Method and device for measuring atmospheric density in space

Abstract

The invention discloses a method and a device for measuring atmospheric density in space. The method comprises the following steps: acquiring a target sound velocity acquired by a sound receiving and transmitting device in a spacecraft and a target navigation speed of the spacecraft; obtaining a target sound velocity of the spacecraft according to the target sound velocity and the target navigation velocity; and obtaining atmospheric density data of the spacecraft according to the target sound velocity. According to the method, the spacecraft can obtain real-time more accurate atmospheric density data when the external factors change and the atmospheric density rapidly changes, and then the attitude and task of the spacecraft are adjusted according to the change of the atmospheric density, so that the service life of the spacecraft is prolonged.

Description

Technical Field

[0001] The present application relates to the field of aerospace technology, and in particular to a method and device for measuring atmospheric density in space. Background Art

[0002] Spacecraft mainly move in the space above the Kármán line, which corresponds to the thermosphere and exosphere in the Earth's atmospheric stratification. The higher the altitude, the thinner the atmosphere. However, the atmosphere does not suddenly disappear at a certain altitude. If the thermosphere and exosphere are considered part of the atmosphere instead of part of outer space, the boundary of the atmosphere can be extended to the sky at an altitude of about 10,000 km (33,000,000 feet). The Kármán line is a line located at an altitude of 100 km (330,000 feet) and is generally recognized as the boundary between outer space and the Earth's atmosphere. This line is the current boundary between the atmosphere and space.

[0003] Low-orbit satellites and space stations are mainly active in the thermosphere. They are mainly affected by conservative perturbations such as the Earth's gravity, tidal force, and the gravity of the sun and moon, as well as non-conservative perturbations such as atmospheric drag, light pressure, and Earth's albedo, and they make approximately elliptical motions around the Earth. The gravity at the center of the Earth is the largest force on artificial spacecraft. For low-orbit spacecraft, the gravity at the center of the Earth is about 8m / s 2 The second is the second-order non-spherical gravity, which is 10 -2 m / s 2 The gravity of the Earth's center and other non-spherical gravity of various orders gradually decrease as the spacecraft's orbital altitude increases. The gravity of the sun and the moon is also an important perturbation force. For low-orbit spacecraft, the magnitude of the gravity of the sun and the moon is about 10 -6 m / s 2 , and gradually increases with increasing altitude.

[0004] The thermosphere will produce drag on the spacecraft. The spacecraft is usually flying at an altitude of more than 200 km. The atmosphere is very thin and the free path of atmospheric molecules is more than 100 m, which is much larger than the size of the spacecraft. Therefore, the thermosphere interacts with the spacecraft in the form of free molecular flow, generating drag. As the altitude increases, the atmospheric mass density decays exponentially, and the atmospheric drag decreases rapidly. For a spacecraft at an altitude of 300 km, the atmospheric drag can reach about 10 -5 m / s 2 At an altitude of about 800 km, the atmospheric drag force rapidly decays to about 10 -10 m / s 2The drag of the thermosphere will cause the spacecraft's mechanical energy to decrease, the orbital altitude to drop, and eventually fall into the atmosphere (without additional power to increase the orbital altitude). The lower the satellite orbit, the denser the atmosphere, the stronger the atmospheric drag, and the faster the spacecraft orbit decays. When the spacecraft orbit altitude is less than 250km, the atmosphere is already very dense and the spacecraft will fall quickly. It should be pointed out that solar radiation and earth-reflected radiation will also produce equivalent pressure on the spacecraft. The magnitude of the acceleration caused by light pressure is about 10 -7 m / s 2 , at about 500km altitude, the light pressure is equivalent to the atmospheric drag force. Therefore, for near-Earth spacecraft, the effect of light pressure can be ignored, while for spacecraft above 500km, the effect of light pressure needs to be accurately calculated.

[0005] Because of changes in external factors such as solar activity, the density of the thermosphere will change rapidly, thus affecting the life of satellites. Due to the significant drag effect of the thermosphere on low-orbit spacecraft, the thermosphere has a crucial impact on many aerospace engineering issues such as spacecraft on-orbit operation time prediction, target tracking, space debris warning, orbit determination, spacecraft orbit maintenance, and meteorite prediction. However, it is currently difficult to measure the density of the thermosphere.

[0006] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0007] The main purpose of this application is to provide a method and device for measuring atmospheric density in space, aiming to solve the problem in the prior art that the thermospheric atmosphere drags on low-orbit spacecraft, and the density of the thermospheric atmosphere changes rapidly due to changes in external factors, making it difficult to measure and affecting the life of the spacecraft.

[0008] A first aspect of an embodiment of the present application provides a method for measuring atmospheric density in space, which is applied to a spacecraft. The method for measuring atmospheric density in space comprises the following steps: obtaining a target sound speed collected by a sound transceiver in the spacecraft and a target navigation speed of the spacecraft; obtaining a target sound speed of the spacecraft based on the target sound speed and the target navigation speed; and obtaining atmospheric density data of the spacecraft based on the target sound speed.

