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Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012An Interview with Shri O P N CallaFormer Area Chairman, CSA, SAC/ISROQuestionnaire: Compiled By Ms Arundhati MisraSignatures: Sir, ISRS-AC is extremely fortunate tohave an eminent personality like you for theinterview session. You are known as the Father ofIndia’s Microwave Remote Sensing activity. Whatprompted you to think about this field of activityduring a time when optical remote sensing systemslike LANDSAT, TM, and SPOT etc. were ruling theworld?any technology or work related to science andtechnology has been done elsewhere then we cando that without any difficulty.” If the technologyhas not been developed anywhere else then weshould initiate it and take the development aschallenge and work very hard to achieve the same.This is how I was able to initiate work hither tounknown to us in India and that is “MicrowaveRemote Sensing”. I very humbly submit that thiscould be possible because I got support from thepolicy makers.Prof. Calla: It was the time (1972) when RemoteSensing was getting introduced in ISRO and at thattime the Microwave division of ISRO was formedwith a view to work on Microwave Systems. LaterMicrowave Division became part of SpaceApplications Centre. This was the time when onglobal scene the Microwave Remote Sensing wasjust getting introduced and various universities andresearch laboratories were being funded by SpaceAgencies to work in the field of Microwave RemoteSensing. For that the Ground based and airbornecampaigns provided and generated inputs forfuturistic Microwave remote Sensing. Looking intoall these developments taking place in NASA, USAand CNES France, DFVLR Germany and USSR Icould see the future of Microwave Remote Sensingin our country as I had always worked for futuristicapplications ahead of times in which we wereworking. I had always even from any college dayswould venture during that time. But I always tookchallenges of taking new possibilities and tried toconvince the policy makers. It was not easy but Icould succeed in some fronts. The MicrowaveRemote Sensing was ONE. The potential ofMicrowave Remote Sensing was definitely visible tome because only using Microwave sensors one cantake image or get target information in night. Mostimportant aspect of initiating Microwave RemoteSensing was that I was firmly convinced that futureis in Microwave Remote Sensing and this was partof my way of working that I always believed intaking challenges. My way of working is that “IfThis philosophy I follow even today while workingat ICRS. I preach my colleague this and my they dofollow this.Signatures: I remember that there was aprogramme called MRSP (Microwave RemoteSensingProgramme)during1986-87. Theprogramme was envisaged as a multi sensormicrowave satellite like SEASAT-A and ERS, withfour proposed sensors of SAR, Scatterometer,Altimeter and MW Radiometer on board. Can youkindly elaborate a little bit on that for the youngergeneration readers of ISRO?Prof. Calla: Yes you are right in year 1986-87,Microwave Remote Sensing programme was givena separate status and I was made ProgrammeDirector of this Microwave Remote SensingProgramme. I was given a team to work with andfirst task was to prepare a Microwave RemoteSensing Programme document. During that wewere looking into the possibility of sensorcombination to meet the requirement of NationalNatural Resource Management System (NNRMS).The group of persons supporting me were fromSAC and ISAC both hardware and application aswell as to look into the space craft and sizing ofpayloads as per the applications.The document was generated where applications11

Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012were the guiding force. We looked at the frequency,polarization and sensors type. Here I should clarifyin short that there are two types of Microwavesensors, they are Passive that includes Non Imagingand Imaging Radiometers that could be TotalPower, Dicke and Noise Injection Radiometer andActive Sensors which include Non Imaging RadarScatterometers, Altimeters and Imaging SideLooking Radar (Airborne) and Synthetic ApertureRadar (SAR). In the programme document welooked at all the applications of Microwave RemoteSensing that included Land, Ocean andAtmosphere. Then we further subdivided theseapplications and looked at the requirement ofspatial resolution, the repetition required for eachapplication and the swath width to cover largeareas.The Microwave Remote Sensing Programmedocument included the ground truth studies,airborne campaign method for data productsgeneration including hardware requirement and theutilization aspect of Microwave Remote SensingProgramme.Signatures: What is your reaction to RISAT-1?What would be the expectation from such acomplex system? Would you suggest a repeatmission for the same, in future? Why?Prof. Calla: The RISAT is a MILE STONE in thejourney of Microwave Remote Sensing activities ofINDIA. It is the culmination of the efforts of thegroup of people, who dreamt of having MicrowaveRemote Sensing as one path of