CN103364836A - Drop point prediction method of lunar probe - Google Patents

Abstract

The invention discloses a drop point prediction method of a lunar probe, and belongs to the field of spaceflight measurement and control. According to the invention, the method comprises the following steps of: processing united S band tracking data and very long baseline intervention measurement data through a multi-star parallel high-precision orbit computing system, performing precision orbit determination on the lunar probe, performing interpolation on the lunar surface terrain height, establishing a lunar terrain model, computing the lunar surface height of the lunar probe through the position vector of a moon-fixed coordinate system, and directly predicating the ephemeris and the lunar surface height of the lunar probe. Verification result shows that the method is high in position precision in the lunar probe drop point prediction and accurate in drop point time prediction. The method solves the problems of computing the time and position when Chang'e 1 impacts the moon, and does technical preparation for the Chang'e Phase III probe soft lunar landing. The method is effectively verified in the Chang'e 1 (CE-1) hard landing moon impact test.

Description

Lunar orbiter impact prediction method

Technical field

Patent of the present invention belongs to aerospace measurement and control field, relates to the lunar orbiter impact prediction.

Background technology

Goddess in the moon's moon exploration project is important engineering duty in China's aerospace industry development, and the target of wherein lunar exploration the third stage of the project is that the detector soft landing moon is finished the detection test task.Consider observing and controlling condition and detector, lunar rover at moonscape stable landing and the smooth needs that launch, engineering has been selected the expected point of impact position and has been proposed corresponding drop point accuracy requirement according to menology physical features, the gradient, soil property, surperficial stone quantity etc.In order to guarantee that detector can drop to expected point of impact smoothly, must carry out the development test work of detector impact prediction and calculating.

Summary of the invention

The objective of the invention is: a kind of general lunar orbiter impact prediction method is provided.

Technical scheme of the present invention is: a kind of lunar orbiter impact prediction method comprises the steps:

Step 1, utilize the parallel high-precision orbital computing system of many stars to process Unified S Band tracking data and VLBI data, lunar orbiter is carried out Precise Orbit to be determined, obtain the position (X of detector in moon heart celestial coordinate system, Y, Z), utilize coordinate conversion further to obtain the position (x that the detector moon is admittedly, y, z);

Step 2 is carried out interpolation to the topography of lunar surface height, sets up the lunar topography model, utilizes month position vector of solid system to calculate lunar orbiter lunar surface height;

Step 3, determine on the basis at the detector track, directly forecast detector ephemeris and lunar surface height, set to judge the bump condition, when detector lunar surface height during less than preset value, think that detector has clashed into the moon, the calculating detector drop point, be the longitude of detector drop point, latitude and elevation, and fall a month moment.

The present invention shows by the result, and this method positional precision in the lunar orbiter impact prediction is higher, and drop point forecasts accurately constantly.The method has solved the moment of the Chang'e I bump moon and the computational problem of position, and does technology for the goddess in the moon's three phases detector soft lunar landing and prepare.

Embodiment

Lunar orbiter impact prediction method in the present embodiment is for the impact prediction that carries out Chang'e I.This forecasting procedure comprises the steps:

Step 1: detector is carried out Precise Orbit determine, the position (x, y, z) that obtains the detector moon and admittedly be.Track determines to hit month prerequisite of some forecast, track determines to be exactly to utilize observation data to estimate actual motion parameter and the precision thereof of satellite, the present embodiment has adopted the parallel high-precision orbital computing system (PASAX) of many stars of independent research, utilize Unified S Band tracking data very short after the detector braking and VLBI data to carry out the short arc track definite, wherein PASAX short arc track is determined, about 14 minute datas after the control of employing Chang'e I rail, adopt the parallel high-precision orbital computing system (PASAX) of many stars of aerospace dynamics National Key Laboratory independent research, carrying out the detector track calculates, utilize observation data to estimate actual motion parameter and the precision thereof of satellite, it comprises orbit integration, following several substeps such as theoretical measurement calculating and least-squares parameter statistics:

Substep 1: set up rational kinetic model, carry out orbit integration.Be that basic frame of reference is set up equation of satellite motion with moon heart J2000 coordinate, the main perturbation power of considering comprises the non-spherical gravitational field of the moon, the sun and earth grade in an imperial examination trisome gravitation, moon solid tide, direct solar radiation pressure and general relativity model, and orbit integration adopts 8 rank Gauss-Jackson-Merson multistep processes Numerical integrators.

Substep 2: set up observation model, theory of computation observed quantity.Except traditional Unified S Band carrier wave (USB) bidirectional ranging with testing the speed, Chang'e I has added high precision angle-measuring observation, i.e. very long baseline interferometry(VLBI (VLBI) data.PASAX software has added the VLBI observation model specially for this reason.

Substep 3: the detector track resolves.Optimal estimation of parameters adopts Bayes (Bayes) weighted least-squares method of estimation, and solve for parameter is that satellite initial position, speed and part kinetic parameters and measuring system are poor.

The present embodiment has selected dynamics of orbits model and the track optimized to determine strategy.Wherein

The main perturbation power that the dynamics of orbits model is considered comprises the non-spherical gravitational field of the moon, the sun and earth grade in an imperial examination trisome gravitation, moon solid tide, direct solar radiation pressure and general relativity model, and orbit integration adopts 8 rank Gauss-Jackson-Merson multistep processes Numerical integrators.Optimal estimation of parameters adopts Bayes (Bayes) weighted least-squares method of estimation, and solve for parameter is that satellite initial position, speed and part kinetic parameters and measuring system are poor.

