What are artificial satellites?
An artificial Earth satellite (AES) is a spacecraft
To move in orbit around the Earth, the device must have an initial speed equal to or greater than the first escape velocity. AES flights are carried out at altitudes of up to several hundred thousand kilometers.
The lower limit of the satellite flight altitude is determined bythe need to avoid the process of rapid braking in the atmosphere. The orbital period of a satellite, depending on the average flight altitude, can range from one and a half hours to several years.
Of particular importance are satellites on the geostationaryorbit, the orbital period of which is strictly equal to days, and therefore, for a ground observer, they "hang" motionless in the sky, which makes it possible to get rid of rotary devices in the antennas.
Automatic interplanetary stations (AMS) andinterplanetary spaceships can be launched into deep space both bypassing the satellite stage (that is, right ascension), and after preliminary launching into the so-called reference orbit of the satellite.
At the beginning of the space age, satellites were launchedonly through launch vehicles, and by the end of the 20th century, the launch of satellites from other satellites - orbital stations and spacecraft (primarily from the MTKK Space Shuttle) also became widespread.
As a means of launching satellites theoreticallyMTKK spaceships, space guns, and space elevators are also possible, but have not yet been implemented. Just a short time after the start of the space age, it became common to launch more than one satellite on a single launch vehicle, and by the end of 2013, the number of simultaneously launched satellites in some launch vehicles exceeded three dozen.
In some launches, the last stages of the launch vehicles also go into orbit and, for a time, actually become satellites.
Unmanned satellites have a mass of severalkilograms to two dozen tons and sizes from several centimeters to (in particular when using solar panels and retractable antennas) several tens of meters.
Spaceships and spaceplanes that are satellites reach several tens of tons and meters, and prefabricated orbital stations reach hundreds of tons and meters.
In the 21st century, with the development of microminiaturization andnanotechnology, the creation of ultra-small cubesat satellites (from one to several kilograms and from several to several tens of centimeters) has become a mass phenomenon, and a new format has also appeared: pocketcube (literallypocket cube) in a few hundred or tens of grams and a few centimeters.
Satellites are predominantly created asnon-returnable, however, some of them (first of all, manned and some cargo spaceships) are recoverable partially (having a descent vehicle) or completely (spaceplanes and satellites returning on board).
Artificial earth satellites are widely usedfor scientific research and applied problems, as well as in education (the so-called "university" satellites have become a mass phenomenon in the world) and a hobby - radio amateur satellites.
How many satellites are in Earth's orbit now?
It depends on how you count. Since the launch of Sputnik on October 4, 1957, more than 9,000 vehicles have been launched into space, but only about 2,000 of them are currently operational.
The rest burned out in the atmosphere or broke andbecame "space debris" in orbit. Therefore, by the way, most of the maneuvers are carried out to avoid uncontrolled objects, and not working satellites.
Types of satellites
The following types of satellites are distinguished:
- Astronomical satellites are satellites designed to explore planets, galaxies and other space objects.
- Biosatellites are satellites designed to conduct scientific experiments on living organisms in space.
- Earth remote sensing satellites.
- Meteorological satellites are satellites designed to transmit data for the purpose of predicting weather, as well as for observing the Earth's climate.
- Small satellites - satellites of light weight (less than 1or 0.5 tons) and size. Includes minisatellites (over 100 kg), microsatellites (over 10 kg) and nanosatellites (lighter than 10 kg), including cubesats and pocket cubes.
- Military satellite.
- Communication satellites.
- Navigation satellites.
- Spaceships are manned spacecraft.
- Orbital stations are long-term spaceships.
- Golosatellites are the latest satellites designed to explore other planets.
How is the movement of satellites in space regulated?
There is no uniform regulation for this. Space is free space. Therefore, participants in space activities are guided only by their own national laws, which, however, must comply with agreements adopted within the framework of the work of the UN Committee on the Peaceful Uses of Outer Space (COPUOS).
- Legally
After the adoption in 1974 of the convention onregistration of space objects launched into outer space, the United Nations Office for Outer Space Affairs maintains a register of objects launched into outer space. However, registration in it is declarative, and the UN does not have the technical ability to control the real orbits and targets of spacecraft.
- Military satellites
The main obstacle standing in the way of creationa comprehensive satellite database and the ability to automatically monitor near-earth space - these are military satellites. The American system NORAD does not publish data on US intelligence satellites, while publishing data on the orbits of Russian and Chinese military vehicles. Russia's aerospace forces do not publish anything at all, although they monitor American military satellites with radar and optical means.
Commercial satellite operators nowone has to actually act blindly, hoping that the military themselves will not allow a clash. Moreover, it is military vehicles that most often maneuver in orbit, changing altitude. There is even a conventional class of "inspector satellites" that purposefully approach other people's vehicles in order to photograph them.
- Collision risk
In early April, the satellites of OneWeb and SpaceXavoided a dangerous approach with each other in orbit, representatives of the US Space Force and OneWeb said. This is the first perilous situation of two rival companies that are expanding their broadband networks in space.
