GREAT CONJUCTION OF SATURN AND JUPITER

Introduction:

A great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky. Great conjunctions occur approximately every 20 years when Jupiter "overtakes" Saturn in its orbit. They are named "great" for being by far the rarest of the conjunctions between naked-eye planets (i.e. excluding Uranus and Neptune). 

Stitched photograph of the great conjunction of 2020 four hours before closest approach, with Jupiter 6–7 arcminutes below Saturn.

The spacing between the planets varies from conjunction to conjunction with most events being 0.5 to 1.3 degrees (30 to 78 arcminutes, or 1 to 2.5 times the width of a full moon). Very close conjunctions happen much less frequently (though the maximum of 1.3° is still close by inner planet standards): separations of less than 10 arcminutes have only happened four times since 1200, most recently in 2020.

History:

Great conjunctions attracted considerable attention in the past as omens. During the late Middle Ages and Renaissance, they were a topic broached by the pre-scientific and transitional astronomer-astrologers of the period up to the time of Tycho Brahe and Johannes Kepler, by scholastic thinkers such as Roger Bacon and Pierre d'Ailly, and they are mentioned in popular and literary works by authors such as Dante and Shakespeare. This interest is traced back in Europe to translations of Arabic texts especially Albumasar's book on conjunctions.

Despite mathematical errors and some disagreement among astrologers about when trigons began, belief in the significance of such events generated a stream of publications that grew steadily until the end of the 16th century. As the great conjunction of 1583 was last in the water trigon it was widely supposed to herald apocalyptic changes; a papal bull against divination was issued in 1586 but as nothing significant happened by the feared event of 1603, public interest rapidly died. By the start of the next trigon, modern scientific consensus had long-established astrology as pseudoscience, and planetary alignments were no longer perceived as omens.

Celestial mechanics: 

Diagram of longitude pattern from joannes kepler’s 1606 book De stella nova 

On average, great conjunction seasons occur once every 19.859 Julian years (each of which is 365.25 days). This number can be calculated by the synodic period formula in which J and S are the orbital periods of Jupiter (4332.59 days) and Saturn (10759.22 days), respectively. (In practice, Earth's orbit size can cause great conjunctions to reoccur up to some months away from the average time or the time they happen on the Sun). Since the equivalent periods of other naked-eye planet pairs are all under 27 months, this makes great conjunctions the rarest.

Occasionally there is more than one great conjunction in a season when they occur close enough to opposition: this is called a triple conjunction (which is not exclusive to great conjunctions). A triple conjunction is a conjunction of Jupiter and Saturn at or near their opposition to the Sun. In this scenario, Jupiter and Saturn will occupy the same right ascension on three occasions or same ecliptic longitude on three occasions depending on which definition of "conjunction" one uses (this is due to apparent retrograde motion and happens within months). The most recent triple conjunction occurred in 1980–81 while the next will be in 2238–39.

Diagram showing the movements of Jupiter and Saturn during the 1980–81 triple conjunction.

The most recent great conjunction occurred on 21 December 2020, and the next will occur on 4 November 2040. During the 2020 great conjunction, the two planets were separated in the sky by 6 arcminutes at their closest point, which was the closest distance between the two planets since 1623. The closeness is the result of the conjunction occurring in the vicinity of one of the two longitudes where the two orbits appear to intersect when viewed from the Sun (which has a point of view similar to Earth).

Because 19.859 years is equal to 1.674 Jupiter orbits and 0.674 Saturn orbits, three of these periods come close to a whole number of revolutions. This is why the longitude cycle, as shown in the diagram, has a triangular pattern. The three points of the triangle revolve in the same direction as the planets at the rate of approximately one-sixth of a revolution per four centuries, thus creating especially close conjunctions on an approximately four-century cycle. Currently the longitudes of close great conjunctions are about 307.4 and 127.4 degrees in the constellations Capricornus and Cancer respectively. The position of Earth in its orbit, however, can make the planets appear up to about 10 degrees ahead of or behind their heliocentric longitude.

Saturn's orbit plane is inclined 2.485 degrees relative to Earth's, and Jupiter's is inclined 1.303 degrees. The ascending nodes of both planets are similar (100.6 degrees for Jupiter and 113.7 degrees for Saturn), meaning if Saturn is above or below Earth's orbital plane Jupiter usually is too. Because these nodes align so well it would be expected that no closest approach will ever be much worse than the difference between the two inclinations. Indeed, between year 1 and 3000, the maximum conjunction distances were 1.3 degrees in 1306 and 1940. Conjunctions in both years occurred when the planets were tilted most out of the plane: longitude 206 degrees (therefore above the plane) in 1306, and longitude 39 degrees (therefore below the plane) in 1940. 

