they were understood, we devised a set of tests that were much more rigorous and involved than what we did earlier. All these tests were done without a single item being dropped. All the tests’ results were reviewed and analysed, and corrective action taken meticulously. It took almost four years of work to be done. That is why there was such a long gap between Chandrayaan-2 and Chandrayaan-3.

You know every success comes not (repeat not) out of review or checks but it is the work of the people… So you have to challenge them. Unless you challenge them, unless they feel insecure, they will not do a great job. Complacency is dangerous. My job was to create an awareness about themselves… You have to stir them, challenge them. This is what we did.

Last time [during the Chandrayaan-2 mission], we had a problem with the software; we had problems with algorithms; we had problems with hardware; and we had problems with implementation. There was inadequacy of thrust.

Was the removal of the central, fifth engine in the lander a contributing factor to Chandrayaan-3’s success? Originally, there were only four engines in Chandrayaan-2 but a fifth engine was added. This additional fifth, middle engine in Chandrayaan-2 did not perform well. Time was running out. Fuel was running out.

No, no. I will explain. It had nothing to do with the failure or success of the fifth engine. The fifth engine was necessary in [the lander of] Chandrayaan-2 because only that much thrust was necessary. Only the central engine was used for the final landing. If you have four engines, a fifth engine is a possibility. A central engine was necessary in Chandrayaan-2 because the thrust of that engine matched with the thrust of the mass of the craft. But when it came to Chandrayaan-3, the mass of the craft was 250 kg more. A single engine would be unable to sustain such a mass. So you have to fire two engines.  When you have to fire two engines, four is a better configuration. The fifth engine was deleted in Chandrayaan-3 because the mass of the landing craft increased [and you needed two engines to fire]. The fifth engine in Chandrayaan-2 had nothing to do with the mission’s failure or success.

You had chosen a bigger area on the lunar surface to land now. Was it another contributing factor to Vikram’s successful landing?

Last time, we had an area of half a km by half a km to land. One of the biggest flaws last time was that we were trying to land exactly at a [particular] location. So the programme was trying to move the lander to that point and then land. Although it could have landed safely, it was not allowing. The software was trying to push it to that point. This was not really necessary.  We could have landed in a place away. We could have been left with no time to land.

We had a wider area this time. But a wider area was not possible last time because we did not have good images of the [lunar surface then]. We were actually imaging prior to the orbit and identifying the landing location from the previous orbit, sending it to the earth, and saying, “This is the location.”

This time, we already had the pictures from Chandrayaan-2. Using those pictures, we could choose a wider area. It was pre-planned.  This time, there was no taking pictures from the previous orbit and analysing them. So Chandrayaan-2 helped Chandrayaan-3 to land safely. A wider area of 4.5 km by 2.5 km was selected this time. We were supposed to land in the middle of it. We landed within 300 metres of it. 

You listed five “critical events” during the entire Chandrayaan-3 mission. They were the launch of the LVM3 (Launch Vehicle Mark 3) rocket and its putting Chandrayaan-3 first into earth-bound orbit; the propulsion module with the lander being put into trans-lunar orbit; the propulsion module being captured by the moon’s gravity; the separation of the lander from the propulsion module; and the lander Vikram soft-landing on the moon. In your estimate, which was the most critical of these five events?

Undoubtedly, it was the launch.

But the LVM-3 (Launch Vehicle Mark 3) rocket had had six successful flights in a row already.

People take it for granted that the launch is just a routine affair. But the launch is much more complex than even the Chandrayaan-3 satellite which is such a simple, upper stage of the PSLV only. But it has a little more sensors and software. That is all. But a rocket is much more complex. It has to go through the atmosphere, do the turning, do the work under severe conditions, experience stress and strain, and reach the correct orbit. The number of systems [working in a rocket] is ten times more than that of Chandrayaan-3 craft. The propulsion, algorithms, gyros, mechanisms, sensors and so many complex events are taking place. Yet the rocket has to be successful. But people take it for granted. “It is all child’s play” [people think]. The good part is that we are doing the launch multiple times. If we do it again and again, we have the confidence. That is all the result of the work of thousands of people. Chandrayaan-3 is also such a result.

