Magellan's fleet circles the earth - History

Magellan's fleet circles the earth - History


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Magellan ExpeditionCompletes Circle of Globe- 1522

Ferdinand Magellan spent seven years sailing for the Portuguese in the Far East. He believed it would be easier to sail westward than to sail around Africa. King Manuel of Portugal was unwilling to support such a voyage, but King Charles V of Spain gave him a fleet of five ships. Magellan sailed in August 1519 from Seville.

The fleet wintered at Port St. Julian. The captains of the four ships mutinied. Magellan won. He hung many of those who mutinied. The ships then made their way south, along the coast of South America. On October 21st, 1520, Magellan discovered the straits that continue to bear his name. The fleet, which was down to three ships, spent 38 days making its way through the three hundred thirty eight mile straits. On November 28, 1520, Magellan's three ships emerged into the Pacific Ocean.

The ships then sailed across the Pacific Ocean. The first part of the voyage took fourteen weeks. They finally reached Guam, where they were able to obtain food and supplies. They continued on to Philippines. There, Magellan became involved in a civil war. He died in that war at Mactan on April 27, 1521. On December 21, one remaining ship, the Vittoria, set off on a westward course, under the leadership of Captain Juan Sebastian del Cano. Over a year later, on September 9, 1522, 18 of the 239 men who had set forth on the voyage arrived back in Seville.



Circumnavigation

Circumnavigation is the complete navigation around an entire island, continent, or astronomical body (e.g. a planet or moon). This article focuses on the circumnavigation of Earth.

The first recorded circumnavigation of the Earth was the Magellan-Elcano expedition, which sailed from Seville, Spain in 1519 and returned in 1522, after crossing the Atlantic, Pacific, and Indian oceans. Since the rise of commercial aviation in the late 20th century, circumnavigating Earth is straightforward, usually taking days instead of years. [1] Today, the challenge of circumnavigating Earth has shifted towards human and technological endurance, speed, and less conventional methods.


Contents

1519 Edit

September 20: Departure from Sanlúcar de Barrameda.

September 26 - October 3: Stopping in the Canary Islands to take in provisions. [3]

November 29: Fleet reaches the vicinity of Cape St. Augustine. [4]

December 13: Entering the bay of Rio de Janeiro.

December 27: Departure from Rio de Janeiro. [5]

1520 Edit

January 10: Cape Santa María. Severe storm then forces Magellan to reverse course and head north, toward Paranaguá Bay. [6]

January 12: Rio de la Plata

February 3: the fleet resumes its southward course but San Antonio found to be leaking badly. Halted for repairs. [6]

February 5: Cape Corrientes

February 24: San Matías Gulf

February 27: Entering Bahia de los Patos.

March 31: Beginning of the overwintering stay at Puerto San Julián.

April 1 and 2: Mutiny on Victoria, Concepcion and San Antonio death of Louis de Mendoza. Later execution of de Quesada, marooning of de Cartagena. Alvaro de Mesquita becomes captain of San Antonio, Duarte Barbosa of Victoria.

End of April: Santiago is sent on a mission to find the passage. The ship is caught in a storm and wrecked. Survivors return to Puerto San Julián. Serrano (João Serrão) becomes captain of the Concepcion. [7]

August 23 or 24: Fleet departs Puerto San Julián for Río Santa Cruz. [8] [9]

October 18: Fleet leaves Santa Cruz. [10]

October 21: Arriving at the Cape of the Eleven Thousand Virgins, entry to what would be known as Strait of Magellan.

End of October: San Antonio, charged to explore Magdalen Sound, fails to return to the fleet, instead sails back to Spain under Estêvão Gomes who imprisoned captain de Mesquita. The ship arrives in Spain on May 21, 1521.

November 28: The fleet leaves the strait and enters the Pacific Ocean. [11]

When out in the Pacific some of the crew get scurvy.

1521 Edit

January 24/25-28: Landfall on an uninhabited island, which Magellan names St Paul's (probably Puka-Puka). They stay for a few days before continuing on. [12] [13]

March 6: Arrival at Guam and encounters with the Chamorro people.

March 16: Arrival of Magellan's expedition to one of the Philippine Islands. They headed to Suluan and dropped anchor for a few hours of respite. Suluan is a small island in the province of Eastern Samar. They next dropped anchor at Homonhon, another small island in the province of Eastern Samar. They were detected by the boats of Rajah Kolambu who was visiting Mazaua, who later guided them to Cebu, on April 7.

April 27: Death of Magellan in the Battle of Mactan. Serrano and Barbosa are voted co-commanders.

May 1: At a local banquet Barbosa and 27 sailors (including Afonso de Góis, the new captain of Victoria after the election of Barbosa and Serrano) are murdered and Serrano captured, later killed. The three remaining ships escape.

May 2: There are not enough men to handle three ships, thus the worm-infested Concepcion is burned down. Two ships remain: Victoria and Trinidad. Gonzalo Gomez de Espinosa becomes captain of Victoria. Joao Lopez Carvalho is made as the Captain General. The ships sail to Mindanao and Brunei.

September 21: Carvalho is replaced by Espinosa as Captain-General. Juan Sebastian Elcano becomes captain of Victoria.

November 8: Arriving at Tidore in the Moluccas.

December 21: Victoria under the command of Elcano leaves the Moluccas to return home, sailing west towards the Cape of Good Hope. Trinidad remains at Tidore for repairs.