Notable great conjunctions (1200 to 2400):

7 BC 

When studying the great conjunction of 1603, Johannes Kepler thought that the Star of Bethlehem might have been the occurrence of a great conjunction. He calculated that a triple conjunction of Jupiter and Saturn occurred in 7 BC (−6 using astronomical year numbering).

In the year 1563,

The astronomers from the Cracow Academy (Jan Muscenius, Stanisław Jakobejusz, Nicolaus Schadeck, Petrus Probosczowicze, and others) observed the great conjunction of 1563 to compare Alfonsine tables (based on a geocentric model) with the Prutenic Tables (based on Copernican heliocentrism). In the Prutenic Tables the astronomers found Jupiter and Saturn so close to each other that Jupiter covered Saturn (actual angular separation was 6.8 minutes on 25 August 1563). The Alfonsine tables suggested that the conjunction should be observed on another day but on the day indicated by the Alfonsine tables the angular separation was a full 141 minutes. The Cracow professors suggested following the more accurate Copernican predictions and between 1578 and 1580 Copernican heliocentrism was lectured on three times by Valentin Fontani. 

In the year 2020, 

Separation of Jupiter and Saturn around the time of the 2020 great conjunction 

The great conjunction of 2020 was the closest since 1623 and eighth closest of the first three millennia AD, with a minimum separation between the two planets of 6.1 arcminutes. This great conjunction was also the most easily visible close conjunction since 1226 (as the previous close conjunctions in 1563 and 1623 were closer to the Sun and therefore more difficult to see). It occurred seven weeks after the heliocentric conjunction, when Jupiter and Saturn shared the same heliocentric longitude.

The closest separation occurred on 21st December at 18:20 UTC, when Jupiter was 0.1° south of Saturn and 30° east of the Sun. This meant both planets appeared together in the field of view of most small- and medium-sized telescopes (though they were distinguishable from each other without optical aid). During the closest approach, both planets appeared to be a binary object to the naked eye. From mid-northern latitudes, the planets were visible one hour after sunset at less than 15° in altitude above the southwestern horizon in the constellation of Capricornus.

The conjunction attracted considerable media attention, with news sources calling it the "Christmas Star" due to the proximity of the date of the conjunction to Christmas, and for a great conjunction being one of the hypothesized explanations for the biblical Star of Bethlehem. 

Sky watching programme on great conjugation of Saturn and Jupiter at St.Philomena College, Puttur

Reference:-

1. Wikipedia 

2. Newspaper
3. Journals

SUBMITTED BY:- 

Anagha R 

Ananya Rai S
Bhavya DSouza
Deeksha M
Dileep Delmond D Souza
Kadhija Tabhseera

1st M.Sc. {1st Semester}
SUBMITTED ON:- 11-01-2021

Security Ink Technology: A New Invention from Indian Physicists

Technology has made remarkable progress with the time and touched new horizons in this 21st century. This technology proved to be a boon world widely for society. Despite of being achieving so many milestones with latest scientific inventions it have also affected adversely up to a certain extent. One among these adverse affects is ‘counterfeiting or forgery’ i.e. the biggest crime of this century. The crucial solution of this crux is ‘Security Printing’ as every problem has a solution. Security printing facilitates protection against counterfeiting and tempering overtly as well as covertly by combining numerous printing methodologies.

Source: http://www.rotatek.com

Security inks are a special segment and another foundation of security printing. Its importance cannot be underestimated It is the security ink that fosters the credibility of security printing. Various types of security inks are enlisted as below

1. Thermochromic Ink: Thermochromic inks are sensitive to temperature. These inks are reversible or irreversible color changing inks.
2. Invisible Ink: These inks are invisible under normal lighting conditions. In order to detect these inks UV light source is required.
3. Solvent Sensitive Ink: When someone attempts to alter any credentials then it shows a visible indicator and ink will run resulting smudged area. Such inks are sensitive to solvents. 
4. Magnetic Ink: Magnetic inks usually consist of small magnetic particles which are machine readable. Such types of inks are usually used for serial numbering purposes. 
5. Anti-absorption Ink: These inks are used for printing of security documents. Printed areas are visible under Infra-Red light spectrum. These inks are available for letterpress, gravure, offset, screen and intaglio printing. 
6. UV Fluorescent Inks: UV fluorescent ink appears to glow when exposed to ultraviolet light but under normal lighting conditions these inks are invisible
7. Biometric Ink: Biometric inks contain DNA taggants which are machine readable.