It is tactful in table 1 that the present embodiment selects track to determine:

Table 1 orbit determination strategy

Step 2: utilize the lunar topography model, the topography of lunar surface height is carried out interpolation, calculating detector lunar surface height comprises following substep:

Substep 1: choose suitable lunar topography model.The lunar topography model that the present embodiment uses is ULCN2005 raster data product, and the plane precision of this relief block (1 σ) is about 0.9 pixel, and vertical accuracy is about 102m, and is higher at the lunar maria pixel accuracy of near side of the moon, satisfies testing requirements.

Substep 2; Parameter in the preference pattern.Getting moon reference ellipsoid radius is 1737.4km, according to latitude from-90 to 90 degree, and precision from-180 to 180 degree, 16 grids of every degree, the size of each grid is 0.0625X0.0625 degree (corresponding 1.8km).

Substep 3: the height value that provides interpolation.Under the condition of known moonscape longitude and latitude, calculate the height value of this point, the raster data interpolation that uses a model goes out the information at impact point place.The method that the present embodiment is chosen is the bilinear interpolation algorithm, can interpolation go out the height that the arbitrfary point is located in the model scope.Known 4 points

With

Find the solution

Corresponding h.Wherein,

λ≤λ ₁,λ≤λ ₂,λ≥λ ₃,λ≥λ ₄,λ ₁≤λ ₂,λ ₃≤λ ₄

Then have Solving equations obtains coefficient a, b, and c, thus d has

Substep 4: calculating detector at moon reason longitude and latitude and elevation is

h=r-am

$\mathrm{\λ}=\mathrm{arctg}\left(\frac{y}{x}\right)$

Wherein: x, y, z are the position that the detector moon admittedly is, r=(x ²+ y ²+ z ²) 1/2, am is moon reference ellipsoid radius.

Step 3: carry out the detector drop point and calculate, comprise following substep:

Substep 1: utilize outer survey data and KINETIC METHOD to growing month moment of point.Utilize measured data to provide the position of detector in the moon is admittedly, the latitude that obtains as CE-1 in conjunction with the lunar surface terrain data is 52.269 °, and longitude is-1.597 °, elevation is-and 2871.0m (with respect to 1738km with reference to the moon radius of a ball).Utilize height that lunar surface relief block ULCN2005 obtains this point to be-2869.9m, both differ 1.1m, and thinking falls month occurs in this moment, and its value is 16: 13: 12.1,

Substep 2: estimate above-mentioned impact prediction precision constantly.Hit in moon process at Chang'e I, USB surveys outward, VIBI follows the tracks of and remote measurement is normal.The last frame telemetry was received in 16: 13: 13 in the station, Qingdao, deducted a moon earth signal propagation delay time, and this shows that detector may be in the 13 minutes 11.7 seconds bump moon, and signal thoroughly disappears, and might as well be referred to as hitting a month moment of " remote measurement observation ".This moment is constantly very approaching with hitting month of forecast, has verified validity and the precision of impact prediction method.

The present embodiment has adopted the parallel high-precision orbital computing system (PASAX) of many stars of independent research very short measurement data after the detector braking to carry out the short arc track to determine, utilize satellite dynamics theoretical on the basis that track is determined, obtain the prediction orbit of detector, adopt the ULCN2005 raster data to carry out planetary surface Terrain Elevation interpolation, judge the bump condition in conjunction with the lunar surface terrain data, forecast is hit month point constantly and the position.Method and technology among the present invention " Chang'e I " (CE-1) " hard landing formula " hit month in the test and obtained effective checking.

The present embodiment is according to the position of detector in the moon is admittedly, in conjunction with the lunar surface terrain data, draw at 16: 13: 12.1, the moon latitude of Chang'e I is 52.269 °, longitude is-1.597 °, elevation is-and 2871.0m (with respect to 1738km with reference to the moon radius of a ball).Lunar surface relief block ULCN2005 is-2869.9m that both differ 1.1m, reach the bump decision condition at the height of this point.The moon that hits of forecast is 16: 13: 12.1 constantly, and the moon that hits that telemetry provides is 16: 13: 11.7 constantly, error 0.4 second, and both satisfy error requirements at degree of closeness, have verified validity of the present invention.

Claims (1)

1. lunar orbiter impact prediction method comprises the steps:

Step 1, utilize the parallel high-precision orbital computing system of many stars to process Unified S Band tracking data and VLBI data, lunar orbiter is carried out Precise Orbit to be determined, obtain the position (X of detector in moon heart celestial coordinate system, Y, Z), utilize coordinate conversion further to obtain the position (x that the detector moon is admittedly, y, z);

Step 2 is carried out interpolation to the topography of lunar surface height, sets up the lunar topography model, utilizes month position vector of solid system to calculate lunar orbiter lunar surface height;

Step 3, determine on the basis at the detector track, directly forecast detector ephemeris and lunar surface height, set to judge the bump condition, when detector lunar surface height during less than preset value, think that detector has clashed into the moon, the calculating detector drop point, be the longitude of detector drop point, latitude and elevation, and fall a month moment.