NASA launched a telescope to search for other planets. Launch and getting started

21.10.2023 -

Space telescopes are typically telescopes that operate outside the Earth's atmosphere and thus do not bother to peer through that atmosphere. The most famous space telescope today is the Hubble Space Telescope, which has discovered hundreds of exoplanets, revealed many spectacular galaxies, cosmic events, and expanded the horizons of our view into space. Hubble will be replaced by the James Webb Space Telescope, which will be launched into space in 2018 and whose mirror will be almost three times the diameter of Hubble's mirror. After James Webb, scientists plan to send the High-Definition Space Telescope (HDST) into space, but this is only in the plans for now. Be that as it may, space telescopes have and will continue to account for the majority of our discoveries in deep space.

If we ever have giant inflatable telescopes in space, you can thank Chris Walker's mom. A few years ago, Walker was making chocolate pudding when he suddenly had to stop what he was doing cooking and call his mom. He took the pudding off the stove, covered it with plastic wrap, and placed the pot on the floor next to the couch. After the conversation, he was surprised to find an image of a light bulb from a lamp nearby, hovering over the end of the couch. After investigating the cause of this phenomenon, he discovered that the pocket of cold air that had formed as the pudding cooled caused the plastic packaging of the pudding to sag. This actually formed a lens that reflected the light bulb.

Recently, humanity has been busy searching for exoplanets and for several years the European Space Agency () has been developing the Cheops space telescope, designed to search for planets similar to ours. Cheops is also called an "exoplanet hunter" and has high hopes. And recently the launch date of the space telescope, as well as some other details, became known.

Hubble as seen from Space Shuttle Atlantis STS-125

Hubble Space Telescope ( KTH; Hubble Space Telescope, HST; observatory code "250") - in orbit around , named after Edwin Hubble. The Hubble Telescope is a joint project between NASA and the European Space Agency; it is one of NASA's Large Observatories.

Placing a telescope in space makes it possible to detect electromagnetic radiation in ranges in which the earth’s atmosphere is opaque; primarily in the infrared range. Due to the absence of atmospheric influence, the resolution of the telescope is 7-10 times greater than that of a similar telescope located on Earth.

Story

Background, concepts, early projects

The first mention of the concept of an orbital telescope occurs in the book “Rocket in Interplanetary Space” by Hermann Oberth ( Die Rakete zu den Planetenraumen ), published in 1923.

In 1946, American astrophysicist Lyman Spitzer published the article "The Astronomical Advantages of an Extraterrestrial Observatory" ( Astronomical advantages of an extra-terrestrial observatory ). The article highlights two main advantages of such a telescope. First, its angular resolution will be limited only by diffraction, and not by turbulent flows in the atmosphere; at that time, the resolution of ground-based telescopes was between 0.5 and 1.0 arcseconds, whereas the theoretical diffraction resolution limit for an orbiting telescope with a 2.5-meter mirror is about 0.1 seconds. Secondly, the space telescope could observe in the infrared and ultraviolet ranges, in which the absorption of radiation by the earth's atmosphere is very significant.

Spitzer devoted a significant portion of his scientific career to advancing the project. In 1962, a report published by the US National Academy of Sciences recommended that the development of an orbiting telescope be included in the space program, and in 1965 Spitzer was appointed head of a committee tasked with defining the scientific objectives for a large space telescope.

Space astronomy began to develop after the end of World War II. In 1946, the ultraviolet spectrum was obtained for the first time. An orbiting telescope for solar research was launched by the UK in 1962 as part of the Ariel program, and in 1966 NASA launched the first orbital observatory OAO-1 into space. The mission was unsuccessful due to battery failure three days after launch. In 1968, OAO-2 was launched, which made observations of ultraviolet radiation until 1972, significantly exceeding its design life of 1 year.

The OAO missions served as a clear demonstration of the role that orbiting telescopes could play, and in 1968 NASA approved a plan to build a reflecting telescope with a 3 m diameter mirror. The project was codenamed LST ( Large Space Telescope). The launch was planned for 1972. The program emphasized the need for regular manned expeditions to maintain the telescope in order to ensure long-term operation of the expensive instrument. The Space Shuttle program, which was developing in parallel, gave hope for obtaining corresponding opportunities.