1522 Edit

January 25: Victoria reaches Timor and starts to cross the Indian Ocean.

April 6: Trinidad under the command of Espinosa leaves the Moluccas heading home sailing east. After five weeks, Espinosa decides to return to the Moluccas where he and his ship are captured by a Portuguese fleet under Antonio de Brito. However, the ship was wrecked during a storm.

May 22: Victoria passes the Cape of Good Hope and enters the Atlantic Ocean.

July 9: Victoria reaches Santiago, Cape Verde.

September 6: Victoria returns to Sanlúcar de Barrameda under the command of Elcano, two weeks shy of three years after setting sail.

September 8: Victoria arrives at Seville, technically completing the circumnavigation.


Magellan’s voyage 1519-1522

This map is part of a series of 16 animated maps showing the history of The Age of Discovery.

The expedition led by Magellan was expected to sail as far as the Spice Islands to the west by sailing around the American continent.

It was financed by Spain, which hoped to gain access to these islands and their spices without crossing the Indian Ocean, then dominated by the Portuguese.

Magellan knew that there was an ocean between the New World and Asia, and he had information on the South American coast as far as the Rio de la Plata.

The presence of this deep bay at roughly the same latitude as the southernmost point in Africa made Magellan hope that there was a passage across the new continent.

His fleet of five ships left Spain on 20 September 1519.

In December, it made its first port of call in the bay of what is now Rio de Janeiro.

By mid-January, the ships had reached the Rio de la Plata. Magellan soon realized that this bay did not offer a passage across the continent.

Continuing south, the fleet had to sail through increasingly difficult weather conditions. At the end of March, Magellan decided to wait until the end of the southern winter in a sheltered bay known as the San Julian Bay.

During these 5 winter months, the explorer had to put down a mutiny with force, and one of his ships, the Santiago, which had been sent to explore a neighbouring bay, capsized.

The fleet set off again in August. By the end of October, it had reached a large bay in which the strong currents made Magellan think that he had found the long-sought-after passage.

It took him another month to navigate through the maze of canals, and during this time the crew of the San Antonio mutinied and decided to return to Spain.

The three remaining ships finally found their way into the new sea on 27 November.

The crossing of the Pacific Ocean was particularly long and arduous. After three and a half months, the crew was weak with hunger and scurvy, but they finally reached the Mariana Islands, where they were able to take on stores before continuing on their journey west.

The expedition made land in the Philippines on 17 March 1521, but Magellan was killed a few weeks later during a fight with the local population.

Since they had lost a lot of men, it was decided to burn one of the three ships. The last two ships, the Trinidad and the Victoria, reached their target, the Spice Islands, on 28 November.

Laden with spices, the two ships set off on their return journey, taking two opposite directions. The Trinidad did not succeed in making the journey back to Europe via the Pacific Ocean, while the Victoria decided to sail to Spain via the Indian Ocean.

It rounded the Cape of Good Hope on 18 May, and sailed north through the Atlantic, making a port call in the Islands of Cap Verde. The Victoria reached Spain on 6 September 1522, almost exactly three years after its departure.

This expedition, which succeeded the crossing of an immense and totally unknown ocean, is one of the greatest adventures in the history of navigation and proved that it was possible to sail around the world.


Contents

Beginning in the late 1970s, scientists advocated for a radar mapping mission to Venus. They first sought to construct a spacecraft named the Venus Orbiting Imaging Radar (VOIR), but it became clear that the mission would be beyond the budget constraints during the ensuing years. The VOIR mission was canceled in 1982.

A simplified radar mission proposal was recommended by the Solar System Exploration Committee, and this one was submitted and accepted as the Venus Radar Mapper program in 1983. The proposal included a limited focus and a single primary scientific instrument. In 1985, the mission was renamed Magellan, in honor of the sixteenth-century Portuguese explorer Ferdinand Magellan, known for his exploration, mapping, and circumnavigation of the Earth. [1] [2] [3]

The objectives of the mission included: [4]

  • Obtain near-global radar images of the Venusian surface with a resolution equivalent to optical imaging of 1.0 km per line pair. (primary)
  • Obtain a near-global topographic map with 50 km spatial and 100 m vertical resolution.
  • Obtain near-global gravity field data with 700 km resolution and two to three milligals of accuracy.
  • Develop an understanding of the geological structure of the planet, including its density distribution and dynamics.

The spacecraft was designed and built by the Martin Marietta Company, [5] and the Jet Propulsion Laboratory (JPL) managed the mission for NASA. Elizabeth Beyer served as the program manager and Joseph Boyce served as the lead program scientist for the NASA headquarters. For JPL, Douglas Griffith served as the Magellan project manager and R. Stephen Saunders served as the lead project scientist. [1]

To save costs, most of the Magellan probe was made up of flight spare parts and reused design elements from other spacecraft: [6]

Component Origin
Attitude control computer Galileo
Bus Voyager program
Command and data subsystem Galileo
High- and low-gain antenna Voyager program
Medium-gain antenna Mariner 9
Power distribution unit Galileo
Propellant tank Space Shuttle auxiliary power unit
Pyrotechnic control Galileo
Radio-frequency traveling-wave tube assemblies Ulysses
Solid rocket motor Space Shuttle Payload Assist Module
Star scanner Inertial Upper Stage
Thrusters Voyager program

