阅读说明：本技术 一种计算火星探测器大气阻力的方法 (Method for calculating atmospheric resistance of Mars detector ) 是由 刘舒莳 李勰 陈光明 满海钧 曹建峰 于 2021-05-28 设计创作，主要内容包括：本发明涉及一种计算火星探测器大气阻力的方法,属于深空探测专业领域；步骤一、计算火星大气的阻力系数C-(D)；步骤二、通过火星气候数据库MCD-V5.3获得火星大气密度ρ；步骤三、计算卫星探测器相对火星大气的速度v-(rel)；步骤四、计算卫星探测器的迎风面积A；步骤五、计算卫星探测器受到的大气阻力f；本发明能够提高火星探测器在环绕火星飞行时的轨道计算和轨道预报精度,能够计算火星环绕探测器的自然陨落寿命。(The invention relates to a method for calculating atmospheric resistance of a Mars detector, belonging to the field of deep space exploration; step one, calculating a resistance coefficient C of the atmosphere of the mars D (ii) a Step two, acquiring a Mars atmospheric density rho through a Mars climate database MCD _ V5.3; step three, calculating the speed v of the satellite detector relative to the atmosphere of the mars rel (ii) a Step four, calculating the windward area A of the satellite detector; step five, calculating the atmospheric resistance f borne by the satellite detector; the invention can improve the orbit calculation and orbit prediction precision of the Mars surrounding detector when flying around the Mars, and can calculate the natural fall life of the Mars surrounding detector.)

1. A method for calculating atmospheric resistance of a Mars probe is characterized by comprising the following steps: the method comprises the following steps:

step one, calculating a resistance coefficient C of the atmosphere of the mars_D；

Step two, acquiring a Mars atmospheric density rho through a Mars climate database MCD _ V5.3;

step three, calculating the speed v of the satellite detector relative to the atmosphere of the mars_rel；

Step four, calculating the windward area A of the satellite detector;

and step five, calculating the atmospheric resistance f borne by the satellite detector.

2. The method of calculating Mars probe atmospheric drag of claim 1, wherein: in the first step, the resistance coefficient C of the atmosphere of the mars_DThe calculation method comprises the following steps:

in the formula, T_siThe temperature of each surface of the detector;

T_ais the temperature of the atmosphere;

β_ithe included angle between the movement direction of the atmosphere and each surface of the detector is obtained by a satellite detector attitude monitoring system;

μ_iis the ratio of the average mass of the incident gas molecules to the mass of the molecules on the scattering surface of the satellite detector.

3. A method of calculating the mars probe atmospheric resistance of claim 2, wherein: in the second step, the Mars climate database MCD _ V5.3 is a meteorological field database obtained from numerical simulation of a Mars atmospheric circulation model, and verification is completed by using observation data; the Mars climate database MCD _ V5.3 provides temperature, pressure, wind field and atmospheric density within the range of 0-260 kilometers, and three scenes of calmness, medium and activity are set according to the degree of solar activity.

4. A method of calculating the mars probe atmospheric resistance of claim 3, wherein: in the second step, a specific method for obtaining the Mars atmospheric density rho through the Mars climate database MCD _ V5.3 is as follows:

calling a subprogram call _ MCD of a mars climate database MCD _ V5.3, inputting parameters of a preset ordinate type zkey, a preset mars ground point ordinate xz, a preset mars ground point longitude xlon, a preset mars ground point latitude xlat, a preset data resolution hireskey, a preset epoch representation mode datakey, a preset epoch time xdate, a mars local time locame, a database file storage path dset and a preset mars dust storm and solar EUV radiation scene scena, and outputting a result, namely the mars atmospheric density rho.

5. The method of calculating Mars probe atmospheric drag of claim 4, wherein: in the third step, the speed v of the satellite detector relative to the atmosphere of the Mars_relThe calculation method comprises the following steps:

s31, establishing a mars fixed connection coordinate system oxyz; wherein, the origin o is the centroid of the Mars; selecting a Mars flat equatorial plane as a first reference plane; the x axis points to the focal point of the initial meridian and the first reference plane; the z-axis points to the Mars rotation axis; the y-axis is determined by the right hand rule;

s32, establishing a Martian celestial coordinate system o1x1y1z 1; wherein the origin o1 is the Mars centroid; the x1 axis points in the direction of epoch peaceful spring minute point; the z-axis points to the earth rotation axis; the y-axis is determined by the right hand rule;

s33, calculating each axis from the fixed Mars coordinate system oxyz to the Mars celestial coordinate system o1x1y1z1Of the unit rotation matrix R_i(α)＝[R_x(α)、R_y(α)、R_z(α)](ii) a Setting the rotation angles from the x axis to the x1 axis, the y axis to the y1 axis and the z axis to the z1 axis as alpha;

s34, calculating a coordinate transformation matrix RT2C from a mars fixed connection coordinate system oxyz to a mars celestial coordinate system o1x1y1z1 at the moment t;

s35, calculating Mars atmospheric velocity omega under Mars celestial coordinate system_inPosition vector r of satellite detector_inVelocity vector v of satellite probe_in(ii) a Calculating the velocity v of the satellite detector relative to the Martian atmosphere_rel。