I consider the launch [to have been] the most critical event because there is no intervention in that. It is fully autonomous. There is no human intervention.

It is totally autonomous…

From lift off, you give the command, up to the injection of the satellite into orbit, there is no human intervention. But manoeuvres of Chandrayaan-3 spacecraft such as its trans-lunar injection, its being captured by the moon, Vikram landing on the moon, everything is with our intervention. All of these, we can intervene at any point. We can change the software. We can change the parameters. We can land appropriately. All these are possible except in the launch. That is why the launch is more critical.

Can you explain the expected behaviour and the actual behaviour of Vikram during the landing process?

Actually, the landing process is a very complex process. It is the reverse of the rocket taking off. The rocket takes off vertically and finally becomes horizontal.

It will become tangential to the earth. It will continuously take an arc from the lift-off to the injection of the satellite into orbit. 

During the landing process, the lander has to come down from a high velocity to low velocity. In this case, the lander could have come down straight away. But we did not plan it like that. In this mission, in-between, we introduced a lot of check-points. From 30 km, it will come down to 7.80 km, then it will come down to 150 metres. It will then do certain checks. The lander will hover at these points. This hovering was necessary to do certain instruments’ verification. [For instance) Altimeter. In the general soft-landing, all these are not necessary. It made the whole landing process a little more complex. It is longer than needed. It will consume more fuel.

After the confidence building resulting from Chandrayaan-3, the landing process in the future missions will be smoother and without break. It will be continuously coming down from one point to another. It will be more fuel-efficient and faster.

One of the problems during the Chandrayaan-2 landing was the way of landing. We had one section called the rough braking phase, then the camera coasting phase, the fine braking phase and the terminal descent phase. Conversion into four different phases is not really necessary. It can seamlessly continue.

We did a scenario of continuous landing in case of some emergency where the sensors need not come into picture. In future missions, we will do [it] like that. This landing in Chandrayaan-3 followed exactly what we had planned. The velocity reduction, orientation changes etc. happened perfectly. It did the hovering exactly. In the last 150 metres, we had some time to study the lunar surface and see whether there were any boulders. The lander moved a little bit. We identified that it moved a little bit to see whether it was clear of rocks. It landed very safely. Almost all the sensors worked… So I must say it was a perfect landing.

What is the significance of the hop test done by the Vikram lander? It hopped 50 cm and it rose a little bit in the air.

In any mission, the craft which goes to the moon or Mars should come back. Otherwise, it will be a one-way mission. The vehicle is supposed to do a two-way mission. If you do a two-way mission, the vehicle will take off from the moon’s surface and come back to the earth. When you take off from the moon’s surface, it is a different algorithm. It is not a landing algorithm. It is a rocket algorithm. It has to go into orbit. From the orbit, it has to restart and come back to the earth. If you do it, the cycle is complete

When human beings go to the moon, all these have to be achieved. We have to learn all these in steps. I thought that after this primary mission goes off well, why don’t we start trying it out [the hop test]. It is new thinking. A week after the landing, we mooted this idea. Once all the mission’s objectives were met, why can’t we do some trials … to see whether it is possible. But we could not do it fully. If you take off, it can actually take off. There was no issue. But people were scared. The lander can fail. It can topple. It should not jeopardise the mission. After a week, the daylight will come. So we decided that we will do a short pulse.

A short jump?

Yes, a short jump. If you don’t stop, it will continue. The hopping is to show it rises to a certain height, it can land and to see whether our control systems, propulsion systems and sensors have worked well. This is the trial here. It worked reasonably well.

Is it a trial for the sample-return mission?

Chandrayaan-3 configuration cannot work for a sample return mission. You have to design a new craft, a new approach. It requires more mass, a higher payload. Then a sample return mission is possible. The travel for coming back from the moon to the earth requires energy. We have to plan for that. We are in the process of thinking about it.

You have sent Aditya-L1 to study the sun’s corona, the solar flares, the solar winds etc. What made you choose the sun for study? Is it because “Without the sun, you cannot study the earth”?

