PRL - BEGINNING & GROWTH

Countries have to provide facilities for its nationals to do front rank research within the resources that are available.
It is equally necessary having produced the men who can do research, to organize task oriented projects for the nation's practical problems.
                                                                        .......... Vikram A. Sarabhai.

The Physical Research Laboratory, which is in the fifth decade of its existence, was founded by Dr. Vikram A. Sarabhai in November 1947 following an agreement between the Ahmedabad Education Society and Karmakshetra Educational Foundation. The laboratory had its humble beginning in the M.G. Science Institute and its research programme then were oriented and pioneered by the scientific interests of its principal workers - Dr. Vikram A. Sarabhai, PRL's founder and Prof. K.R. Ramanathan, its first Director.

The laboratory grew out of a quest and a dream of Dr. Sarabhai. The quest was to know more about the then mysterious particles of very high energy, known as the 'Cosmic Radiation' that have been known to bombard the earth's surface. The dream was for establishing a front rank institute at Ahmedabad for conducting basic research in cosmic rays and few other selected areas of Physics. While working for his doctoral thesis, Dr. Sarabhai had this vision and on his return to India from Cambridge, after his Ph.D., he set about the task of setting up such laboratory in "RETREAT" where he conducted experiments on Cosmic Rays.  This laboratory was funded by the Karmakshetra Educational Foundation created by his parents for carrying out advanced  educational activities of all types.

Born on August 12, 1919 Dr. Vikram Ambalal Sarabhai obtained the Tripos in 1939 from St. John's College, Cambridge. With the beginning of the Second World War he returned to India. He joined the Indian Institute of Science, Bangalore, to work with Professor C.V. Raman. Dr. Sarabhai began work on cosmic ray intensity variations which later led him directly into the studies of interplanetary space, solar terrestrial relationships and geomagnetism. In 1945, he returned to Cambridge University to continue investigation on cosmic rays and obtained a Ph.D. degree in 1947 with a thesis on "Cosmic Ray Investigation in Tropical Latitudes".
Dr. Sarabhai's laboratory at RETREAT soon attracted the attention of the Ahmedabad Education Society and in November 1947,  Physical Research Laboratory (PRL) was founded following an agreement between the Karmakshetra Educational Foundation and the  Ahmedabad Education Society. Prof. K.R. Ramanathan joined as the first Director of the laboratory after retiring from the India Meteorological Department. The scope of the research activities was expanded by adding a department of Atmospheric Physics which was Prof. Ramanathan's main scientific interest. The laboratory started with few research students and assistants in a
few rooms of the M.G. Science Institute. Soon a large devoted group of research scholars joined , many of whom have now become leaders in their respective fields of research. Dr. Sarabhai continued to guide and shape the destiny of PRl, first as a Professor of Cosmic Rays and then as its Director during 1965-71.

As the laboratory grew the overall scientific programmes evolved towards an integrated study of the different kinds of radiations which  are received on the Earth, and of their geophysical consequences. In order to carry out such a programme satisfactorily, it was felt necessary to add theoretical physics, radio physics and an electronic group to the then existing cosmic ray and atmospheric physics groups. The Atomic Energy Commission of the Government of India was approached for financial assistance to create the above groups and the request was granted in 1949.

In 1950, a Council of Management for PRL was formed with representation from the Ahmedabad Education Society, the Karmakshetra  Educational Foundation, the Ministry of Natural Resources and Scientific research, the Atomic Energy Commission and the Government of Bombay.

In 1951, Prof. Ramanathan established the ozone observing station at Mount Abu. The first observation of ozone using Dobson Spectrophotometer was carried out on 12 October 1951. Later this station was used for twilight and air-glow observations.

With expanding activities and an increasing number of workers, the need for a separate building became urgent. Land was provided by the Ahmedabad Education Society, adjoining the Gujarat University. The cost of the building was borne by the Ahmedabad Education Society and the Karmakshetra educational Foundation. The Ministry of Natural Resources and Scientific Research had made a generous grant of rupees one and half lakhs for equipments. The foundation stone of the laboratory was laid by the late Prof. C.V. Raman, Nobel Laureate on 15 February 1952. The first building on the campus was opened by the late Prime Minister Pandit Jawaharlal Nehru on 10 April 1954. A second floor to this building was added in 1960-61.