Basically, UV Fluorescent Inks have been used to find fake currency notes. As per security purpose, the finding of duplication of the currency notes is challenging task. According to the Reserve Bank of India’s (RBI) report, the new Rs 500 and Rs 2,000 notes introduced after demonetisation are at the risk of duplication. According to the report, the duplication of a new design of Rs 500 notes is accounted to be 121 per cent and of Rs 2,000 notes to be 21.9 per cent in the last year. So, in a latest research, scientists from CSIR-National Physical Laboratory (NPL) in New Delhi have come up with a security ink — which can prevent duplication of printable documents and counterfeiting of currency notes. This research was worked under the combination of fluorescence and phosphorescence phenomenon.

Source: Wikipedia

Counterfeiting is defined as the reproduction of an intellectual property right without receiving permission from the proprietor. It has grown to be a serious global threat nowadays and this includes the duplication of currencies, merchandise, electronic products, official documents, passports, pharmaceuticals, and so forth which causes enormous loss to the economy of any country, as well as a constant risk to the health and safety of consumers worldwide.

The main task of the team was to select compounds, which do not obstruct the formation of the colours on the excitation of the wavelength. For the production of luminescent pigment, two chemical compounds — sodium yttrium fluorite, europium-doped and strontium aluminate with europium-dysprosium — were synthesised to emit red and green colours, respectively. The fluorescence property is through sodium yttrium fluorite, while the phosphorescence is by compound strontium aluminate.

For the feasibility test of the ink, an image was printed on a non-fluorescent white bond paper using a standard screen printing technique. The results showcased the emission of red and green colours under the 254 nm UV excitation when the source was turned on and off. The experimental test was conducted for optical photographs of Tajmahal.

Source: Amit Kumar Gangwar et al, Journal of Materials Chemistry C, 2019

The emissive luminescent security ink and the ink after six months of storage exhibit almost the same viscosity, which confirms that it can be stored for long durations without undergoing any significant changes in its properties. The technique which was a new scalable and inexpensive opportunity to generate unbreakable security features, which are essential for protection against counterfeiting. This can be used in legal confidential certificates, merchandise and electronic barcodes also to avoid duplication or sale of fake products.

References:

Amit Kumar Gangwar et al., Single excitable dual emissive novel luminescent pigment to generate advanced security features for anti-counterfeiting applications, Journal of Materials Chemistry C, 2019.
Vikas Jangra Security Printing: Innovative Technologies with Comprehensive Approach as an Anti-Counterfeiting Tool, International Journal for Scientific Research & Development, 2016

Written By: Ashith VK

Nikola Tesla: The Genius

Nikola Tesla was born on July 10, 1856 in Smiljan, Lika, which was then part of the Austo-Hungarian Empire, region of Croatia. His father, Milutin Tesla was a Serbian Orthodox Priest and his mother Djuka Mandic was an inventor in her own right of household appliances. 

Rebuilt, Tesla’s house (parish hall) in Smiljan, now in Croatia, where he was born, and the rebuilt church, where his father served. During the Yugoslav Wars, several of the buildings were severely damaged by fire. They were restored and reopened in 2006.

Tesla studied at the Realschule, Karlstadt in 1873, the Polytechnic Institute in Graz, Austria and the University of Prague. At first, he intended to specialize in physics and mathematics, but soon he became fascinated with electricity. He began his career as an electrical engineer with a telephone company in Budapest in 1881. It was there, as Tesla was walking with a friend through the city park that the elusive solution to the rotating magnetic field flashed through his mind. With a stick, he drew a diagram in the sand explaining to his friend the principle of the induction motor. 

Tesla aged 23, c. 1879

Drawing from U.S. Patent 381,968, illustrating principle of Tesla’s alternating current induction motor

Before going to America, Tesla joined Continental EdisonCompany in Paris where he designed dynamos. While in Strassbourg in 1883, he privately built a prototype of the induction motor and ran it successfully. Unable to interest anyone in Europe in promoting this radical device, Tesla accepted an offer to work for Thomas Edison in New York. His childhood dream was to come to America to harness the power of Niagara Falls. 

Edison Machine Works on Goerck Street, New York.