The study of the sun is not a new thing. We have the Physical Research Laboratory (PRL) in Ahmedabad. It has a research group which is focused on the study of the sun. We have a solar observatory at Udaipur. It is under the PRL. There are ground-based observations of the sun happening regularly. There are multiple institutions such as the Indian Institute of Astrophysics (IIA), the Inter-University Centre for Astronomy and Astrophysics (IUCAA) and others concentrating on sun-related studies.

Once a small team of scientists is there, it is good to look at the sun. Then the question of developing the instruments to study the sun came up. Three years ago, a discussion on how to develop these instruments began… From the time of U R Rao [former ISRO Chairman], discussions have been taking place. The idea is good but somebody has to develop the instruments.

Vikram Sarabhai was interested in the study of the sun.

Many missions to study the sun had already taken place. They were done the world-over by the Americans, the Europeans and others. We now have a little more understanding of the type of instruments needed to be built. We decided that our instruments must be unique in their ability to observe the sun. That is how the seven instruments were identified for Aditya L1. Solar coronagraph was developed by ISRO and the IIA. It looks at the solar corona, solar mass ejection etc. They help us in modelling the corona.

IUCAA’s instrument is for ultraviolet radiation. They have reasonable expertise in it. The VSSC, the PRL and others built the remaining instruments. The Space Physics Laboratory (SPL), Thiruvananthapuram, looks at the sun’s particles, its low-energy and high-energy X-rays, particle emissions, its magnetic influence and so on.

The importance of Aditya L1 is that it actually connects the solar emissions to particle emissions to X-ray emissions to magnetic influence. So there is a chain of connected events. In other missions, these types of [connected] measurements are not done. You measure coronal mass ejections and no other correlated measurements. If you do correlated measurements and there is a magnetic influence happening, I can relate to coronal mass ejections. This means these measurements are inter-related. They help in long-term predictions of the impact of such emissions on our sun.

What is the current status of the propulsion module of the Chandrayaan-3 mission? And what is its SHAPE (Spectro-polarimetry of Habitable Planet Earth) payload doing?

The propulsion module is going around the moon in a 100-km orbit. Its SHAPE payload is observing the earth… That data is being continuously collected.

With the success of the Mars orbiter, Chandrayaan-3, and Aditya L1 missions, will ISRO be concentrating more on interplanetary missions? Will you ask the private companies to build and launch application satellites?

Nothing like that. Scientific missions have been done by ISRO only. It may not have commercial value. If commercial values are there, industries will be interested. Otherwise, going to the moon and doing the sun mission, who will be interested? They are national missions with a certain objective of growing a scientific pool within the country and creating a certain capability. It has to be publicly funded. It cannot be private.

Of course, tomorrow, there is asteroid-mining and commercial opportunities are there, private companies will be interested. Private companies cannot work without profitability.

Another point you mentioned is whether all application-oriented satellites will be launched by private companies. That may not be possible because it goes with commercial viability. If they are not commercially viable, they will not implement some of the technologies. We have to build advanced communication satellites, with R&D components. We will be building hundreds of satellites. We will look at [satellites with] synthetic aperture radars, which are scientific in nature than observation. Such things as strategic satellites, we will continue to build.

How do you view in totality the three Chandrayaan, the Mars Orbiter, and the Aditya-L1 missions?

Space has always been an inspirational domain for scientists who want to pursue a career in science, engineering and technology. Every young boy and girl will say that he or she wants to become an astronomer, astrophysicist, and so on. Their career will take them to many places. They are fascinated by celestial bodies… Space technology is such an inspirational domain. We also know it is a complex domain. For countries like India, there are questions being asked even today about its relevance. During Sarabhai’s time, there were a lot of such questions. These types of missions [to the moon, Mars and so on] will reduce the number of such questions.

Indian Space Research Organisation (ISRO) had shared a video of the Pragyan rover being rotated on the surface of the moon that was captured by a Lander Image Camera. The rover was put into sleep mode on September 2.
| Photo Credit: ANI

Chairman of the Indian Space Research Organisation (ISRO) S. Somanath on Thursday said the Pragyan rover of its moon mission Chandrayaan-3 has done what it was expected to do, and it would not be a problem even if it fails to `wake up’ from the current sleep mode.

