Dr. Pal, a  Space Communication Technologist of repute, starting, at the inception of ISRO’s satellite activities , from scratch, is responsible for design, development and fabrication  of space-borne telecommunication systems (TT&C & data transmitting systems) for all Indian scientific, remote sensing and communication  satellites [52 launched and 10 more are scheduled for launch in next three years]. He has also pioneered the activities of satellite-based navigation in India and initiated the following activities:

1. Satellite Based Navigation Related Activities

The usage of GPS receiver on-board the Low Earth satellites, for providing navigation solution was initiated as technology development effort. This was later translated as operational system to support the data product generation all over the world, where Indian Remote Sensing Satellite Systems (IRS) data is being utilized for image applications. Many on-board requirements for precise orbits are being served by the GPS receivers flying on-board the satellites. The social significance of these activities is derivable from the fact that the IRS data products are currently generated with greater accuracy and minimum external interface.

GPS Aided & Geo Augmented Navigation (GAGAN), a satellite based augmentation system for India, built over the GPS system, is expected to provide seamless navigation support over the Asia-Pacific regions. This system is being built with the participation of the Airports Authority of India. The system consists of fifteen monitoring stations located in the land mass in India, two master control centres and an uplink station co-located in Bangalore. The final operations phase of the project has been taken up currently. The Airports Authority of India will be able to reduce the operational and maintenance costs of aircraft operations across the country.  The AAI being service providers for all airlines using the Indian airspace for over-flying, landing etc is expected to earn very large revenue.   Although primarily built for AAI, the services will be available as a free-to air service and numerous users will benefit through higher navigational accuracies. The system will be operational by 2011 and will be certified by 2013 for civil aviation applications (the Technolody Demonstration Phase was completed in 2007).

An innovative proposal based on a unique concept of using geo-stationary satellite for navigation application is being implemented for India. The system is named as  IRNSS (Indian Regional Navigational Satellite System), a regional self-reliant, all weather, 24 hour navigation support system over the Indian region (+1500 KMS) for land, air and sea users. This constellation concept is distinctive constellation consisting of only 7 satellites in the GEO (3) and inclined GSO (4), and is a regional system equivalent of GPS constellation of the US. By virtue of the fact that these satellites will be visible over the Indian region all the satellites will be in the visibility of ground stations within the country, thereby providing an opportunity of uplink the clock, iono and ephemeris parameters as and when required from the ground uplink stations, as against other navigation satellite constellation like the GPS, GLONASS or the GALILEO, thereby improving the accuracy of the solution to the user. With the development of ground and space infrastructure, together with the development of IRNSS receivers, this concept is expected to support all the navigation requirements of air, sea and land users in the region. With the advent of IRNSS, India will be able to have a self-reliant navigation with entire control and operations over Indian region.  The concept of IRNSS when implemented is expected to yield numerous civil and strategic benefits for the navigation user community in Indian region; together with the regional supremacy of Indian space organization in the international navigation scenario. The usage of the IRNSS receiver is expected to earn significant revenue. The system jwill be operational by 2013-14.

*The first phase of GAGAN called GAGAN-TDS has been completed with promising results.

2. Antenna/Microwaves and Space Communication related activities

Dr. Pal is responsible for  design, development and fabrication  of space-borne telecommunication systems, from the inception of Indian satellite Programme, in VHF, L,S,C,X and Ku bands for all Indian scientific, remote sensing and communication  satellites [51 launched and 10 more are scheduled for launch in next three years starting from Aryabhata to INSAT, IRS series of Satellites including Chandrayan-I] A few developed systems for GEO & LEO satellites are: (i) High sensitivity Telemetry Tracking and Command (TT&C) transponders in S & C band (ii) X-band High bit-rate  (200 »MBPS) QPSK data transmitters (iii) Space-borne Satellite Positioning System based on GPS constellation (iv) Omni-directional and wide beam TT&C antennas for spacecraft of different sizes and shapes with varying requirements (v) Directional, Shaped Beam & Array Antennas at C,X & Ku & Ka bands. In the process of the said developments he has also built up a strong team of RF engineers at ISRO. Besides these, he has also developed high efficiency ground station antennas with feeds, of novel design using dielectric spheres, cones at X,C and S bands. He has developed expertise in the area of microstrip large array antennas for air surveillance,  multiple beam phased array antennas and use of light weight (less than 30 gms) integrated quadrifilar helix  for  TT&C omni-antennas for  spacecraft.  His long dedicated service of 34 years has resulted in putting Indian Space Research Organization (ISRO) on  firm footing in the area of Antenna  and Microwave Communication for Space.  The matter of significance is the fact, that developments were carried out in a very short time at a modest cost of about less than 20% of the similar systems available elsewhere.  This is achieved by incorporating many innovative ideas and techniques to suit Indian technological needs. The most significant achievement is RF design of Indian Deep Space Network-32 meter antenna and its beam waveguide for tracking Chandrayan-I mission.