Researchers assessed the likelihood of collision1.3%, while two satellites approached 57 meters - this is a dangerous proximity for satellites in orbit. If satellites collided in orbit, it could cause a catastrophe that would lead to the formation of hundreds of pieces of debris, and their trajectory would change, endangering other devices.
Experts also noted that now there is nono national or global space organization that regulates satellite operators to respond to potential collisions. Companies only have Space Force urgent alerts to companies that require devices to keep a safe distance from each other.
How do satellites change the sky?
Constellations of satellites and pieces of space debrisorbiting the Earth and reflecting sunlight, made the night sky 10% brighter. This is stated in a joint study by an international team of astrophysicists.
“We expected the increase in sky brightness to beinsignificant, but our first theoretical assessments were surprising and thus prompted us to report the results immediately, ”said Miroslav Kocifai, Senior Researcher at the Slovak Academy of Sciences and lead author of the study on light pollution.
Scientists believe that the problem will only beaggravated as more satellites are sent into the sky. Other culprits for the change also include spent rocket components and other debris that reflect and scatter light from the Sun.
Where and what satellites are working now?
The most densely populated orbit is geostationary (GSO). Now there are about 400 satellites on it, that is, approximately every fifth operating spacecraft.
In general, the orbits of satellites are divided into low (up to 2000 kilometers from Earth), medium and high, and geostationary belongs to the latter group. Earth remote sensing satellites fly in low orbit, communication satellites, for example, such as Iridium, Globalstar, Orbcomm, the Russian system "Gonets". On the middle ones there are navigation systems - GLONASS (Russia), GPS (USA), Galileo (Europe) and Beidou (China).
The popularity of the geostationary orbit is a consequencethe fact that only on it the satellite does not change its position in the sky, as if hovering over the selected point of the equator at an altitude of 35,786 kilometers. This allows you to communicate with him using stationary terrestrial antennas, once and for all directed to one point.
- Starlink
In March 2021, SpaceX conducted a series of successful launches of Starlink satellites, bringing their number in orbit to 1,300 - about 8% of the plan for 2027.
SpaceX launches satellites into orbit in batches60 units since May 2019, and in March 2021 there were four such launches. Each satellite weighs 260 kg, and the stage for their launch is designed for 100 missions: each time it returns to the floating platform Of Course I Still Love You ("Of course, I still love you") in the Atlantic Ocean, 630 km from Cape Canaveral ...
The idea is to envelop in a net ofsmall telecom satellites the entire planet in low earth orbit - 500-2000 km from the surface. One satellite covers a small area, for example, the size of Alaska. Therefore, they are launched in groups to cover a specific area. The success of any LEO project will lead to a complete change in the telecom infrastructure around the world.
- Mars Express
Thanks to constant monitoring of Mars Expressscientists analyzed the last two global dust storms, in 2007 and 2018. They compared the performance of those years with years without storms to understand how storms affected the leakage of water from Mars.
With the change of seasons, moisture freezes in the atmosphereMars. However, instead of returning to the planet's surface in the form of precipitation, something else is happening. Dust storms interfere with the process. They heat and destroy the atmosphere of Mars, and also deliver water to even greater heights.
Both studies used extensive multi-year datasets from Mars Express's SPICAM instrument.
- Explosion of the NOAA satellite 17
The US meteorological satellite NOAA 17, which is notwas involved in the work, exploded in space into 16 debris. Scientists are now monitoring 16 debris associated with the explosion so that they do not disrupt the operation of other objects. Whether the debris poses a threat to operating satellites is not specified.
The squadron reported:There is no indication yet that the incident was caused by a collision with another object. According to the US Air Force, before the explosion, the satellite was in orbit with a minimum altitude of 800 km and a maximum altitude of 817 km.
The NOAA 17 satellite was launched into space in June 2002 and decommissioned in 2013. It is noted that earlier such satellites have already been destroyed in space due to the explosion of onboard batteries.
- ICESat-2
Scientists examined high-resolution data collected by the ICESat-2 satellite over the Amery Ice Shelf between October 2018 and November 2019.
Laser pulses from the satellite are directed tosurface of the Earth and use reflected photons to determine the height of the surface. Unlike other satellites, ICESat-2 resolution allows it to see finer fractures and their morphology.
Scientists processed satellite data usingalgorithm. It identifies surface ice depressions to locate and characterize cracks. Let us recall that depression of the snow line is its decrease due to climate changes favorable for maintaining the balance of glacier mass.
Since mass balance is a direct function of accumulation and ablation, fluctuations in the height of the snow line reflect the cumulative effects of changes in temperature and precipitation.
- OneWeb
In 2012, American Technicalentrepreneur, engineer and inventor Greg Wyler founded WorldVu Satellites, a telecommunications company that aims to provide hundreds of millions of people with Internet access. Later, the organization was renamed OneWeb - in honor of the project of the same name to spread the network to hard-to-reach places.
It is Russia that provides the project with the greatestresistance. In 2018, the FSB and Roskomnadzor opposed assigning the frequencies requested by OneWeb to satellites. Intelligence agencies said that there is a risk of espionage - they say that the British company will monitor the Russians. In 2019, OneWeb withdrew the application and promised to revise it to meet Russian national security requirements.
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