II.1 the Corot Observations A

The CoRoT Legacy Book c The authors, 2016 DOI: 10.1051/978-2-7598-1876-1.c021 II.1 The CoRoT observations A. Baglin1, S. Chaintreuil1, and O. Vandermarcq2 1 LESIA, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universites,´ UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cite,´ 5 place Jules Janssen, 92195 Meudon, France 2 CNES, Centre spatial de Toulouse, 18 avenue Edouard Belin, 31 401 Toulouse Cedex 9, France This chapter explains how it has been possible to propose Calls for AP proposals are sent as soon as the field of a reasonable mission, taking into account the scientific ob- a run is approximately chosen. They contain either general jectives and the mission constraints. scientific studies or specific targets. It shows how the scientific specifications have been The necessity to observe at the same time, for long dura- translated in the observation programme and its successive tions, bright targets devoted to the seismology programme, runs. and faint ones for the exoplanet finding objective have lead It describes the observations from all aspects: selection to difficult compromises on the instrument, the satellite and criteria (scientific and operational), tools, implementation, the mission profile. global results and specific results. A preliminary proposal for a nominal mission of 2.5 yr A particular focus is made on evolution, showing how was built before the mission, but has been adjusted during scientists and engineers in charge of the operations at CNES the flight before each observing period, taking into account and in the laboratories have adapted the major principles the previous results. to the results of the first observations and to the instrument And it was also adapted to the instrumental realisation, in flight. and \in flight" performances. The first section deals with science and presents the Before the end of the nominal phase (3 yr), a new pro- process to choose the targets and the result of this scientific gramme has been proposed for a 3-yr extension, which choice, i.e. the observed targets, individually for the bright focussed on the CoRoT \niches", as discovered during stars and statistically for the faint stars. the 3 first years. The following section gathers many operational aspects: At the end of this period, as the instrument was still the tools used for the operations as well as for the scientific in a good shape, a programme for a second 3-yr extension choices, the work flow followed at the beginning of each run, has been worked out and accepted in October 2012. But the resulting overall duty cycle. unfortunately the instrument stopped sending data a few The last section concerns the runs one by one. A first days later. table indicates the periods of lack of data. Then specific scientific information is given for each run and, in some cases, complementary remarks useful to interpret the data, such as special processing, anomalies, ... 1.2. The choice of the fields to be observed The concept of the instrument and the definition phase were extensively described in Fridlund et al. (2006), called Setting the observational programme consists in defining for \The CoRoT book". each run, successively, a preliminary position of the Field of View (FOV), of the line of sight (LOS), of the roll and a preliminary choice of the targets. For each run, the process starts by a proposal from the 1. The scientific programme Scientific Committee (SC), based only on the scientific requirements. 1.1. General overview The \Core programme" had the highest priority, with The choice of the fields and the targets to be observed has an equal weight for seismology and planet hunting. been driven first by the initial objectives of the Core Pro- Additional programmes have been taken into account gramme and its evolution (see Michel et al. 2006). Addi- with a lower priority, essentially in the faint star field. tional Programmes (AP) are accommodated as much as It starts with a preliminary list of bright targets fulfill- possible, following the proposals of the GIs. ing the seismology objectives (as selected in the CoRoTSky 29 The CoRoT Legacy Book database), and the planet hunting requirements on the faint 1.4. Evolution during the mission star density, as defined by the Scientific Committee. During the six years of the mission, the strategy has been Then each proposed pointing is defined by a bright adapted to both the evolution of the instrument and the star, the \principal target", with some evaluation of its results already acquired. Let us cite the major ones: surrounding in the field of view. The requirement of the exoplanet-hunting programme (a sufficient number of faint { in the BSF, it appeared that most of the A/early F dwarf stars) is checked. stellar types, are generally \constant", so their priority Through an