The national space agency is now gearing up for XPoSat or X-ray Polarimeter Satellite launch which may take place in November or December, he said at a press conference here after visiting the famous Somnath temple in Gir Somnath district of Gujarat.

On the status of Pragyan, currently in sleep mode on the moon, the ISRO chief said it will wake up if its electronic circuits have not been damaged due to the extreme weather on the moon as the temperature dipped nearly 200 degrees Celsius below zero.

“It is OK if it does not wake up because the rover has done what it was expected to do,” he added.

ISRO had said last week that with dawn breaking on moon, it made efforts to establish communication with lunar mission Chandrayaan-3’s lander Vikram and rover Pragyan to ascertain their ‘wake-up condition’ after they had been put into sleep mode early this month, but no signals were being received.

Both the lander and rover were put into sleep mode on September 4 and 2, ahead of the lunar night setting in.

Talking about upcoming missions, Mr. Somanath said ISRO is now gearing up for XPoSat or X-ray Polarimeter Satellite.

“This XpoSat is ready and it will be launched through our PSLV rocket. Though we have not announced any dates yet, it may be launched in November or December. It is a mission to study black holes, nebulas and pulsars,” he said.

Another mission in the pipeline is INSAT-3DS, a climate satellite which will be launched in December, said Mr. Somanath.

“Then we will launch SSLV D3. As you know it is our Small Satellite Launch Vehicle. This is the third launch. It will be done in November or December. Then it will be the turn of the NASA-ISRO Synthetic Aperture Radar or NISAR. It will be launched in February next year,” he added.

The Gaganyaan mission’s test vehicle `D1′ will be launched in October, he said.

In an exciting milestone for lunar scientists around the globe, India’s Chandrayaan-3 lander touched down 600 km from the south pole of the moon on August 23, 2023.

In just under 14 Earth days, Chandrayaan-3 provided scientists with valuable new data and further inspiration to explore the moon. And the Indian Space Research Organisation has shared these initial results with the world.

While the data from Chandrayaan-3’s rover, named Pragyan, or “wisdom” in Sanskrit, showed the lunar soil contains expected elements such as iron, titanium, aluminum and calcium, it also showed an unexpected surprise – sulphur.

Planetary scientists like me have known that sulphur exists in lunar rocks and soils, but only at a very low concentration. These new measurements imply there may be a higher sulphur concentration than anticipated.

Pragyan has two instruments that analyse the elemental composition of the soil – an alpha particle X-ray spectrometer and a laser-induced breakdown spectrometer, or LIBS for short. Both of these instruments measured sulphur in the soil near the landing site.

Sulphur in soils near the moon’s poles might help astronauts live off the land one day, making these measurements an example of science that enables exploration.

Geology of the moon

There are two main rock types on the moon’s surface – dark volcanic rock and the brighter highland rock. The brightness difference between these two materials forms the familiar “man in the moon” face or “rabbit picking rice” image to the naked eye.

Scientists measuring lunar rock and soil compositions in labs on Earth have found that materials from the dark volcanic plains tend to have more sulphur than the brighter highlands material.

Sulphur mainly comes from volcanic activity. Rocks deep in the moon contain sulphur, and when these rocks melt, the sulfphur becomes part of the magma. When the melted rock nears the surface, most of the sulphur in the magma becomes a gas that is released along with water vapor and carbon dioxide.

Some of the sulphur does stay in the magma and is retained within the rock after it cools. This process explains why sulphur is primarily associated with the moon’s dark volcanic rocks.

Chandrayaan-3’s measurements of sulphur in soils are the first to occur on the moon. The exact amount of sulphur cannot be determined until the data calibration is completed.

The uncalibrated data collected by the LIBS instrument on Pragyan suggests that the moon’s highland soils near the poles might have a higher sulphur concentration than highland soils from the equator and possibly even higher than the dark volcanic soils.

These initial results give planetary scientists like me who study the moon new insights into how it works as a geologic system. But we’ll still have to wait and see if the fully calibrated data from the Chandrayaan-3 team confirms an elevated sulphur concentration.

