Category Physics

Why can t we bounce radar signal off the sun and determine 1 au directly

 

On April 7, 1959, a three-member team led by Stanford electrical engineer Von R. Eshleman recorded the first distinguishable echo of a radar signal bounced off the sun. A.S.Ganesh tells you more about Eshleman and how his team achieved this success…

When we generally say “reach for the stars,” we use it as a phrase to convey having high or ambitious aims. Some people, however, reach for the stars in the real sense. Stanford electrical engineer Von R. Eshleman was one of them and the star he reached out for was our sun.

Born into a farming community in Ohio, U.S. on September 17, 1924, Eshleman attended the General Motors Institute of Technology in Flint, Michigan, while still being a high school student. Similarly, even before earning his bachelor’s degree in electrical engineering from George Washington University in 1949, he started attending Ohio State University.

Intrigued by wave science

Before this, he had a stint with the navy during World War II, working as an electrical technician from 1943-46. It was during this period that he was drawn towards wave science. Intrigued by both sonar and radar, Eshleman had the idea that he could bounce radio signals off the surfaces of the sun and the moon, in order to study their hidden structures. While his own ship-based experiments of the time weren’t successful, they paved the way for his future research.

Having received his master’s degree from Stanford in 1950, he went on to earn his Ph.D. in 1952. He was recruited by Stanford to be a research professor, a position he held until 1957, when he was promoted to the teaching faculty as an Assistant Professor (Associate Professor back then). By 1962, he had not only managed to bounce radar off the sun, but also became a full professor at Stanford.

The same war that had planted the idea in Eshleman’s mind for bouncing radar off surfaces also saw the rapid development of radar. Bouncing radar off distant surfaces wasn’t an idea exclusive to Eshleman. Radar was successfully bounced off the moon in the 1940s itself and the first attempts to bounce radar off Venus were made in the late 1950s, albeit with mixed results.

16-minute round-trip

Eshleman’s three-member team, including Lt. Col. Robert C. Barthle and Dr. Philip Gallagher, achieved success in bouncing radar off the sun on April 7, 1959. The tests, in fact, were run on April 7, 10 and 12, with an average time of 16 minutes and 32 seconds spent for the signals to travel the 149 million km distance between the Earth and the sun and back again.

The researchers needed many months to confirm that they had indeed succeeded and when they finally made their announcement public with a press conference in February 1960, it was with 99.999% certainty.

Coded pulse

Eshleman had explained to the gathered media persons that the radar antenna consisted of 5 miles of wire that was spread out across over 10 acres of land, and a 40,000 watt transformer.

Every time the test was conducted, a coded pulse was beamed at the sun in 30-second bursts. This was done to enable identification once it returned after bouncing off the sun.

While 40,000 watts were sent out, atmospheric and spatial dissipation meant that only about 100 watts reached the sun. Similar losses during the return journey meant that only a miniscule amount of energy returned, making detection difficult. The task was further complicated by the fact that this small amount of energy was now part of the vast amounts of similar energy that the sun itself radiates. The other wavelengths. By spending over six months with some of the best computers of the time, they were able to conclude that the coded pulse that they sent out was among the radio emissions of the sun.

In 1962, Eshleman, along with Stanford colleagues, founded the Stanford Center for Radar Astronomy to oversee radio experiments. Even though he began his career in radar astronomy, Eshleman is now best remembered for his pioneering work using spacecraft radio signals for precise measurements in planetary exploration. While he briefly served as Deputy Director of the Office of Technology Policy and Space Affairs in the U.S. Department of State, he was most comfortable among academic circles and hence returned to Stanford, where he flourished. Eshleman died in Palo Alto on September 22, 2017, five days after turning 93.

Picture Credit: Google

What will replace the ISS in 2031?

The International Space Station or ISS is to be deorbited by 2031. Where will it go? Satellites and spacecraft are machines, similar to washing machines and vacuum cleaners. They will not last forever. It doesn’t matter what job they do, whether it’s to observe weather, measure greenhouse gases in the atmosphere, or study the stars. All space machines grow old, wear out and die.

For satellites in Low Earth Orbit (LEO), engineers use the last bit of fuel to slow it down. When the fuel runs out, it falls out of orbit and burns up in the atmosphere. The satellites in very high orbits are sent even further away from Earth, since more fuel is required to bring them down! These satellites are sent into a so-called ‘graveyard orbit, almost 36,000 km above Earth. Space stations and large spacecraft that are in LEO are too large to incinerate entirely on re-entry. So the deorbiting is monitored closely to ensure the debris falls on a remote, uninhabited area. There is an area like this. It’s nicknamed ‘spacecraft cemetery’ and it lies in the middle of the South Pacific Ocean at a spot called Point Nemo. (‘Nemo’ is Latin for ‘nobody’.) Point Nemo is so remote that the ISS will meet its watery grave there. It is considered ideal for dumping space debris as the waters are said to be poor in nutrients and biodiversity. No one has really studied the marine life or lack of it in Point Nemo. Environmentalists fear that in addition to the space junk already present in Point Nemo, the ISS debris will add tons of experimental equipment, materials and even traces of altered human DNA.  