The main body of the spacecraft, a spare one from the Voyager missions, was a 10-sided aluminum bus, containing the computers, data recorders, and other subsystems. The spacecraft measured 6.4 meters tall and 4.6 meters in diameter. Overall, the spacecraft weighed 1,035 kilograms and carried 2,141 kilograms of propellant for a total mass of 3,449 kilograms. [2] [7]

Attitude control and propulsion Edit

The spacecraft's attitude control (orientation) was designed to be three-axis stabilized, including during the firing of the Star 48B solid rocket motor (SRM) used to place it into orbit around Venus. Prior to Magellan, all spacecraft SRM firings had involved spinning spacecraft, which made control of the SRM a much easier task. In a typical spin mode, any unwanted forces related to SRM or nozzle mis-alignments are cancelled out. In the case of Magellan, the spacecraft design did not lend itself to spinning, so the resulting propulsion system design had to accommodate the challenging control issues with the large Star 48B SRM. The Star 48B, containing 2,014 kg of solid propellant, developed a thrust of

89,000 Newton (20,000 lbf) shortly after firing therefore, even a 0.5% SRM alignment error could generate side forces of 445 N (100 lbf). Final conservative estimates of worst-case side forces resulted in the need for eight 445 N thrusters, two in each quadrant, located out on booms at the maximum radius that the Space Shuttle Orbiter Payload Bay would accommodate (4.4-m or 14.5-ft diameter). [ citation needed ]

The actual propulsion system design consisted of a total of 24 monopropellant hydrazine thrusters fed from a single 71 cm (28 in) diameter titanium tank. The tank contained 133 kg (293 lb) of purified hydrazine. The design also included a pyrotechnically-isolated external high pressure tank with additional helium that could be connected to the main tank prior to the critical Venus orbit insertion burn to ensure maximum thrust from the 445 N thrusters during the SRM firing. Other hardware regarding orientation of the spacecraft consists of a set of gyroscopes and a star scanner. [2] [3] [7] [8]

Communications Edit

For communications, the spacecraft included a lightweight graphite/aluminum, 3.7-meter high-gain antenna left over from the Voyager Program and a medium-gain antenna spare from the Mariner 9 mission. A low-gain antenna attached to the high-gain antenna was also included for contingencies. When communicating with the Deep Space Network, the spacecraft was able to simultaneously receive commands at 1.2 kilobits/second in the S-band and transmit data at 268.8 kilobits/second in the X-band. [2] [3] [7] [8]

Power Edit

Magellan was powered by two square solar arrays, each measuring 2.5 meters across. Together, the arrays supplied 1,200 watts of power at the beginning of the mission. However, over the course of the mission the solar arrays gradually degraded due to frequent, extreme temperature changes. To power the spacecraft while occulted from the Sun, twin 30 amp-hour, 26-cell, nickel-cadmium batteries were included. The batteries recharged as the spacecraft received direct sunlight. [2] [7]

Computers and data processing Edit

The computing system on the spacecraft was partially modified equipment from the Galileo. There were two ATAC-16 computers forming one redundant system, located in the attitude-control subsystem, and four RCA 1802 microprocessors, as two redundant systems, to control the command and data subsystem (CDS). The CDS was able to store commands for up to three days, and also to autonomously control the spacecraft if problems were to arise while mission operators were not in contact with the spacecraft. [9]

For storing the commands and recorded data, the spacecraft also included two multitrack digital tape recorders, able to store up to 225 megabytes of data until contact with the Earth was restored and the tapes were played back. [2] [7] [8]

Scientific instruments Edit

Thick and opaque, the atmosphere of Venus required a method beyond optical survey, to map the surface of the planet. The resolution of conventional radar depends entirely on the size of the antenna, which is greatly restricted by costs, physical constraints by launch vehicles and the complexity of maneuvering a large apparatus to provide high resolution data. Magellan addressed this problem by using a method known as synthetic aperture, where a large antenna is imitated by processing the information gathered by ground computers. [10] [11]

The Magellan high-gain parabolic antenna, oriented 28°–78° to the right or left of nadir, emitted thousands of microwave pulses per second that passed through the clouds and to the surface of Venus, illuminating a swath of land. The Radar System then recorded the brightness of each pulse as it reflected back off the side surfaces of rocks, cliffs, volcanoes and other geologic features, as a form of backscatter. To increase the imaging resolution, Magellan recorded a series of data bursts for a particular location during multiple instances called, "looks". Each "look" slightly overlapped the previous, returning slightly different information for the same location, as the spacecraft moved in orbit. After transmitting the data back to Earth, Doppler modeling was used to take the overlapping "looks" and combine them into a continuous, high resolution image of the surface. [10] [11] [12]

The data was collected at 750 kilobits/second to the tape recorder and later transmitted to Earth to be processed into usable images, by the Radar Data Processing Subsystem (RDPS), a collection of ground computers operated by JPL. [10] [13] [14] [15]

Other science Edit

In addition to the radar data, Magellan collected several other types of scientific measurements. These included detailed measurements of the Venus gravitational field, [16] measurements of the atmospheric density, and radio occultation data on the atmospheric profile.