6. The method of calculating Mars probe atmospheric drag of claim 5, wherein: in the S33, the unit rotation matrix R_iThe calculation method of (alpha) is as follows:

7. the method of calculating Mars probe atmospheric drag of claim 6, wherein: in S34, the calculation method of the coordinate transformation matrix RT2C is:

wherein, N is pointing parameter, and N is 3.37919183 degrees;

j is pointing parameter, J is 24.67682669 °;

nutating the Mars;

i is the inclination angle of the Mars orbit;

phi is a spark self-rotation angle;

X_pand Y_pThe polar motion of the spark rotation shaft.

8. The method of calculating Mars probe atmospheric drag of claim 7, wherein: in the S35, the star atmospheric velocity omega_inThe calculation method comprises the following steps:

position vector r of satellite detector under Mars celestial coordinate system_inObtaining the measurement;

velocity vector v of satellite detector under Martian celestial coordinate system_inObtaining the measurement;

velocity v of satellite detector relative to Martian atmosphere_relThe calculation method comprises the following steps:

9. the method of calculating Mars probe atmospheric drag of claim 8, wherein: in the fourth step, the method for calculating the windward area a of the satellite detector comprises the following steps:

in the formula, A_sIs the windward area of the satellite detector body,measurement at the ground is obtained;

A_PNthe windward area of the sailboard;

A_Pthe total area of the sailboard;

and N is a sailboard normal vector and is obtained according to the position measurement of the sun and the detector.

10. The method of calculating the Mars probe atmospheric drag of claim 9, wherein: in the fifth step, the calculation method of the atmospheric resistance f borne by the satellite detector comprises the following steps:

Technical Field

The invention belongs to the field of deep space exploration and relates to a method for calculating atmospheric resistance of a Mars detector.

Background

The resistance generated by the atmosphere above the Mars influences the Mars detector orbit, so that the semi-major axis of the detector orbit flying around the Mars is reduced, and the service life of the satellite is influenced. Meanwhile, the atmospheric resistance is an important perturbation force in the track calculation process, and the quantitative description of the atmospheric resistance borne by the detector is beneficial to improving the precision of track calculation and track forecast of the Mars detector. In the current Mars detection plan of China, because the time for the detector to fly around the Mars in a short distance (below 500km height) is short, the influence of Mars atmospheric resistance is not considered in orbit calculation and forecast. With the subsequent deep detection of the mars, a close-range and long-time mars-surrounding flight detection task must be carried out, and at the moment, the mars atmospheric resistance becomes a non-negligible influence factor.

Disclosure of Invention

The technical problem solved by the invention is as follows: the method overcomes the defects of the prior art, provides a method for calculating atmospheric resistance of the Mars detector, can improve the track calculation and track forecast precision of the Mars detector when flying around the Mars, and can calculate the natural fall life of the Mars surrounding detector.

The technical scheme of the invention is as follows:

a method for calculating atmospheric resistance of a Mars probe comprises the following steps:

step one, calculating a resistance coefficient C of the atmosphere of the mars_D；

Step two, acquiring a Mars atmospheric density rho through a Mars climate database MCD _ V5.3;

step three, calculating the speed v of the satellite detector relative to the atmosphere of the mars_rel；

Step four, calculating the windward area A of the satellite detector;

and step five, calculating the atmospheric resistance f borne by the satellite detector.

In the above method for calculating the atmospheric resistance of the Mars probe, in the first step, the resistance coefficient C of the Mars atmosphere_DThe calculation method comprises the following steps:

in the formula, T_siThe temperature of each surface of the detector;

T_ais the temperature of the atmosphere;

β_ithe included angle between the movement direction of the atmosphere and each surface of the detector is obtained by a satellite detector attitude monitoring system;

μ_iis the ratio of the average mass of the incident gas molecules to the mass of the molecules on the scattering surface of the satellite detector.

