How do people communicate with satellites on the ground?

The way of satellite data transmission can be divided into 4 categories: The use of communication satellites as relay stations to realize data transmission between points on the earth is called satellite communication. This is the most widely used method of satellite data transmission.

Communications satellites in synchronous orbit can cover about 40 percent of the earth's surface, enabling any communication station on the ground, at sea, and in the air in the coverage area to communicate with each other at the same time. Three geostationary satellites are spaced equally apart in geostationary orbits over the equator to enable global communications except for parts of the poles.

In high latitudes, large elliptical orbit communication satellites with large inclination angles and apogees of up to 40,000 kilometers are also used. The satellite communication system consists of a satellite component and a communication station. The satellite segment also includes a satellite tracking and control station on the ground, which is used to control the satellite to be stationary relative to the earth, so as to simplify the antenna tracking system of the communication station.

The attitude of the communication satellite must be controlled more precisely to ensure that the antenna beam is always aimed at the coverage area. The key equipment to realize the signal (that is, the signal is sent to the satellite by the communication station of place A, and then sent by the satellite to the communication station of place B to realize the communication between place A and B) is the first device, which mostly uses traveling wave tube power amplifier.

The main development trends in satellite communications are the adoption of frequency multiplexing technology, the introduction of higher frequency bands and the development of information processing technology on satellites.

。Communications satellites can transmit**, telegrams, faxes, data and images, and are widely used in international, domestic or regional communications, military communications, maritime communications and television broadcasting, as well asSpacecrafttracking and data relaying。By the early 80s, satellite communications had taken on two-thirds of the intercontinental communications service and almost all of the intercontinental television transmissions.

Transmit data information sensed by satellites to the ground, including satellite telemetry and satellite remote sensing. Satellite telemetry is a technology that transmits satellites and their main internal operating states and performance parameters to the ground in real time or with delay. Various scientific, technical and application satellites transmit telemetry data to the ground in order to keep abreast of the satellite's work on the ground.

Satellite remote sensing is a technology that transmits information obtained by remote sensing devices and observation instruments installed on satellites to ground receiving points.

Meteorological satellites use remote sensors to detect meteorological elements and weather data of the earth's atmosphere; Astronomical satellites observe cosmic objects and other space objects with scientific instruments; Resource satellites were obtained with remote sensorsEarth's resourcesimage information; Reconnaissance satellites use optoelectronic remote sensors or radio receivers to gather intelligence on ground, sea or air targets. The ground TT&C station transmits the data transmission of command information to the satellite, also known as satellite remote control. Generally, satellites need to transmit control information to them through radio multi-channel channels to control the working status and parameter changes of satellites and ensure that satellites work according to ground requirements.

Various types of spacecraft are transmitted through data relay satellites and between the ground and the ground. Tracking and data relay satellite in geostationary orbit earth station tracking and remote control information of medium and low orbit spacecraft, and at the same time real-time artificial satellite.

Space shuttles, manned spacecraft.

and telemetry, remote sensing and communication data sent back to the ground by various spacecraft such as space stations.

The use of communication satellites as relay stations to realize data transmission between points on the earth is called satellite communication. This is the most widely used method of satellite data transmission.

Satellite communications are used to communicate as if they were radio transmission.

Humans realize communication according to the characteristics of radio propagation speed block, no need for medium, propagation stability, etc.

There are many ways to do this, such as using communication satellites as relay stations to transmit data from point to point on Earth.

Communication with the ground is achieved through communication satellites as conversion points.

By using radio, people communicate with satellites on the ground.

Satellite remote sensing is the technology of transmitting the information obtained by remote sensing devices and observation instruments installed on satellites to ground receiving points through professional tools.

When the satellite enters the second circle, the tracking and control station responsible for tracking it must immediately capture the target and make accurate measurements. The TT&C center uses this data to calculate the exact number of orbit roots.

There are many ways to do this, such as through satellites, etc.

Satellite earth station composition: antenna and servo subsystem, RF transceiver subsystem, modem and demodulation subsystem, baseband subsystem, monitoring subsystem, (interface subsystem), power supply subsystem, etc

Antenna and tracking servo subsystem: satellite signal transmission and reception, and antenna drive (automatic, electric, manual tracking).

Uplink: The RF signal output by HPA is amplified through the antenna and transmitted to the satellite.

Downlink: Receives RF signals from satellites.

Tracking servo: Controls the antenna to align with the satellite.

RF transceiver subsystem: complete the frequency conversion and amplification of the signal;

Uplink: Upconverts the modulated signal to the communication frequency (c@4 6G, ku@12 14G, ka@30 40GHz), amplifies it by HPA and transmits it to the satellite through the antenna.