The struggle to finance the project

Due to the success of the JSC program, there is a consensus in the astronomical community that building a large orbiting telescope should be a priority. In 1970, NASA established two committees, one to study and plan technical aspects, the second to develop a scientific research program. The next major obstacle was financing the project, the costs of which were expected to exceed the cost of any ground-based telescope. The US Congress questioned many of the proposed estimates and significantly cut the appropriations, which initially involved large-scale research into the instruments and design of the observatory. In 1974, as part of a program of budget cuts initiated by President Ford, Congress completely canceled funding for the project.

In response, astronomers launched a broad lobbying campaign. Many astronomers met personally with senators and congressmen, and several large mailings of letters were also carried out in support of the project. The National Academy of Sciences published a report emphasizing the importance of building a large orbiting telescope, and as a result, the Senate agreed to allocate half of the budget originally approved by Congress.

Financial problems led to cutbacks, chief among them the decision to reduce the diameter of the mirror from 3 to 2.4 meters to reduce costs and achieve a more compact design. The project of a telescope with a one and a half meter mirror, which was supposed to be launched for the purpose of testing and testing the systems, was also canceled, and a decision was made to cooperate with the European Space Agency. ESA agreed to participate in financing, as well as to provide a number of instruments for the observatory, in return for European astronomers to reserve at least 15% of the observing time. In 1978, Congress approved $36 million in funding, and full-scale design work began immediately thereafter. The launch date was planned for 1983. In the early 1980s, the telescope was named after Edwin Hubble.

Organization of design and construction

The work on creating the space telescope was divided among many companies and institutions. The Marshall Space Center was responsible for the development, design and construction of the telescope, the Goddard Space Flight Center was responsible for the overall management of the development of scientific instruments and was chosen as the ground control center. The Marshall Center contracted with Perkin-Elmer to design and manufacture the telescope's optical system ( Optical Telescope Assembly - OTA) and precision guidance sensors. Lockheed Corporation received the construction contract for the telescope.

Manufacturing of the optical system

Polishing the telescope's primary mirror, Perkin-Elmer Laboratory, May 1979

The mirror and the optical system as a whole were the most important parts of the telescope design, and particularly stringent requirements were placed on them. Typically, telescope mirrors are made to a tolerance of about one-tenth the wavelength of visible light, but since the space telescope was intended to observe from ultraviolet to near-infrared, and the resolution had to be ten times higher than that of ground-based instruments, the manufacturing tolerance its primary mirror was set at 1/20 the wavelength of visible light, or approximately 30 nm.

The Perkin-Elmer company intended to use new computer numerical control machines to produce a mirror of a given shape. Kodak was contracted to manufacture a replacement mirror using traditional polishing methods in case of unforeseen problems with unproven technologies (the Kodak-manufactured mirror is currently on display at the Smithsonian Institution museum). Work on the main mirror began in 1979, using glass with an ultra-low coefficient of thermal expansion. To reduce weight, the mirror consisted of two surfaces - lower and upper, connected by a lattice structure of a honeycomb structure.

Telescope backup mirror, Smithsonian Air and Space Museum, Washington DC

Work on polishing the mirror continued until May 1981, but the original deadlines were missed and the budget was significantly exceeded. NASA reports from the period expressed doubts about the competence of Perkin-Elmer's management and its ability to successfully complete a project of such importance and complexity. To save money, NASA canceled the backup mirror order and moved the launch date to October 1984. The work was finally completed by the end of 1981, after applying a reflective coating of aluminum 75 nm thick and a protective coating of magnesium fluoride 25 nm thick.

Despite this, doubts about Perkin-Elmer's competence remained as the completion date for the remaining components of the optical system was constantly pushed back and the project budget grew. NASA described the company's schedule as "uncertain and changing daily" and delayed the telescope's launch until April 1985. However, the deadlines continued to be missed, the delay grew by an average of one month every quarter, and at the final stage it grew by one day every day. NASA was forced to postpone the launch twice more, first to March and then to September 1986. By that time, the total project budget had grown to $1.175 billion.

Spacecraft

The initial stages of work on the spacecraft, 1980

Another difficult engineering problem was the creation of a carrier apparatus for the telescope and other instruments. The main requirements were protection of the equipment from constant temperature changes during heating from direct sunlight and cooling in the Earth's shadow, and particularly precise orientation of the telescope. The telescope is mounted inside a lightweight aluminum capsule, which is covered with multi-layer thermal insulation, ensuring a stable temperature. The rigidity of the capsule and the fastening of instruments is provided by an internal spatial frame made of carbon fiber.