In the above method for calculating atmospheric resistance of a mars probe, in the second step, the mars climate database MCD _ V5.3 is a meteorological domain database obtained from numerical simulation of a mars atmospheric circulation model, and verification is completed using observation data; the Mars climate database MCD _ V5.3 provides temperature, pressure, wind field and atmospheric density within the range of 0-260 kilometers, and three scenes of calmness, medium and activity are set according to the degree of solar activity.

In the above method for calculating atmospheric resistance of the mars probe, in the second step, a specific method for obtaining the mars atmospheric density ρ through the mars climate database MCD _ V5.3 is as follows:

calling a subprogram call _ MCD of a mars climate database MCD _ V5.3, inputting parameters of a preset ordinate type zkey, a preset mars ground point ordinate xz, a preset mars ground point longitude xlon, a preset mars ground point latitude xlat, a preset data resolution hireskey, a preset epoch representation mode datakey, a preset epoch time xdate, a mars local time locame, a database file storage path dset and a preset mars dust storm and solar EUV radiation scene scena, and outputting a result, namely the mars atmospheric density rho.

In the above method for calculating the atmospheric resistance of the Mars probe, in the third step, the velocity v of the satellite probe relative to the Mars atmosphere_relThe calculation method comprises the following steps:

s31, establishing a mars fixed connection coordinate system oxyz; wherein, the origin o is the centroid of the Mars; selecting a Mars flat equatorial plane as a first reference plane; the x axis points to the focal point of the initial meridian and the first reference plane; the z-axis points to the Mars rotation axis; the y-axis is determined by the right hand rule.

S32, establishing a Martian celestial coordinate system o1x1y1z 1; the Mars celestial coordinate system translates the Earth celestial coordinate system to Mars, and the origin o1 is the centroid of the Mars; the second reference plane is the equator of the earth epoch; the x1 axis points in the direction of epoch peaceful spring minute point; the z-axis points to the earth rotation axis; the y-axis is determined by the right hand rule.

S33, calculating a unit rotation matrix R of each axis from the Mars fixed connection coordinate system oxyz to the Mars celestial coordinate system o1x1y1z1_i(α)＝[R_x(α)、R_y(α)、R_z(α)](ii) a Wherein, the rotation angles from the x axis to the x1 axis, the rotation angle from the y axis to the y1 axis and the rotation angle from the z axis to the z1 axis are all set to be alpha.

S34, calculating a coordinate transformation matrix RT2C from a Mars fixed connection coordinate system oxyz to a Mars celestial coordinate system o1x1y1z1 at the time t.

S35, calculating Mars atmospheric velocity omega under Mars celestial coordinate system_inPosition vector r of satellite detector_inVelocity vector v of satellite probe_in(ii) a Calculating the velocity v of the satellite detector relative to the Martian atmosphere_rel。

In the method for calculating the atmospheric resistance of the Mars probe, in the step S33, the unit rotation matrix R_iThe calculation method of (alpha) is as follows:

in the above method for calculating the atmospheric resistance of the mars probe, in S34, the coordinate transformation matrix RT2C is calculated by:

wherein, N is pointing parameter, and N is 3.37919183 degrees;

j is pointing parameter, J is 24.67682669 °;

nutating the Mars;

i is the inclination angle of the Mars orbit;

phi is a spark self-rotation angle;

X_pand Y_pThe polar motion of the spark rotation shaft.

In the method for calculating the atmospheric resistance of the mars probe, in the step S35, the star atmospheric velocity Ω_inThe calculation method comprises the following steps:

position vector r of satellite detector under Mars celestial coordinate system_inObtaining the measurement;

velocity vector v of satellite detector under Martian celestial coordinate system_inObtaining the measurement;

velocity v of satellite detector relative to Martian atmosphere_relThe calculation method comprises the following steps:

in the above method for calculating the atmospheric resistance of the mars probe, in the fourth step, the method for calculating the windward area a of the satellite probe includes:

in the formula, A_sThe area of the satellite detector body facing the wind is obtained by measuring in the ground;

A_PNthe windward area of the sailboard;

A_Pthe total area of the sailboard;

and N is a sailboard normal vector and is obtained according to the position measurement of the sun and the detector.