Atmospheric sulphur formation

The measurement of sulphur is interesting to scientists for at least two reasons. First, these findings indicate that the highland soils at the lunar poles could have fundamentally different compositions, compared with highland soils at the lunar equatorial regions. This compositional difference likely comes from the different environmental conditions between the two regions – the poles get less direct sunlight.

Second, these results suggest that there’s somehow more sulphur in the polar regions. Sulphur concentrated here could have formed from the exceedingly thin lunar atmosphere.

The polar regions of the moon receive less direct sunlight and, as a result, experience extremely low temperatures compared with the rest of the moon. If the surface temperature falls, below -73 degrees C, then sulphur from the lunar atmosphere could collect on the surface in solid form – like frost on a window.

Sulphur at the poles could also have originated from ancient volcanic eruptions occurring on the lunar surface, or from meteorites containing sulphur that struck the surface and vaporised on impact.

Lunar sulphur as a resource

For long-lasting space missions, many agencies have thought about building some sort of base on the moon. Astronauts and robots could travel from the south pole base to collect, process, store and use naturally occurring materials like sulphur on the moon – a concept called in-situ resource utilisation.

In-situ resource utilisation means fewer trips back to Earth to get supplies and more time and energy spent exploring. Using sulphur as a resource, astronauts could build solar cells and batteries that use sulphur, mix up sulphur-based fertiliser and make sulphur-based concrete for construction.

Sulphur-based concrete actually has several benefits compared with the concrete normally used in building projects on Earth.

For one, sulphur-based concrete hardens and becomes strong within hours rather than weeks, and it’s more resistant to wear. It also doesn’t require water in the mixture, so astronauts could save their valuable water for drinking, crafting breathable oxygen and making rocket fuel.

While seven missions are currently operating on or around the moon, the lunar south pole region hasn’t been studied from the surface before, so Pragyan’s new measurements will help planetary scientists understand the geologic history of the moon. It’ll also allow lunar scientists like me to ask new questions about how the moon formed and evolved.

For now, the scientists at Indian Space Research Organisation are busy processing and calibrating the data. On the lunar surface, Chandrayaan-3 is hibernating through the two-week-long lunar night, where temperatures will drop to -120 degrees C. The night will last until September 22.

There’s no guarantee that the lander component of Chandrayaan-3, called Vikram, or Pragyan will survive the extremely low temperatures, but should Pragyan awaken, scientists can expect more valuable measurements.

Jeffrey Gillis-Davis is research professor of physics, Arts & Sciences at Washington University in St. Louis. This article is republished from The Conversation.

A 3D image of the Vikram lander. ISRO created the image by using the anaglyph technique. Anaglyph is a simple visualization of the object or terrain in three dimensions from stereo or multi-view images. Photo: X/@isro via PTI

The Indian Space Research Organisation (ISRO) is looking to awaken the Chandrayaan-3’s Vikram Lander and Pragyan Rover as dawn will be breaking on the moon on September 22.

The lander and the rover went to sleep after the end of one lunar day (14 earth days).

On September 2, the Pragyan was put in sleep mode and two days later on September 4, the space agency put Vikram too in sleep mode with its payloads switched off. Both the Vikram’s and Pragyan’s receivers however have been kept on.

Now, on September 22, with sunlight back on the moon, ISRO is hoping that their solar panel would get charged and that it could establish contact with the two.

Also Read | What helped Vikram lander to soft-land on the moon 

Once the sun sets on the moon after the completion of one lunar day, temperature could plunge below minus 200°C.

“The temperature there goes down to -200 degrees [Celcius]. In such an environment, there is no guarantee that the battery, electronics will survive, but we did some tests and we get the feeling that they will survive even in such harsh conditions,” Mr. Somnath had said earlier.

Since their landing on the moon on August 23, Vikram and Pragyan have carried out many in-situ measurements like confirmation of the presence of Sulphur in the region, and detecting the presence of minor elements, among others.

Vikram also achieved a significant milestone as it successfully undertook a hop experiment when the lander on command fired the engines, elevated itself by about 40 cm, and landed safely at a distance of 30–40 cm away.

Also Read | Chandrayaan-3 | Vikram hops on the Moon and lands safely

This successful hop experiment and kickstart could have significant bearing on the future missions which are launched with an objective to bring back samples from the moon and also future human missions to the moon.

