arXiv subjects

E. Serpell

Publications and source records attributed to E. Serpell.

3 recordsLinked to original sources

arXiv2026

The First Look of Gaia: Daily data quality and instrument health assessment with automated early warnings

The ESA Gaia mission is a 10+ year astrometric whole-sky scan, demanding consistent data quality over the whole timespan of operations Aims. The Gaia First Look (FL) is a system whose aim is monitoring the data quality to identify problems, which includes early warning capabilities for potential upcoming issues. Methods. In order to achieve its goals, the Gaia FL implemented its own limited astrometric solution, and used the daily calibrations from other segments of the Data Processing and Analysis Consortium (DPAC), as well as the diagnostic data from the satellite itself, in order to obtain a complete picture of the situation of the Gaia satellite on a daily basis. This led to a short-term health and data quality check, but also to a broader overview of the longer-term trends and evolutions within the payload. Potential issues that were encountered were reported to other groups within DPAC for further analysis purposes. When required, ways to mitigate the problems were discussed, and implemented. Results. We show a number of findings by the Gaia FL concerning longer-term evolution, individual but common effects, as well as detrimental impacts, all of which occurred over the operational phase of the Gaia mission

astro-ph.IM↗

arXiv2016

Gaia: focus, straylight and basic angle

The Gaia all-sky astrometric survey is challenged by several issues affecting the spacecraft stability. Amongst them, we find the focus evolution, straylight and basic angle variations Contrary to pre-launch expectations, the image quality is continuously evolving, during commissioning and the nominal mission. Payload decontaminations and wavefront sensor assisted refocuses have been carried out to recover optimum performance. Straylight and basic angle variations several orders of magnitude greater than foreseen were found and studied during commissioning by the Gaia scientists (payload experts). Building on their investigations, an ESA-Airbus DS working group was established during the early nominal mission and worked on a detailed root cause analysis. In parallel, Gaia scientists have also continued analysing the data, most notably comparing the BAM signal to global astrometric solutions, with remarkable agreement. In this contribution, a status review of these issues will be provided, with emphasis on the mitigation schemes and the lessons learned for future space missions where extreme stability is a key requirement.

astro-ph.IM↗

arXiv2014

Gaia on-board metrology: basic angle and best focus

The Gaia payload ensures maximum passive stability using a single material, SiC, for most of its elements. Dedicated metrology instruments are, however, required to carry out two functions: monitoring the basic angle and refocusing the telescope. Two interferometers fed by the same laser are used to measure the basic angle changes at the level of $\mu$as (prad, micropixel), which is the highest level ever achieved in space. Two Shack-Hartmann wavefront sensors, combined with an ad-hoc analysis of the scientific data are used to define and reach the overall best-focus. In this contribution, the systems, data analysis, procedures and performance achieved during commissioning are presented

astro-ph.IM↗