[0009] Optionally, in one embodiment of the present application, the sound transceiver includes an audio sending device and an audio receiving device, and the distance between the audio sending device and the audio receiving device is a preset distance; obtaining the target sound speed collected by the sound transceiver in the spacecraft specifically includes: when the audio receiving device receives the sound signal sent by the audio sending device, obtaining the transmission time of the sound signal from sending to receiving; and taking the ratio of the preset distance to the transmission time as the target sound speed.

[0010] Optionally, in one embodiment of the present application, obtaining the target navigation speed of the spacecraft specifically includes: obtaining the spacecraft speed in the current traveling direction of the spacecraft; determining a preset angle between the current traveling direction and the target direction; and obtaining the target navigation speed of the spacecraft based on the spacecraft speed and the preset angle.

[0011] Optionally, in one embodiment of the present application, when the audio receiving device receives the sound signal sent by the audio sending device, the transmission time of the sound signal from sending to receiving is obtained, specifically including: when the audio sending device sends a test wave to the audio receiving device, obtaining the sending end waveform of the audio sending device and the receiving end waveform of the audio receiving device receiving the test wave; if the receiving end waveform matches the sending end waveform, it is determined that the audio receiving device has received the sound signal sent by the audio sending device; and obtaining the transmission time between the sending end waveform and the receiving end waveform corresponding to the sound signal.

[0012] Optionally, in one embodiment of the present application, determining the preset angle between the current driving direction and the target direction specifically includes: obtaining a vector navigation speed within a speed range below the order of magnitude of the target speed of sound; and determining the preset angle between the current driving direction and the target direction based on the vector navigation speed and the spacecraft speed.

[0013] Optionally, in one embodiment of the present application, the target sound speed includes a first sound speed and a second sound speed at adjacent times, and the atmospheric density data includes an order of magnitude of atmospheric density change; obtaining the atmospheric density data of the spacecraft based on the target sound speed specifically includes: obtaining the order of magnitude of sound speed change based on the first sound speed and the second sound speed; acquiring relationship information between the sound speed and the atmospheric density, and determining the order of magnitude of atmospheric density change based on the relationship information and the order of magnitude of sound speed change.

[0014] Optionally, in one embodiment of the present application, the relationship information includes a relationship equation and a variable constant between the speed of sound and the atmospheric density; the obtaining of the relationship information between the speed of sound and the atmospheric density specifically includes: obtaining a relationship equation between the speed of sound and the atmospheric density and a variable constant collected by a calibration device in the spacecraft; and determining the order of magnitude of the change in the atmospheric density based on the relationship equation, the variable constant and the order of magnitude of the change in the speed of sound.

[0015] A second aspect of an embodiment of the present application further provides a device for measuring atmospheric density in space, wherein the device for measuring atmospheric density in space comprises:

[0016] The device for measuring atmospheric density in space comprises:

[0017] A speed acquisition module, used to acquire a target sound speed collected by a sound transceiver in the spacecraft and a target navigation speed of the spacecraft;

[0018] A sound speed calculation module, used for obtaining a target sound speed of the spacecraft according to the target sound speed and the target navigation speed;

[0019] The atmospheric density calculation module obtains the atmospheric density data of the spacecraft according to the target sound speed.

[0020] A third aspect of an embodiment of the present application also provides a spacecraft, wherein the spacecraft includes: a memory, a processor, and a program for measuring atmospheric density in space stored in the memory and executable on the processor, wherein the program for measuring atmospheric density in space implements the steps of the method for measuring atmospheric density in space as described above when executed by the processor.

[0021] The fourth aspect of an embodiment of the present application also provides a computer-readable storage medium, wherein the computer-readable storage medium stores a program for measuring atmospheric density in space, and when the program for measuring atmospheric density in space is executed by a processor, the steps of the method for measuring atmospheric density in space as described above are implemented.

[0022] Beneficial effect: The present application provides a method and device for measuring atmospheric density in space. The method determines the sound speed around the spacecraft through the sound speed collected by a sound transceiver installed inside the spacecraft and the spacecraft vector speed of the spacecraft in low orbit, thereby determining the atmospheric density data of the spacecraft's surrounding environment based on the sound speed. This method enables the spacecraft to obtain real-time and more accurate atmospheric density data when the atmospheric density changes rapidly due to changes in external factors, and then adjust the spacecraft's attitude and mission according to the change in atmospheric density, thereby extending the life of the spacecraft and increasing the accuracy and economy of mission execution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is a flow chart of a preferred embodiment of the method for measuring atmospheric density in space of the present application;

[0025] Figure 2 It is a waveform diagram of a test wave emitted by a sound transceiver in a preferred embodiment of the method for measuring atmospheric density in space of the present application;

[0026] Figure 3 It is a schematic diagram of the angle between the direction of travel of the spacecraft and the direction in which the sound transceiver is placed in a preferred embodiment of the method for measuring the atmospheric density in space of the present application;

[0027] Figure 4 It is a structural diagram of a preferred embodiment of the device for measuring atmospheric density in space of the present application;

[0028] Figure 5 This is a structural diagram of a preferred embodiment of the spacecraft of this application.