providing thesolution to the last man of the society that may be aFarmer in the field, Fisherman in open seas, aPerson living in the snow bound areas and the mostneedy person of the society by giving the requiredinformation to help him live better than what he isgoing through day to day. This is a dream that hasbeen fulfilled for me and for many others.Based upon the literature survey and with our ownexperience of applications and available technologystatus, the programme was formulated. This was acomprehensive programme that included Spaceborne systems, airborne campaign as well asground studies.The Microwave Remote Sensing satellites that wereproposed were multi sensor satellites. Theprogramme document was written in 1986-Feb andby that time Sir A, Sir B and Sir C have been up inspace. Looking into the application requirementmulti sensor satellites were proposed.For this singular achievement by the ISRO scientistsI BOW to all includes ISRO CHAIRMAN,DIRECTORS of ISRO centers and all theScientists/Engineers who have contributed to thesuccess of RISAT. The date 26th April 2012 will beremembered as the Golden Day in the history ofMicrowave Remote Sensing in India and the 1stMay 2012 on which the images for the FIRST timefrom RADAR a Microwave EYE were obtained willgo in the history as the day of remembrance for all.The satellites were Microwave Remote Sensing 1A,Microwave Remote Sensing 1B, Microwave RemoteSensing 1C and Microwave Remote Sensing-2.These were to carry multi frequency Radiometersand multi polarization SAR and later multifrequency and multi polarization SAR, Altimeterand Scatterometers. Microwave Remote Sensing-2was planned with Terra Hertz radiometers alongwith active sensors like SAR, Scatterometer andAltimeter.Thus I have given you in very brief about theMicrowave Remote Sensing Programme but thisdocument is a comprehensive document which isstill valid in terms of the thought process and themethodology covering from objectives toachievement of the objectives.The RISAT-1 is a multi functional full polarimetrySynthetic Aperture Radar of the STATE OF THEART technology. This is a very complex system andthe successful operation of this Radar in space isindicative of the level of technology, our scientistsand engineers have developed which is as good asanywhere in the world and achieving resolution of3 meter in STRIP MAP MODE is as good asanywhere else in the world.12

Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012The RISAT which has four modes of operation withvarying resolution and swath is a complex systemand best resolution of 3m with 30 Km swathprovides to the application Scientists theopportunities to work for different applications. Allthe application Scientists have been eagerly waitingto have the data products of RISAT.data for various applications. As we know thatmicrowaves have unique capabilities in terms ofpenetration through clouds, day and nightavailability of data, soil moisture and penetrationthrough vegetation. Because of these uniquecapabilities users of these data for land, ocean andsnow studies will need microwave data on regularbasis. My experience of using MSMR data forSNOW studies, SMOS data for Soil Moisture andSalinity and SSMI and AMSRE data for land, oceanand snow has created appetite for getting more andmore data for the utilization of microwave data ofboth passive and active sensors on regular basis.This has happened to us at ICRS who are usingthese data in limited way but for those scientistswho will be using these data on operational or semioperational mode, these data will be of utmostimportance and they would like to receive thesedata regularly.The RISAT utilization plan in which different Govt.agencies, Educational Institutions, Non Govt.Research organization in India are getting ready forutilizing the RISAT data.I can understand as the SAR of RISAT is veryComplex. So also the generation of data product forsuch a complex sensor will also be challenging and Iam sure my Colleagues at Space ApplicationsCenter will take this challenge and generate thedata products to be utilized by applicationScientists for Land, Ocean, Cryosphere andAtmospheric applications.Signatures: Sir, India is primarily a tropicalcountry with a very long coastline. Apart from theregular monsoon, a large part of the eastern andsouthern part of India is prone to the vagaries ofnature. The role of MW remote sensing during suchtimes does not need to be under scored. Yet we dosee a lacuna in developing and using MW sensors ina large scale in our country. Can you please give apossible reason as to why MW RS had taken a backseat in India during the early part of this century,when the whole world marched ahead?Now the question is whether we should haverepeat of RISAT-1. My personal view will be thatwe should repeat RISAT-1 but with littlemodification. In RISAT-1B, we should have alongwith the SAR at 5.35GHz couple of Radiometersoperating in frequency band 1.4GHz, 6.6GHz,10.65GHz, 18GHz, 21GHz and 37GHz. If there isweight constraint the choice of frequency could belimited. Then at least 1.4GHz, 2.5GHz, 21GHz