The year 1957-58 was the period of International Geophysical year and the scientists of PRL under the leadership of Dr. Sarabhai and Prof. Ramanathan actively participated in various scientific programmes chalked out for Earth Sciences including Geomagnetism and Cosmic Rays. These studies required the in-house development of electronic equipments and radiation detectors. PRL successfully  developed and put into operation Geiger-Muller Counters, Meson Telescopes, Dobson Spectrophotometers, Ionosonde, Photometers etc.

The PRL set up a research station at Gulmarg in Kashmir in 1955 for the measurements of cosmic ray intensities as well as atmospheric ozone and night airglow. The successful working of this station and the important results obtained there led to the establishment of  full-fledged High Altitude Research Laboratory at Gulmarg in 1963. In addition to Gulmarg, Dr. Sarbhai also had set up outstations of PRL at Kodaikanal and Trivendrum to continue the investigations of cosmic ray time variations.

After the IGY period a request was made to the Department of Atomic Energy (DAE) to support the laboratory's growing activities in the field of Space Research. The request was subsequently approved and the DAE gave substantial block grants to the laboratory. It was also decided that the laboratory would be managed through a council of management consisting of representatives of the Government of India, Government of Gujarat, Ahmedabad Education Society, Karmakshetra Educational Foundation and the Director of the laboratory. This was accepted by all parties and a quadripartite agreement on behalf of the four parties was signed on  February 5, 1963.

By the early sixties the use of satellites for exploring the Earth's environment had become quite common. It was foreseen by Dr. Sarabhai that the satellite technology  could play a seminal role in the advancement of education, agriculture, meteorology, defence and remote sensing of the Earth's resources. This led to the creation of the Indian National Committee for Space Research (INCOSPAR) in the Department of Atomic  Energy in 1962 with Dr. Sarabhai as the Chairman and eleven other scientific members which included several PRL scientists. Furthermore a rocket launching station at Thumba,  very close to the magnetic equator, was established. On the evening of 21 November 1963, the first scientific rocket went up from Thumba releasing sodium vapour and showing  up the winds and turbulence above 90 km. With nearly  all of the early rocket payloads having been fabricated here, PRL, rapidly became the centre for developing and building scientific payloads for use in rockets. In February 1968, the Thumba Equatorial Rocket Launching Station (TERLS) was dedicated by the then Prime Minister Smt. Indira Gandhi to the UN as the International Equatorial  Rocket Launching Station.

A satellite telemetry station was installed at PRL in 1961 with NASA's  collaboration. Recordings of the Faraday  rotation at 20, 40 and 41 MHz transmitted by the US satellites BE-B and BE-C were regularly recorded from 1964 onwards. In 1965 an Experimental Satellite Communication Earth Station (ESCES) was established with UNDP assistance.

In 1969 Indian Space Research Organization (ISRO) was created, with Dr. Sarabhai as its Chairman, under the Department of Atomic Energy to carry on national programmes of  Space Research and its applications to the social economic development of the country. With this in view, Dr. Sarabhai  initiated the Remote Sensing Programme with Prof. P.R. Pisharoty as its head. This later  became a major activity of the Space Applications Centre.

While he was in the midst of a very bold and vigorous  formulation of the space programme of the country including that of PRL, Dr. Sarabhai passed away rather  suddenly on December 30, 1971. He had combined in him the Directorship of PRL, the Directorship of the then Space Science and Technology Centre (SSTC) besides the Chairmanship of the Indian Space Research Organization (ISRO) and the Atomic  Energy Commission (AEC). However, for him PRL was his base, while PRL and its   scientists played a crucial role in the evolution of  the country's space programme.

After the sad demise of Dr. Sarabhai, Prof. M.G.K. Menon, Director, Tata Institute of Fundamental Research and Chairman, Electronic Commission, served as the  Director of the laboratory for ten months. He continued to be associated with the laboratory, first as a member and then as the Chairman of its Council of Management till January 1990.

