Patent Document ID: 9599744
Application ID: 15025560
Patent Flag: 1

Claim One:
1. A method for parsing and calculating performance of satellite gravity field measurement by low-to-low satellite-to-satellite tracking, comprising steps of: step (1): acquiring at least one parameter of a gravity satellite system by low-to-low satellite-to-satellite tracking by the gravity satellite system; step (2): according to the parameter of the gravity satellite system by low-to-low satellite-to-satellite tracking, calculating an effect of a measuring error of a gravity satellite load on a power spectrum of a nonspherical perturbation potential of earth gravity, so as to obtain an degree error variance of a potential coefficient in a gravity field recovery model; step (3): comparing the degree error variance of the potential coefficient in the gravity field recovery model with an degree variance of a potential coefficient given by Kaula Rule, wherein with an increase of an order of the gravity field recovery model, the degree error variance gradually increases and the degree variance gradually decreases; when the degree error variance is equal to the degree variance, considering that a maximum valid order of the gravity field measurement is obtained, wherein the degree error variance, the degree variance and the maximum valid order are obtained by the gravity field model; step (4): according to the degree error variance of the gravity field recovery model, calculating a geoid-order error, an accumulative error, an gravity-anomaly order error and an accumulative error of the gravity field recovery model, wherein the geoid-order error, the accumulative error, the gravity-anomaly order error and the accumulative error are obtained by the gravity field model; and step (5): summarizing the valid degree of the gravity field measurement, the geoid-order error, the accumulative error, the gravity-anomaly order error and the accumulative error, so as to obtain the performance of satellite gravity field measurement by low-to-low satellite-to-satellite tracking, wherein the valid degree of the gravity field measurement, the geoid-order error, the accumulative error, the gravity-anomaly order error and the accumulative error are obtained by the gravity field model; wherein the parameter of the gravity satellite system by low-to-low satellite-to-satellite tracking comprises but not limited to at least one orbit parameter of the gravity satellite system and at least one load indicator of the gravity satellite system; wherein the orbit parameter of the gravity satellite system comprises at least one member of: a maximum valid order of the gravity field recovery N max , a gravity-anomaly order error Δ n of an nth order, a geoid-order accumulative error Δ of the nth order, a gravity-anomaly order error Δg n of the nth order and a gravity-anomaly accumulative error Δg of the nth order, wherein N max , Δ n , Δ, Δg n and Δg are obtained by the gravity field model; the parameter of the gravity satellite system comprises: a gravity satellite orbit height h and an included angle θ 0 of satellite-to-satellite geocentric vectors, wherein h and θ 0 are obtained by the gravity satellite system, the load indicator of the gravity satellite system comprises: an inter-satellite range change rate measurement error (Δ{dot over (ρ)}) m , a satellite orbit determining position error (Δr) m , a non-gravitational interference ΔF, an inter-satellite range rate data sampling interval (Δt) Δ{dot over (ρ)} , a non-gravitational interference data interval (Δt) ΔF , satellite orbit position data sampling interval (Δt) Δr and a gravity field measurement service life T, wherein (Δ{dot over (ρ)}) m is obtained by an inter-satellite range measurement device, (Δr) m is obtained