Gallery Edit

Annotated diagram of Magellan

Magellan during pre-flight checkout

Magellan with its Star 48B solid rocket motor undergoing final checks at the Kennedy Space Center

Magellan being fixed into position inside the payload bay of Atlantis prior to launch

Launch and trajectory Edit

Magellan was launched on May 4, 1989, at 18:46:59 UTC by the National Aeronautics and Space Administration from KSC Launch Complex 39B at the Kennedy Space Center in Florida, aboard Space Shuttle Atlantis during mission STS-30. Once in orbit, the Magellan and its attached Inertial Upper Stage booster were deployed from Atlantis and launched on May 5, 1989 01:06:00 UTC, sending the spacecraft into a Type IV heliocentric orbit where it would circle the Sun 1.5 times, before reaching Venus 15 months later on August 10, 1990. [3] [7] [8]

Originally, the Magellan had been scheduled for launch in 1988 with a trajectory lasting six months. However, due to the Space Shuttle Challenger disaster in 1986, several missions, including Galileo and Magellan, were deferred until shuttle flights resumed in September 1988. Magellan was planned to be launched with a liquid-fueled, Centaur G upper-stage booster, carried in the cargo bay of the Space Shuttle. However, the entire Centaur G program was canceled after the Challenger disaster, and the Magellan probe had to be modified to be attached to the less-powerful Inertial Upper Stage. The next best opportunity for launching occurred in October 1989. [3] [7]

Further complicating the launch however, was the launching of the Galileo mission to Jupiter, one that included a fly-by of Venus. Intended for launch in 1986, the pressures to ensure a launch for Galileo in 1989, mixed with a short launch-window necessitating a mid-October launch, resulted in replanning the Magellan mission. Wary of rapid shuttle launches, the decision was made to launch Magellan in May, and into an orbit that would require one year, three months, before encountering Venus. [3] [7]

The spacecraft in a deployment position in Atlantis' payload bay

Deployment of Magellan with Inertial Upper Stage booster

Trajectory of Magellan to Venus

Orbital encounter of Venus Edit

On August 10, 1990, Magellan encountered Venus and began the orbital insertion maneuver which placed the spacecraft into a three-hour, nine minute, elliptical orbit that brought the spacecraft 295-kilometers from the surface at about 10 degrees North during the periapsis and out to 7762-kilometers during apoapsis. [7] [8]

During each orbit, the space probe captured radar data while the spacecraft was closest to the surface, and then transmit it back to Earth as it moved away from Venus. This maneuver required extensive use of the reaction wheels to rotate the spacecraft as it imaged the surface for 37-minutes and as it pointed toward Earth for two hours. The primary mission intended for the spacecraft to return images of at least 70 percent of the surface during one Venusian day, which lasts 243 Earth days as the planet slowly spins. To avoid overly-redundant data at the highest and lowest latitudes, the Magellan probe alternated between a Northern-swath, a region designated as 90 degrees north latitude to 54 degrees south latitude, and a Southern-swath, designated as 76 degrees north latitude to 68 degrees south latitude. However, due to periapsis being 10 degrees north of the equatorial line, imaging the South Pole region was unlikely. [7] [8]

Mapping cycle 1 Edit

The primary mission began on September 15, 1990, with the intention to provide a "left-looking" map of 70% of the Venusian surface at a minimum resolution of 1-kilometer/pixel. During cycle 1, the altitude of the spacecraft varied from 2000-kilometers at the north pole, to 290-kilometers near periapsis. Upon completion during May 15, 1991, having made 1,792 orbits, Magellan had mapped approximately 83.7% of the surface with a resolution between 101 and 250-meters/pixel. [8] [18]

Mission extension Edit

Mapping cycle 2 Edit

  • Goal: Image the south pole region and gaps from Cycle 1.[19]
  • May 15, 1991 – January 14, 1992

Beginning immediately after the end of cycle 1, cycle 2 was intended to provide data for the existing gaps in the map collected during first cycle, including a large portion of the southern hemisphere. To do this, Magellan had to be reoriented, changing the gathering method to "right-looking". Upon completion during mid-January 1992, cycle 2 provided data for 54.5% of the surface, and combined with the previous cycle, a map containing 96% of the surface could be constructed. [8] [18]

Mapping cycle 3 Edit

  • Goal: Fill remaining gaps and collect stereo imagery.[19]
  • January 15, 1992 – September 13, 1992

Immediately after cycle 2, cycle 3 began collecting data for stereo imagery on the surface that would later allow the ground team to construct, clear, three-dimensional renderings of the surface. Approximately 21.3% of the surface was imaged in stereo by the end of the cycle on September 13, 1992, increasing the overall coverage of the surface to 98%. [8] [18]

Map of the stereo imaging collected by Magellan during cycle 3

Eistla Regio featuring Gula Mons reprojected in 3D from stereo data

Volcanic dome in Alpha Regio observed from reprojecting stereo data

Mapping cycle 4 Edit

Upon completing cycle 3, Magellan ceased imaging the surface. Instead, beginning mid-September 1992, the Magellan maintained pointing of the high-gain antenna toward Earth where the Deep Space Network began recording a constant stream of telemetry. This constant signal allowed the DSN to collect information on the gravitational field of Venus by monitoring the velocity of the spacecraft. Areas of higher gravitation would slightly increase the velocity of the spacecraft, registering as a Doppler shift in the signal. The space craft completed 1,878 orbits until completion of the cycle on May 23, 1993 a loss of data at the beginning of the cycle necessitated an additional 10 days of gravitational study. [8] [18]