The year 1972 was a landmark in the national space programme. In June 1972, the Space Commission and the Department of Space was created to develop the national space effort with Prof. M.G.K. Menon taking over the Chairmanship of the Space Commission. To develop and implement the ten year profile for space research as envisioned by Dr. Vikram Sarabhai, a  National Seminar on the Indian Programme for Space Research and Applications was held in Ahmedabad from 7-12 August, 1972. PRL served as the cradle of this programme.

Prof. Devendra Lal joined as the  Director, PRL in November 1972. Two new areas of research, which were his fields of interest, were added to the laboratory's scientific activities; (i) the studies of moon rocks and meteorites and (ii) the Earth Sciences. The moon and meteorite research was aimed at understanding the formation of solar system objects. The studies in Earth Sciences were focussed on the application of environmental isotopes to study surface processes such as the evolution of the Indian sub-continent, ocean circulation, groundwater movement and the palaeoclimate.

Prof. Lal was the Director of PRL during November 1972 - March 1983. During this period Professor Lal contributed immensely to the growth of PRL. Several new programmes in the fields of plasma physics, astronomy, atmospheric physics and earth sciences were initiated and nurtured during his tenure.

A new activity, namely the plasma physics activity which was initiated in 1968 developed rather vigorously during the seventies. This had twin objectives : (i) to provide a theoretical and laboratory support to the existing ionospheric and space research activities at PRL and (ii) to initiate a high temperature plasma research activity which may form the basis in the future of fusion-oriented research and development programme. The second part of the activity having been nucleated at PRL has since been separated from PRL as the institute for Plasma Research at Bhat, Gandhinagar.

Furthermore, having realized the important role that atomic and molecular reactions play in atmospheric  chemistry and astrophysics, another activity  on the studies of atomic and molecular reactions was initiated in the early seventies. This also has evolved considerably over the years.

Two major disciplines were initiated at PRL around  1975. They were (i) the infra-red astronomy and (ii) the interplanetary scintillation (IPS) studies. The major aim of the  infra-red astronomy group is to study the stars, the galaxies and molecular clouds and to understand the star formation processes as well as energy production and emission processes from active galaxies. Towards this a variety of sophisticated back end instruments to be used with telescopes were fabricated. An infra-red observatory was also planned to be set up at Gurushikhar with a 1.2 metre mirror-telescope with both Cassegrain and Coude foci.

Past studies of the radio emissions from the Sun as well as from solar flares and bursts have yielded important information regarding the  plasma processes in the Sun's atmosphere. These studies later culminated into the development  of the exciting programme of setting up three radio telescopes at Thaltej (near Ahmedabad), Rajkot and Surat. The main objective  of this 3-station telescope was to estimate the solar wind velocity by simultaneous measurements of scintillations of the radio sources with the three radio telescopes. The scintillations are produced by the interplanetary medium  through which flows the solar wind.

On August 12, 1974, the fifty fifth  birthday of Dr. Vikram A. Sarabhai, the Hari Om Ashram instituted at PRL a set of four awards named as "Shri Hari Om Ashram Prerit Award" to outstanding Indian scientists. The awards are given biennially  to outstanding Indian scientists for their contribution in the fields of Space Sciences; Space Applications; Electronics, Informatics, Telematics and Automation; and System  Analysis or Management. The awards are given to the distinguished recipients on August 12, the birthday of Dr. Sarabhai.

The Vikram Sarabhai Professorship was instituted at PRL in 1977 to provide a continuing stimulus to the young researchers at PRL and to expose them to the latest developments in the various areas of research through interaction with distinguished researchers around the world. The Institution of this professorship was made possible mainly through the funds provided by the Sarabhai Foundation, Karmakshetra Charity Trust (No. 2) and the Kasturbhai Lalbhai Charity Trust. This scheme provides for  inviting distinguished  scientists to spend  some time at PRL in delivering lectures, on topics of high current interest and participating in research programmes of the laboratory if possible. Under this scheme fourteen Vikram Professors have so far visited PRL.