[0029] Description of reference numerals:

[0030] 100. Speed ​​acquisition module; 200. Sound speed calculation module; 300. Atmospheric density calculation module. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and effect of the present application clearer and more specific, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. The described embodiments are only possible technical implementations of the present application, not all possible implementations. Based on the embodiments in the present application, those skilled in the art can completely combine the embodiments of the present application to obtain other embodiments without creative work, and these embodiments are also within the scope of protection of the present application.

[0032] In related technologies, since the atmospheric density of the thermosphere has a great impact on spacecraft, the atmospheric density of the activity space and other data can be used to better perform operations such as orbit change, thereby achieving practical significance such as extending the life of the spacecraft. It is also possible to more reasonably calculate the docking orbit of the spacecraft based on these data, thereby improving the docking efficiency of the spacecraft and increasing the safety and efficiency of human space activities. Therefore, humans have been constantly exploring the surrounding operating environment of spacecraft, space risks, etc. for decades. The thermosphere, the most important space for low-orbit spacecraft activities, is also a key area for human exploration. There are currently two mainstream methods: First, the photoelectric method: using professional instruments, such as mass spectrometers, far-ultraviolet remote sensing detectors, etc., this type of equipment is deployed on satellites. Due to the complex working principle of the main body, high manufacturing cost, reliability and other reasons, although there have been attempts, it cannot be used on a large scale. Even if it is used, it will increase the complexity of the satellite body, which is not conducive to large-scale deployment. Second, the orbital method: based on the changes in the satellite's orbit, the orbital changes are observed on the ground, and a mathematical model is established. The model is calculated and corrected from the existing data, and the changes in atmospheric density are inferred based on the existing model. This type of method is affected by factors such as historical data, the satellite's own attitude data (such as the angle of the drag surface), and the rationality of the model. It is impossible to accurately calculate the atmospheric density. The more important problem is that this type of method has a time lag, usually more than 12 hours, and cannot provide real-time data warnings for spacecraft, thus missing the best time to respond.

[0033] The following describes the method and device for measuring atmospheric density in space according to the embodiment of the present application with reference to the accompanying drawings. In view of the above-mentioned related art, the thermosphere atmosphere drags the low-orbit spacecraft, and the thermosphere atmosphere density changes rapidly due to changes in external factors, which makes it difficult to measure and affect the life of the spacecraft. The present application provides a method for measuring atmospheric density in space. In this method, the sound speed around the spacecraft is determined by the sound speed collected by the sound transceiver device set inside the spacecraft and the spacecraft vector speed of the spacecraft running in the low orbit, so as to determine the atmospheric density data of the surrounding environment of the spacecraft according to the sound speed, so that when the external factors change and the atmospheric density changes rapidly, the spacecraft can obtain more accurate atmospheric density data in real time, and then adjust the attitude and mission of the spacecraft according to the change of atmospheric density, so as to extend the life of the spacecraft and increase the accuracy and economy of mission execution. As a result, the technical problem that the thermosphere atmosphere drags the low-orbit spacecraft in the related art, and the thermosphere atmosphere density changes rapidly due to changes in external factors, which makes it difficult to measure and affect the life of the spacecraft is solved.

[0034] In this application, based on the speed of sound propagation and the speed of low-orbit spacecraft, the distribution of the thermosphere atmosphere can be calculated in a timely manner, and the distribution of the atmospheric density around the spacecraft can be effectively measured, thereby providing better data support for satellite orbit, attitude control and mission decision-making. Furthermore, through constellation deployment, the distribution of atmospheric density in different spheres around the world can also be obtained, providing more accurate operating environment data for spacecraft.

[0035] This application can also be deployed through multiple satellites or constellations, combined with inter-satellite or satellite-to-ground networks, to quickly calculate real-time data on the global thermospheric atmospheric density distribution and changes, thereby increasing the response of spacecraft, improving the life of spacecraft, and reducing safety hazards of spacecraft.

[0036] The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

[0037] The method for measuring atmospheric density in space described in the preferred embodiment of the present application is applied to spacecraft.

[0038] like Figure 1 As shown, the method for measuring atmospheric density in space comprises the following steps:

[0039] In step S101, the target sound speed collected by the sound transceiver in the spacecraft and the target navigation speed of the spacecraft are obtained.