Mapping cycle 5 Edit

  • Goal: Aerobraking to circular orbit and global gravity measurements.[19]
  • May 24, 1993 – August 29, 1994

At the end of the fourth cycle in May 1993, the orbit of Magellan was circularized using a technique known as aerobraking. The circularized orbit allowed a much higher resolution of gravimetric data to be acquired when cycle 5 began on August 3, 1993. The spacecraft performed 2,855 orbits and provided high-resolution gravimetric data for 94% of the planet, before the end of the cycle on August 29, 1994. [2] [3] [8] [18]

Aerobraking Edit

Aerobraking had long been sought as a method for slowing the orbit of interplanetary spacecraft. Previous suggestions included the need for aeroshells that proved too complicated and expensive for most missions. Testing a new approach to the method, a plan was devised to drop the orbit of Magellan into the outermost region of the Venusian atmosphere. Slight friction on the spacecraft slowed the velocity over a period, slightly longer than two months, bringing the spacecraft into an approximately circular orbit with periapse altitude at 180 km and apoapse altitude at 540 km, down from an apoapse altitude at 8467 km. [20] The method has since been used extensively on later interplanetary missions. [8] [18]

Mapping cycle 6 Edit

  • Goal: Collect high-resolution gravity data and conduct radio science experiments.[19]
  • April 16, 1994 – October 13, 1994

The sixth and final orbiting cycle was another extension to the two previous gravimetric studies. Toward the end of the cycle, a final experiment was conducted, known as the "Windmill" experiment to provide data on the composition of the upper atmosphere of Venus. Magellan performed 1,783 orbits before the end of the cycle on October 13, 1994, when the spacecraft entered the atmosphere and disintegrated. [8]

Windmill experiment Edit
  • Goal: Collect data on atmospheric dynamics.[21]
  • September 6, 1994 – September 14, 1994

In September 1994, the orbit of Magellan was lowered to begin the "Windmill experiment". During the experiment, the spacecraft was oriented with the solar arrays broadly, perpendicular to the orbital path, where they could act as paddles as they impacted molecules of the upper-Venusian atmosphere. Countering this force, the thrusters fired to keep the spacecraft from spinning. This provided data on the basic oxygen gas-surface interaction. This was useful for understanding the impact of upper-atmospheric forces which aided in designing future Earth-orbiting satellites, and methods for aerobraking during future planetary spacecraft missions. [18] [21] [22]

Results Edit

  • Study of the Magellan high-resolution global images is providing evidence to better understand Venusian geology and the role of impacts, volcanism, and tectonics in the formation of Venusian surface structures.
  • The surface of Venus is mostly covered by volcanic materials. Volcanic surface features, such as vast lava plains, fields of small lava domes, and large shield volcanoes are common.
  • There are few impact craters on Venus, suggesting that the surface is, in general, geologically young - less than 800 million years old.
  • The presence of lava channels over 6,000 kilometers long suggests river-like flows of extremely low-viscosity lava that probably erupted at a high rate.
  • Large pancake-shaped volcanic domes suggest the presence of a type of lava produced by extensive evolution of crustal rocks.
  • The typical signs of terrestrial plate tectonics - continental drift and basin floor spreading - are not evident on Venus. The planet's tectonics is dominated by a system of global rift zones and numerous broad, low domical structures called coronae, produced by the upwelling and subsidence of magma from the mantle.
  • Although Venus has a dense atmosphere, the surface reveals no evidence of substantial wind erosion, and only evidence of limited wind transport of dust and sand. This contrasts with Mars, where there is a thin atmosphere, but substantial evidence of wind erosion and transport of dust and sand.

Magellan created the first (and currently the best) near-photographic quality, high resolution radar mapping of the planet's surface features. Prior Venus missions had created low resolution radar globes of general, continent-sized formations. Magellan, however, finally allowed detailed imaging and analysis of craters, hills, ridges, and other geologic formations, to a degree comparable to the visible-light photographic mapping of other planets. Magellan's global radar map currently remains as the most detailed Venus map in existence, although the upcoming NASA VERITAS and Roskosmos Venera-D probes will carry a radar that can achieve a much higher resolution compared to the radar used by Magellan. Both probes are expected to launch in 2029.

Volcanoes as seen in the Fortuna region of Venus

A meandering lava channel from Fortuna Tessera to Sedna Planitia

An unusual volcanic edifice in the Eistla region

The Magellan project was set up so that the initial images and data from the Magellan probe were only for use and study by a team of principal investigators from a variety of universities and institutions, and by the Magellan Project Science Team. These scientists were responsible for validating the data, contributing input for spacecraft acquisition of data, and interpreting the data results for their release to the public. Data was shared with three visiting Soviet scientists (Alexander Basilevsky, Effaim Akim and Alexander Zacharov), a first, and sensitive issue, for NASA at the time considering the Cold War was just coming to a close.

The Magellan Project Science room became notorious for its hanging of long thermal print strips of image data (FBIDRs) along the walls of a spacious room. This was the first form in which the imagery of the surface of Venus was seen due to the long, narrow swathes acquired by the spacecraft. Significant guests during the mission's operation included Margaret Thatcher.

After the initial investigation stage Magellan's full data set was released for public consumption.