If ISRO manages to wake up Vikram and Pragyan it would be a bonus for the space agency as it would be hoping to carry out some more experiments on the moon.

The Chandrayaan-3 spacecraft was launched on July 14 and touched down on the lunar surface on August 23, making India the fourth country to successfully land on the moon, and the first nation to touch down on the polar region of the moon.

On July 22, 2019, India successfully launched Chandrayaan-2, the second mission to the moon. Twenty-two days later (August 14), after a series of orbit raising manoeuvres, the spacecraft finally escaped the earth’s gravity and followed a path towards the moon. Six days later, Chandrayaan-2 was successfully inserted into lunar orbit. Finally, on September 2, the Vikram lander separated from the Orbiter, performed two de-orbit manoeuvres and on September 6, began its descent to the moon’s surface. The descent went as planned up to an altitude of 2.1 km from the Moon’s surface before communication from the lander to the ground stations was lost. The Vikram lander had apparently crash-landed on the Moon. 

Soon a national-level failure analysis committee headed by Dr. V. Narayanan, Director of the Liquid Propulsion Systems Centre (LPSC), was formed with experts drawn from national institutes and ISRO to study the cause of failure and to propose necessary corrections. The committee pinpointed three crucial mistakes that had happened in succession resulting in the crash.

There are four important phases before the touchdown on the moon — the rough braking phase, the attitude-hold (orientation) phase, the fine braking phase, and the landing phase.

Cause of crash

During the rough braking phase, the velocity of the lander was successfully reduced to a maximum. The problem with the touchdown began when the Vikram lander entered the second phase — the attitude-hold (orientation) phase. During this phase, the thrust had to be maintained at half the level. “But when the engines were commanded to provide half the thrust, the achieved thrust was more than half. The dispersion level [variation in the thrust] was more than what we had assumed during the pre-flight simulations,” explains Dr. K. Sivan, former Chairman of ISRO under whose watch the Chandrayaan-2 was launched in 2019.

The guidance system was supposed to have halved the thrust but it malfunctioned. “The guidance system was not designed to handle large dispersions, and this resulted in the guidance system malfunctioning leading to full thrust being given to the lander,” says Dr. Sivan. “At the end of the attitude-hold phase, the altitude and velocity were very different from the expected values. The guidance-system malfunction was the second crucial error.” 

According to Dr. Sivan, during the fine braking phase, the system was trying to correct the large errors. The large-scale corrections to velocity and altitude demanded large orientation manoeuvres. Changes to orientation are carried out by the control system, but unfortunately the control system was not designed to produce large changes. “Even though there was a large demand for orientation change, the control system restricted the rate. As a result, the control system was unable to provide the necessary large corrections to orientation,” Dr. Sivan says. “The control system was taking more time to correct the orientation due to rate restriction. But by that time the lander had reached the moon’s surface.” This resulted in the lander crashing on the moon.

The crash was caused by three mistakes — the thrust (dispersion level) was more than assumed for design, the flaw in the guidance system resulted in more thrust being given, and the rate restriction in the control system failed to make large-scale changes in the orientation. “The Chandrayaan-2 mission would have been a success if any of the three errors was not there. The three cumulative errors led to the failure,” he says.

Correcting the mistakes

Taking the learnings from Chandrayaan-2 failure, ISRO corrected for all the three major mistakes in the latest mission — the system was corrected to ensure extra dispersion does not happen, the guidance system was corrected, and the restriction in the control system was removed. “These were the major corrections in Chandrayaan-3 lander.

Redundancy was also built into Chandrayaan-3 lander in terms of extra sensors, and extra propellant to allow it to travel to an alternate landing site, if required. And the landing area was expanded from a narrow patch of 500 metres x 500 metres to a 4 km x 2.4 km region.

In addition, other improvements suggested by the failure analysis committee were also incorporated in the Chandrayaan-3 mission.

Extra fuel, sensors and stronger lander legs designed for higher landing velocity led to a net increase in the weight (about 250 kg) of the lander. Since Chandrayaan-3 was not carrying an orbiter like its predecessor, it became possible to accommodate the increased weight.