[0040] It is worth noting that the signal-to-noise ratio is S / N, S is the signal, and N is the noise. The larger the signal-to-noise ratio, the better the sound speed measurement effect and the atmospheric density measurement effect. Therefore, this application increases the signal-to-noise ratio, that is, the order of magnitude of the target sound speed (V1) is set to be greater than or equal to the target navigation speed (V2cosα, V2 is the spacecraft speed in the direction of the spacecraft's travel, and α is the angle between the spacecraft's travel direction and the target direction), so that the accuracy of the subsequent step of calculating the target sound speed (V3, V3 = V1-V2cosα) is better, and then the atmospheric density data (the order of magnitude of atmospheric density change) is measured through the relationship between the sound speed and the atmospheric density (the square of the sound speed is proportional to the atmospheric density), so as to control and adjust the spacecraft accordingly and improve the service life of the spacecraft. It should be noted that the placement direction of the sound transceiver is the same as the target direction of the spacecraft (the travel direction and the target direction are at an angle α).

[0041] In a possible implementation, the sound transceiver includes an audio transmitter and an audio receiver, and the distance between the audio transmitter and the audio receiver is a preset distance. In the step of obtaining the target sound speed of the spacecraft, when the audio receiver receives the sound signal sent by the audio transmitter, the transmission time of the sound signal from the transmission to the reception is obtained; and the ratio of the preset distance to the transmission time is used as the target sound speed.

[0042] Specifically, in the formula for setting up a sound transceiver (i.e., sonic payload device) inside an on-orbit spacecraft: there is a group of sound transceivers on the spacecraft, and the distance between the two transceiver components is L (the distance between the internal transceiver sensors of the audio transceiver. Due to the limited space of the spacecraft itself, L is set to a larger value as much as possible so that the order of magnitude of the target sound speed is above the order of magnitude of the target navigation speed, such as one order of magnitude larger or the two are the same order of magnitude, thereby ensuring that the target navigation speed has a lower impact on the sound speed), the transmission time is t, so the target sound speed V1 tested by the device = L / t, that is, V1 is the target sound speed collected by the sound transceiver in the spacecraft.

[0043] In one possible implementation, when the audio sending device sends a test wave to the audio receiving device, the sending end waveform of the audio sending device and the receiving end waveform of the audio receiving device receiving the test wave are obtained; if the receiving end waveform matches the sending end waveform, it is determined that the audio receiving device has received the sound signal sent by the audio sending device; and the transmission time between the sending end waveform and the receiving end waveform corresponding to the sound signal is obtained.

[0044] It should be noted that the test wave is any one of a sine wave, a square wave and a triangular wave. The influence of the thermosphere atmospheric density on the spacecraft is caused by the change of the order of magnitude. Usually, the atmospheric density is 10 -5 m 3 Around, due to solar particle storms and other reasons, the atmospheric density will quickly rise by one or two orders of magnitude, thus affecting the flight trajectory of the spacecraft. Through the formula, the relationship between air density and sound speed can be effectively derived; for scenarios with atmospheric density that change by orders of magnitude, the audio transceiver also needs to be modulated to select the frequency that best suits the current atmospheric density scenario for more accurate measurements. This application can select a variety of waveforms for measurement, such as sine waves, square waves, triangle waves, and the like. Here, a sine wave is selected as the test audio for example. In actual implementation, it is more convenient to use a square wave.

[0045] When the atmospheric density increases, based on the result of formula V3, it can be concluded that the square of the speed of sound is proportional to the atmospheric density. When the atmospheric density increases, the speed of sound increases. Ideally, the frequency of the test wave is appropriate and the waveform at the receiving end does not change. When the speed of sound increases and the frequency of the test wave remains unchanged, the waveform received by the receiving end will be compressed. Conversely, when the speed of sound decreases and the frequency of the test wave remains unchanged, the waveform received by the receiving end will be stretched. As the speed of sound changes, the received wave will be fragmented, overlapped, and even undetectable.

[0046] like Figure 2 As shown, the waveform received by the audio receiving device matches the waveform sent by the audio transmitting device (e.g. Figure 2 The received waveform in the audio receiving device is consistent with the transmitted waveform), the time t can be determined; if the receiving waveform received by the audio receiving device does not match the transmitting waveform sent by the audio transmitting device, such as Figure 2 If the received waveform is a compressed or stretched waveform compared to the transmitted waveform, the negative feedback modulation method can be used to continuously adjust the waveform of the transmitting end according to the current test results, so that the waveform of the receiving end matches the waveform frequency and shape of the transmitting end as much as possible, thereby calculating the current speed of sound. In addition, in order to avoid the inherent influence of the current spacecraft orbit, a filter can be added to the receiving end, and a filtering algorithm can be added to the algorithm to obtain a cleaner receiving end waveform.

[0047] In one possible implementation, in the step of obtaining the target navigation speed of the spacecraft, the spacecraft speed of the current traveling direction a of the spacecraft is obtained; a preset angle α between the current traveling direction and the target direction is determined; and the target navigation speed of the spacecraft is obtained based on the spacecraft speed and the preset angle.

[0048] See also Figure 3 , the spacecraft's traveling direction corresponding to the spacecraft's speed is a, and the placement direction of the sound transceiver and the vector direction corresponding to the spacecraft's vector navigation speed is b.

