# lamberthub

A collection of Lambert’s problem solvers

## Package Contents

### Functions

 avanzini2008(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False) Solves Lambert problem using Gooding's devised algorithm. battin1984(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False) Battin's elegant algortihm for solving the Lambert's problem. This algorithm gauss1809(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=250, atol=1e-05, rtol=1e-07, full_output=False) Lambert's problem solver devised by Carl Friedrich Gauss in 1809. The method arora2013(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False) Solves Lambert problem using Arora's devised algorithm gooding1990(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False) Lambert's problem solver using the method proposed by R. H. Gooding in 1990. izzo2015(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False) Solves Lambert problem using Izzo's devised algorithm. vallado2013(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=100, atol=1e-05, rtol=1e-07, full_output=False) Vallado's algorithm makes use of the universal formulation to solve for the
lamberthub.avanzini2008(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False)

Solves Lambert problem using Gooding’s devised algorithm.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

The following routine might be simplified making use of private functions. However, we decided to expose all the auxiliary routines to properly reproduce original report figures.

lamberthub.battin1984(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False)

Battin’s elegant algortihm for solving the Lambert’s problem. This algorithm is known to improve Gauss original one by removing the singularity for 180 transfer angles and increasing its performance.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

The algorithm originally devised by Gauss exploits the so-called ratio of sector to triangle area, which is a numerical value related with the orbital parameter. This Algorithm was used to the discovery of the orbit of Ceres by the genius and adopted by many other authors of his time due to its simplicity. However, the Algorithm is found to be singular for transfer angles of 180 degrees and shows a low performance for really small angles.

References

[1] Battin, R. H., & Vaughan, R. M. (1984). An elegant Lambert algorithm. Journal of Guidance, Control, and Dynamics, 7(6), 662-670.

[2] Battin, R. H. (1999). An introduction to the mathematics and methods of astrodynamics. Aiaa.

[3] Vaughan, R. M. (1983). An improvement of Gauss’ method for solving Lambert’s problem (Doctoral dissertation, Massachusetts Institute of Technology).

lamberthub.gauss1809(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=250, atol=1e-05, rtol=1e-07, full_output=False)

Lambert’s problem solver devised by Carl Friedrich Gauss in 1809. The method has been implemented according to Bate’s book (see [2]) and extended to the hyperbolic case. This method shows poor accuracy, being only suitable for low transfer angles.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

The algorithm originally devised by Gauss exploits the so-called ratio of sector to triangle area, which is a numerical value related with the orbital parameter. This Algorithm was used to the discovery of the orbit of Ceres by the genius and adopted by many other authors of his time due to its simplicity. However, the Algorithm is found to be singular for transfer angles of 180 degrees and shows a low performance for really small angles.

References

[1] Gauss, C. F. (1809). Theoria motus corporum coelestium in sectionibus conicis solem ambientium auctore Carolo Friderico Gauss. sumtibus Frid. Perthes et IH Besser.

[2] Bate, R. R., Mueller, D. D., White, J. E., & Saylor, W. W. (2020). Fundamentals of astrodynamics. Courier Dover Publications.

lamberthub.arora2013(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False)

Solves Lambert problem using Arora’s devised algorithm

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance $$abs(x_{i+1} - x_{i})$$

• rtol (float) – Relative tolerance $$abs(\frac{x_{i+1}}{x_{i}} - 1)$$

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector

• v2 (numpy.array) – Final velocity vector

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

Lambert’s problem solver using the method proposed by Nitin Arora and Ryan P. Rusell in 2013, see [1]. This algorithm exploits the universal formulae by defining a new cosine-based transformation and developing a robust initial guess. Although based on arbitrary conditions, the algorithm shows a high performance.

References

[1] Arora, N., & Russell, R. P. (2013). A fast and robust multiple revolution Lambert algorithm using a cosine transformation. Paper AAS, 13, 728.

lamberthub.gooding1990(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False)

Lambert’s problem solver using the method proposed by R. H. Gooding in 1990.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

This module holds the Lambert’s problem solver devised by R. H. Gooding in his technical report 1 originally published in 1988. However, the implementation corresponds to the one proposed by the author a couple of years later in his article 2 from 1990. Some improvements to the originally algorithm were also made by Klumpp in his performance comparison 3 between Lamberts problem solvers. Those have been added to this code to prevent failures for particular inputs. The result is a fully working algorithm for both single and multi-revolution orbits.

