(Image coutesy: Pallava Bagla)

J A Kamlakar, is a specialist on LASERS and on Chandrayaan-1 he is flying an instrument that will help measure the height variation of the moon surface, by shining a high power laser beam down on the moon surface. This laser ranging instrument will help Indian scientists zero in on locations where to attempt landings in future missions. He is the Deputy Director for Sensor Development at the Laboratory for Electro Optics Systems, in Bangalore.

Pallava Bagla: Kamlakar, what does this instrument do and how will it work on Chandrayaan?
J A Kamlakar: Laser based instrument is one of the payloads which we are flying for the first time on Chandrayaan

Pallava Bagla: First time on Chandrayaan? Chandrayaan is also the first time.
J A Kamlakar: For that matter on any of our space missions. What it does is the laser from this unit goes on to 10 hz rate, high power laser beam, pulsed laser beam goes on from Chandrayaan moon and then reflected back. Reflected beam is actually received by this

Pallava Bagla: Oh this, this mirror receives the beam?
J A Kamlakar: This 200 mm telescope, it is optical telescope, corresponding data has got detectors, and to receive that signal, and the received signal is processed, and with this process we can actually identify the terrain, topography.

Pallava Bagla: Oh so you can measure the height difference?
J A Kamlakar: Height difference..

Pallava Bagla: By sending it and bringing it back you can measure the ..so you can actually measure how high a mountain or a crater is on the moon? Is that correct?
J A Kamlakar: That's how . that is how it is done. The light, velocity of light is known, so since we know it, we can always determine what is height variation on the surface of the moon. Using that information, science, we can further extend it to gravity modeling and in turn we can actually do the cluster mapping of the moon.

Pallava Bagla: So how unique is this? How many countries have this technology?
J A Kamlakar: Hardly few moon missions have actually flown a laser based altimeter. For that matter the Clementine which is flown by NASA, did not cover the polar region, wherein we are actually targeting to cover that area

Pallava Bagla: Oh you are going over the poles again and again?
J A Kamlakar: And then because we are having multiple orbits over that, we'll be covering the entire polar region at 100 km altitude for the first time. So this instrument is going to provide us the information over the poles, very in detail, compared to Clementine. Also the Clementine

Pallava Bagla: What is the height difference? What is the minimum variation?
J A Kamlakar: Variation as from the literature of earlier missions what we know is that depth of crater can go as low as 10 km down compared to some of the hillocks which are around 6 km variation, and the diameter is also very large for these craters, so as we go, because of the fifty meter, basically this one can resolve up to 50 m spot on the moon, so we can measure continuously line, the topography line of 50 m over moon basically of

Pallava Bagla: So you will get one line at a time which you will match and make a map?
J A Kamlakar: Match and make a map, and then we'll also, because of the orbit variation, orbit shifts, okay, so then we can get again one more line of information at 50 m. But the basic height resolution we can get better than 5 m.

Pallava Bagla: 5 m difference?
J A Kamlakar: Yes. So the craters, say for example 10 km and the hillocks are at 66 km, so we should be able to actually measure such a vast variation on the topography with a 5 m resolution.

Pallava Bagla: So will this help us find where to put the lander and the rover when we land the Chandrayaan-2?
J A Kamlakar: Once we complete the entire mapping, it will take about, the Polar Regions take only about 2-3 months whereas the equatorial regions take a longer duration because of the diameter. By the end of one year we should get sufficient elevation information wherein we can make a digital elevation model of the entire what we are planning to

Pallava Bagla: So up and down, everything, topography
J A Kamlakar: Up and down, what we are trying to do is, the moon radius is also not uniform. So that also gives certain information about gravity modeling from radius of the moon, varies along the equator as well as the poles. All this information can be mapped. It is not easily available although many, 2-3 countries might have flown this instrument, like only NASA so far and then Selene recently and maybe Chinese, but the information, science information based on the laser ultimately is not easily available. So we need to do it. And then we will be doing the digital elevation modeling five degree by five degree maps of this entire thing by which we can determine a lot of science information. Also the instrument has got capability to measure .

Pallava Bagla: Sir, will it find out where we can land upon the moon?
J A Kamlakar: Of course.

Pallava Bagla: It can..
J A Kamlakar: It can.

Pallava Bagla: It can find that out. So that later when you want to put an Indian on the moon from our maps we can say this is the place where you go, there is flat terrain?
J A Kamlakar: Yes, the entire terrain, flat as well as surface, slopes of the craters, how deep they are, we can definitely determine, and the advantage of this is on normal visible cameras can only visualize where the actual sun information is aware so they can, they need visible light.

Pallava Bagla: Oh you are sending your own light?
J A Kamlakar: Own light. So it can map places where the regular cameras cannot see. So this one can see where it is not illuminated.

Pallava Bagla: So what was the big challenge in this developing..
J A Kamlakar: See, the one major challenge was the laser. Laser is a major challenge. Laser is a big challenge, you know space based laser and the developing, having a solid state laser to this high power, that too working in a space environment with high vacuum, and then cold and hot environmental, it is very-very, you know one of the challenges, and that has to work for one billion shots of information continuously. It is non-stop, the information what we are trying to gather. So the laser has to work for its entire moon life, mission life, which is two years.

Pallava Bagla: Sir, how much time did you take to develop this?
J A Kamlakar: We have taken about four years to come to this..

Pallava Bagla: To develop this?
J A Kamlakar: To develop this. Various intricate parts are there - the laser, the optics, then the receiver electronics and the, you know subsequent processing electronics, and then characterizing the engineering model.

Pallava Bagla: Did you enjoy doing this?
J A Kamlakar: Of course. We all did our challenges. Everyone, what we all do we enjoy. That is why we definitely enjoy what we are doing and that is why we are taking up more and more challenging activities for future, Chandrayaan-2 and Mars mission, subsequently satellite, lot of interest is there in the science team also now, so we are definitely interested in doing more and more laser based ..we enjoyed. And definitely to give us so far satisfactory results and soon after the launch we hope to have much more science information that gives us the maximum mappings.