[0049] It can be understood that the first cosmic velocity refers to the speed at which an object moves in uniform circular motion around the earth near the ground. The first cosmic velocity is also known as: minimum launch velocity of spacecraft, maximum operating velocity of spacecraft, and orbital velocity. The first cosmic velocity refers to the speed at which an artificial satellite moves in uniform circular motion just close to the surface of the earth. It is the maximum orbital velocity of an artificial satellite orbiting the earth, and it is also the minimum launch velocity at which it will never fall back to the earth. When a spacecraft moves at the first cosmic velocity, it means that the spacecraft is moving along the first cosmic velocity on the surface of the earth. According to the theory of mechanics, v = 7.9 km / s can be calculated. In fact, there is a dense atmosphere on the surface of the earth, and it is impossible for a spacecraft to move in a circular motion close to the surface of the earth. It must be at a flight altitude of 150 kilometers to move in a circular motion around the earth. The spacecraft is operating at an altitude of hundreds of kilometers above the ground surface. The gravity of the earth on the spacecraft is smaller than when it is on the ground, so its speed is also slightly less than v. The orbital velocity at this altitude is 7.8 km / s.

[0050] Specifically, the spacecraft speed V2 (i.e., the spacecraft speed in the current direction of travel) of the spacecraft in the low orbit is derived as follows:

[0051]

[0052] Where, GM = V 2 r, the gas constant R = 6.375 × 10 6 m, Earth mass M = 5.965 × 10 24 kg, gravitational constant 6.67259×10 -11 m 3 / (kg·s 2 ) is substituted and the square root is taken to obtain v≈7.9 km / s. It is generally believed that GM is a constant, and the square of the spacecraft's flight speed is inversely proportional to the distance from the Earth's orbit, and the general speed is 7.8 km / s (i.e., V2=7.8 km / s in the embodiment of the present application).

[0053] In a possible implementation, in the step of determining the preset angle α, a vector navigation speed within a speed range below the order of magnitude of the target speed of sound is obtained; and a preset angle between the current driving direction and the target direction is determined based on the vector navigation speed and the spacecraft speed.

[0054] It is worth mentioning that there is an ideal setting, that is, the flight direction of the spacecraft is the same as the placement direction of the sound transceiver, so that V1 can be obtained. However, due to the large difference between V3 and V2, the value of V1 has a very small effect on the change of V3. If we only rely on V1 and V2, there will still be very large inaccuracies and errors. Therefore, two methods are used to increase the influence of V1 relative to V2.

[0055] In one embodiment of the present application, the placement of the measuring device is first adjusted so that it has a larger angle α with the flight direction of the spacecraft, such as 89.5°. The measuring device is a component of the flight direction of the spacecraft:

[0056] V2A=V2×cosα;

[0057] Among them, V2A is the target navigation speed. If α=89.5°, it will increase by 3 orders of magnitude. If it is set to α=89°, it will increase by 2 orders of magnitude. Based on the common sense of ground atmosphere, the ground sound speed is V1=340m / s, and V2 in space is 7.8km / s, so V1 will be 1 to 2 orders of magnitude higher than V2A.

[0058] In one embodiment of the present application, the transmission frequency is adjusted. Since the air density in space is much lower than that on the ground, the speed of sound will still be lower than V2A by placing it higher. The relative magnitude difference between V1 and V2 can be further optimized by adjusting the frequency. Therefore, the frequency of the transmitted sound can be modulated, and the difference between V2A and V1 can be further adjusted by calculating the frequency offset. The change in atmospheric density in low-Earth orbit is an order of magnitude change, ranging from 10 -5 m 3 to 10 -8 m 3 Current technology can detect frequency deviation in ppm (parts per million), that is, 10 -6 m 3 About, based on the relationship between density and speed, the corresponding value is 10 -3 m 3 Therefore, audio frequency modulation can fully detect the magnitude of atmospheric density.

[0059] Furthermore, after adjusting the angle and frequency, the specific logical steps to obtain V3 are as follows: Determine the angle α: Select a suitable angle α, such as 89.5° or 89°, to increase the influence of V1 relative to V2. The choice of angle depends on the order of magnitude you want to increase; Calculate V2A: Use the formula V2A=V2×cosα to calculate the component V2A of V2 in the direction of the measuring device, where V2 is the flight speed of the spacecraft, and α is the angle between the measuring device and the flight direction of the spacecraft; Adjust the sending frequency: Adjust the frequency of the transmitted sound according to the atmospheric density in space and the expected sound speed V3 (such as 340m / s), and further optimize the relative order of magnitude difference between V1 and V2A by calculating the frequency offset; Measure V1, and measure the sound propagation speed V in space at the adjusted frequency; Calculate V3 based on V2A, V3 and the relationship between them and V1.

[0060] In step S102, the target sound speed V3 of the spacecraft is obtained according to the target sound speed V1 and the target navigation speed V2cosα.

