Category The Universe, Exploring the Universe, Solar System, The Moon, Space, Space Travel

In May 2002, NASA chose two TPF mission architecture concepts for further study and technology development. Each would use a different means to achieve the same goal—to block the light from a parent star in order to see its much smaller, dimmer planets. The technological challenge of imaging planets near their much brighter star has been likened to finding a firefly near the beam of a distant searchlight. Additional goals of the mission would include the characterization of the surfaces and atmospheres of newfound planets, and looking for the chemical signatures of life.

Purpose: To search for Earth-like planets that might harbor life. Terrestrial Planet Finder will use multiple telescopes working together to take family portraits of stars and their orbiting planets and determine which planets may have the right chemistry to sustain life.

The mission will study all aspects of planets, from their formation as disks of dust and gas around newly forming stars to their subsequent development. It will also look for planets orbiting the nearest stars and study their suitability as homes for any possible life.

One great challenge is how to detect planets against the blinding glare of their parent star, an effort that has been compared to trying to find a firefly in the glare of a searchlight. Terrestrial Planet Finder will reduce the glare of parent stars to see planetary systems up to 50 light-years away. Using spectroscopic instruments on Terrestrial Planet Finder, scientists will measure relative amounts of gases like carbon dioxide, water vapor, ozone and methane. This study will help determine whether a planet is suitable for life–or even whether life already exists there.

NASA has chosen two mission architecture concepts for further study and technology development. The two candidate architectures are: Multiple small telescopes on a fixed structure or on separated spacecraft flying in precision formation would simulate a much larger, very powerful telescope. A technique called nulling would reduce starlight by a factor of one million, enabling the detection of the very dim infrared emission from planets.

Visible Light Coronagraph: A large optical telescope, with a mirror three to four times bigger and at least 10 times more precise than the Hubble Space Telescope, would collect starlight and the very dim light reflected from planets. Its special optics would reduce starlight by a factor of one billion, enabling astronomers to detect the faint planets.

Four hundred years ago, an astronomer named Giordano Bruno was burned at the stake for suggesting the existence of other Earth-like worlds. Today we know that there are potentially billions of extra solar planets in the Milky Way. None found so far resemble Earth. Indeed, many are shockingly different from our world. Although none of the planets investigated so far have shown any signs of life, many astronomers believe that it is only a matter of time before Earth’s twin planet is discovered.

Our solar system is just one specific planetary system—a star with planets orbiting around it. Our planetary system is the only one officially called “solar system,” but astronomers have discovered more than 2,500 other stars with planets orbiting them in our galaxy. That’s just how many we’ve found so far. There are likely to be many more planetary systems out there waiting to be discovered! Our Sun is just one of about 200 billion stars in our galaxy. That gives scientists plenty of places to hunt for exoplanets, or planets outside our solar system. But our capabilities have only recently progressed to the point where astronomers can actually find such planets.

Even our closest neighboring stars are trillions of miles away. And all stars are enormous and extremely bright compared to any planets circling them. That means that picking out a planet near a distant star is like spotting a firefly right next to brilliant lighthouse miles away.

So far, the planets outside our solar system have proven to be fascinating and diverse. One planet, known as HD 40307g, is a “super Earth,” with a mass about eight times that of Earth. The force of gravity there would be much stronger than here at home. You would weigh twice as much there as you do on Earth! Another planet, called Kepler-16b, turns out to orbit two stars. A sunset there would provide a view of two setting stars!

In another planetary system, called TRAPPIST-1, there are not one…not two…but seven Earth-sized planets that could be covered in liquid water. The planets are relatively close together, too. If you were to stand on the surface of a TRAPPIST-1 planet, you might see six other planets on the horizon!

Extra-solar planets are very difficult to see because they are outshone by the light from their parent stars. It can be deter-mined whether or not a star has a planetary system by observing whether or not the star’s- light “wobbles”. As a planet orbits a star, its gravitational pull will cause the star’s light to bend slightly, and thus to change colour. This technique only works for giant planets, however, because an Earth-sized world would have little effect on its parent.

It is not easy to detect another planet so far away from Earth. Unlike stars which are fueled by nuclear reactions, planets only reflect the optical light of their stellar companion. In our solar system, for example, the Sun outshines its planets about one billion times in visible light. Because of the distant planets’ faintness near the brightness of the nearby star, astronomers have had to devise clever methods to detect them. Currently, the most successful approach is based on the fact that a nearby planet will cause the star to wobble back and forth just a bit as the planet revolves around it. Astronomers can detect this tiny wobble and then calculate the orbit and mass of the object which is causing it. Even using this technique, however, it is still not easy to detect planets around other stars. Consider this: someone looking at our Sun from 30 light-years away would see it wobbling in a circle whose size would be about as big as a quarter viewed from 10,000 kilometers away!

During the past few years, researchers have detected over a dozen planets orbiting sunlike stars. The first was reported in October 1995 by Michel Mayor and Didier Queloz of the Geneva Observatory in Switzerland. While observing the star 51 Pegasi, they noticed a change in the light from the star – its light repeatedly shifted back and forth between the blue and red ends of the electromagnetic spectrum. The timing of this Doppler shift implied that the star was “wobbling” a little because of a closely orbiting planet. In fact, the planet appeared to be revolving around the star every 4.2 days. Shortly thereafter, a survey of over a hundred other sunlike stars performed by the team of Geoff Marcy and Paul Butler at San Francisco State University and the University of California at Berkeley, turned up six more such planets. Of those, one planet circling the star 16 Cygni B was independently discovered by astronomers William D. Cochran and Artie P. Hatzes of the University of Texas McDonald Observatory. Since 1996, the announcement of the detection of new planets has become fairly routine….but always exciting!