Young Nikola Tesla came to the United States in 1884 with an introduction letter from Charles Batchelor to Thomas Edison: “I know two great men,” wrote Batchelor, “one is you and the other is this young man.” Tesla spent the next 59 years of his productive life living in New York. Tesla set about improving Edison’s line of dynamos while working in Edison’s lab in New Jersey. It was here that his divergence of opinion with Edison over direct current versus alternating current began. This disagreement climaxed in the war of the currents as Edison fought a losing battle to protect his investment in direct current equipment and facilities.

Tesla pointed out the inefficiency of Edison’s direct current electrical powerhouses that have been build up and down the Atlantic seaboard. The secret, he felt, lay in the use of alternating current, because to him all energies were cyclic. Why not build generators that would send electrical energy along distribution lines first one way, than another, in multiple waves using the polyphase principle?

Edison’s lamps were weak and inefficient when supplied by direct current. This system had a severe disadvantage in that it could not be transported more than two miles due to its inability to step up to high voltage levels necessary for long distance transmission. Consequently, a direct current power station was required at two mile intervals.

Direct current flows continuously in one direction; alternating current changes direction 50 or 60 times per second and can be stepped up to vary high voltage levels, minimizing power loss across great distances. The future belongs to alternating current.

Nikola Tesla developed polyphase alternating current system of generators, motors and transformers and held 40 basic U.S. patents on the system, which George Westinghouse bought, determined to supply America with the Tesla system. Edison did not want to lose his DC empire, and a bitter war ensued. This was the war of the currents between AC and DC. Tesla -Westinghouse ultimately emerged the victor because AC was a superior technology. It was a war won for the progress of both America and the world.

Tesla introduced his motors and electrical systems in a classic paper, “A New System of Alternating Current Motors and Transformers” which he delivered before the American Institute of Electrical Engineers in 1888. One of the most impressed was the industrialist and inventor George Westinghouse. One day he visited Tesla’s laboratory and was amazed at what he saw. Tesla had constructed a model polyphase system consisting of an alternating current dynamo, step-up and step-down transformers and A.C. motor at the other end. The perfect partnership between Tesla and Westinghouse for the nationwide use of electricity in America had begun.

In February 1882, Tesla discovered the rotating magnetic field, a fundamental principle in physics and the basis of nearly all devices that use alternating current. Tesla brilliantly adapted the principle of rotating magnetic field for the construction of alternating current induction motor and the polyphase system for the generation, transmission, distribution and use of electrical power.

Nikola Tesla’s AC dynamo-electric machine (AC electric generator) in an 1888 U.S. Patent 390,721

Tesla’s A.C. induction motor is widely used throughout the world in industry and household appliances. It started the industrial revolution at the turn of the century. Electricity today is generated transmitted and converted to mechanical power by means of his inventions. Tesla’s greatest achievement is his polyphase alternating current system, which is today lighting the entire globe.

Tesla astonished the world by demonstrating the wonders of alternating current electricity at the World Columbian Exposition in Chicago in 1893. Alternating current became standard power in the 20th Century. This accomplishment changed the world. He designed the first hydroelectric powerplant in Niagara Falls in 1895, which was the final victory of alternating current. The achievement was covered widely in the world press, and Tesla was praised as a hero worldwide. King Nikola of Montenegro conferred upon him the Order of Danilo.

Tesla was a pioneer in many fields. The Tesla coil, which he invented in 1891, is widely used today in radio and television sets and other electronic equipment. That year also marked the date of Tesla’s United States citizenship. His alternating current induction motor is considered one of the ten greatest discoveries of all time. Among his discoveries are the fluorescent light, laser beam, wireless communications, wireless transmission of electrical energy, remote control, robotics, Tesla’s turbines and vertical take off aircraft. Tesla is the father of the radio and the modern electrical transmissions systems. He registered over 700 patents worldwide. His vision included exploration of solar energy and the power of the sea. He foresaw interplanetary communications and satellites.

The Century Magazine published Tesla’s principles of telegraphy without wires, popularizing scientific lectures given before Franklin Institute in February 1893. The Electrical Review in 1896 published X-rays of a man, made by Tesla, with X-ray tubes of his own design. They appeared at the same time as when Roentgen announced his discovery of X-rays. Tesla never attempted to proclaim priority. Roentgen congratulated Tesla on his sophisticated X-ray pictures, and Tesla even wrote Roentgen’s name on one of his films. He experimented with shadowgraphs similar to those that later were to be used by Wilhelm Rontgen when he discovered X-rays in 1895. Tesla’s countless experiments included work on a carbon button lamp, on the power of electrical resonance, and on various types of lightning. Tesla invented the special vacuum tube which emitted light to be used in photography.