The code has been kept as close as possible to the original FORTRAN-77 one. However, some statements (like “goto line” ones) have been deprecated as they introduce “spaghetti code”. Since the original implementation imposed a relative tolerance together with the number of iterations, these parameters have been modified so the user can freely choose their values.

References

1

Gooding, R. H. (1988). On the solution of Lambert’s orbital boundary-value problem. ROYAL AEROSPACE ESTABLISHMENT FARNBOROUGH (UNITED KINGDOM).

2

Gooding, R. H. (1990). A procedure for the solution of Lambert’s orbital boundary-value problem. Celestial Mechanics and Dynamical Astronomy, 48(2), 145-165.

3

Klumpp, A. (1999). Performance Comparison of Lambert and Kepler Algorithms, Interoffice Memorandum, JPL.

lamberthub.izzo2015(mu, r1, r2, tof, M=0, prograde=True, low_path=True, maxiter=35, atol=1e-05, rtol=1e-07, full_output=False)

Solves Lambert problem using Izzo’s devised algorithm.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations is also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (list) – Number of iterations.

Notes

This is the algorithm devised by Dario Izzo[1] in 2015. It inherits from the one developed by Lancaster[2] during the 60s, following the universal formulae approach. It is one of the most modern solvers, being a complete Lambert’s problem solver (zero and Multiple-revolution solutions). It shows high performance and robustness while requiring no more than four iterations to reach a solution.

All credits of the implementation go to Juan Luis Cano Rodríguez and the poliastro development team, from which this routine inherits. Some changes were made to adapt it to lamberthub API. In addition, the hypergeometric function is the one from SciPy.

Copyright (c) 2012-2021 Juan Luis Cano Rodríguez and the poliastro development team

References

[1] Izzo, D. (2015). Revisiting Lambert’s problem. Celestial Mechanics

and Dynamical Astronomy, 121(1), 1-15.

[2] Lancaster, E. R., & Blanchard, R. C. (1969). A unified form of

Lambert’s theorem (Vol. 5368). National Aeronautics and Space Administration.

Vallado’s algorithm makes use of the universal formulation to solve for the Lambert’s problem. By making use of a bisection method, it guarantees the convergence to the solution but the amount of iterations require dramatically increases.

Parameters
• mu (float) – Gravitational parameter, equivalent to $$GM$$ of attractor body.

• r1 (numpy.array) – Initial position vector.

• r2 (numpy.array) – Final position vector.

• M (int) – Number of revolutions. Must be equal or greater than 0 value.

• low_path (bool) – If two solutions are available, it selects between high or low path.

• maxiter (int) – Maximum number of iterations.

• atol (float) – Absolute tolerance.

• rtol (float) – Relative tolerance.

• full_output (bool) – If True, the number of iterations and time per iteration are also returned.

Returns

• v1 (numpy.array) – Initial velocity vector.

• v2 (numpy.array) – Final velocity vector.

• numiter (int) – Number of iterations.

• tpi (float) – Time per iteration in seconds.

Notes

This algorithm is presented as an alternative to the one developed by Bate in 1971. Bate did not impose a particular numerical solver for his algorithm but cited both bisection and Newton’s one. However, for some values of the boundary problem, the initial guess might diverge if Newton’s solver is used. That’s why Vallado decided to employ a bisection method instead. Although detrimental from the point of view of performance, this algorithm properly reaches solution in the majority of the cases.

All credits of the implementation go to Juan Luis Cano Rodríguez and the poliastro development team, from which this routine inherits. Some changes were made to adapt it to lamberthub API.

Copyright (c) 2012-2021 Juan Luis Cano Rodríguez and the poliastro development team.

References

[1] Vallado, D. A. (2001). Fundamentals of astrodynamics and applications (Vol. 12). Springer Science & Business Media.

lamberthub.__version__ = 0.2.dev0
lamberthub.ALL_SOLVERS

A list holding all lamberthub available solvers

lamberthub.ZERO_REV_SOLVERS

A list holding all direct-revolution lamberthub solvers

lamberthub.MULTI_REV_SOLVERS

A list holding all multi-revolution lamberthub solvers

lamberthub.NON_ROBUST_SOLVERS

A list holding non-robust lamberthub solvers

lamberthub.ROBUST_SOLVERS

A list holding all robust lamberthub solvers