The astrometric core solution for the Gaia mission Overview of models, algorithms, and software implementation
(2012) In Astronomy & Astrophysics 538. Abstract
 Context. The Gaia satellite will observe about one billion stars and other pointlike sources. The astrometric core solution will determine the astrometric parameters (position, parallax, and proper motion) for a subset of these sources, using a global solution approach which must also include a large number of parameters for the satellite attitude and optical instrument. The accurate and efficient implementation of this solution is an extremely demanding task, but crucial for the outcome of the mission. Aims. We aim to provide a comprehensive overview of the mathematical and physical models applicable to this solution, as well as its numerical and algorithmic framework. Methods. The astrometric core solution is a simultaneous... (More)
 Context. The Gaia satellite will observe about one billion stars and other pointlike sources. The astrometric core solution will determine the astrometric parameters (position, parallax, and proper motion) for a subset of these sources, using a global solution approach which must also include a large number of parameters for the satellite attitude and optical instrument. The accurate and efficient implementation of this solution is an extremely demanding task, but crucial for the outcome of the mission. Aims. We aim to provide a comprehensive overview of the mathematical and physical models applicable to this solution, as well as its numerical and algorithmic framework. Methods. The astrometric core solution is a simultaneous leastsquares estimation of about half a billion parameters, including the astrometric parameters for some 100 million wellbehaved socalled primary sources. The global nature of the solution requires an iterative approach, which can be broken down into a small number of distinct processing blocks (source, attitude, calibration and global updating) and auxiliary processes (including the frame rotator and selection of primary sources). We describe each of these processes in some detail, formulate the underlying models, from which the observation equations are derived, and outline the adopted numerical solution methods with due consideration of robustness and the structure of the resulting system of equations. Appendices provide brief introductions to some important mathematical tools (quaternions and Bsplines for the attitude representation, and a modified Cholesky algorithm for positive semidefinite problems) and discuss some complications expected in the real mission data. Results. A complete software system called AGIS (Astrometric Global Iterative Solution) is being built according to the methods described in the paper. Based on simulated data for 2 million primary sources we present some initial results, demonstrating the basic mathematical and numerical validity of the approach and, by a reasonable extrapolation, its practical feasibility in terms of data management and computations for the real mission. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/record/2517386
 author
 Lindegren, Lennart ^{LU} ; Lammers, U.; Hobbs, David ^{LU} ; O'Mullane, W.; Bastian, U. and Hernandez, J.
 organization
 publishing date
 2012
 type
 Contribution to journal
 publication status
 published
 subject
 keywords
 instruments, space vehicles:, methods: numerical, methods: data analysis, astrometry
 in
 Astronomy & Astrophysics
 volume
 538
 publisher
 EDP Sciences
 external identifiers

 wos:000300614100078
 scopus:84856714107
 ISSN
 00046361
 DOI
 10.1051/00046361/201117905
 language
 English
 LU publication?
 yes
 id
 a37af6fd14594c9d882adc14b4ec5343 (old id 2517386)
 date added to LUP
 20120515 08:22:55
 date last changed
 20180311 03:43:26
@article{a37af6fd14594c9d882adc14b4ec5343, abstract = {Context. The Gaia satellite will observe about one billion stars and other pointlike sources. The astrometric core solution will determine the astrometric parameters (position, parallax, and proper motion) for a subset of these sources, using a global solution approach which must also include a large number of parameters for the satellite attitude and optical instrument. The accurate and efficient implementation of this solution is an extremely demanding task, but crucial for the outcome of the mission. Aims. We aim to provide a comprehensive overview of the mathematical and physical models applicable to this solution, as well as its numerical and algorithmic framework. Methods. The astrometric core solution is a simultaneous leastsquares estimation of about half a billion parameters, including the astrometric parameters for some 100 million wellbehaved socalled primary sources. The global nature of the solution requires an iterative approach, which can be broken down into a small number of distinct processing blocks (source, attitude, calibration and global updating) and auxiliary processes (including the frame rotator and selection of primary sources). We describe each of these processes in some detail, formulate the underlying models, from which the observation equations are derived, and outline the adopted numerical solution methods with due consideration of robustness and the structure of the resulting system of equations. Appendices provide brief introductions to some important mathematical tools (quaternions and Bsplines for the attitude representation, and a modified Cholesky algorithm for positive semidefinite problems) and discuss some complications expected in the real mission data. Results. A complete software system called AGIS (Astrometric Global Iterative Solution) is being built according to the methods described in the paper. Based on simulated data for 2 million primary sources we present some initial results, demonstrating the basic mathematical and numerical validity of the approach and, by a reasonable extrapolation, its practical feasibility in terms of data management and computations for the real mission.}, articleno = {A78}, author = {Lindegren, Lennart and Lammers, U. and Hobbs, David and O'Mullane, W. and Bastian, U. and Hernandez, J.}, issn = {00046361}, keyword = {instruments,space vehicles:,methods: numerical,methods: data analysis,astrometry}, language = {eng}, publisher = {EDP Sciences}, series = {Astronomy & Astrophysics}, title = {The astrometric core solution for the Gaia mission Overview of models, algorithms, and software implementation}, url = {http://dx.doi.org/10.1051/00046361/201117905}, volume = {538}, year = {2012}, }