X-ray Tesla took of his hand

The breadth of his inventions is demonstrated by his patents for a bladeless steam turbine based on a spiral flow principle. Tesla also patented a pump design to operate at extremely high temperature.

Tesla’s bladeless turbine design

Nikola Tesla patented the basic system of radio in 1896. His published schematic diagrams describing all the basic elements of the radio transmitter which was later used by Marconi.

In 1896 Tesla constructed an instrument to receive radio waves. He experimented with this device and transmitted radio waves from his laboratory on South 5th Avenue to the Gerlach Hotel at 27th Street in Manhattan. The device had a magnet which gave off intense magnetic fields up to 20,000 lines per centimeter. The radio device clearly establishes his priority in the discovery of radio.

The shipboard quench-spark transmitter produced by the Lowenstein Radio Company and licensed under Nikola Tesla Company patents, was installed on the U.S. Naval vessels prior to World War I.

In December 1901, Marconi established wireless communication between Britain and the Newfoundland, Canada, earning him the Nobel prize in 1909. But much of Marconi’s work was not original. In 1864, James Maxwell theorized electromagnetic waves. In 1887, Heinrich Hertz proved Maxwell’s theories. Later, Sir Oliver Logde extended the Hertz prototype system. The Brandley coherer increased the distance messages could be transmitted. The coherer was perfected by Marconi.

However, the heart of radio transmission is based upon four tuned circuits for transmitting and receiving. It is Tesla’s original concept demonstrated in his famous lecture at the Franklin Institute in Philadelphia in 1893. The four circuits, used in two pairs, are still a fundamental part of all radio and television equipment.

The United States Supreme Court, in 1943 held Marconi’s most important patent invalid, recognizing Tesla’s more significant contribution as the inventor of radio technology.

Tesla built an experimental station in Colorado Springs, Colorado in 1899, to experiment with high voltage, high frequency electricity and other phenomena.

Tesla’s Colorado Springs laboratory

When the Colorado Springs Tesla Coil magnifying transmitter was energized, it created sparks 30 feet long. From the outside antenna, these sparks could be seen from a distance of ten miles. From this laboratory, Tesla generated and sent out wireless waves which mediated energy, without wires for miles.

In Colorado Springs, where he stayed from May 1899 until 1900, Tesla made what he regarded as his most important discovery– terrestrial stationary waves. By this discovery he proved that the Earth could be used as a conductor and would be as responsive as a tuning fork to electrical vibrations of a certain frequency. He also lighted 200 lamps without wires from a distance of 25 miles (40 kilometers) and created man-made lightning. At one time he was certain he had received signals from another planet in his Colorado laboratory, a claim that was met with disbelief in some scientific journals.

Nikola Tesla sitting in his Colorado Springs laboratory next to his huge “magnifying transmitter” Tesla coil which is producing 22 foot bolts of electricity

The old Waldorf Astoria was the residence of Nikola Tesla for many years. He lived there when he was at the height of financial and intellectual power. Tesla organized elaborate dinners, inviting famous people who later witnessed spectacular electrical experiments in his laboratory.

Financially supported by J. Pierpont Morgan, Tesla built the Wardenclyffe laboratory and its famous transmitting tower in Shoreham, Long Island between 1901 and 1905. This huge landmark was 187 feet high, capped by a 68-foot copper dome which housed the magnifying transmitter. It was planned to be the first broadcast system, transmitting both signals and power without wires to any point on the globe. The huge magnifying transmitter, discharging high frequency electricity, would turn the earth into a gigantic dynamo which would project its electricity in unlimited amounts anywhere in the world.

Tesla’s Wardenclyffe plant on Long Island in 1904. From this facility, Tesla hoped to demonstrate wireless transmission of electrical energy across the Atlantic.

Tesla’s concept of wireless electricity was used to power ocean liners, destroy warships, run industry and transportation and send communications instantaneously all over the globe. To stimulate the public’s imagination, Tesla suggested that this wireless power could even be used for interplanetary communication. If Tesla were confident to reach Mars, how much less difficult to reach Paris. Many newspapers and periodicals interviewed Tesla and described his new system for supplying wireless power to run all of the earth’s industry.

Because of a dispute between Morgan and Tesla as to the final use of the tower. Morgan withdrew his funds. The financier’s classic comment was, “If anyone can draw on the power, where do we put the meter?”

The erected, but incomplete tower was demolished in 1917 for wartime security reasons. The site where the Wardenclyffe tower stood still exists with its 100 feet deep foundation still intact. Tesla’s laboratory designed by Stanford White in 1901 is today still in good condition and is graced with a bicentennial plaque.