In December 1981, the Department of Space took over the Udaipur Solar Observatory and entrusted its administration to PRL. The observatory was established in 1975 by the Vedshala Trust, Ahmedabad, in an island in Fatehsagar Lake, Udaipur. This site was chosen for its extremely good solar 'seeing' over long uninterrupted periods. Since its inception the solar observatory has been  engaged in exciting and 'front line' researches pertaining to the Sun.

On March 30, 1983 Prof. Devendra Lal stepped down from the Directorship and continued to be at PRL as a Senior Professor till his retirement. At present he is Honorary Fellow of PRL. On April 1, 1983 Prof. S.P. Pandya took over the Directorship of PRL. Some of the exciting programmes like the Plasma Physics Programme, the Infra-red and the Interplanetary  Scintillations matured during this period.

The mid eighties has been an important period in the history of  PRL. The building of the Gurukshikhar Observatory was completed around this period. The year 1985 - 86 was also the period of Comet Halley and the observations on Halley by out scientists marked the beginning of the astronomical observations from Gurukshikhar Observatory using the 14" Celestron Telescope. Final assembling and testing  of the 1.2m IR telescope is in progress and is expected to be completed soon.

During the year 1986 - 87, the three radio telescopes at Thaltej, Rajkot and Surat, which constituted the interplanetary scintillation network, became operational.

The K.R. Ramanathan Memorial Lecture was instituted at PRL in 1987 in honour of Professor  K.R. Ramanathan. This lectureship provides for inviting distinguished meteorologists to deliver lectures related to  meteorology and climate. The lectureship was instituted with funds provided by his son Dr. K. Ramanathan and supplemented by PRL.

Prof. S.P. Pandya laid down the office of the Directorship of PRL on May 31, 1987 and Prof. R.K. Varma took over. Prof. Pandya continues to be at PRL as an INSA (Indian National Science Academy) Senior Scientist.

As it stands today, PRL has a number of disciplines under investigations. Recently, programmes which have common goals have been grouped together and the activities of the laboratory have been reorganized into four divisions (i) astronomy and astrophysics, (ii) theoretical physics (iii) planetary atmospheres and aeronomy and (iv) earth sciences and solar system studies. These areas onto which the future PRL activities are projected, are in fact the front-line areas of future scientific activity all over the world and each one of these  areas has the potential of growing in future into centres devoted to these studies.

PRL is planning to go vigorously into the astronomical studies of active galactic nuclei (AGN), star formation etc. using ground based optical techniques and ion microprobe, earth's middle and upper atmosphere using rockets and satellites and also earth-system processes using various dating techniques.

The intellectually rich past of the laboratory  owes its being on the one hand to the vision and scientific contribution of Dr. Vikram Sarabhai and Prof. K.R. Ramanathan, and on the other to a number of PRL scientists who grew with the laboratory, and worked in it with great devotion and untiring spirits. As we, reminisce over the past forty years, we pay our homage to our founder, to our founder director and to all those dedicated scientists who shaped the destiny of PRL.
 
 

 
 


Evolution of the scientific activities of PRL

Ever since his advent on this planet, man has been aware and conscious of his environment both terrestrial and extra-terrestrial. He has looked around on the Earth and identified "elements" of the environment crucial for his existence: the air and the water. He discovered fire and realized the all pervading existence of "akash" (space). In course of time, he realized that the weather and climate played a very crucial role in his day-to-day activities and requirements. He also soon realized that an extra terrestrial object - the Sun played a very dominant role in the very sustenance of life and gave it the status of God - the Sun God. It was also quickly realized that the Sun also played a central role in determining the weather and climate on Earth through the generation of wind, evaporation of water from the ocean etc.

When the Sun is set and the night falls, man is exposed to the spectacle and the splendour of the night sky - his extra - terrestrial environment. His curiosity and the power of observation led him to discern the heavenly bodies - planets which were found to move at different time scales against the background of "fixed" stars - the other innumerable luminous point like objects which appeared fixed over the time scale of observation. The heavenly sphere itself was found to rotate around the Earth which is attributable, as proposed by  Aryabhata, to the rotation of Earth around its axis. The early observations of the motions of the planets were made painstaking by astronomers with the unaided eye through the medium of the visible light of the Sun reflected by the planets. With the development of the telescope, more detailed observations of the planets began to be made, in particular, Galileo was led to discover the four moons of Jupiter. Subsequent improvements and breakthroughs in the observational  techniques led to the unravelling of deeper layer of space and to the discoveries of "nebulae" which are recognized to be huge  clusters of billions of stars, of  a variety of shapes and sizes now, known as "galaxies". It was also recognized that our sun itself is one of the billions of stars that also constitute a galaxy - our own galaxy - known now as the Milky Way.