In the above method for calculating the atmospheric resistance of the mars probe, in the fifth step, the method for calculating the atmospheric resistance f suffered by the satellite probe includes:

compared with the prior art, the invention has the beneficial effects that:

(1) the method for calculating the atmospheric resistance of the Mars probe innovatively provided by the invention is suitable for Mars detection plans, and under the premise that the time for the probe to fly around the Mars in a short distance (below 500km height) is short, the influence of the Mars atmospheric resistance is considered in orbit calculation and prediction, so that the accuracy of orbit calculation and prediction of the Mars probe is effectively improved;

(2) the invention calculates the resistance coefficient C of the atmosphere of the Mars_DAnd acquiring Mars atmospheric density rho through a Mars climate database MCD _ V5.3, and sequentially calculating the speed V of the satellite detector relative to the Mars atmosphere_relAnd the windward area A of the satellite detector is finally calculated to obtain the atmospheric resistance f borne by the satellite detector, all relevant parameters are taken into consideration, the calculation is accurate, and the problem of service life prediction of the Mars surrounding detector can be solved.

Drawings

FIG. 1 is a flow chart of calculation of atmospheric resistance of the Mars probe according to the present invention.

Detailed Description

The invention is further illustrated by the following examples.

The resistance generated by the atmosphere above the Mars influences the Mars detector orbit, so that the semi-major axis of the detector orbit flying around the Mars is reduced, and the service life of the satellite is influenced. Meanwhile, the atmospheric resistance is an important perturbation force in the track calculation process, and the quantitative description of the atmospheric resistance borne by the detector is beneficial to improving the precision of track calculation and track forecast of the Mars detector. In the current Mars detection plan of China, because the time for the detector to fly around the Mars in a short distance (below 500km height) is short, the influence of Mars atmospheric resistance is not considered in orbit calculation and forecast. With the subsequent deep detection of the mars, a close-range and long-time mars-surrounding flight detection task must be carried out, and at the moment, the mars atmospheric resistance becomes a non-negligible influence factor.

The invention provides a method for calculating atmospheric resistance of a Mars detector, which can effectively improve the precision of calculation and prediction of a Mars detector orbit and solve the problem of service life prediction of a Mars surrounding detector. The method is convenient to operate, high in accuracy and capable of being used for real-time and quasi-real-time track calculation.

The calculation flow of the atmospheric resistance of the Mars detector is shown in figure 1, and specifically comprises the following steps:

step one, calculating a resistance coefficient C of the atmosphere of the mars_D(ii) a The atmospheric drag coefficient CD is a parameter that characterizes the momentum exchange between the satellite surface and the impinging particles and is determined based on two assumptions, the atmospheric free molecular flow assumption. The Mars atmosphere is thin, and for a detector with the characteristic length within 10 meters, an area above 100km can be regarded as free molecular flow; the second is the scattering assumption for atmospheric particles. Experiments have shown that the particle reflection properties are related to the temperature of the surface of the object, which is scattering if the temperature of the surface of the object is close to room temperature, and almost specular if the temperature reaches a high temperature of 1600K. The Mars atmospheric temperature is in the range of 120-220K, so the scattering assumption of the atmospheric particles is true. Therefore the coefficient of resistance C of the Mars atmosphere_DThe calculation method comprises the following steps:

in the formula, T_siThe temperature of each surface of the detector;

T_ais the temperature of the atmosphere;

β_ithe angle between the direction of movement of the atmosphere and the surfaces of the detectorThe attitude of the satellite detector is obtained by a satellite detector attitude monitoring system;

μ_iis the ratio of the average mass of the incident gas molecules to the mass of the molecules on the scattering surface of the satellite detector.

Step two, comprehensively considering the solar activity, the Mars season, the Mars local time and the Mars dust storm conditions according to the position of the detector, and obtaining the Mars atmospheric density rho through a Mars climate database MCD _ V5.3; the Mars climate database MCD _ V5.3 is a meteorological domain database obtained from numerical simulation of a Mars atmospheric circulation model, and verification is completed by using observation data; the Mars climate database MCD _ V5.3 provides temperature, pressure, wind field and atmospheric density within the range of 0-260 kilometers, and three scenes of calmness, medium and activity are set according to the degree of solar activity.

The specific method for obtaining the Mars atmospheric density rho through the Mars climate database MCD _ V5.3 comprises the following steps:

calling a subprogram call _ MCD of a mars climate database MCD _ V5.3, inputting parameters of a preset ordinate type zkey, a preset mars ground point ordinate xz, a preset mars ground point longitude xlon, a preset mars ground point latitude xlat, a preset data resolution hireskey, a preset epoch representation mode datakey, a preset epoch time xdate, a mars local time locame, a database file storage path dset and a preset mars dust storm and solar EUV radiation scene scena, and outputting a result, namely the mars atmospheric density rho.