Tesla lectured to the scientific community on his inventions in New York, Philadelphia and St. Louis and before scientific organizations in both England and France in 1892. Tesla’s lectures and writings of the 1890s aroused wide admiration among contemporaries popularized his inventions and inspired untold numbers of younger men to enter the new field of radio and electrical science.

Nikola Tesla was one of the most celebrated personalities in the American press, in this century. According to Life Magazine’s special issue of September, 1997, Tesla is among the 100 most famous people of the last 1,000 years. He is one of the great men who divert the stream of human history. Tesla’s celebrity was in its height at the turn of the century. His discoveries, inventions and vision had widespread acceptance by the public, the scientific community and American press. Tesla’s discoveries had extensive coverage in the scientific journals, the daily and weekly press as well as in the foremost literary and intellectual publications of the day. He was the Super Star.

Tesla wrote many autobiographical articles for the prominent journal Electrical Experimenter, collected in the book, My Inventions. Tesla was gifted with intense powers of visualization and exceptional memory from early youth on. He was able to fully construct, develop and perfect his inventions completely in his mind before committing them to paper.

According to Hugo Gernsback, Tesla was possessed of a striking physical appearance over six feet tall with deep set eyes and a stately manner. His impressions of Tesla, were of a man endowed with remarkable physical and mental freshness, ready to surprise the world with more and more inventions as he grew older. A lifelong bachelor he led a somewhat isolated existence, devoting his full energies to science.

In 1894, he was given honorary doctoral degrees by Columbia and Yale University and the Elliot Cresson medal by the Franklin Institute. In 1934, the city of Philadelphia awarded him the John Scott medal for his polyphase power system. He was an honorary member of the National Electric Light Association and a fellow of the American Association for the Advancement of Science. On one occasion, he turned down an invitation from Kaiser Wilhelm II to come to Germany to demonstrate his experiments and to receive a high decoration.

In 1915, a New York Times article announced that Tesla and Edison were to share the Nobel Prize for physics. Oddly, neither man received the prize, the reason being unclear. It was rumored that Tesla refused the prize because he would not share with Edison, and because Marconi had already received his.

On his 75th birthday in 1931, the inventor appeared on the cover of Time Magazine. On this occasion, Tesla received congratulatory letters from more than 70 pioneers in science and engineering including Albert Einstein. These letters were mounted and presented to Tesla in the form of a testimonial volume.

Tesla on Time magazine commemorating his 75th birthday

Tesla died on January 7th, 1943 in the Hotel New Yorker, where he had lived for the last ten years of his life. Room 3327 on the 33rd floor is the two-room suites he occupied.

A state funeral was held at St. John the Divine Cathedral in New York City. Telegrams of condolence were received from many notables, including the first lady Eleanor Roosevelt and Vice President Wallace. Over 2000 people attended, including several Nobel Laureates. He was cremated in Ardsley on the Hudson, New York. His ashes were interned in a golden sphere, Tesla’s favorite shape, on permanent display at the Tesla Museum in Belgrade along with his death mask.

In his speech presenting Tesla with the Edison medal, Vice President Behrend of the Institute of Electrical Engineers eloquently expressed the following: “Were we to seize and eliminate from our industrial world the result of Mr. Tesla’s work, the wheels of industry would cease to turn, our electric cars and trains would stop, our towns would be dark and our mills would be idle and dead. His name marks an epoch in the advance of electrical science.” Mr. Behrend ended his speech with a paraphrase of Pope’s lines on Newton: “Nature and nature’s laws lay hid by night. God said ‘Let Tesla be’ and all was light.”

Nikola Tesla’s Awards and Recognition
In 1917, Tesla was awarded the Edison Medal, the most coveted electrical prize in the United States.
Nikola Tesla’s name has been honored with an International Unit of Magnetic Flux Density called “Tesla.”
The United States Postal Service honored Tesla with a commemorative stamp in 1983.
Tesla was inducted into the Inventor’s Hall of Fame in 1975.
The Nikola Tesla Award is one of the most distinguished honors presented by the Institute of Electrical Engineers. The award has been given annually since 1976.
The Nikola Tesla Statue is located on Goat Island to honor the man whose inventions were incorporated into the Niagara Falls Power Station in 1895. Tesla is known as the inventor of polyphase alternating current.
The Nikola Tesla Corner Sign, located at the intersection of 40th Street and 6th Avenue in Manhattan, is a constant reminder to all New Yorkers of the greatness of this genius.