Man's curiosity knows no bound. He is now looking beyond the galaxy, at "clusters of galaxies" and at the structure of the Universe at the largest scales.

Beyond the discoveries of the mere existence of the various objects, the Earth, the Sun, the solar system, the galaxies and the clusters of galaxies, man is now asking about the how's and whys of the various objects and structures observed through a variety of astronomical windows from radio through infrared, optical to X-rays and gamma rays.

The Sun, our own star, being so close to us offers us a unique opportunity to study its structure and dynamics, the structure of its surface features, magnetic field and a variety of  explosive and spectacular processes that have been observed over the last few centuries since Galileo first discovered the "Sun Spots".

Our Sun is also, perhaps, one of the very few stars, if not the only one, in the  galaxy which has a rich  system of planets around it with most of the planets in turn having a rich system of satellites around them.

Looking homeward, the earthsystem itself presents a very complex and fascinating object to study. One of the most challenging problem is understanding its weather and climate which is of direct interest and relevance to mankind. Perhaps, the first of the phenomena that man began to investigate about his environment were the winds and the rainfall -winds because they played a dominant role in the sea navigation which was intimately tied to trade and economic activity of man; and monsoon and rainfall because they affected the water resources and the agriculture - the two life lines of man.

A variety of phenomena relating to our environment as enumerated above thus present very fascinating and challenging area of study. The Physical Research Laboratory was established by Dr. Vikram Sarabhai with this broad objective in view. When the laboratory was started in 1947, the cosmic radiation was one of the most exciting areas of study and research and was being vigorously pursued around the globe. Cosmic radiation may be regarded as nature's messenger which can tell us about the electromagnetic state of the medium through which they travel before reaching us. The study of the primary cosmic radiation was one of the major disciplines of choice which was started at PRL. A number of pioneering discoveries were made by Dr. Vikram Sarabhai and his students over more than two and a half decades.

The other important area which constituted the thrust of research activity at PRL was the area of atmospheric sciences. A number of important and pioneering investigations were carried out under the stewardship of Prof. K.R.  Ramanathan, the first Director of PRL. These include,

The measurement of total ozone content of the atmosphere and its variability on various time scales in response to changes in the solar  radiation input as well as changes in atmospheric circulation and

A study of night airglow - the faint radiations that emanate from different regions of the atmosphere whose measurements can be used to study the structure, energetic and dynamics of these regions.

Scientific investigations in other directions, namely  the propagation of radio waves through the Earth's  atmosphere, let to the outstanding discovery by Appleton, of what is known as the "Ionosphere". It opened up entirely new vistas to the knowledge of our atmospheric envelope. The role of the ultra-violet (UV) radiation in producing the ionized layer was soon appreciated and this led to an entirely new field of study, the "Ionospheric Physics" in which vigorous researches were carried out all over the world and also at PRL. Our scientists made full use of our special geographical locations - the equatorial latitudes - to make pioneering contributions in the field.

The early work in cosmic rays and atmospheric and ionospheric research was carried out using ground-based instruments: for instance, Geiger-Muller counters, meson telescopes, neutron monitors were used to measure the cosmic ray intensity, its time variation and anisotropies. Likewise, the measurements of the atmospheric and ionospheric constituents, parameters and the electromagnetic states were carried out using the ozonesondes, the ionosondes, the magnetometers, photo-electric photometers (for night air glow) and the riometer.