Naming planetary objects?

On August 23, India celebrated a technological triumph when Chandrayaan-3 landed near the Moon’s South Pole at 6:04 p.m. Since then, there has been a discussion on the naming of the landing spot, which Prime Minister Narendra Modi has termed Shiv Shakti.

Do you know how are planetary objects are usually named?

International Astronomical Union             

The International Astronomical Union (IAU), founded in 1919, is responsible for assigning names to celestial bodies and surface features on them. In the IAU, there are numerous Working Groups that suggest the names of astronomical objects and features.

In 1982, the United Nations, at its ‘Fourth Conference on the Standardisation of Geographical Names held in Geneva, recognised the role of the IAU by adopting its resolution on extraterrestrial feature names.

Key rules

The IAU has set some rules for naming planetary objects. Some of the most important rules are -the names should be simple, clear, and unambiguous; there should not be duplication of names; no names having political, military or religious significance may be used, except for names of political figures prior to the 19th Century; and if a name of a person is suggested, then he/she must have been deceased for at least three years, before a proposal may be submitted.

Process of naming

When the first images of the surface of a planet or satellite are obtained, themes for naming features are chosen and names of a few important features are proposed, usually by members of the appropriate IAU Working Group. However, there is no guarantee that the name will be accepted.

Names reviewed by an IAU Working Group are submitted by the group’s chairperson to the Working Group for Planetary System Nomenclature (WGPSN). After this, the members of the WGPSN vote on the names.

The names approved by the WGPSN members are considered as official IAU nomenclature and can be used on maps and in publications. The approved names are then entered into the Gazetteer of Planetary Nomenclature, and posted on the website of IAU.

Objections

If there are any objections to the proposed names, an application has to be sent to the IAU general secretary within three months from the time the name was placed on the website. The general secretary will make a recommendation to the WGPSN Chair as to whether or not the approved name(s) should be reconsidered.

 In 1966, the Outer Space Treaty was formed by the United Nations Office for Outer Space Affairs to set rules for international space law. One of the key aspects of this treaty was that the outer space, including the moon and other celestial bodies, shall be free for exploration and use by all states without discrimination of any kind, on a basis of equality and in accordance with international law, and there shall be free access to all areas of celestial bodies.

Picture Credit : Google

 

What is the mission of Helios 2?

On April 16-17, 1976, Helios-B made its closest approach to the sun, thereby setting a record for the closest flyby of the sun.

April is here and with it comes searing heat as the sun beats down heavily on most parts of India. You must be aware, however, that the sun, with its entire mass of glowing, boiling heat, is the source of all life on Earth. Our sun, in fact, influences how every object in the solar system is shaped and behaves.

Studying solar processes

This means that learning more about the sun and understanding it better has always been a priority. Apart from studying it from here on Earth, which is what we did for most of our history, we have also started sending spacecraft to explore its secrets. The Helios mission was one such mission, sending out a pair of probes into heliocentric orbit (an orbit around the sun) to study solar processes.

Following the success of the Pioneer probes, which formed a ring of solar weather stations along Earth’s orbit to measure solar wind and predict solar storms, the Helios mission was planned. While the Pioneer probes orbited within 0.8 AU (astronomical unit, mean distance between Earth and sun) of the sun, the Helios probes shattered that record within years.

A joint German-American deep-space mission to study solar-terrestrial relationships and many solar processes, it was NASA’s largest bilateral project up until then. The Federal Republic of Germany (West Germany) paid around $180 million of the total $260 million cost and provided the spacecraft, while NASA provided the launch vehicles.

Named Helios-A and Helios-B and equipped with state-of-the-art thermal control systems, the pair of probes were renamed Helios 1 and Helios 2 after their launches. Launched late in 1974, Helios 1 passed within 47 million km (0.31 AU) of the sun at a speed of 2,38,000 km per hour on March 15, 1975. While this was clearly the closest any human-made object had ever been to the sun, the record was broken again in a little over a year by its twin probe.

Even though Helios-B was very similar to Helios-A, the second spacecraft had improvements in terms of system design in order to help it survive longer in the harsh conditions it was heading for. Launched early in 1976, Helios 2 was also put into heliocentric orbit like its twin.

Achieves perihelion

Helios 2, however, flew 3 million km closer to the sun when compared to Helios 1. On April 16-17, 1976, Helios 2 achieved its perihelion or closest approach to the sun at a distance of 0.29 AU or 43.432 million km. At that distance, Helios 2 took the record for the closest flyby of the sun, a record that it didn’t relinquish for over four decades. It also set a new speed record for a spacecraft in the process, reaching a maximum velocity of 68.6 km/s (2.46.960 km/h).

Helios 2’s position relative to the sun meant that it was exposed to 10% more heat or 20 degrees Celsius more heat when compared to Helios 1. In addition to providing information on solar plasma, solar wind, cosmic rays, and cosmic dust, Helios 2 also performed magnetic field and electrical field experiments.