iterative process, the best compromise be- has decreased; tween both programmes optimises the scientific return. { using the light curves already obtained, it has been Table II.1.1 summarises the major scientific objectives demonstrated that the optimum duration of a run for of each run. planet hunting is slightly smaller than previously said: decreasing the length of the run to 80 to 90 days does not decrease significantly the detection rate, and allows 1.3. The scientific selection criteria to observe more fields. But the optimum duration for seismology remains as long as possible! * In the Bright Stars Filed (BSF), the order of the priorities was: After the loss of chain 1, which reduced the observed area { solar-like stars; by a factor 2, Daniel Rouan proposed a strategy in which { A and early F stars to detect/study in more details a long period is cut in almost equal parts, of 80 days. Then Delta Scuti and Gamma Doradus variables (already a rotation of the field allows to keep the same seismol- known or suspected); ogy targets and to observe a new region in the FSF. This { peculiar stars; method has been applied for LRc05/LRc06, LRa04/LRa05 { rare objects and LRc07/LRc08. as extensively described in Michel et al. (2015). For each run, the observed targets, classified by the \star type" are listed in Table II.1.2. 2. The operational phase And the total number is given in the last line. 2.1. Concept of the operations * In the Faint Stars Field (FSF) The scientific priority was to detect planets, but the max- The programme of observations is based on a yearly cycle imum number of windows (5724) is generally larger than of 4 runs which impulses the rhythms of the operations. the number of good candidates. During the \summer period" from October to March, the telescope is pointed towards the \anticentre" of the * The criteria for planet detection were almost always the Milky Way and during the \winter period" from April to same: September, in the opposite direction. { MV 10-15, Spectral type FGKM, Luminosity class V Two observation runs are achieved during each summer and IV, contamination <0.2; and winter period in general. { MV 15-16, Spectral type FGKM, Luminosity class III, Using the CoRoTSky tool and the associated stellar contamination <0.2; databases (see below), the scientific programme is turned { MV 10-16, Spectral type FGKM, Luminosity class V into a precise proposal for the pointing with chosen targets and IV; and the technical feasibility is assessed. { MV 10-16, Spectral type OBA, Luminosity class V In parallel, the evolution of the CCD temperature is and IV, contamination <0.2; evaluated over the whole run; the temperature at the be- { MV 10-16, contamination <0.3. ginning of the run is set in order to minimise the total The result of the choice based on these scientific criteria is number of changes. a collection of thousands stars, with priorities built using The operations themselves begin then in close collab- CoRoTSky and the EXODAT database. The result of the oration between the team in charge of the operations at choice is called the \Exobasket". CNES and the science and instrument specialists from the * To broaden the scientific objectives, the concept of Ad- laboratories. ditional Programmes (AP) has been created, which can As the bright stars are used for the pointing, they are be easily implemented as generally the core programme always observed first. The observation of the faint stars does not use all the available windows. generally begins between 2 and 4 days after the observation of the bright stars. The successive steps of the procedure are detailed below. After the preliminary choice of the field, a call for proposals was send to the Co-Is and GIs. The requested targets were selected after a review by the Additional Programme Work- 2.2. Tuning of the pointing and setting ing Group. In a few cases, AP targets are bright stars, but generally they are faint ones; their total number depends the parameters of the population of the field, but was limited to 500. * The full image stage: first, the satellite uses its own point- When a specific target is requested by an AP, it can ing mode, often called rough pointing, to record images be put in the exobasket with a high priority, to force its over 3 orbits (excluding the SAA crossing) to built an selection in EXOWIN. image of the sky in the position defined by CoRoTSky. 30 Table II.1.1. The scientific objectives of the successive runs and their characteristics. Abbreviations of the Star types: SL Solar-like, DS: Delta Scuti, EB: Eclipsing binaries, GD: Gamma Dor, RG: Red giants, OBA: spectral type OBA, LPV: long period variable. The scientific objectives of the successive runs and their characteristics Run Start SAA crossing driver bright stars choice

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