The International Geophysical Year (IGY) was launched on July 01, 1957 and PRL  became an active participant in the programmes associated with the IGY, thanks primarily to the initiative and drive of Dr. Vikram Sarabhai and Prof. K.R. Ramanathan. This led to a great spurt of activity at PRL in a large variety of areas: the cosmic rays, the geomagnetism, solar physics, atmospheric physics and meteorology. This, in turn, contributed a great deal to the evolution of PRL into a space science laboratory that it became known for. With rare foresight, Prof. Ramanathan took the opportunity of the IGY to establish the Indian Dobson network - a chain of stations to study the behaviour of ozone in the tropics. Looked at in a broader perspective, the studies at PRL could be considered at that time to constitute an exploration of the solar terrestrial relationship through the agency of particles, fields and electromagnetic radiation  in its widest possible scope.

The setting up of Thumba Equatorial Rocket Launching Station (TERLS) was watershed in the history of the development of the Indian space programme in general, and space sciences in particular. It was from here that the rockets that carried the scientific payloads relating to the various scientific experiments also launched India's space programme. History should record the crucial part played by PRL in the initial stages of space sciences which led to the subsequent development of the space programme. Indeed many of the scientists who were at PRL played a leading role in the formulation of the space programme, with Dr. Vikram Sarabhai being its chief architect. PRL is thus rightly regarded as the cradle of the Indian space programme.

Thus, the era of the rocket-based space programme in India  began on the evening of November 21, 1963, when the first scientific rocket went up from  Thumba releasing sodium vapour which showed up the state of winds and turbulence above 90 kilometres. Over subsequent year, PRL became a centre for developing and building scientific payloads for use in rockets, in high flying balloons and later satellites. Between 1963 and 1975, a total of twenty five scientific payloads were fabricated and flown to measure a variety of atmospheric and ionospheric parameters. Thus, in the sixties and seventies, rockets played an important part in space research whereby electron density profiles at day and night were measured. Magnetometers were flown to measure the magnetic field and study the height structure of  the electrojet currents over Thumba. Special Langmuir probes were flown to measure electron density irregularities in the E- and F- regions, while vapour releases were used to measure the neutral winds. In addition, the ground based instruments, such as the ionosonde, the magnetometer etc.  continued to play important complementary role.

The rocket-based space programme also provided an opportunity to carry out astronomical investigations besides the aeronomy studies. Thus payloads were fabricated and flown to study the energy spectra of the X-ray sources such as SCO-XI, CYG-XI and CEN-XI.

Studies aimed at understanding the extra-terrestrial environments in its totality cannot remain confined to one or two windows as represented by cosmic radiation and X-rays. To understand the various dynamical and electromagnetic aspects of the gamut of phenomena occurring within the solar system and beyond, one has eventually to view the phenomena through all the available windows of the electromagnetic spectrum. Radioastronomical studies of the sun and its corona have been carried out since 1967, even though some instruments, such as the cosmic radio noise monitor and riometer have been operated since 1956.  Subsequently, a three station IPS (interplanetary scintillation) telescope at Thaltej (Ahmedabad), Surat and Rajkot has been installed by PRL which is, inter alia, capable of measuring the solar wind velocities at higher helio-latitudes.

Infra-red is another important window in the electromagnetic spectrum which yields information about phenomena and processes in the universe, which have hitherto been hidden from our vision. Thus, infra-red astronomy gives information about objects which are not yet hot enough to glow and thus gives clues about possible sites where stars may be forming. An infra-red telescope (1.2 metre diameter) is being installed by PRL at Gurushikhar (1500 metre above the mean sea level) in Rajasthan, to carry out such studies.

Following the sad demise in December 1971, of Dr. Vikram Sarabhai, who was the then Director of PRL (as also the Chairman, Atomic Energy Commission and Indian Space Research Organisation), Dr. Devendra Lal came to PRL as its new Director. He brought with him his group on Earth Sciences and Solar system studies. A new dimension was thus added to PRL's scientific activities. Studies of the solid Earth and oceans complemented the studies of the Earth's atmosphere, so that at least some aspects of the total earth system came under the purview of the studies at PRL. Likewise, the studies of meteorites and the moon which are directed towards understanding the early history of the evolution of the solar system extended the scope of the earlier studies of solar-terrestrial system.