[0061] Specifically, based on the spacecraft, the Newton sound speed (i.e., the target sound speed of this application) formula can be expressed as:

[0062]

[0063] Among them, v represents the speed of sound, γ represents the adiabatic index of the atmosphere, R represents the gas constant, and T represents the temperature. The γ in the formula is a constant related to the properties of the gas. For most ideal gases, γ is approximately equal to 1.4. R is the gas constant. For air, its value is approximately 287J / (kg·K). T represents temperature in Kelvin (K). The derivation process of Newton's sound speed formula is based on the ideal gas state equation. The ideal gas state equation can be expressed as:

[0064] pV=nRT;

[0065] Among them, p represents the pressure of the gas, V represents the volume of the gas, n represents the amount of gas, R represents the gas constant, and T represents the temperature. In the ideal gas state equation, the amount of gas n can be expressed as the mass of the gas m divided by the molar mass of the gas M. At the same time, the volume of the gas V is expressed as the mass of the gas m divided by the density of the gas ρ. Substituting these two expressions into the ideal gas state equation, we can get:

[0066] p = ρRT / M;

[0067] Through further transformation, we can get:

[0068]

[0069] This expression is another form of Newton's formula for the speed of sound. The square of the speed of sound is proportional to the density of the atmosphere. It can be understood that v 2 = kρ, k is a constant, ρ is the atmospheric density, and v is the target sound speed. It can be understood that, assuming that under certain conditions (such as standard atmospheric pressure and temperature), the constant k makes the sound speed a known value (such as the ground sound speed is 343 meters per second, which is the sound speed in air at 20 degrees Celsius), then this value can be used to calculate the sound speed at the current density.

[0070] Furthermore, V3=V1-V2cosα (the placement direction of the sound transceiver is the same as the target direction of the spacecraft, and the target direction is the direction with a preset angle α with the current direction of travel of the spacecraft); the target speed of sound V1 can be accurately tested by the device, V2 is related to the orbit of the spacecraft and can also be effectively measured, and V3 can be obtained through the above-mentioned public announcement, thereby calculating the atmospheric density.

[0071] It is worth noting that the speed of sound on the ground is 343 meters per second, while the speed of the spacecraft in the low orbit of space is 7.8 kilometers per second or 7.9 kilometers per second (in this embodiment, 7.8 kilometers per second is used as the spacecraft speed along the direction of travel). By setting the order of magnitude of V1 to be greater than or equal to the order of magnitude of V2cosα, that is, the order of magnitude of V3 on the ground is the same as the order of magnitude of V2cosα, that is to say, the spacecraft speed (7.8km / s) is reduced by two orders of magnitude (about 780m / s), α is set to 89.5°, cos89.5°≈0.0087, so that the accuracy of calculating V3 (V3=V1-V2cosα) in the subsequent steps is better.

[0072] In step S103, atmospheric density data of the spacecraft is obtained according to the target sound speed.

[0073] In a possible implementation, the target sound speed includes a first sound speed and a second sound speed at adjacent times, and the atmospheric density data includes an order of magnitude of atmospheric density change. In the step of obtaining the atmospheric density data, the order of magnitude of the sound speed change is obtained according to the first sound speed and the second sound speed; the relationship information between the sound speed and the atmospheric density is obtained, and the order of magnitude of the atmospheric density change is determined according to the relationship information and the order of magnitude of the sound speed change.

[0074] Specifically, the square of the speed of sound is proportional to the atmospheric density, that is, v 2 = kρ, according to the above steps, the first sound speed and the second sound speed are obtained at adjacent times, and the magnitude of the sound speed change can be determined. If the second sound speed changes by one level (i.e., changes by ten times) than the second sound speed, then the atmospheric density changes by two levels (i.e., changes by one hundred times, such as from 10 -3 Change to 10 -5 ), determine the order of magnitude of atmospheric density changes.

[0075] In a possible implementation, the relationship information includes a relationship between the speed of sound and the atmospheric density and a variable constant. In the step of acquiring the relationship information, the relationship between the speed of sound and the atmospheric density and the variable constant collected by the calibration device in the spacecraft are acquired; the magnitude of the change in the atmospheric density is determined based on the relationship, the variable constant and the magnitude of the change in the speed of sound.

[0076] Specifically, the current density in space tested by the photoelectric method is combined with the formula of velocity v and atmospheric density ρ in this embodiment to recalculate the constant k, avoiding the difference in the value of k in space and on the ground caused by temperature, light intensity and other environmental factors, so as to more accurately test the atmospheric density in space. The present application can accurately calibrate the constant, v 2 =kρ in k, and then substitute the calibrated variable constant into the formula to obtain the accurate order of magnitude of atmospheric density change.

[0077] It should be noted that solar particle storms can cause changes in the atmospheric density, which will drag the spacecraft. If the attitude of the spacecraft is changed, the life of the spacecraft can be extended. If the changes in atmospheric density and the corresponding sound speed are mastered, the attitude of the spacecraft during the mission can be adjusted in real time to obtain better business results.