“Increased weight of the lander meant that a single engine was not sufficient. So the central engine was removed and two engines were used for landing,” Dr. Sivan says. “The central engine was added in the earlier mission as it was suspected that dust stirred by other engines would affect the electronic components. But our analysis found that dust wasn’t a problem.”

File picture of Chandrayaan-3 Vikram lander.
| Photo Credit: ISRO

The Indian Space Research Organisation (ISRO) landed on the Moon on August 23, 2023. This monumental achievement firmly cemented India’s position as one major players in the space community. Since then Chandrayaan-3 has found sulphur, a temperature difference of 50°C between the surface and 10 cm below the soil and even landed safely after the Vikram lander ‘hopped’ 30-40 cm away. Here are some video clips that capture the journey of Chandrayaan-3.

August 5 | A view of the moon as Chandrayaan-3 enters lunar orbit

On August 5, Chandrayaan-3 achieved a crucial milestone by completing Lunar Orbit Insertion (LOI). This was the third time that ISRO successfully inserted a spacecraft into the lunar orbit. The video clip shows the lunar surface as the Chandrayaan-3 spacecraft enters the orbit.

August 15 | Lander Position Detection Camera captures images of the moon

This video clip shows a range of pictures of the rugged lunar surface captured by Chandrayaan-3’s Lander Position Detection Camera while in the moon’s orbit.

August 17 | The moon as seen by the Lander Imager Camera 1

The video clip shows the Chandrayaan-3 gliding over the moon. The images in the video was captured by the Lander Imager Camera 1 right after the Propulsion module separated from the Lander Module on August 17. The video also showed the craters on the moon’s surface such as the Fabry crater and Giordano Bruno.

August 20 | The moon as seen by Lander Imager Camera 4

The Lander Imager Camera 4 aboard the Chandrayaan-3 spacecraft captures the pockmarked lunar surface as it orbits closer to the moon. Portions of the spacecraft is also visible in the video.

August 23 | Chandrayaan-3 lands on the Moon

On August 23, Chandrayaan-3 finally descended on the lunar surface. The video clip shows the footage of the Vikram lander on the Moon’s surface followed by the deployment of the rover named, Pragyan, as it rolled down the lander ramp and executed a turn on the lunar surface. The video clip also shows a simulation of the Chnadrayaan-3 spacecraft soft landing on the moon as a visual depiction.

August 29 | Chandrayaan-3 conducts experiments

On August 29, ISRO released two more videos showing the instruments onboard the spacecraft conducting experiments. The video clip also shows the Vikram lander camera recording Pragyan, as the rover rotates on the lunar surface.

This particular video captured by lander shows Pragyan operating an Alpha Particle X-ray spectrometer which is used to analyse the chemical composition of a sample.

File picture of Chandrayaan-3 Vikram lander
| Photo Credit: ISRO

ISRO on Monday said the Vikram lander of Chandrayaan-3 successfully underwent a hop test when it made the soft-landing again on the lunar surface.

On command it (Vikram lander) fired the engines, elevated itself by about 40 cm as expected and landed safely at a distance of 30 to 40 cm away, ISRO said in an update on ‘X’.

Noting that the Vikram lander exceeded its mission objectives, ISRO said the importance of the exercise was that this ‘kick-start’ enthuses future sample return and human missions.

“Vikram soft-landed on the moon, again! Vikram Lander exceeded its mission objectives. It successfully underwent a hop experiment. On command, it fired the engines, elevated itself by about 40 cm as expected and landed safely at a distance of 30-40 cm away,” ISRO said in a post.

“Importance?: This ‘kick-start’ enthuses future sample return and human missions! All systems performed nominally and are healthy. Deployed Ramp, ChaSTE and ILSA were folded back and redeployed successfully after the experiment,” the space agency added.

India scripted history by soft-landing the Vikram lander of Chandrayaan-3 on the lunar surface on August 23.

India became the fourth country to touch the lunar surface and first to ever reach the south pole of the moon.

New Delhi:

Days after Chandrayaan-3’s successful moon landing, the Vikram Lander has “soft-landed” on the lunar surface again, the Indian space agency said today. 