While experimental programmes are the very backbone of scientific investigations, an understanding of the variety of natural phenomena require a conceptual and a theoretical framework. Such a framework enables the various phenomena to be understood in terms of a small number of basic laws. It is the continuous quest of scientists to reduce all the observed phenomena to a smaller and smaller set of basic laws. It is, therefore, essential to have a theoretical physics group in a scientific institution which provides a broad theoretical environment. While it is desirable to have a theoretical and modelling activity associated with every major experimental programme, it may not always be possible. Nevertheless theoretical physics is a highly desirable activity in its own right and provides a core around which a meaningful and sustainable modelling activity can develop.

Perhaps it was with this view that a small theoretical physics activity was initiated at PRL from the very beginning. For historical reasons the activity started with nuclear physics as the main discipline. It was, however, soon realized that the discipline which was most relevant from the point of view of the experimental programme of the laboratory at that time, was plasma physics. Thus plasma physics activity started with a one member group in 1968, which rapidly grew to a sizable group by 1972. Both plasma physics and nuclear physics activities have continued vigorously, with plasma group addressing problems of space and astrophysical interest besides those pertaining to basic plasma physics.

With time, the nuclear physics activity which earlier concentrated on low energy regime and nuclear spectroscopy has gone on to address problems of high energy regime involving the quark degrees of freedom and  the studies of the state of high energy nuclear matter known as the "quark-gluon-plasma". Very recently a small high energy particle physics group has also been added to address the problems of cosmology.

The other areas of theoretical physics which have relevance from the point of view of the atmospheric sciences programme of the laboratory are atomic and molecular physics and atmospheric dynamics including the monsoon studies. Small theoretical groups devoted to these studies have thus been developed. Together, their expertise can be used to model both dynamical and the chemical aspects of not only the Earth's atmosphere but also atmospheres of other planets.

The decade of the eighties have given the first ever glimpses of the outer planets (Jupiter, Saturn, Uranus and Neptune) and brought forth spectacular revelations about their physical structure through the agency of the deep space probes, the Pioneer I and II. The decade has also seen an increasing emphasis on the  study of the middle atmosphere - its chemistry and dynamics. This study has been prompted by the increasing concern of man about his environment - particularly the environment as it is being affected by anthropogenic causes, the alarmingly increasing levels of the so-called "green house" gases in the atmosphere - the CO2, H2O and methane. He is now feeling that his abode  on earth is getting threatened as he has begun to fear  that the green house effect may lead to warming of the atmosphere and consequent melting of the  polar ice caps. This may lead to the submergence of  large coastal areas of land under  the oceans.

Man's attention is no drawn towards these important survival issues and so there has been increasing scientific activity to understand, what has so far been a rather neglected area, namely the middle atmosphere. It has now been realized that so little is known about the middle atmosphere - its chemistry, it dynamics, its minor constituents and the radiation transport and budget. All these aspects of the middle atmosphere, it is now appreciated, play an important role in determining our weather and climate. Perhaps, the minor constituents of the middle atmosphere which has drawn the greatest attention is Ozone. Man is now worried that he has, by his own actions, been depleting the protective ozone layer  that nature has so generously provided to protect him against the hazards of the solar ultraviolet radiation. The  discovery of the Antarctica  Ozone Hole in 1985  has sent alarm bells up his spine. The importance of  monitoring the Chloro-fluoro carbons (CFCs) and Nox compounds in the stratosphere injected by freons and use of spray can and by supersonic aircrafts was realized. Likewise, the importance of monitoring the aerosols for the radiation budget of the atmosphere has also been appreciated.

Oceans are extremely important in determining our climate through the gaseous (CO2) exchange processes and other chemical reactions involving nitrogen exchange, and most importantly, in supplying water vapour to the atmosphere which eventually appears as rain. Water vapour in the atmosphere is also responsible for green house warming of the planet. Our understanding of the variety of processes involved in the ocean-atmosphere interaction is still very rudimentary. It is both a highly interesting and extremely important area of investigation for the understanding of the monsoon dynamics. It is crucial to study the wind induced ocean currents and evaporation in order to be able to understand the moisture budget in the atmosphere particularly during active monsoon period.

