Definition of astrometry how to#

In addition to the overall scientific coordinating responsibilities, he developed many of the approaches and algorithms related to the mission: his innovation, insight, and mathematical rigour impacted the optical and focal plane design, the instrument calibration, the scanning law, the attitude determination (and the associated 'dynamical smoothing'), the double star analysis (as observed via a signal modulated by a grid), the effects of chromaticity and thermal load fluctuations, the optimum combination of the NDAC and FAST catalogue solutions, and the link to an extragalactic reference frame. Innovation, efficiency, completeness, clarity, and mathematical rigour have been the hallmarks of his many and varied fundamental contributions to space astrometry since that time.ДЇrom 1990 Lennart Lindegren led the Consortium NDAC (Northern Data Analysis Consortium) sharing with FAST (led by Jean Kovalevsky) the data processing of Hipparcos.

Definition of astrometry how to#

Already by the end of 1976, Lindegren had produced a set of definitive technical notes and simulations showing how to obtain a 'rigid sphere' with all astrometric parameters from a scanning satellite.

The numerical principles had to be demonstrated, together with the solutionвЂ™s statistical properties. The principle of reconstructing space astrometric positions from one-dimensional observations carried out in the innovative Hipparcos sky scanning mode was fully original (and frequently questioned outside the project), and at the very limit of available computational power even by the end of the mission in 1997. This crucial '3-step procedure' was used successfully by the two consortia (NDAC and FAST) later entrusted by ESA with the Hipparcos data processing. He set out the overall principles of the astrometric data reduction aiming to combine and solve together the attitude, the system and the astrometric parameters of the stars. During the early studies of ESA's Hipparcos space astrometry mission, and while still a graduate student in 1976, he was 'recruited' to the project by Erik HГёg and thereafter played a crucial role in various aspects of the mission definition and in the data analysis.