Project Science Team Edit

The Magellan Project Science Team consisted of Dr. R. Stephen Saunders, the Project Scientist Dr. Ellen Stofan, the Deputy Project Scientist research assistants Tim Parker, Dr. Jeff Plaut, and Annette deCharon and Project Science Aide, Gregory Michaels.

Other Magellan scientists were involved with the mission's science including principal investigators and three visiting Soviet scientists.

On September 9, 1994, a press release outlined the termination of the Magellan mission. Due to the degradation of the power output from the solar arrays and onboard components, and having completed all objectives successfully, the mission was to end in mid-October. The termination sequence began in late August 1994, with a series of orbital trim maneuvers which lowered the spacecraft into the outermost layers of the Venusian atmosphere to allow the Windmill experiment to begin on September 6, 1994. The experiment lasted for two weeks and was followed by subsequent orbital trim maneuvers, further lowering the altitude of the spacecraft for the final termination phase. [21]

On October 11, 1994, moving at a velocity of 7 kilometers/second, the final orbital trim maneuver was performed, placing the spacecraft 139.7 kilometers above the surface, well within the atmosphere. At this altitude the spacecraft encountered sufficient ram pressure to raise temperatures on the solar arrays to 126 degrees Celsius. [17] [23]

On October 13, 1994 at 10:05:00 UTC, communication was lost when the spacecraft entered radio occultation behind Venus. The team continued to listen for another signal from the spacecraft until 18:00:00 UTC, when the mission was determined to have concluded. Although much of Magellan was expected to vaporize due to atmospheric stresses, some amount of wreckage is thought have hit the surface by 20:00:00 UTC. [17] [18]

Quoted from Status Report - October 13, 1994 [17]

Communication with the Magellan spacecraft was lost early Wednesday morning, following an aggressive series of five Orbit Trim Maneuvers (OTMs) on Tuesday, October 11, which took the orbit down into the upper atmosphere of Venus. The Termination experiment (extension of September "Windmill" experiment) design was expected to result in final loss of the spacecraft due to a negative power margin. This was not a problem since spacecraft power would have been too low to sustain operations in the next few weeks due to continuing solar cell loss.

Thus, a final controlled experiment was designed to maximize mission return. This final, low altitude was necessary to study the effects of a carbon dioxide atmosphere.

The final OTM took the periapsis to 139.7 km (86.8 mi) where the sensible drag on the spacecraft was very evident. The solar panel temperatures rose to 126 deg. C. and the attitude control system fired all available Y-axis thrusters to counteract the torques. However, attitude control was maintained to the end.

The main bus voltage dropped to 24.7 volts after five orbits, and it was predicted that attitude control would be lost if the power dropped below 24 volts. It was decided to enhance the Windmill experiment by changing the panel angles for the remaining orbits. This was also a preplanned experiment option.

At this point, the spacecraft was expected to survive only two orbits.

Magellan continued to maintain communication for three more orbits, even though the power continued to drop below 23 volts and eventually reached 20.4 volts. At this time, one battery went off-line, and the spacecraft was defined as power starved.

Communication was lost at 3:02 AM PDT just as Magellan was about to enter an Earth occultation on orbit 15032. Contact was not re-established. Tracking operations were continued to 11:00 AM but no signal was seen, and none was expected. The spacecraft should land on Venus by 1:00 PM PDT Thursday, October 13, 1994.


Legacy

Magellan was undoubtedly one of the most skilled sailors of the great age of European maritime discoveries. Yet because he sailed in the service of the king of Spain, Portuguese historians have tended not to grant him the credit given to other eminent Portuguese navigators, such as Bartolomeu Dias and Vasco da Gama. Spanish historians, on the other hand, have preferred to emphasize the role of the Spanish (actually Basque) navigator Cano. However, Magellan did only what his predecessors Christopher Columbus, John Cabot, and Amerigo Vespucci had done: lacking the opportunity to pursue their goals under the sponsorship of their own country, they looked for support elsewhere. This was a common attitude in the 15th and 16th centuries, a time before the age of nationalism and a time when men pledged allegiance not to the place where they were born but to a king. The early explorers served the monarch who supported their goals of fortune and fame, and the monarch in turn accepted the fealty of men who would enhance the wealth and power of the crown.

Notwithstanding the neglect of Iberian historians, Magellan’s complex character, his uncommonly eventful life, and the extreme difficulty of the voyage itself have fueled imaginations ever since the first account of the expedition—recorded by one of its few survivors, Antonio Pigafetta—appeared in the 16th century. Later biographers, such as the 20th-century writer Stefan Zweig, have portrayed Magellan as a symbol of the human capacity to succeed against all odds. Other contemporary authors have attempted to illustrate the magnitude of his accomplishment by likening his voyage through unknown waters to the first explorations of space.

Such a comparison might even be said to underestimate Magellan’s feat—a 16th-century maritime expedition was arguably much more unpredictable, and hence far more perilous, than computer-assisted space travel—but in any case, the achievements of Magellan were of profound importance. His supreme accomplishment was the discovery and crossing of the South American strait that bears his name—a major navigational task, considering the knowledge of the period. Moreover, being the first to traverse the “Sea of the South” from east to west, he demonstrated the immensity of the Pacific Ocean and the challenges it posed to navigation. Finally, the idea of the voyage itself had relied on the not-undisputed idea of a spherical Earth. The circumnavigation completed by Magellan’s expedition thus confirmed the conception of the world as a globe.


