Data & Analysis

All data taken by CHEOPS is processed and reduced at the Science Operations Centre (SOC) using a common CHEOPS Data Reduction Pipeline (DRP). The DRP pipeline is not available to the user, however, detailed descriptions of the reduction steps, including assumptions and algorithms are provided as part of the SOC documentation.

CHEOPS data can be accessed via the Mission Archive. This includes both public and propietary data. Public data is freely accessible without login, while proprietary data can only be accessed by the respective GO programme's Principal Investigators (PI) after login. This includes the following levels of data products: 

​Level 0 - data as received from the MOC (science, housekeeping, and ancilliary)
Level 0.5 - data converted to FITS files, sorted according to visit and pass (downlink)
Level 1 - calibrated/corrected images and quality reports
Level 2 - light curves/time series (final CHEOPS data product)
as well as on-ground calibration products, reference files, housekeeping data, ancilliary data, and monitoring&characterisation (M&C) data.

Public data takEN during in-orbit commissioning (January - March 2020)

A selection of 4 data sets taken during in-orbit commissioning is available. A discussion on the analysis of observations of HD88111, TYC5502-1037-1 and Kelt 11b can be found in the paper on CHEOPS by Benz et al. (2021) and in this presentation summarising IOC performances prepared by the CHEOPS Mission Consortium. Details of the DRP can be found in Hoyer et al. (2020) A&A, 635, A24. These data have been reduced using the Data Reduction Pipeline (DRP) version cn02-20200619T125718. Details of the observations, together with the results of the data reduction, can be found in the individual DRP reports. You may also download the data from this page by clicking on the target names below. Data reduced using the most recent version of the pipeline can be retrieved from the Mission Archive.

• 47 hr duration observation of HD88111, a relatively bright (magnitude V= 9.18), G5 dwarf star (Teff=5330K, R=0.9Rsun), chosen to determine the photometric precision that can be achieved for bright stars. The particular target was picked because of its a-priori relative lack of stellar activitiy, and because it was not known to host an exoplanet. The observations were made on 22 February 2020 (PR300005_TG000101)
• 47 hr duration observation of  TYC5502-1037-1, a fainter (magnitude V= 11.9) K-type dwarf star (Teff=4750K), radius R=0.7Rsun), chosen to determine the photometric precision that can be achieved for fainter stars. The particular target was picked because of its a-priori relative lack of stellar activitiy, and because it was not known to host an exoplanet. The observations were made on 21 March 2020 (PR300005_TG000501)
• 1 hr observation of Pollux, a magnitude V= 1.12 dwarf star, considered to be an ultra-bright target for CHEOPS. The observations were made on 10 March 2020 (PR300050_TG000101). It should be noted that the data reduction pipeline is not currently optimised for processing obssrvations of ultra-bright targets, which is reflected in the performances that are reported in the data reduction pipeline report.
• 10 hr observation of HD93396, an evolved subgiant (magnitude V= 8). Included in the data is the transit of Kelt 11b, a hot-Jupiter with an orbital period of just under 4.74 days (see web article for further details). The observations were made on 9 March 2020 (PR300024_TG000101). Note: to find the data in the CHEOPS mission archive you will need to search for KELT- 11b.

Additionally:

• In early June 2021 the first CHEOPS phase curve, an observation of 55 Cnc e, and a primary transit of the same planet were made public. The obserations were made during and shortly after IOC. The datsa reduction pipeline reports for the c. 26 hour phase curve observation taken over 23-34 March 2021 and the c. 6 hr transit observation taken on 9th March 2021 can be found here (phase curve: transit). The paper on the observations by Morris et al. (2021) includes a detailed discussion of spacecraft and instrument-related systematics introduced into CHEOPS light curves and how they are corrected for in the analysis. An overview of systematics seen in CHEOPS light curves is given in a presentation prepared by the CHEOPS Science Team which can be found here. Version 13.1.0 of the data reduction pipline was used to process the data.

simuLated data

Data simulating a selection of representative CHEOPS observations, generated using the simulation tool CHEOPSim, can be downloaded from this link. The data are described in the Section 2.2.2.2 in the CHEOPS Observers Manual. Included in the tar files are the "raw" data, together with products that are produced by the data reduction pipline during processing. Please read the README file for details on the content of the tar files. Details of CHEOPSim can be found in Futyan et al. (2020) A&A 635, A23. 

Reference DATA/files

There are number of files which contain data which is used by the data reduction pipeline. These so-called reference files include:

• EXT_APP_DE1
• EXT_PRE_StarCatalogue
• REF_APP_BadPixelMap
• REF_APP_BiasFrame
• REF_APP_DarkFrame
• REF_APP_FlatField
• REF_APP_WhitePSF
• REF_APP_OversampledWhitePSF
• REF_APP_CCDLinearisation
• REF_APP_GainCorrection
• REF_APP_Throughput 
• REF_APP_SED
• REF_APP_PixelScale
• REF_APP_QE
• REF_APP_Limits-ScienceHk
• REF_APP_ObtReset

A description of the contents of each of FITS files can be found in the Data Product Description Document. The files themselves are available from the Mission Archive, and can be found by querying for reference files.

Details of the CHEOPS data reduction approach and pipeline can be found in Hoyer et al. (2020) A&A, 635, A24.