He is also on the GNSS expert panel of UN-Office of Outer Space, Vienna.

Dr. Pal’s contribution stands apart in providing timely, cheaper, better and appropriate solutions in highly demanding and critical areas, where India in general & ISRO in particular has to face export sanctions and technology denials. The result is all there to see with systems developed, providing flawless performance in orbit and saving millions of $ worth precious Foreign Exchange. The following three examples of his (out of numerous developments) innovative thinking & leadership speaks for him:

 Development of a dual beam (RHC polarized, operating simultaneously at two frequencies) spherical phased array scanning antenna system at X-band for IRS series of spacecrafts.  The two beams can dump data over two geographically widely separated ground stations, from an imaging satellite, taking in to account the orbital velocity & all the orientation of the spacecraft, encountered during various imaging modes. The development of this novel Phased Array Antenna indigenously has enabled ISRO to realise high performance Remote Sensing Satellites and smaller satellites which is always the aim in satellite technology Similar system as of today does not exist.  A conical array with single beam from M/s Alcatel would have costed Rs.60 crores while a far superior in performance developed here costs  less than Rs. 2 crores.  The inorbit performance of the phased array in TES, IRS-P5, CARTOSAT-2 spacecraft had been flawless in simultaneously transmitting data to Delhi & Hyderabad ground stations .  A lighter and more efficient version is developed for Cartosat 2A & 2B.  A dual polarized version for RISAT is under development. In the civilian domain except India, such a concept and antenna has not been used by any other space agency

Development of L,S,C,X and Ku band ground station composite feeds with monopulse tracking.  Along with feeds reflectors have been shaped and a typical ≈70%.  The indigenous feed cost is <Rs.10 lakhs against Rs.60 lakhs for an imported system. 

Work on air-surveillance radar for DRDO  and SAR antennas have shown way that microstrip radiators can be used for high power and bandwidth applications (1.5 MW peak and 12% BW). Shaped beam and omni antenna developed by him are lighter and smaller in size to the ones used by contemporary spacecraft of other space agencies.  

His work on IRNSS & GAGAN will make India self sufficient in the area of GNSS. He is the initiator of Satellite Based Navigation Systems (GNSS) in India 

Other individual contributions :

Besides the various contributions to  India's Space programme, he has developed systems  for India’s Defence Research & Development Organization and INMARSAT/ICO-UK.  He has been consultant to ITU on Regional African Satellite Communication and INMARSAT-UK for Project-21-LEO Mobile Satellite Definition. He had also developed satellite hand held telephone antenna systems at L,S & FPLMTS band for ICO. He has given courses on Satellite Communication at IISc under Proficience Programme, published/presented more than 200 technical papers in national/international journals/conferences,  guided 50 M.Tech and 7 Ph.D. students for their dissertations. He is also a Distinguished Visiting Professor of INAE & Distinguished Lecturer, IEEE-AES.  He is also Chairman of the review board for Communication Payload of India's INSAT series of geostationary communication satellites  and Launch Vehicle Range Related Programmes.  He has been on the editorial board of various technical journals and founder editor of the Journal of Spacecraft Technology. He is also co-editor of a book "Perspectives in Communications" published by World Scientific Publications, Singapore.  He is a Ph.D. examiner for various Indian technological institutions and Universities. He has also  been associated with the framing of  syllabus for Communication Systems  at Post Graduate level. He had been Chairman of Working Group on Information Infrastructure of the Ministry of Information Technology,  Govt. of India for popularizing research activity in the field of E-commerce and Information Technology (2000-2002). 