Was Magellan the first person to circumnavigate the globe?

The Portuguese explorer Ferdinand Magellan is often credited as being the first person to have circumnavigated the globe, but the reality of his journey is a bit more complicated. Magellan first set sail in September 1519 as part of an epic attempt to find a western route to the spice-rich East Indies in modern-day Indonesia. While he successfully led his crew across the Atlantic, through a strait in southern South America and over the vast expanse of the Pacific, he was killed only halfway through the circuit in a skirmish with natives on the Philippine island of Mactan. Magellan’s death meant that he personally failed to circle the world, but his expedition continued on without him. In September 1522, one of his ships arrived safely back in Spain having completed a successful circumnavigation of the globe. Of the mission’s 260 original crewmen, only 18 had survived the perilous three-year journey.

If Magellan wasn’t the first person to circle the globe, then who was? The most obvious candidate is Juan Sebastian Elcano, a Basque mariner who took control of the expedition after Magellan’s death in 1521 and captained its lone surviving vessel, the “Victoria,” on its journey back to Spain. Elcano and his sailors stand as the first people to have successfully voyaged around the world as part of a single journey, but they might not be the first humans to have circumnavigated the globe over the course of a lifetime. Opinions differ, but many historians give the honor to Magellan’s Malay slave, Enrique. Magellan had seized Enrique from Malacca during an earlier 1511 voyage to the East Indies, and the Malay later served as the round-the-world expedition’s interpreter in the Pacific islands. Enrique had previously traveled west with Magellan from Asia to Europe before joining in the voyage across the Atlantic and Pacific, so by the time the mission reached Southeast Asia, he had very nearly circled the globe and returned to his homeland𠅊lbeit over the course of several years and multiple voyages. Enrique abandoned the expedition and disappeared shortly after Magellan’s death in the Philippines. By then, he was only a few hundred miles short of his point of origin in Malacca. If he ever returned to his homeland, then Enrique may deserve the true credit for being the first person to circumnavigate globe.


A posthumous hero

The Victoria was en route in the name of the Spanish crown for two years, 11 months and two weeks. The ship was one of five with which captain Ferdinand Magellan set off in September 1519 from the Spanish port of Sanlucar. Magellan didn't survive to return in 1522, nor did most of the 244 crew members, but they remain unforgotten as pioneers of circumnavigation.

Once around the world


Who First Circled the Globe? Not Magellan, Spain Wants You to Know

GETARIA, Spain — On Sept. 20, 1519, the Portuguese explorer Ferdinand Magellan set out on what was to become the first circumnavigation of the world.

The expedition helped reshape world trade and wrote Magellan’s name into the history books. It remains a major point of pride for Portugal, which two years ago asked UNESCO to grant world heritage status to what it called “the Magellan route.”

But another country has at least as strong a claim on the circumnavigation, in the name of another sailor. On the 500th anniversary of the expedition’s departure, Spain — whose king sponsored the voyage — is seeking to reassert its role, and that of the Spanish navigator Juan Sebastián Elcano.

Magellan set sail from Spain with a fleet of five ships, but he himself only made it halfway around the world. After crossing the strait at the southern tip of the Americas that now bears his name, he was killed in battle in the Philippines.

Only one of the ships completed the three-year circumnavigation, guided home by Elcano, a Spanish officer from the Basque Country.

“The focus has always been on Magellan, but everybody should know that this was the project of a Spanish king, financed with Spanish money and completed by a great Spanish navigator whose role has unfortunately been forgotten,” said Carmen Iglesias, the president of Spain’s Royal Academy of History. “This commemoration should absolutely serve to rebalance the relationship” between Magellan and Elcano, she added.

The commemoration events in both Spain and Portugal will mostly focus on the achievements of Magellan and Elcano. But the three-year journey also contained episodes of violent conflict between the navigators and local people. Lapu-Lapu, the ruler whose troops killed Magellan, is celebrated in the Philippines as a hero of resistance to European imperialism.

The expedition helped consolidate European colonial dominance, departing 25 years after Spain and Portugal had signed a treaty to divide control over the vast territories that they had already conquered.

Ms. Iglesias acknowledged that Elcano was playing catch-up to Magellan in part because Spain itself had failed to highlight his achievements. His birthplace, the scenic coastal town of Getaria, has a glossy, recently built museum, but it is dedicated to another famous son, the fashion designer Cristóbal Balenciaga. The town has a monument to Elcano and a couple of statues, but the most prominent use of his name is a Michelin-starred restaurant, Elkano, which at present probably draws as many pilgrims as the navigator himself.

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“We have simply not done enough to honor Elcano, who also represents our love and understanding of the sea,” said Emeterio Urresti, the president of a guild for Getaria’s 400 fishermen.

After a diplomatic spat, Portugal and Spain submitted a new joint application to UNESCO this year to honor the circumnavigation route.

Over the coming three years, the two countries are staging dozens of events, some of them jointly, to commemorate the anniversary of the circumnavigation, including a current exhibition in Seville, Spain, and another one in Porto, Portugal, next year. On Friday, a celebration was held in Sanlúcar de Barrameda, the port where the expedition set off exactly 500 years earlier.

“We started with a misunderstanding, because this is an episode of history in which each country has its own narrative,” said Camilo Vázquez Bello, a former deputy director in the Spanish Education Ministry who started the commemoration project.