and37GHz should be included. Another importantpoint is the time of launch. I suggest that RISAT-1Bshould be launched as early as possible because theapplication Scientists will need regular data fortheir applications projects.Prof. Calla: The Microwave Remote Sensingactivity in India was initiated in 1973-74. In factafter AUG 1972, when Microwave division of ISROwas formed which later became part of SAC, we gotpeople trained and that was the time whenMicrowave Remote Sensing was getting initiated allover the world NASA, CNES, DFVLR, USSR hadstarted working in the field of Microwave RemoteSensing. In India also more or less at the same timewe started working on ground based scatterometerin eighties but the golden opportunity we got wasthe start of Earth Observation Satellite (EOS) whichwas renamed as BHASKARA.In future we should have series of MicrowaveRemote Sensing Missions which will have thecombination of the Microwave Sensors both Activeand Passive. That will give us opportunity of usingMicrowave Remote Sensing for the applicationsrelated to Land, Ocean and Cryosphere as well asAtmosphereThe ARYABHATTA BUS was utilized for makingEOS. In this EOS we were able to get satelliteMicrowave Radiometer (SAMIR) accepted as one ofThe continuity of the programme is requiredbecause the users will start utilizing the microwave13

Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012the primary payload. The SAMIR in BHASKARA-Ihad three channels, two of 19 and one 22.235GHzradiometers and in BHASKARA-II we put 19, 22and 31GHz radiometers. They were launched in1979 (BHASKARA-I) and 1981 (BHASKARA-II).Then only in 1999 that we launched OCEANSAT-1with MSMR multi frequency scanning microwaveradiometer operating at 6.6, 10.65, 18 and 21GHz.Then we had OCEANSAT-2 with a scatterometeroperating at 13.4GHz and now in 2012, we haveRISAT, with Megha Tropiques launched in 2011having multi frequency radiometers working uptoTerra Hertz.Now time has come that in the area of rsities and the user agencies should getinvolved and more and more investment inMicrowave Remote Sensing is the need of the day.Signatures: There is a popular saying – ‘If you can’tbeat them, join them’. Taking cue from that, Iwould like to ask you, whether India should jointhe global community (international cooperation)in developing microwave remote sensors, especiallyfor the high frequency bands? Or should we ratherstay apart, develop our own industries and becomeself sufficient in building such complextechnologies? Why?Yes, I agree that during these years that is from1979-2012 almost 33/34 years, we could launch onlythree satellites whereas world over launching ofERS, ENVISAT, RADARSAT, JERS, Poseidon toname a few have been working in space withpassive and active microwave sensors but we werenot able to keep the same pace. Finally I can sayIndia has arrived now and there is a popular saying“BETTER LATE THEN NEVER”.Prof. Calla: This popular saying ‘If you can’t beatthem, join them’ is applicable when one finds thatthere is an urgent need of taking on the applicationsthat need to be answered to meet the requirementof the country. The joining hands with othersshould always be done at equal level. We should bestrong in areas to a level that if required we shouldbe able to take up the activity in case of thecollaborator agency has some difficulty in meetingthe schedule. There is no harm in collaborating withthe agencies those who are willing to collaboratewith us. In the space programme, this is true forevery country. Recently in COSPAR meeting ISROChairman has indicated that ISRO will collaboratewith other countries and this is indeed excellentidea and we should do this for the good of ourpeople.I agree with you and your concern is right. Lookingat the geographical location of our country forocean studies, Cryosphere studies and quite a fewLand applications the microwave remote sensingonly has answer. I feel now having started withRISAT, (the RADAR Imaging Satellite). We havearrived and our technology is as good as thatavailable in other countries. The unique capabilitiesof Microwave Remote Sensing has stand aloneapplications in some areas does provide answerwhich are of great value for NNRMS. As wasmentioned in the programme document ofMicrowave Remote Sensing Programme preparedin 1986 the role of Microwave Remote Sensing wasenvisaged for NNRMS. Now we have to move fastand invest more in Microwave Remote Sensingactivities all over India that includes ISRO anduniversities and Research Institutions. The area ofactivities of Microwave Remote Sensing has to beincreased and more and more Institutions of ourcountry should be involved in enhancing theutilization of Microwave Remote Sensing data.We should develop these complex technologies athigher frequencies like Terra Hertz in very nearfuture. The present example of Megha Tropiqueswhere sapphire pay load working in THz has beensupplied by CNES but in future ISRO shoulddevelop these technologies to become self reliant.Another point is that the MICROWAVE REMOTESENSING activity is for helping our countrythrough National Natural Resource ManagementSystem and the needs as well as the solutions forproviding answers to the demand put in by theNNRMS will not be same for agencies outside ourcountry. Every Nation has their own priorities andso for meeting our priorities we have to be on our14

Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012own. We cannot depend on the collaboratingagency and wait for their inputs for meeting ourneeds.At that time Dr. Keith Raney and Dr. WolfgangMartin Boerner had not proposed the Hybridpolarimetry and fully polarimetry sensors and sothese concepts were not available but we did planthe linear multiple polarization that is HH, VV, HVand VH.I would say India should have options open andshould have participation in Internationalcooperation but should not be at the cost of ourown programmes and the National needs.It is true that after Shuttle Imaging Radar there havenot been such operational satellites, But the ERS-I,ERS-2, ENVI SAT, RADARSAT-1, RADARSAT-2have been providing the data of Activesensors(synthetic aperture Radar) and separatelyAltimeter like Poseidon has been available. Also theseparately passive sensors in NIMBUS, SSMI,AMSR-E and now SMOS and SMAP in future haveradiometers. SMAP has both Active and Passivesensors. I think this multi sensor approach wasdropped possibly because non availability oflauncher which could carry such heavy payloadweighing some Tons, in case of our own RISATRadar Imaging satellite is the heaviest payloadlaunched by ISRO till date. In case of MicrowaveRemote Sensing the requirement of the launcherswhich could carry heavy satellites is a majorconcern. Thus the payloads are separated and asISRO did they launched Oceansat-I withradiometers, in 1999 and OCEANSAT-2 withscatterometer in 2000 and now planning to launchSARAL with altimeter. The OCEANSAT-2 is givingvery good data and is in operational mode. I amvery much hopeful that RISAT which has givenexcellent images of our mother land India will alsobecome operational very soon.Lastly as said earlier it is always advisable to havecollaboration with other countries which will be forthe Good of our Country.Signatures: How do you foresee the future ofMicrowave Remote Sensing using multi frequency,and multi polarization sensors (for SAR), fromspace borne platforms, in operational mode?Shuttle imaging Radar, SIR-C was the only suchmission, but none afterwards for the routineoperational satellites.Prof. Calla: To me it is crystal clear that the futureof Microwave Remote Sensing is in Multi-frequencyand Multi-polarization SAR as well as Multifrequency Radiometers from space borne ters.You can see as early as in 1986 in the MicrowaveRemote Sensing programme document we hadproposed multi-frequency multi-polarization SARin MRS 1-C. This had multi-frequency and multipolarization SAR operating at frequencies – C, L orX with like and cross polarization and multifrequency Radiometers operating at 6.6, 10.6 , 18,21, and 37 GHz in horizontal and verticalpolarization along with scatterometer and Altimeterboth operating in Ku band of Microwavefrequencies.Signatures: ‘Seeing is believing’. Hence opticalimages are not only beautiful to see, but easier tointerpret, as it is the same as that provided by ourvision sensor-‘netra’! Microwave images from SARsensors or data from Microwave sensors such asscatterometer, radiometer etc. are not directlyunderstandable to the normal users. Advancedtechniques and rigorous analysis tools are neededto utilize such data. However, the scientificcommunities all over the world have been workingrelentlessly during the last three decades to developtools to render such data more and more useful tothe end user community .What is your vision aboutthe means by which the Microwave Remote Sensingdata can be of maximum use to the users in India?Also the MRS-2 satellite was similar to MRS 1-C interms of Active Sensors and there were additionallower & higher frequency channels for Radiometerthat included 1.6, 6.6, 10.65, 18, 21, 31, 37, 50.3,53.74, 57.95, 183.1, 183.3, and 183.5.Thus you can see that in 1986 itself we had thoughtof having multi-frequency, multi-polarizationsensors to be placed on the space borne MicrowaveRemote Sensing missions.15

Signatures, Newsletter of the ISRS–AC, Vol. 24, No.2, Apr-Jun 2012Signatures: How do you foresee the future ofRemote Sensing in India using THz bands?Prof. Calla: I agree “Seeing is believing” but Iwould like to be excused for differing from yourpoint of view because the SAR images are as goodas optical images even at first look. I have seenimages obtained by RISAT and they have beencompared with other optical sensors onboardRESOURCESAT and I can say that they are as goodas that obtained from RESOURCESAT andespecially of Gangotri Glacier RISAT give muc

Dr. Mehul Pandya Dr. Abha Chhabra Dr. Arun Bhardwaj (a) Room No. 4372, Space Applications Centre (SAC), ISRO, Ahmedabad-380015. Email: parul@sac.isro.gov.in Phone: 91 79 2691 4372 Simulated Circular polarimetric data C/o Indian Institute of Remote Sensing, 4, Kalidas Road, Dehradun - 248 001, India. Fax: 91 135 2741 987 Web: www.isrsindia.org