[0078] Specifically, there is a certain relationship between the speed of sound and the atmospheric density, but this relationship usually involves multiple physical parameters, such as temperature, pressure, etc., and will vary under different atmospheric conditions. If some basic physical constants and atmospheric conditions are known, a corresponding mathematical model can be established to estimate the atmospheric density.

[0079] Furthermore, according to the changes in atmospheric density and the mission requirements of the spacecraft, a decision plan for attitude adjustment is formulated. The decision plan should include parameters such as the direction, angle, and speed of the attitude adjustment to ensure that the spacecraft can stably maintain the required attitude; the decision plan is input into the attitude control system of the spacecraft, and the attitude adjustment program is started. The attitude control system will automatically adjust the attitude of the spacecraft according to the input parameters and the current state of the spacecraft. During the adjustment process, the attitude control system will continuously monitor the attitude changes of the spacecraft and make fine adjustments as needed to ensure the accuracy and stability of the attitude adjustment; after the attitude adjustment is completed, the attitude of the spacecraft is verified and confirmed, and the accuracy and effect of the attitude adjustment are evaluated by comparing the difference between the adjusted attitude and the expected attitude. If there are differences or problems, corrections and adjustments are made in a timely manner to ensure that the spacecraft can continue to perform its mission stably.

[0080] It is understandable that other factors that interfere with the calculation of the speed of sound are as follows:

[0081] Temperature has a certain influence on the propagation speed of sound. The fundamental reason is that temperature causes changes in the activity of atmospheric particles. That is, at the same atmospheric density and different temperatures, the higher the temperature, the faster the sound speed. This part of the influence is not an order of magnitude influence, and can be further corrected by continuously accumulating data;

[0082] The flight speed of the spacecraft, in the above formula and calculation, the default speed of the spacecraft in low orbit is 7.8km / s. Due to factors such as flight altitude and flight angle, there will be some deviation from 7.8km / s. The actual speed of the spacecraft can be obtained in real time based on the current orbit of the spacecraft, as well as the data of onboard GNSS and star sensitivity, replacing the current default first cosmic speed;

[0083] Normal velocity of the spacecraft. The orbit of a spacecraft in low-Earth orbit is a large ellipse, not a straight line. Therefore, when calculating the speed of sound V2A, the influence of the current angle can be considered. According to the trajectory and flight speed of the spacecraft, the normal velocity is calculated in real time to replace the first cosmic velocity mentioned above;

[0084] Audio frequency. Different audio frequencies have different effects in the same atmospheric density. You can try different frequencies and make corrections.

[0085] It should be noted that the frequency detection method is not specifically limited here and can be modified according to actual conditions.

[0086] Next, a device for measuring atmospheric density in space proposed according to an embodiment of the present application will be described with reference to the accompanying drawings.

[0087] Figure 4 It is a structural diagram of a device for measuring atmospheric density in space according to an embodiment of the present application.

[0088] like Figure 4 As shown, the device for measuring atmospheric density in space includes: a velocity acquisition module 100, a sound speed calculation module 200, and an atmospheric density calculation module 300.

[0089] Specifically, the speed acquisition module 100 is used to acquire the target sound speed collected by the sound transceiver in the spacecraft and the target navigation speed of the spacecraft;

[0090] A sound speed calculation module 200, configured to obtain a target sound speed of the spacecraft according to the target sound speed and the target navigation speed;

[0091] The atmospheric density calculation module 300 obtains the atmospheric density data of the spacecraft according to the target sound speed.

[0092] Figure 5 A structural diagram of a spacecraft provided in an embodiment of the present application. The spacecraft may include:

[0093] A memory 501 , a processor 502 , and a computer program stored in the memory 501 and executable on the processor 502 .

[0094] When the processor 502 executes the program, the method for measuring atmospheric density in space provided in the above embodiment is implemented.

[0095] Furthermore, the spacecraft includes:

[0096] The communication interface 503 is used for communication between the memory 501 and the processor 502 .

[0097] The memory 501 is used to store computer programs that can be executed on the processor 502 .

[0098] The memory 501 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0099] If the memory 501, the processor 502 and the communication interface 503 are implemented independently, the communication interface 503, the memory 501 and the processor 502 can be connected to each other through a bus and communicate with each other. The bus can be an Industry Standard Architecture (ISA) bus, a Peripheral Component (PCI) bus or an Extended Industry Standard Architecture (EIS) bus. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 5 Only one thick line is used in the diagram, but this does not mean that there is only one bus or only one type of bus.

[0100] Optionally, in a specific implementation, if the memory 501, the processor 502 and the communication interface 503 are integrated on a chip, the memory 501, the processor 502 and the communication interface 503 can communicate with each other through an internal interface.

[0101] The processor 502 may be a central processing unit (CPU), or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the embodiments of the present application.

[0102] This embodiment also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the above method for measuring atmospheric density in space.

[0103] One embodiment of the present application provides a computer program product, including a computer program, which, when executed by a processor, implements the present application Figure 1 Any embodiment of the corresponding embodiment provides a method for measuring atmospheric density in space.