Although the spacecraft was more successful than the optical system, Lockheed also ran somewhat behind schedule and over budget. By May 1985, cost overruns amounted to about 30% of the original volume, and the lag behind the plan was 3 months. A report prepared by the Marshall Space Center noted that the company did not show initiative in carrying out work, preferring to rely on NASA instructions.

Research coordination and flight control

In 1983, after some confrontation between NASA and the scientific community, the Space Telescope Science Institute was established. The institute is managed by the Universities Association for Astronomical Research ( Association of Universities for Research in Astronomy ) (AURA) and is located on the campus of Johns Hopkins University in Baltimore, Maryland. Hopkins University is one of 32 American universities and foreign institutions that are members of the association. The Space Telescope Science Institute is responsible for organizing scientific work and providing astronomers with access to the data obtained; NASA wanted to keep these functions under its control, but scientists preferred to transfer them to academic institutions.

The European Space Telescope Coordination Center was founded in 1984 in Garching, Germany, to provide similar facilities to European astronomers.

Flight control was entrusted to the Goddard Space Flight Center, which is located in Greenbelt, Maryland, 48 kilometers from the Space Telescope Science Institute. The functioning of the telescope is monitored round-the-clock in shifts by four groups of specialists. Technical support is provided by NASA and contracting companies through the Goddard Center.

Launch and getting started

Launch of the Discovery shuttle with the Hubble telescope on board

The telescope was originally scheduled to be launched into orbit in October 1986, but on January 28 the Space Shuttle program was suspended for several years, and the launch had to be postponed.

All this time, the telescope was stored in a room with an artificially purified atmosphere, its on-board systems were partially turned on. Storage costs were approximately $6 million per month, which further increased the cost of the project.

The forced delay allowed for a number of improvements: solar panels were replaced with more efficient ones, the on-board computer complex and communication systems were modernized, and the design of the aft protective casing was changed in order to facilitate the maintenance of the telescope in orbit. In addition, the software for controlling the telescope was not ready in 1986 and was actually only finalized by the time of its launch in 1990.

After the resumption of shuttle flights in 1988, the launch was finally scheduled for 1990. Before launch, dust accumulated on the mirror was removed using compressed nitrogen, and all systems were thoroughly tested.

The Hubble Space Telescope (HST, HST, observatory code “250”) is an automatic observatory in orbit around , named after Edwin Hubble. The Hubble telescope is a joint project with the European Space Agency; it is one of NASA's Large Observatories.

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A Delta II rocket with the Kepler orbital telescope on the launch pad. Photo from NASA website

On Saturday, at 06:49 Moscow time, the Kepler orbital telescope, designed to search for exoplanets, was launched from the Cape Canaveral Space Center in Florida. The device was launched into orbit by a Delta II launch vehicle. The message about the launch of the device is given on the NASA website.

The Kepler mission will last three and a half years. All this time, he will observe about 100 thousand stars similar to the Sun, around which exoplanets can orbit. The device will search for planets located outside the solar system using the transit method. When a planet passes across the disk of its star, it blocks part of its radiation from the observer. By analyzing variations in the brightness of stars, astronomers can not only find planets, but also roughly estimate their size.

Kepler will orbit the Sun in an orbit one astronomical unit (AU) altitude. A.e. equal to 150 million kilometers and equal to the distance from the Earth to the Sun. In fact, Kepler will follow the path of our planet as it orbits the Sun. This position allows the telescope to constantly monitor the same stars. The Hubble telescope, for example, lacks this advantage.

Currently, astronomers have discovered more than 300 exoplanets. Most of them are gas giants like Jupiter. On such planets, Earth-type organisms cannot develop, and it is the habitability of ecoplanets that ultimately interests scientists. Kepler will be able to find smaller planets that are more habitable.

Kepler telescope at work. Image from nasa.gov

Other Earths

NASA launches telescope to search for terrestrial planets

Early on the morning of March 7, 2009, the Kepler orbital telescope was launched from the Cape Canaveral Space Center in Florida. Long before this date, reports about the future launch appeared in many media. The close attention of the press to the telescope is understandable: it will search for planets similar to Earth in deep space.