Apart from studying these parameters about the sun and its environment, both Helios 1 and Helios 2 also had the opportunity to observe the dust and ion tails of at least three comets. While data from Helios 1 was received until late 1982, Helios 2’s downlink transmitter failed on March 3, 1980. No further usable data was received from Helios 2 and ground controllers shut down the spacecraft on January 7, 1981.

This was done to avoid any possible radio interference with other spacecraft in the future as both probes continue to orbit the sun.

Parker Solar Probe gets closer and faster

After enjoying its position for over 40 years, Helios 2’s records were finally broken by NASA’s Parker Solar Probe. Launched on August 12, 2018 to study the sun in unprecedented detail, the probe became the first to “touch” the sun during its eighth flyby on April 28, 2021 when it swooped inside the sun’s outer atmosphere. Already holding both the distance and speed records, it is expected to further break them both during its 24 orbits of the sun over its seven-year lifespan. When it completed its 15th closest approach to the sun a month ago on March 17, it came within 8.5 million km of the sun’s surface.

Picture Credit : Google

Why does the European Space Agency want to give the Moon its own time?

The European Space Agency announced that space organisations around the world are considering how best to keep time on the moon. The need is for an internationally accepted lunar time zone.

How do you keep track of time on the moon?  What is the lunar reference point? The moon needs to be given its own time zone, the European Space Agency announced recently. As the race to the moon begins and more and more lunar missions are getting deployed, it is become, pertinent to come with a common refer time.

The European Space Agency announced that space organisations and the world are considering how best to keep time on the moon. The idea took out at a meeting in the Netherlands last year in such the participants agreed on the imminent need to set up    “ a common lunar reference time” Pietro Giordana, a navigation system engineer of the space agency said.

“A joint international effort is now being launched towards achieving this, “Giordano said in a statement.

As of now, a moon missions on the time of the country that is operating the spacecraft. The need is for an internationally accepted lunar time zone. This will be easier for all space-faring nations as mare countries and even private companies are aiming for the moon. The NASA is also getting art to send astronauts there.

 The question of time confounded NASA as it was designing and building the international Space Station, fast approaching the 25th anniversary of the launch of its first pierce. The space station doesn’t have its a time zone, But it runs on Coordinated Universal Time, or UTC which is meticulously based on atomic clocks. This ensures in splitting the time difference between NASA and the Canadian Space Agency, and the other partnering space programmes in Russia, Japan and Europe.

Debate is going on among the international team looking into lunar time on whether a single organisation should set and maintain time on the moon.

When it comes to keeping time on the moon, there are technical issues involved. One being that clocks run faster on the moon than on Earth, gaining about 56 microseconds each day, according to the space agency. Also, ticking occur differently on the lunar surface than in bar orbit.

The lunar time will have to be practical for astronauts there, noted the space agency’s Bernhard Hufenbach. NASA is gearing up for its first flight to the moon with astronauts in more than a half-century in 2024, with a lunar landing as early as 2025.

“This will be quite a challenge” with each day lasting as long as 29.5 Earth days, Hufenbach said in a statement. “But having established a working time system for the moon, we can go on to do the same for other planetary destination.” Mars standard Time, anyone?

Picture Credit : Google 

What is a planet beyond our solar system called?

A planet beyond our own solar system is referred to as an exoplanet. While most exoplanets orbit other stars, there are also free-floating exoplanets, called rogue planets, that are not tethered to any star and orbit the galactic centre.

“Blind” surveys

Traditionally, ground-based means have been employed to detect exoplanets. Astronomers use “blind” surveys to look for stars in the sky with the potential for housing giant planets, which can then be directly imaged from Earth based on the stars age and distance. This technique, however, has a very low yield, meaning that exoplanets are detected very infrequently. Astronomers have developed a new technique to detect exoplanets whose portraits can be taken using large ground-based telescopes on Earth. They have tasted success with this method and the result is the direct image of a Jupiter-like gas giant – HIP 99770 b-132.8 light years away in the Cygnus constellation. The study behind this success was published in the journal Science in April.

Combining astrometry and direct imaging

HIP 99770 b is the first exoplanet detected by combining astrometry and direct imaging. While two observatories on Hawaii Island did the direct imaging, the astrometry- responsible for measuring the position and motion of HIP 99770 b’s home star – came from Gaia space observatory and its predecessor Hipparcos.

Precision astrometry is the method of detecting the movement of stars. This allows researchers to identify those stars that are tugged at by the gravitational pull of an unseen companion like a planet. A picture of the star systems that are close enough is then captured to directly image.

The detection of HIP 99770 b serves as proof of a concept developed by an international research team. They were also able to determine that this exoplanet is 14-16 times the mass of Jupiter and orbits a star that is almost twice as massive as our sun. It receives a similar amount of light as Jupiter as its host star is far more luminous than the sun. The team characterised the nature of HIP 99770 b’s atmosphere and showed that the planet’s atmosphere has signs of water and carbon monoxide.

This new method of searching for exoplanets is believed to be a major improvement to the existing, traditional method of “blind” surveys. The researchers also hope that this new approach would lead to further advances that eventually lead to the discovery of an Earth-twin around a nearby star.

Picture Credit : Google