EVIDENCE OF TECHNICAL ACCOMPLISHMENT.

Note: Indian Space Research Organization, being a government body and hence developments are not widely published in the public domain.

PART I (Three Most Important Items of tangible and verifiable evidence of technical accomplishment)

Design, Development and Fabrication of a high bit-rate data transmitters at X band (QPSK modulations, data rates »200MBPS, RF output power 12, 20 and 40W) along with QPSK modulators, SSPAs and shaped wide beam antenna (path loss variation is compensated by onboard antenna gain pattern), for India's IRS series of remote sensing spacecraft.  The  varying power and bit-rate requirements for all the orbiting satellites have been successfully met. 

Design, Development and Fabrication of a light weight Space Borne Hemispherical Phased Array Antenna at X-band, capable of generating two beams to point to two different ground stations, compensating the spacecraft orbital motion as well as pitch, roll and yaw movements during complex imaging mode  of a spot from a sun synchronous orbiting remote sensing spacecraft (IRS-TES,IRS-P5 & Cartosat-2).  The minimum eirp is  »22dBW  in any  beam.  The development  restricts: (i) interference from satellite to other networks (ii) spill over of RF signal and remote sensing data to undesired regions. 

Design Development and Fabrication of a Ultra Low Side Lobe Array Antenna (4M x 1.1M, -36dB SLL, 12% Bandwidth, 1.5MW Peak and 8.4 kW average power handling capability) using Microstrip Patch Antennas.  The complex development has broken the myth that microstrip antennas are of narrow band width and low power handling capability.  The antenna is developed for India's Air Borne Surveillance Radar Programme.  The same technology is used for Air Borne SAR antennas (Radar Symposium – IRSI-99-Dec 99, Bangalore-India pp-114-119)).

 PART-II (15 more additional items)

S-band PLL based coherent TT&C Transponder (with associated diplexers) with -127 dBm sensitivity, used in IRS and SROSS series of Spacecraft (Total No. orbited  11, slated for launch in the next two years  5). The import cost of such a system is »1.5M US $; per piece.  The same is made in-house for  » 80K US $ (Total no qualified so far  42).

 

-110dBm sensitivity, C-Band TT&C Transponders, along with associated filters for India's Geostationary INSAT series of spacecraft (Total satellites launched :10).  International cost »1.00 million US $; indigenous cost »100K US$ 

 

Space Borne Satellite Positioning System utilizing GPS constellation along with its antenna system.  The in-orbit position accuracy obtained in IRS series of  spacecraft is ±10meters.  Such systems will henceforth become a part of the main bus of India's all orbiting spacecraft. (Import cost per piece : 150K US$, Indigenous cost 25K US$) (Total No. used in space till date : 12)

 

Monopulse Tracking feed for ground stations at S and X band.  The conventional corrugated or pyramidal horns for such a system have been replaced by dielectric spheres reducing the cost & weight by almost a factor of TEN.  The feeds are  compact and provide for 10mj paraboloid with a G/T of ³33dBo/k.  These are  being extensively used at various ground stations in India for tracking remote sensing satellites.

 

Light Weight Miniaturized Multi Frequency (FPLMTS and L/S band)) Antenna (weight <30 gms, 10mmj, 14mm long) for Mobile Satellite Hand Held Antenna for INMARSAT/ICO U.K.  The first successful trials for mobile satellite communication were carried out by INMARSAT using this antenna system.  ISRO along with ICO holds a patent for it.  The antenna can be used for variety of other applications.

 

Different types of omni antenna systems ( at VHF, S and C bands) for India's various spacecraft with varying size and requirements.  The antennas are wide band, light weight  and provides >85% of the radiation sphere coverage.  The systems have been used in 40 orbited spacecraft (including IRS and INSAT series) and 10 more are slated for launch in the near future.

 

Study of Spherical Dielectric Antennas which had led to the development of  item (1) above.(S Pal, "Spherical Dielectric Antenna", Proceedings of RF Technology Expo, Anaheim, California USA, pp. 451-472, Jan-Feb 1986)