All at once

To detect exoplanets (planets outside the solar system), Kepler will use the so-called transit method. When a planet passes across the disk of its star, it blocks some of its radiation. The new telescope will precisely look for such “winking” luminaries. By analyzing the wink parameters, astronomers will be able to learn some of the characteristics of the exoplanets found.

Based on the frequency of brightness fluctuations, one can determine the planet's orbital period and the altitude of its orbit. This information, along with data on the temperature of the star, will allow scientists to calculate how hot the exoplanet is. In addition, by knowing the length of the orbit, astronomers can use Kepler's third law, after which the telescope was named, to determine the mass of the planet. The amount of stellar radiation it blocks will give researchers information about its size.

Scientists are primarily interested in small planets orbiting in the habitable zone of their stars. The habitable zone is a narrow segment of space around a star, once inside which a planet can be theoretically suitable for the survival of Earth-type organisms. In the case of stars similar to the Sun (namely, they will be primarily considered by scientists), the habitable zone will be at a distance of about one astronomical unit from the star. That is, the distance from the exoplanet to the star will approximately correspond to the distance from the Earth to the Sun.

Lots of problems

It seems that the transit method is ideally suited for finding new worlds, and it is not clear why only about 15 percent of exoplanets have been found with its help (astronomers currently know about 350 planets orbiting distant stars). The method seems very simple in words, but it has a number of limitations, and its effective use requires very sensitive technology.

Even large planets (the point on the right side of the star in the figure) cause minor changes in the brightness of the star. Image from nasa.gov

Searching for exoplanets (especially small ones) using the transit method is a non-trivial task simply because the change in the brightness of a star when a planet passes by it is minimal. The Earth would block only 0.008 percent of the Sun's light from an observer in deep space. Such minor disturbances can occur for a variety of reasons. For example, they can be caused by the appearance of spots on the star being studied.

“Correct” oscillations, that is, oscillations caused by the passage of a planet across the disk of a star, should be periodic. Therefore, before attributing an exoplanet nature to the “wink,” astronomers need to detect brightness changes with similar characteristics several times. For terrestrial planets and for stars similar to the Sun, the orbital period is about a year. That is, you will have to follow the “winking” stars for several years. At the same time, the probability of missing the very moment of the planet’s transit is very high: the duration of this event is several hours.

In addition to all these difficulties, the transit method is only suitable for a very limited sample of stars. In order for a telescope to notice a change in the brightness of a star, the orbit of the planet orbiting it must be oriented in a strictly defined way. According to calculations, this requirement is met on average for one star out of a hundred.

Everything at once and without problems

The Kepler mission designers tried to take all these complexities into account. The sensitivity of its telescope is sufficient to detect minimal changes in brightness. According to engineers, Kepler can see a fly fly past the headlights of a car several kilometers away. To avoid missing the planet's transit, Kepler will observe the starry sky almost continuously. The telescope will take readings every half hour. Since it is located outside the Earth's atmosphere, weather conditions and day/night cycles will not interfere with measurements.

Kepler's orbit is chosen so that its field of view is not periodically intruded by the Moon and the Sun. Scientifically speaking, the field of view of the new telescope lies outside the ecliptic plane.

In this region of the Milky Way, the Kepler telescope will search for terrestrial exoplanets. Image by Jon Lomberg from nasa.gov. Click on the picture to enlarge the image.

In its movement around the Sun, Kepler will follow the Earth, gradually moving away from it. The telescope will complete one revolution in approximately 372.5 days. An additional advantage of this position is the absence of torque caused by the gravitational influence of the Earth (since the shape of our planet is not ideal, satellites are attracted to the Earth slightly differently over different parts of it). Another advantage of an orbit “independent” of the Earth is a stable level of solar radiation. Constant changes in the amount of sunlight falling on the apparatus due to the Earth's shadow could lead to interference in the operation of the instruments.

Compared to other telescopes, Kepler has a very wide field of view. He will survey an area of the sky approximately corresponding to the area of the palm of an outstretched hand - its size will be 105 square degrees. Other orbital telescopes, including the famous Hubble, do not have such a breadth of view. They are designed to study the most distant areas of space, and the size of the area being studied is not so important for them.