Global positioning satellites beam signals to special receivers on Earth. These receivers, which are not much larger than mobile phones, know the difference between when the satellite signal was sent and when it was received. This allows the receiver to work out the distance between each of the satellites and itself, and there-fore calculate its position.

GPS is accurate and handy to use, so much so that we rely on it more and more every day. It’s not often we take the time to learn how it works. The idea of GPS refers to a Global Positioning System; a collection of satellites in orbit above the Earth that transmit location data down to our devices. As hobbyists, we can get GPS modules that will read and interpret this data for us! They’re known as GPS receivers, and they are used everywhere, like your phone, tablet, and other electronic devices. GPS receivers will relay a satellite’s location data directly to a microcontroller in the form of serial data strings, which we can break down into relevant bite-sized chunks of data about where we are and how we are moving!

Firstly, the signal of time is sent from a GPS satellite at a given point. Subsequently, the time difference between GPS time and the point of time clock which GPS receiver receives the time signal will be calculated to generate the distance from the receiver to the satellite. The same process will be done with three other available satellites. It is possible to calculate the position of the GPS receiver from distance from the GPS receiver to three satellites. However, the position generated by means of this method is not accurate, for there is an error in calculated distance between satellites and a GPS receiver, which arises from a time error on the clock incorporated into a GPS receiver. For a satellite, an atomic clock is incorporated to generate on-the-spot time information, but the time generated by clocks incorporated into GPS receivers is not as precise as the time generated by atomic clocks on satellites. Here, the fourth satellite comes to play its role: the distance from the fourth satellite to the receiver can be used to compute the position in relations to the position data generated by distance between three satellites and the receiver, hence reducing the margin of error in position accuracy.

The Fig 1-3 below illustrates an example of positioning by two dimensions (position acquisition by using two given points). We can compute where we are at by calculating distance from two given points, and the GPS is the system that can be illustrated by multiplying given points and replacing them with GPS satellites on this figure.

GPS, or the Global Positioning System, is designed to aid navigation around the planet. It consists of 24 satellites in six different orbits around Earth. Their position in these orbits means that any receiver, anywhere on Earth, can always receive a signal from four satellites or more. Using data from these signals, a GPS receiver can work out its position, including altitude, to within a few metres.

The Global Positioning System (GPS), originally NAVSTAR GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite systems (GNSS) that provides geolocation and time information to a GPS receiver anywhere on or near the Earth where there is an unobstructed line of sight to four or more GPS satellites. Obstacles such as mountains and buildings block the relatively weak GPS signals.

The GPS does not require the user to transmit any data, and it operates independently of any telephonic or internet reception, though these technologies can enhance the usefulness of the GPS positioning information. The GPS provides critical positioning capabilities to military, civil, and commercial users around the world. The United States government created the system, maintains it, and makes it freely accessible to anyone with a GPS receiver.

The GPS project was started by the U.S. Department of Defense in 1973, with the first prototype spacecraft launched in 1978 and the full constellation of 24 satellites operational in 1993. Originally limited to use by the United States military, civilian use was allowed from the 1980s following an executive order from President Ronald Reagan. Advances in technology and new demands on the existing system have now led to efforts to modernize the GPS and implement the next generation of GPS Block IIIA satellites and Next Generation Operational Control System (OCX). Announcements from Vice President AL Gore and the White House in 1998 initiated these changes. In 2000, the U.S. Congress authorized the modernization effort, GPS III. During the 1990s, GPS quality was degraded by the United States government in a program called “Selective Availability”; this was discontinued in May 2000 by a law signed by President Bill Clinton.

When selective availability was lifted in 2000, GPS had about five-meter (16 ft.) accuracy. The latest stage of accuracy enhancement uses the L5 band and is now fully deployed. GPS receivers released in 2018 that use the L5 band can have much higher accuracy, pinpointing to within 30 centimeters or 11.8 inches.

A satellite cannot do its job properly if it is not stable. A satellite dish must always point towards its location, or signals will be lost in space. In order to keep satellites from flying out of control, some are deliberately designed to spin. In the same way that a spinning top remains stable if it is spinning quickly, a satellite that is spinning will not deviate from its course. Some satellites have small, spinning wheels at various points on their frame. These wheels can be used to realign the satellite if it moves off course.

If you throw a ball into the air, the ball comes right back down. That’s because of gravity—the same force that holds us on Earth and keeps us all from floating away. To get into orbit, satellites first have to launch on a rocket. A rocket can go 25,000 miles per hour! That’s fast enough to overcome the strong pull of gravity and leave Earth’s atmosphere. Once the rocket reaches the right location above Earth, it lets go of the satellite.

The satellite uses the energy it picked up from the rocket to stay in motion. That motion is called momentum. But how does the satellite stay in orbit? Wouldn’t it just fly off in a straight line out into space? Not quite. You see, even when a satellite is thousands of miles away, Earth’s gravity is still tugging on it. That tug toward Earth–combined with the momentum from the rocket… …causes the satellite to follow a circular path around Earth: an orbit. When a satellite is in orbit, it has a perfect balance between its momentum and Earth’s gravity. But finding this balance is sort of tricky.

Gravity is stronger the closer you are to Earth. And satellites that orbit close to Earth must travel at very high speeds to stay in orbit.

For example, the satellite NOAA-20 orbits just a few hundred miles above Earth. It has to travel at 17,000 miles per hour to stay in orbit. On the other hand, NOAA’s GOES-East satellite orbits 22,000 miles above Earth. It only has to travel about 6,700 miles per hour to overcome gravity and stay in orbit. Satellites can stay in an orbit for hundreds of years like this, so we don’t have to worry about them falling down to Earth.