[0104] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or N embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0105] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, "N" means at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0106] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, fragment or portion of code comprising one or N executable instructions for implementing the steps of a custom logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0107] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable storage medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this specification, a "computer-readable storage medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples (non-exhaustive list) of computer-readable storage media include the following: an electrical connection with one or N wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable storage medium may even be paper or other suitable medium on which the program is printed, since the program can be obtained electronically by optically scanning the paper or other medium and then editing, interpreting or processing in other suitable ways as necessary, and then storing it in a computer memory.

[0108] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiment, the N steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0109] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0110] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0111] The storage medium mentioned above may be a read-only memory, a magnetic disk or an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application. A person of ordinary skill in the art may change, modify, replace and modify the above embodiments within the scope of the present application.

[0112] It should be understood that the application of the present application is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to this application.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for measuring atmospheric density in space, characterized in that: Applied to a spacecraft, the method for measuring atmospheric density in space comprises: Obtaining a target sound speed collected by a sound transceiver in the spacecraft and a target navigation speed of the spacecraft; Obtaining a target sound speed of the spacecraft according to the target sound speed and the target navigation speed; According to the target sound speed, atmospheric density data of the spacecraft is obtained.

2. The method for measuring atmospheric density in space according to claim 1, characterized in that: The sound transceiver device includes an audio transmitter and an audio receiver, and the distance between the audio transmitter and the audio receiver is a preset distance; The obtaining of the target sound speed collected by the sound transceiver in the spacecraft specifically includes: When the audio receiving device receives the sound signal sent by the audio sending device, obtaining the transmission time of the sound signal from sending to receiving; The ratio of the preset distance to the transmission time is used as the target sound speed.

3. The method for measuring atmospheric density in space according to claim 2, characterized in that: Obtaining the target navigation speed of the spacecraft, specifically including: Obtaining the spacecraft speed in the current direction of travel of the spacecraft; Determining a preset angle between the current driving direction and the target direction; The target navigation speed of the spacecraft is obtained according to the spacecraft speed and the preset angle.

4. The method for measuring atmospheric density in space according to claim 2, characterized in that: When the audio receiving device receives the sound signal sent by the audio sending device, obtaining the transmission time of the sound signal from sending to receiving specifically includes: When the audio transmitting device transmits a test wave to the audio receiving device, a waveform of a transmitting end of the audio transmitting device and a waveform of a receiving end of the audio receiving device receiving the test wave are obtained; If the receiving-end waveform matches the sending-end waveform, it is determined that the audio receiving device has received the sound signal sent by the audio sending device; The transmission time between the sending-end waveform and the receiving-end waveform corresponding to the sound signal is obtained.

5. The method for measuring atmospheric density in space according to claim 3, characterized in that: The determining of the preset angle between the current driving direction and the target direction specifically includes: Obtaining a vector navigation speed within a speed range below the target speed of sound; A preset angle between the current driving direction and the target direction is determined according to the vector navigation speed and the spacecraft speed.

6. The method for measuring atmospheric density in space according to claim 1, characterized in that: The target sound speed includes a first sound speed and a second sound speed at adjacent times, and the atmospheric density data includes an order of magnitude of atmospheric density change; The obtaining, according to the target sound speed, the atmospheric density data of the spacecraft specifically includes: According to the first sound speed and the second sound speed, the magnitude of the sound speed change is obtained; Relationship information between the speed of sound and the atmospheric density is obtained, and the magnitude of the change in the atmospheric density is determined based on the relationship information and the magnitude of the change in the speed of sound.

7. The method for measuring atmospheric density in space according to claim 6, characterized in that: The relationship information includes a relationship between the speed of sound and the atmospheric density and a variable constant; The obtaining of the relationship information between the speed of sound and the atmospheric density specifically includes: Obtaining a relationship between the speed of sound and the atmospheric density and a variable constant collected by a calibration device in the spacecraft; The magnitude of the change in atmospheric density is determined based on the relationship, the variable constant and the magnitude of the change in the speed of sound.

8. A device for measuring atmospheric density in space, characterized in that: The device for measuring atmospheric density in space comprises: A speed acquisition module, used to acquire a target sound speed collected by a sound transceiver in the spacecraft and a target navigation speed of the spacecraft; A sound speed calculation module, used for obtaining a target sound speed of the spacecraft according to the target sound speed and the target navigation speed; The atmospheric density calculation module obtains the atmospheric density data of the spacecraft according to the target sound speed.

9. A spacecraft, characterized in that: The spacecraft includes: a memory, a processor, and a program for measuring atmospheric density in space stored in the memory and executable on the processor. When the program for measuring atmospheric density in space is executed by the processor, the steps of the method for measuring atmospheric density in space as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a program for measuring atmospheric density in space, and when the program for measuring atmospheric density in space is executed by a processor, the steps of the method for measuring atmospheric density in space as described in any one of claims 1 to 7 are implemented.

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