The region of space that Kepler will peer into for 3.5 years was also not chosen by chance. The telescope of the device will be aimed at a section of the sky located between the constellations Cygnus and Lyra. Astronomers estimate that there are about 4.5 million stars in this part of the sky. Most of them are similar to our Sun - they are relatively cool, middle-aged stars. Habitable zones are located a short distance away, so Kepler will be able to see the transit of "suitable" planets. The potentially habitable planets of young giant stars are so distant that even Kepler's very sensitive detectors will not notice a change in the star's brightness as they pass across its disk.

To overcome the challenges of searching for exoplanets using the transit method, the mission designers used "brute scientific power," said Natalie Batalha of San Jose State University, who is working on the telescope. “It’s all about the numbers,” she added.

A wide field of view, continuous observations and a huge number of candidate stars make it possible to bypass such factors as a small percentage of suitable stars. Kepler's advanced detectors should be able to detect the tiniest wink, and the mission's three-year duration will allow astronomers to confirm that the planet is the culprit.

Kepler will get its first results in just a few months. The list of new exoplanets will first be supplemented by “hot Jupiters” orbiting their stars at a short distance. A year on such planets can last only a few days, which means that scientists can quickly verify that the star periodically fades precisely because of them. It will take several years to reliably detect terrestrial planets.

Depending on how typical Earth-like planets (that is, planets whose radius ranges from half to two Earth radii) are in our Universe, scientists expect to find from 50 to several hundred of them.

About the speed of progress

Astronomers discovered the first planet outside the solar system as recently as 1995. Now there are more than three hundred such planets known, and in another three years we will find out how often Earth-like planets are found among exoplanets. Finally, scientists and simply those who like to speculate about “whether there is life on Mars” will have factual data that can be used when making forecasts. And although Kepler will not give a final answer to the question of our loneliness in the Universe, it will be able to significantly strengthen the weight of the arguments for or against.

If most of the planets in the universe are approximately the size of Earth, scientists expect to find about 50 Earth-like planets. If the planets are mostly larger than Earth (about 1.3 times the radius), astronomers hope to see about 185 planets. If the radius of a typical planet is 2.2 times the radius of the Earth, 640 new terrestrial planets will appear on star maps. All calculations are based on the assumption that only one Earth-like planet orbits the star.

Named after James Webb, researchers will need to work as quickly as possible and take into account the short lifespan of the multibillion-dollar orbital observatory. What will his gaze be directed to first?

Built in collaboration with the European and Canadian space agencies, the Webb telescope will be NASA's largest, most powerful and expensive observatory in history. Its creation cost $9 billion, and its launch is scheduled for the summer of 2019.

Unlike its famous predecessor, the Hubble Space Telescope, which was designed to collect visible and ultraviolet light, Webb is optimized for viewing space in the infrared.

Webb's infrared eyes make him an x-ray scanner, mass spectrometer, and time machine all in one. It can peer through the creaky, dusty eons of space to explore much that astronomers using Hubble and other telescopes have barely begun to peer into.

The difference between Hubble and Webb is also durability, with multiple repair missions leading the former into its fourth decade in low orbit. But Webb will be stationed out of range of easy maintenance and programmed for 5 years of service. The maximum the fuel will last for is 10 years; it is necessary for maneuvers. The telescope should always be in the shadow of our planet so as not to overheat.

Webb telescope learning curve

“Webb has a limited lifespan and represents a huge intellectual, financial and technological investment, so we need to quickly learn its capabilities,” says Ken Sembach, director of the Space Telescope Science Institute (STScI). “It’s going to be a steep learning curve.”

Hundreds of researchers who have spent decades developing the telescope's hardware, software and core science objectives will be the first to scale this learning curve. Each member of this elite team is guaranteed a small but significant share of Webb's total time in the telescope's first year of observations (called "Cycle 1"). These initial results could then help the rest of the world's astronomers.

Exploring the Youth of the Universe

Webb will be able to view the largest clusters of galaxies, which are so massive that they warp the surrounding space, forming huge "Gravitational Lenses" that magnify the faint light of galaxies born less than a billion years after the Big Bang. In this way, it is possible to study the first periods of the life of the Universe.

Detecting exoplanets and mapping them

Despite the fact that the Webb telescope was created mainly to study distant galaxies, its gaze can also be directed to neighboring star systems to search for exoplanets.

Astronomers will be able to detect water vapor, methane and other gases even as a planet passes in front of its star.

One of the teams plans to study the moons of Jupiter and Saturn, including the famous Encelaad.