The importance of studying our immediate environment, the trophosphee and the middle atmosphere, oceans and ocean-atmosphere interaction, has now been acutely realized. The earth-system is a complex nonlinear one with a large number of feedback loops involvling strong couplings among its various components, the geophere, the hydrosphere, the cryosphere, the atmosphere and the biosphere. Realizing this a  comprehensive programme named as the International Geosphere Biosphere Programme (IGBP) has been launched by the International Council of Scientific Union which has been taken up by countries around the globe.

PRL is a unique laboratory, probably one of its kind in the world which has a good number (certainly not all) of the components of IGBP under its roof. We have an atmospheric sciences programme which aims to study the chemistry and dynamics of the lower and middle atmosphere: We have a theoretical group studying the dynamics of the troposphere as it relates to atmospheric circulation and the monsoons. We have a palaeclimate programme which aims to understand the climatic processes on various time scales, from millions of years to a few tens of years through the studies of oceans and lake sediments, tree rings, sand dunes, loess and palaeosols. We are also involved in hydrological programmes, the ocean circulations - both surface and deep water - ground water movements and recharge, the glacier dynamics, river water chemistry and fluxes of materials to the oceans. We also plan to add another small group on the studies of the ocean-atmosphere interaction which is very important  for the understanding of  both the dynamics of oceans and atmosphere and of the evaporation process so crucial for the monsoons.

With all these components, we plan to embark on a co-ordinated study of the various earth system processes to try to understand our climatic changes on various time scales from tens of thousands of years to the decadal. We shall try to understand how modern man has been tampering with the climate and the biosphere through the chemical releases - the bye-products of his "progress", and what the shore and long term effects of these anthropogenic  factors are going to be on our climate and biosphere. In the  Indian contect, it is very important for us to study the wind induced ocean circulations and evaporation as these constitute a very crucial input  for the monsoon processes.

Looking into the future complexion of PRL scientific activities, we would like to focus our research efforts into three to four directions which are consistent with our existing and  evolving facilities and expertize and with the evolving international scenarios and emphases. We shall, however, also continue to look for areas and problems which may be entirely new and unchartered territories and hope that we would succeed in bringing major "firsts" to PRL's credit.

Thus,  apart from the study of our climate and monsoon and IGBP related activities described above, we would also like to extend the studies of the earth's ionosphere and atmosphere to other planets using groun-based  optical methods such as the Fabry-Perot Interferometry in which PRL is known for its  high degree of expertize. Understanding the structure and dynamics of the planets and satellites and other solar system bodies - the comets and the meteorites - should constitute a natural programme of study for PRL which has made pioneering contributions to the studies of the Earth's ionosphere and atmosphere. On the other hand, the evolution of the solar system itself, the mechanism of the formation of planets and their satellites from the primordial circumsolar nebulae is another  complementary rich area of study. PRL already has a small group which has been studying the chemical composition of meteorites to peep into the early stages of the formation of the solar system bodies. However, these studies must be accompanied and supplemented by appropriate modelling and perhaps, also laboratory studies to understand the process of aggregation which in one of the  most crucial phenomena in the formation of the solar system bodies.

Astronomical studies of the sun and other galactic and extragalactic objects in the optical and infra-red windows will constitute another major area of activity for PRL. With the commissioning of the Infra-red Observatory at Gurushikhar, we will be embarking on an extensive programme of the study of Active Galactic Nuclei (AGN) and star forming regions. The work on these has already been carried out using other telescopes in the country.

Likewise, the Solar Observatory at Udaipur has been studying the eruptive processes on the solar surface, the solar flares and prominences and proposes to map the associated magnetic field using a solar magnetograph. The eruptive processes on the Sun and coronal streams lead to the propagation of associated disturbances into the interplanetary plasma. The plasma turbulence associated with these disturbances will be mapped using a 20,000 sq. mtr. Antenna array operating at 103 Mega Hertz at Thaltej. This is one of a three-station IPS telescopes which is being used to measure the three dimensional solar wind velocity field. The other two are at Surat and Rajkot with 5000 sq. mtr. Antenna area each.