“Vikram Lander has exceeded Chandrayaan-3 mission objectives and successfully completed a “hop experiment”,” said the Indian Space Research Organisation (ISRO).

“On command, it fired the engines, elevated itself by about 40 cm as expected and landed safely at a distance of 30 – 40 cm away,” ISRO said.

Chandrayaan-3 Mission:
Vikram soft-landed on , again!

Vikram Lander exceeded its mission objectives. It successfully underwent a hop experiment.

On command, it fired the engines, elevated itself by about 40 cm as expected and landed safely at a distance of 30 – 40 cm away.… pic.twitter.com/T63t3MVUvI

— ISRO (@isro) September 4, 2023

ISRO said this achievement “kickstart enthuses future sample return and human missions.”

Last week, the Chandrayaan-3 mission’s Pragyan rover was “set into Sleep mode” but with batteries charged and receiver on.

“Hoping for a successful awakening for another set of assignments. Else, it will forever stay there as India’s lunar ambassador,” the space agency said.

India made history as the first country to land near the south pole of the moon with its Chandrayaan-3 lander last month.

Chandrayaan-3’s soft, textbook touchdown after a failed attempt in 2019 has sparked widespread jubilation in the country. The landing, which came just days after a Russian lander crashed in the same region, is being seen as India’s greatest scientific feat.

The country has been steadily matching the achievements of other space programmes at a fraction of their cost. ISRO’s first Sun mission, Aditya-L1, was launched successfully last week. The key objectives of the mission are understanding the coronal heating and solar wind acceleration.

ISRO is slated to launch a three-day crewed mission into Earth’s orbit by next year. It also plans a joint mission with Japan to send another probe to the Moon by 2025 and an orbital mission to Venus within the next two years.

An illustration of Chandrayaan-3’s Pragyan rover roaming on the lunar surface
| Photo Credit: PTI

The ISRO on Thursday said that another instrument onboard the Chandrayaan-3 rover Pragyan has confirmed the presence of Sulphur (S) in the south polar region. On August 28, the Laser-Induced Breakdown Spectroscopy (LIBS) instrument onboard Pragyan confirmed the presence of sulphur in the region unambiguously. Now the Alpha Particle X-ray Spectroscope (APXS) instrument has also confirmed the presence of sulphur.

“Another instrument onboard the Rover confirms the presence of Sulphur (S) in the region, through another technique. The Alpha Particle X-ray Spectroscope (APXS) has detected S, as well as other minor elements. This finding by Ch-3 compels scientists to develop fresh explanations for the source of Sulphur (S) in the area: intrinsic?, volcanic?, meteoritic?,……?.” ISRO posted on X (formerly Twitter).

ISRO said that the APXS instrument is best suited for in-situ analysis of the elemental composition of soil and rocks on the surface of planetary bodies having little atmosphere, such as the Moon.

It carries radioactive sources that emit alpha particles and X-rays onto the surface sample. The atoms present in the sample in turn emit characteristic X-ray lines corresponding to the elements present. By measuring the energies and intensities of these characteristic X-rays, researchers can find the elements present and their abundances.

“APXS observations have discovered the presence of interesting minor elements, including sulphur, apart from the major expected elements such as aluminium, silicon, calcium and iron. It may be recalled that the LIBS instrument onboard the Rover also confirmed the presence of sulphur. Detailed scientific analysis of these observations are in progress,” the space agency said.

APXS is developed by the Physical Research Laboratory (PRL), Ahmedabad, with support from the Space Application Centre (SAC) Ahmedabad, whereas the U.R. Rao Satellite Centre (URSC), Bengaluru, built the deployment mechanism.

The ISRO said that Pragyan, with its scientific instruments, is trying to find answers to questions like “What are lunar soil and rocks made of in the south polar region and how’s it different from other highland regions?”

The ISRO also released a video showing an automated hinge mechanism rotating the 18 cm tall APXS, aligning the detector head to be approximately 5 cm in proximity to the lunar surface. The video is captured by the lander camera.

The ISRO also shared a video of the rover rotating in search of a safe route which was captured by a lander imager camera.