Nikola Tesla Monument in Zagreb, Croatia

Nikola Tesla Corner in New York City

Nikola Tesla statue in Niagara Falls, Ontario

Nicola Tesla Museum in Belgrade, Serbia

Tesla sitting in front of a spiral coil used in his wireless power experiments at his East Houston St. laboratory

Source: https://www.teslasociety.com/biography.htm
https://en.wikipedia.org/wiki/Nikola_Tesla

Geostaionary Satellite-30

INTRODUCTION:-

India’s telecommunication satellite GSAT-30 was successfully launched into a Geosynchronous Transfer Orbit (GTO) on January 17, 2020 from Kourou  launch base, French Guiana by Ariane-5 VA-251.

GSAT-30 is configured on ISRO’s enhanced I-3K Bus structure to provide communication services from Geostationary orbit in C and Ku bands. The satellite derives its heritage from ISRO’s earlier INSAT/GSAT satellite series.

Weighing 3357 kg, GSAT-30 is to serve as replacement to INSAT-4A spacecraft services with enhanced coverage. The satellite provides Indian mainland and islands coverage in Ku-band and extended coverage in C-band covering Gulf countries, a large number of Asian countries and Australia.

The designed in-orbit operational life of GSAT-30 is more than 15 years.

Render of GSAT-30 spacecraft in deployed configuration with solar panels and reflectors extended.

MISSION :-

The satellite's main communication payload is 12 Ku band transponders for covering Indian mainland and islands and 12 C-brand transponders for extended coverage over Asia and Australia. The satellite will act as a replacement for the defunctioning INSAT-4A. The satellite will provide advanced telecommunication services to the Indian subcontinent. It will be used for VSAT networks, television uplinks, digital satellite newsgathering, DTH services and other communication systems. This is the 41^st communication satellite launched by ISRO and the 24^th launch of ISRO satellite by Arianespace

GSAT-30 (left) is positioned on the adapter that will serve as its interface with Ariane 5 prior to installation atop the launch vehicle. At right, KONNECT is lowered for its integration on the SYLDA dispenser. Photograph courtesy of Arianespace.

India set to boost communication services with launch of GSAT-30

SATELLITE:-

The satellite is based on ISRO's I-3K bus. It was assembled by a consortium of mid-sized industries led by Alpha Design Technologies Ltd. at ISRO Satellite Integration and Test Establishment at Bengaluru.

      Indian telecommunication satellite GSAT-30 was successfully launched into a GTO kourou.

LAUNCH:

GSAT-30 satellite was launched aboard Ariane-5 launch vehicle (VA251) from French Guiana on 21:05 UTC, 16 January 2020 or 02:35 IST, 17 January 2020. After three orbit raising burns with cumulative duration of 2 hours 29 minutes, GSAT-30 acquired station at 81°E on 25 January 2020.

ISRO Chairman K. Sivan 

ISRO's U R Rao Satellite Centre Director P Kunhikrishnan, who was present in Kourou, congratulated the ISRO community and Arianespace team on the successful launch.

Calling it an "excellent start" to 2020 for ISRO with the launch, he said, "The mission team at the master control facility have already acquired the satellite and they will immediately complete the post launch operations."

         Scientist group behind GSAT 30

Reference:-

• Journal 
• Website

SUBMITTED BY:-

JASMITHA .K

JENEVIA D’CUNHA

JOMY JOSEPH

JOYLINE REBELLO

KAVYA SURESH

LALITHA

1st M.Sc {2nd Semester}     

ORGANIC SOLAR CELL

INTRODUCTION

An organic solar cell or plastic solar cell is a type of photovoltaic that uses organic electronics, a branch of electronics that deals with conductive organic polymers or small organic molecules, for light absorption and charge transport to produce electricity from sunlight by the photovoltaic effect. Most organic photovoltaic cells are polymer solar cells.

The molecules used in organic solar cells are solution-processable at high throughput and are cheap, resulting in low production costs to fabricate a large volume. Combined with the flexibility of organic molecules, organic solar cells are potentially cost-effective for photovoltaic applications. Molecular engineering (e.g. changing the length and functional group of polymers) can change the band gap, allowing for electronic tunability. The optical absorption coefficient of organic molecules is high, so a large amount of light can be absorbed with a small amount of materials, usually on the order of hundreds of nanometers. The main disadvantages associated with organic photovoltaic cells are low efficiency, low stability and low strength compared to inorganic photovoltaic cells such as silicon solar cells.