Downlink: The signal received from the antenna is first amplified by the LNA low noise amplifier, and then sent to the demodulator for demodulation after downconversion to the demodulation frequency (generally L-band or 70 140MHz);

Modem and demodulation subsystem: Realize the modulation and demodulation of baseband digital signals.

Uplink: Modulate the digital signal brought by the base to the IF (70 140MHz or L-band) and send it to the upconverter.

Downlink: Demodulates the IF signal output by the downconverter into a digital baseband signal and sends it to the baseband subsystem.

Baseband subsystem: baseband digital signal processing;

Monitoring subsystem: realize the monitoring and management of the earth station;

Interface subsystem: complete the interface conversion between user data and satellite communication;

Power subsystem: ensure the safe and effective power supply of the earth station;

The originating earth station, the uplink propagation path, the satellite ** device, the downlink propagation path and the receiving earth station form a complete satellite communication line, which can be directly used for communication.

For two-way communication, each earth station includes a corresponding transmitting and receiving device. The components of the earth station mainly include: satellite antenna, antenna control servo tracking system, HPA, LNA, modulator, codec, etc.

The main function of satellite antenna and antenna control servo tracking system is to complete the transmission and reception of radio waves.

The main function of HPA is to complete the amplification of RF signals.

The main function of LNA is to complete the amplification of the received signal.

Basically correct.

As can be seen from the figure, three communication satellites are distributed over the equator at equal distances, which is enough to cover the whole world. So this statement is true.

But because the satellites are all over the equator, at the poles of the earth, the altitude of the satellites is near the horizon, and the communication effect is very poor. Fortunately, there are almost no permanent populations in the polar regions of the earth (there are simply no people on the Antarctic continent), so the communication effect is poor, and it does not matter.

Yes, but not at the same time, it should be said that the trajectory of the three can be covered, the diameter of the earth is r, each of them is at a distance of r from the earth, and then the trajectory of each of the three is 60 degrees (or 120 degrees) angle.

Similarities: both are microwave communications, and they all have the characteristics of microwave communication - they need to be visual, microwave transmission, refraction, and interference.

Differences: 1. Satellite communication is approximately ideal free-space microwave transmission, while terrestrial microwave communication is greatly affected by terrain and landform interference;

2. Put the ground microwave relay station in the sky (satellite), it becomes satellite communication, so the transmission distance is not limited by the spherical occlusion of the earth's surface (50 km ground microwave relay). Geostationary orbit satellites can cover about 1 3 area of the Earth's surface (ground-based microwave stations cannot do it);

3. The communication distance has nothing to do with the cost, because within the coverage area of the satellite, any site is connected by satellite. Terrestrial microwaves need to be relayed for transmission, and the distance between the two microwave relay stations is generally not more than 50 kilometers.

The media involved in radio waves in microwave communication include the earth's surface, the earth's atmosphere (troposphere, ionosphere, geomagnetic field, etc.), and interstellar space. According to the effect of media distribution on propagation, it can be divided into: continuous (uniform or inhomogeneous) media, such as troposphere, ionosphere, etc., and discrete scatterers, such as raindrops, ice mines, airplanes and other flying objects.

There are quite a few differences:

1.The distance of microwave communication is relatively short (less than 100km), while the distance of satellites is relatively far;

2.The frequency bands used are different;

3.(and the biggest difference) each hop (relay) of microwave communication will do data regeneration, while satellite communication does not do data regeneration when relaying on satellite;

1. Satellite communication is simply the use of satellites as relays between radio communication stations on the earth (including the ground and in the lower atmosphere). Satellite communication mainly uses artificial earth satellites as relay stations to improve radio waves, so as to achieve communication between two or more earth stations. The main purpose of satellite communications is to achieve a "seamless" cover on the ground.

2. The satellite communication system includes all the equipment for communication and support communication. Generally, it is composed of four parts: communication satellite, communication earth station, tracking telemetry and command subsystem, and monitoring and management subsystem. The tracking telemetry and command subsystem ---is mainly responsible for tracking and measuring the satellite, and controlling the cracks to accurately enter the designated position in the geostationary orbit as soon as possible.

After the satellite is in normal operation, the orbit position correction and attitude maintenance of the satellite should be carried out regularly. The monitoring and management subsystem --- is mainly responsible for detecting and controlling the communication performance of fixed-point satellites before and after the service is opened to ensure normal communication. The communication satellite --- mainly includes several parts, such as the communication system, the telemetry command device, the control system and the power supply device.

The main role of communication satellites is relay stations. Communication earth station--- communication earth station is a microwave radio transmitting and transmitting station, through which users access satellite lines for communication.