by a spaceborne GPS system, and the ΔF is obtained by an accelerometer, wherein the inter-satellite range measurement device, the spaceborne GPS system and the accelerometer are conventional and all provided on the gravity satellite system; wherein the step (2) specifically comprises steps of: establishing an analytic formula of a low-to-low satellite-to-satellite tracking gravity field measurement degree error variance δσ n 2 of a potential coefficient: δ ⁢ ⁢ σ n 2 = 1 2 ⁢ n + 1 ⁢ ∑ k = 0 n ⁢ [ ( δ ⁢ ⁢ C _ nk ) 2 + ( δ ⁢ ⁢ S _ nk ) 2 ] = 1 ∑ k = 0 n ⁢ [ B 1 ⁡ ( r 0 , n , k , θ 0 ) + B 2 ⁡ ( r 0 , n , k , θ 0 ) + B 3 ⁡ ( r 0 , n , k , θ 0 ) ] × 1 2 ⁢ n + 1 ⁢ 2 ⁢ ( n + 1 ) ⁢ r 0 2 ⁢ n π ⁢ ⁢ μ 2 ⁢ Ta e 2 ⁢ n - 2 ⁡ [ - D ⁢ ( ( Δ ⁢ ⁢ F ) 2 ⁢ T ar ⁢ ⁢ c 4 36 ⁢ ( Δ ⁢ ⁢ t ) Δ ⁢ ⁢ F + ( Δ ⁢ ⁢ r ) m 2 ⁢ ( Δ ⁢ ⁢ t ) Δ ⁢ ⁢ r ) ⁢ f δ ⁢ ⁢ r ⁡ ( n ) + μ r 0 ⁢ ( ( Δ ⁢ ⁢ F ) 2 ⁢ T ar ⁢ ⁢ c ⁢ 2 4 ⁢ ( Δ ⁢ ⁢ t ) Δ ⁢ ⁢ F + ( Δ ⁢ ⁢ ρ. ) m 2 ⁢ ( Δ ⁢ ⁢ t ) Δ ⁢ ⁢ ρ. ) ⁢ f δ ⁢ ⁢ ρ. ⁡ ( n ) ] 2 wherein: { B 1 ⁡ ( r 0 , n , k , θ 0 ) = A n 2 ⁡ ( n - 1 , k , θ 0 ) + ( a e r 0 ) ⁢  A n ⁡ ( n - 1 , k , θ 0 ) ⁢ A n ⁢ ( n , k , θ 0 )  + ( a e r 0 ) 2 ⁢  A n ⁡ ( n - 1 , k , θ 0 ) ⁢ A n ⁡ ( n + 1 , k , θ 0 )  B 2 ⁡ ( r 0 , n , k , θ 0 ) = ( a e r 0 ) 2 ⁢ A n 2 ⁡ ( n , k , θ 0 ) + ( a e r 0 ) ⁢  A n ⁡ ( n - 1 , k , θ 0 ) ⁢ A n ⁡ ( n , k , θ 0 )  + ( a e r 0 ) 3 ⁢  A n ⁡ ( n , k , θ 0 ) ⁢ A n ⁡ ( n + 1 , k , θ 0 )  B 3 ⁡ ( r 0 , n , k , θ 0 ) = ( a e r 0 ) 4 ⁢ A n 2 ⁡ ( n + 1 , k , θ 0 ) + ( a e r 0 ) 2 ⁢  A n ⁡ ( n - 1 , k , θ 0 ) ⁢ A n ⁡ ( n + 1 , k , θ 0 )  + ( a e r 0 ) 3 ⁢  A n ⁡ ( n , k , θ 0 ) ⁢ A n ⁡ ( n + 1 , k , θ 0 )  A n ⁡ ( l , k , θ 0 ) = δ k ⁢ ∫ 0 π ⁢ [ P _ lk ⁡ ( cos ⁡ ( θ + θ 0 ) ) - P _ lk ⁡ ( cos ⁢ ⁢ θ ) ] ⁢ P _ nk ⁡ ( cos ⁢ ⁢ θ ) ⁢ sin ⁢ ⁢ θ ⁢ ⅆ θ ⁢ ⁢ ⁢ δ k = { 2 , k = 0 1 , k ≠ 0 ⁢ ⁢ ⁢ D = K ( cos ⁢ ⁢ θ 0 2 2 - 4 3 ) ⁢ μ ⁢ ⁢ sin ⁢ ⁢ θ 0 r 0 4 ⁢ ⁢ f δ ⁢ ⁢ r ⁡ ( n ) = ∑ k = 0 n ⁢ ∫ 0 π ⁢ [ P _ nk ⁡ ( cos ⁢ ⁢ θ ) ] 2 ⁢ cos 2 ⁡ ( θ + ξ ) ⁢ sin 2 ⁢ θ ⁢ ⅆ θ = 3 8 ⁢ ( 2 ⁢ n + 1 ) ⁢ π ⁢ ⁢ ⁢ f δ ⁢ ⁢ ρ. ⁡ ( n ) = ( n + 1 2 ) ⁢ π ⁢ ⁢ ⁢ r 0 = a e + h wherein δσ n 2 is an degree error variance of a geopotential coefficient of the gravity field recovery model, r 0 is a geocentric range of a satellite, θ 0 is a geocentric vector included angle, a e is an earth average radius, μ is a product of a gravitation constant and an earth mass, h is the gravity satellite orbit height, T arc is an integral arc length, ΔF is non-gravitational interference, (Δt) ΔF is non-gravitational interference data interval, (Δr) m is a satellite orbit determination position error, (Δt) Δr is a satellite orbit data sampling interval, (Δ{dot over (ρ)}) m is an inter-satellite range change rate measurement error, (Δt) Δ{dot over (ρ)} is an inter-satellite range change rate sampling interval, T is the gravity field measurement service life, wherein (Δ{dot over (ρ)}) m and (Δt) Δ{dot over (ρ)} are obtained by the inter-satellite range measurement device, (Δr) m and (Δt) Δr are obtained by the spaceborne GPS system, ΔF and (Δt) ΔF are obtained by the accelerometer; P nm (x) is the fully normalized associated Legendre polynomial, where n is the degree, m is the order, and x is a specific input P _ nm ⁡ ( x ) = ( 2 ⁢ n + 1 ) ⁢ k ⁢ ( n - m ) ! ( n + m ) ! ⁢ P nm ⁡ ( x ) , k = { 1 , m = 0 2 , m ≠ 0 P nm (x) is the associated Legendre polynomial, where n is the degree, m is the order, and x is a specific input; P nm ⁡ ( x ) = ( - 1 ) m 2 n ⁢ n ! ⁢ ( 1 - x 2 ) m / 2 ⁢ ⅆ n + m ⅆ x n + m ⁢ ( x 2 - 1 ) n C nm and S nm are cosine and sine terms of normalized gravitational coefficients in a gravity field model, respectively, δ C nm or δ S nm is a measure of difference between the observed value of gravitational coefficient and the theoretical value, n is the degree, and m is the order.