“For us, Magellan is very important as the starting point, but he never planned to sail around the world,” he added. “We certainly want to highlight Elcano’s pioneering contribution to globalization, as the first who got all the way round.”

Magellan wanted to open a new route to the Spice Islands. His plan was rejected by the king of Portugal, Manuel I, so he persuaded King Charles I of Spain to finance the trip. Magellan captained a multinational crew on a journey that was chronicled by an Italian scholar, Antonio Pigafetta.

Elcano also achieved a major sailing feat, while struggling to avoid Portuguese checkpoints as he sailed around Africa to return to Spain. But Portuguese historians mostly focus on Magellan as the mastermind of the expedition and first explorer to cross from the Atlantic to the Pacific, which he named. Elcano enlisted as a second-tier officer and also took part in a mutiny in Patagonia in 1520 that Magellan managed to put down.

“There is a continuation from Magellan to Elcano, but with the understanding that the deeds of Magellan came from his own will, while Elcano finished a job he did not start,” said João Paulo Oliveira e Costa, a Portuguese historian. He added: “Elcano achieved a record, but Magellan changed the knowledge of geography. That is why since those times Magellan got more recognition.”

In Spain, those who have promoted Elcano’s name acknowledge that it has been an uphill struggle. “Everybody knows Magellan — and I’m just tired of telling people who was Elcano,” said Emilio Lamo de Espinosa, the chairman of the Elcano Royal Institute, an international affairs research group based in Madrid.

In March, the Spanish Royal Academy of History issued a paper that aimed to set the record straight about Elcano’s importance. It also underlined that “the completely and exclusively Spanish nature of the venture is indisputable.” Ms. Iglesias, the academy’s president, said that Elcano had long been neglected “through inertia” and that it was “time to teach and talk a lot more about him.”

But Elcano may have also suffered from the divisive politics of Spain. Politicians in Getaria complained when the Juan Sebastián Elcano, a four-masted training ship of the Spanish Navy, visited the port in July at the invitation of a local association.

The sailing event drew a large crowd, but the mayor stayed away and some residents held a protest during the celebration.

“Elcano was Basque, and this commemoration should serve to highlight the singularity of our lands,” said Haritz Alberdi Arrillaga, Getaria’s mayor, who represents E.H. Bildu, a Basque separatist party.

Xabier Alberdi, a Basque historian who is the director of the naval museum in San Sebastián, about 15 miles east of Getaria, said that “political nonsense” had undermined the memory of Elcano since the 19th century, when Antonio Cánovas del Castillo, a historian who also became leader of the Spanish government, described Elcano as little more than “an adventurer.”

The fear of Basque nationalism during a period of civil wars within Spain meant that “Spaniards felt more comfortable putting Magellan instead of Elcano near the top of their list of great explorers, just behind Columbus,” Mr. Alberdi said.

There are very few documents about Elcano’s life, but Mr. Alberdi said that Getaria should at least renovate the washed-out plaque that marks the spot of his family home. Nobody is planning an Elcano museum in the town, which is reeling from a fraud scandal involving the Balenciaga museum. In June, a former mayor received a prison sentence for falsifying documents and misusing public funds to build the museum, which cost 30 million euros, about $33 million — six times its initial budget.

“We decided to give Balenciaga rather than Elcano a museum, to discover that we are now left with this big problem,” said Mr. Urresti, the president of the fishermen’s association.


The Early Portion of the Voyage

Since Magellan was a Portuguese explorer in charge of a Spanish fleet, the early part of the voyage to the west was riddled with problems. Several of the Spanish captains on the ships in the expedition plotted to kill him, but none of their plans succeeded. Many of these mutineers were held prisoner and/or executed. In addition, Magellan had to avoid Portuguese territory since he was sailing for Spain.

After months of sailing across the Atlantic Ocean, the fleet anchored at what is today Rio de Janeiro to restock its supplies on December 13, 1519. From there, they moved down the coast of South America looking for a way into the Pacific. As they sailed farther south, however, the weather got worse, so the crew anchored in Patagonia (southern South America) to wait out the winter.

As the weather began to ease in the spring, Magellan sent the Santiago on a mission to look for a way through to the Pacific Ocean. In May, the ship was wrecked and the fleet did not move again until August 1520.

Then, after months of exploring the area, the remaining four ships found a strait in October and sailed through it. This portion of the journey took 38 days, cost them the San Antonio (because its crew decided to abandon the expedition) and a large amount of supplies. Nevertheless, at the end of November, the remaining three ships exited what Magellan named the Strait of All Saints and sailed into the Pacific Ocean.


Return to Spain

After Magellan&rsquos death, Sebastian del Cano took command of the two remaining ships, the Trinidad and the Victoria (the Conception was burned because there were not enough men left to operate it). A former mutineer, del Cano led the ships to the Spice Islands. After securing the spices they had so long ago set out for, the ships set sail for Spain. The Trinidad was attacked by a Portuguese ship and left shipwrecked.

In September 1522 &mdash three years and a month since the journey began &mdash the Victoria docked back in Seville. Only one ship of the original five &mdash and only 18 men of the original 270 &mdash survived the voyage. Among them was Antonio Pigafetta, a scholar who had kept a detailed diary of the expedition.


Watch the video: The story of explorer Ferdinand Magellan