In-orbit updates: performances, tips/reflections from the CHEOPS Science Team AND systematics in CHEOPS DATA

Collected together on this webpage are a number of presentations and links which are relevant to the understanding of CHEOPS and its data that has been gained on CHEOPS in the time since launch in December 2019. These are split into three groups: (a) those relating directly to the performances measured in orbit; (b) systematics in CHEOPS data; (c) tips for and reflections on using CHEOPS

Latest update: 15 February 2022

 

In-orbit performances

The CHEOPS Mission Consortium was responsible for the in-orbit commissioning of the instrument and is now responsible for an on-going monitoring and characterisation programme. Details of the performances that been measured over the course of the mission are summarised in the presentations listed below:

  • Measured photometric performance - overview (updated January 2022)
  • Observing outside of nominal magnitude range of CHEOPS (May 2021)
  • Illustration of photometric performances (includes lightcurves)  (January 2022)

 

Tips and reflections/guidelines

The presentations below capture the understanding/experience of CHEOPS and its data that has been built up by technical working groups in the Science Team.

  • Tips and guidelines for determining the duration of individual visits (Phase 1) , and tips on how to define your individual observations reqeusts (Phase 2) at this link (December 2022)
  • Heading off-piste -  how well multi-epoch observations can be combined (e.g. for stellar monitoring) and the impact of transit stacking (February 2022)

 

systematics

All CHEOPS science observations are processed at the Science Operations Centre at Geneva Observatory, using the CHEOPS data reduction pipeline (DRP). The DRP (Hoyer et al. (2020) https://doi.org/10.1051/0004-6361/201936325)) is designed to calibrate and correct CHEOPS observations, and to extract photometric light curves from the corrected image series. What the DRP does not do is to take out time-dependent trends in the data which are related to, for example, instrument temperature, position of the target on the detector etc. These systematics effects are removed from the data by decorrelation or detrending. Identifying and correcting for systematics has been one of the major tasks of the two technical working groups within the CHEOPS Science Team

 

Systematics in detaIl

In the list below are papers in which the treatment of specific systematics seen in CHEOPS data have been rreated.

  • Bonfanti et al. (2021) "CHEOPS observations of the HD 108236 planetary system: a fifth planet, improved ephemerides, and planetary radii" (https://doi.org/10.1051/0004-6361/202039608)   --      - detailed elaboration of the roll angle, its impact on CHEOPS data and how to decorrelate for it; discussion on smearing patterns (due to bright stars in the field,) and an example of internal reflection and its manifestaion in CHEOPS images.
  • Wilson et al.(2022) "A pair of sub-Neptunes transiting the bright K-dwarf TOI-1064 characterized with CHEOPS", (https://doi.org/10.1093/mnras/stab3799) - includes treatment of the "ramp" and various roll angle-relatred issues, Descirbes the PSF PCA (Principal Compnent Analysis)method that has been developed to remove these systematics.