Compared to silicon-based devices, polymer solar cells are lightweight (which is important for small autonomous sensors), potentially disposable and inexpensive to fabricate (sometimes using printed electronics), flexible, customizable on the molecular level and potentially have less adverse environmental impact. Polymer solar cells also have the potential to exhibit transparency, suggesting applications in windows, walls, flexible electronics, etc. The disadvantages of polymer solar cells are also serious: they offer about 1/3 of the efficiency of hard materials, and experience substantial photochemical degradation.

Polymer solar cells inefficiency and stability problems, combined with their promise of low costs and increased efficiency made them a popular field in solar cell research. As of 2015, polymer solar cells were able to achieve over 10% efficiency via a tandem structure. In 2018, a recordbreaking efficiency for organic photovoltaics of 17.3% was reached via tandem structure.

PHYSICS BEHIND

A photovoltaic cell is a specialized semiconductor diode that converts light into direct current (DC) electricity. Depending on the band gap of the light-absorbing material, photovoltaic cells can also convert low-energy, infrared (IR) or high-energy, ultraviolet (UV) photons into DC electricity. A common characteristic of both the small molecules and polymers used as the light-absorbing material in photovoltaics is that they all have large conjugated systems. A conjugated system is formed where carbon atoms covalently bond with alternating single and double bonds. These hydrocarbons' electrons orbitals delocalize and form a delocalized bonding π orbital with a π* antibonding orbital. The delocalized π orbital is the highest occupied molecular orbital (HOMO), and the π* orbital is the lowest unoccupied molecular orbital (LUMO). In organic semiconductor physics, the HOMO takes the role of the valence band while the LUMO serves as the conduction band. The energy separation between the HOMO and LUMO energy levels is considered as the band gap of organic electronic materials and is typically in the range of 1–4 eV.

All light with energy greater than the band gap of the material can be absorbed, though there is a trade-off to reducing the band gap as photons absorbed with energies higher than the band gap will thermally give off its excess energy, resulting in lower voltages and power conversion efficiencies. When these materials absorb a photon, an excited state is created and confined to a molecule or a region of a polymer chain. The excited state can be regarded as an exciton, or an electron-hole pair bound together by electrostatic interactions. In photovoltaic cells, excitons are broken up into free electron-hole pairs by effective fields. The effective fields are set up by creating a heterojunction between two dissimilar materials. In organic photovoltaics, effective fields break up excitons by causing the electron to fall from the conduction band of the absorber to the conduction band of the acceptor molecule. It is necessary that the acceptor material has a conduction band edge that is lower than that of the absorber material.

COMMERCIALIZATION

Polymer solar cells have yet to commercially compete with silicon solar cells and other thin-film cells. The present efficiency of polymer solar cells lies near 10%, well below silicon cells. Polymer solar cells also suffer from environmental degradation, lacking effective protective coatings.

    

Further improvements in performance are needed to promote charge carrier diffusion; transport must be enhanced through control of order and morphology and interface engineering must be applied to the problem of charge transfer across interfaces.

Research is being conducted into using tandem architecture in order to increase efficiency of polymer solar cells. Similar to inorganic tandem architecture, organic tandem architecture is expected to increase efficiency. Compared with a single-junction device using low-bandgap materials, the tandem structure can reduce heat loss during photon-to-electron conversion.

Polymer solar cells are not widely produced commercially. Starting in 2008, Konarka Technologies started production of polymer-fullerene solar cells. The initial modules were 3–5% efficient, and only last for a few years. Konarka has since filed for bankruptcy, as those polymer solar cells were unable to penetrate the PV market.

CHALLENGES AND FUTURE PLANS

Difficulties associated with organic photovoltaic cells include their low external quantum efficiency (up to 70%) compared to inorganic photovoltaic devices, despite having good internal quantum efficiency; this is due to insufficient absorption with active layers on the order of 100 nanometers. Instabilities against oxidation and reduction, recrystallization and temperature variations can also lead to device degradation and decreased performance over time. This occurs to different extents for devices with different compositions, and is an area into which active research is taking place.

Other important factors include the exciton diffusion length, charge separation and charge collection which are affected by the presence of impurities.

REFERENCE

1.    The Mathrubhumi Printers & Publishers.

2.    Mathrubhumi GK & current Affairs.

3.    Phy.org

4.    Wikipedia

Submitted by,

ABHIJITH K TOMY           

AMRUTHA KT                  

ANUSREE C                      

APARNA                           

GOKUL DAS T                  

GOPIKA A K                      

INDRAJ YATHEENDRAN 

Ist MSc Physics