Step three, calculating the speed v of the satellite detector relative to the atmosphere of the mars_rel(ii) a The method specifically comprises the following steps:

s31, establishing a mars fixed connection coordinate system oxyz; wherein, the origin o is the centroid of the Mars; selecting a Mars flat equatorial plane as a first reference plane; the x axis points to the focal point of the initial meridian and the first reference plane; the z-axis points to the Mars rotation axis; the y-axis is determined by the right hand rule.

S32, establishing a Martian celestial coordinate system o1x1y1z 1; the Mars celestial coordinate system translates the Earth celestial coordinate system to Mars, and the origin o1 is the centroid of the Mars; the second reference plane is the equator of the earth epoch; the x1 axis points in the direction of epoch peaceful spring minute point; the z-axis points to the earth rotation axis; the y-axis is determined by the right hand rule.

S33, calculating a unit rotation matrix R of each axis from the Mars fixed connection coordinate system oxyz to the Mars celestial coordinate system o1x1y1z1_i(α)＝[R_x(α)、R_y(α)、R_z(α)](ii) a Setting the rotation angles from the x axis to the x1 axis, the y axis to the y1 axis and the z axis to the z1 axis as alpha; rotation matrix R_iThe calculation method of (alpha) is as follows:

s34, when the Mars rotation period is T, 24 hours, 37 minutes and 22.6 seconds, the rotation angular speed of the Mars atmosphere under the Mars fixed connection coordinate system can be calculatedBecause the speed of the detector is generally described in a mars celestial sphere system, omega is converted into the celestial sphere system, and a coordinate conversion matrix RT2C from a mars fixed connection coordinate system oxyz to a mars celestial sphere coordinate system o1x1y1z1 at the moment t is calculated; the calculation method of the coordinate transformation matrix RT2C comprises the following steps:

wherein, N is pointing parameter, and N is 3.37919183 degrees;

j is pointing parameter, J is 24.67682669 °;

nutating the Mars; is calculated by the formula

I is the inclination angle of the Mars orbit;

ψ₀and I₀A constant at time of the J2000.0 epoch,in order to provide a change in the rate of Mars nutation,the long term rate of change of the Mars orbit inclination is given in Table 1; psi_nutAnd I_nutNutation corrections for longitude and inclination, respectively, are calculated by:

in the formula, alpha_mAnd theta_mThe calculation method comprises the following steps:

wherein n 'represents the average revolution angular velocity of Mars, l'₀The value of the approximate point angle of the Mars is 19.3871 degrees for J2000.0 Mars, l' is the approximate point angle of the Mars, q is 2 omega, omega is the amplitude angle of the approximate point, q can also be expressed as q is 142 degrees, 0+1 degrees, 3t, t is the number of Julian century counted from J2000.0, and the correlation coefficients are given in tables 1-2.

TABLE 1

TABLE 2

m	Im0	ψm0
			0	–1.4	0
1	–0.4	–632.6
			2	0	–44.2
3	0	–4.0
			4	–49.1	–104.5
5	515.7	1 097.0
			6	112.8	240.1
7	19.2	60.9
			8	3.0	6.5
9	0.4	1.0

Phi is a spark self-rotation angle;

X_pand Y_pThe polar motion of the spark rotating shaft;

s35, calculating Mars atmospheric velocity omega under Mars celestial coordinate system_inPosition vector r of satellite detector_inVelocity vector v of satellite probe_in(ii) a Calculating the velocity v of the satellite detector relative to the Martian atmosphere_rel. Star atmospheric velocity omega_inThe calculation method comprises the following steps:

position vector r of satellite detector under Mars celestial coordinate system_inObtaining the measurement;

velocity vector v of satellite detector under Martian celestial coordinate system_inObtaining the measurement;

velocity v of satellite detector relative to Martian atmosphere_relThe calculation method comprises the following steps:

step four, calculating the windward area A of the satellite detector; the method for calculating the windward area A of the satellite detector comprises the following steps:

in the formula, A_sThe area of the satellite detector body facing the wind is obtained by measuring in the ground;

A_PNthe windward area of the sailboard;

A_Pthe total area of the sailboard;

and N is a sailboard normal vector and is obtained according to the position measurement of the sun and the detector.

Step five, calculating the atmospheric resistance f borne by the satellite detector:

the method for measuring the atmospheric resistance of the Mars probe can effectively improve the accuracy of calculation and prediction of the Mars probe orbit and solve the problem of prediction of the Mars surrounding probe service life. The method is convenient to operate, high in accuracy and capable of being used for real-time and quasi-real-time track calculation.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.