Observing with CHEOPS

Observing time during the 3.5 year duration of CHEOPS nominal operations will be split 80%: 20% between the Guaranteed Time Observing (GTO) Programme, which is under the responsibility of the CHEOPS Science Team, and the ESA-led Guest Observers Programme, through which the Community can conduct scientific investigations of their own choice. 

 

The CHEOPS Guaranteed Time Observing Programme

The GTO Programme is based on the science case for the CHEOPS mission, which is summarised in the CHEOPS Science Requirements Document and the CHEOPS Definition Study Report (Red Book). The programme is currently undergoing refinement by the CHEOPS Science Team - details on the current science themes can be found in presentations given at the 4th CHEOPS Science Workshop in Geneva. 

 

 The CHEOPS Guest Observers' (GO) Programme

Proposals for a share of the time allocated to the CHEOPS GO Programme will be solicited through ESA Announcements of Opportunity (AOs) that will be made to the Scientific Community. The first AO is forseen to be issued six months before launch and will cover the period of the first year of nominal operations. Proposals wll be selected on scientific merit, by a CHEOPS Time Allocation Committee that will be appointed by ESA in consultation with the CHEOPS PI. The TAC will work independently from the CHEOPS Consortium, and will receive technical support from the ESA Project Science and the CHEOPS Consortium Project Science Office. Proposals will be ranked based on scientific merit, and recommendations for CHEOPS observing time will be made to the Director of Science who will award the time. 

It is important to note that the vast majority of CHEOPS observations will be time-critical, and as a result non-trivial to schedule.  Propsective obserers should be aware that the award of time on CHEOPS does not provide any guarantee that the observations will actually be scheduled and completed. 

Proposals for observing time in the Guest Observers' Programme can cover any type of science that can be shown to be both addressable by the performance capabilities of CHEOPS and to be compatible with the operational, observational and technical constraints of the mission. Observations of targets that are on the Reserved Target List (see below) that will be defined by the CHEOPS Science Team be excluded, unless the science case is subtantially different from that/those for which the target was proposed by the  CHEOPS Science Team. PIs will be required to provide evidence that the Reserved Target List has been checked and that there are no conflicts.   

Update of the GTO Reserved Target List to include new targets is foreseen on a regular basis. To enable important new targets to be included in the GO programme, up to 25% of the observing time on the Guest Observers' Programme 

 

Support to the Guest Observer

Tools and documentation to support the Community in preparation of proposals iin response to the ESA AOs will be available through the ESA webpages, and will include descriptions of the mission and payload, user manuals, CHEOPS target visibility plots and exposure time calculators. A webpage with "frequently asked questions" will also be available.  

 

Planning CHEOPS observations 

PIs of successful proposals will be invited to submit detailed information relating to the scheduling of their requested observations. This will be used to generate the long term schedule for CHEOPS. Observers will be informed that their observations have been scheduled no later than the time at which the relevant weekly activity plan is uploaded to the spacecraft.  

 

CHEOPS data processing and data reduction

All data taken by CHEOPS will be processed and reduced at the SOC using a common CHEOPS data reduction (DR) pipeline. The DR pipeline will not be available to the user, however detailed descriptions of the reduction steps, including assumptions and algorithms that have been used will be provided as part of the SOC documentation. 

 

Accessing CHEOPS data: 

All data obtained with CHEOPS will be made available via the CHEOPS science archive which will be hosted by the SOC at Geneva Observatory. This includes the following level data products: 

  • ​Level 0 - data received from the MOC: science + housekeeping + ancilliary 
  • Level 0.5 - converted to FITS fils, 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 callibration products (reference files), all housekeeping+ancilliary data and data taken in-orbit as part of monitoring and characterisation activities. 

WIth the exception of data taken during characterisation and monitoring activities, all CHEOPS observations will be subject to a proprietary period of 1 year. The proprietary period will be set at the level of individual observation requests: it will begin at the time that the data from the last visit in an observation request is declared to be complete by the SOC, following quality checks. The total proprietary period will not exceed a period of 1.5 years which starts from the time of successful completion of the first visit of the observation request. Only the PI of the proposal associated with the observation request, or the CHEOPS Science Team in the case of observations from the Guaranteed Time Observing Programme, will be able to see and retrieve proprietary data  from the archive.

Beyond the proprietary period, data will become public and will be freely available from the archive. 

 

The CHEOPS Reserved target List: 

The first issue of the CHEOPS Reserved target List will comprise targets from the Guaranteed Time Observers Programme and will cover the full 3.5 years of the mission. The list will be fmaintained in a versioned databased for which all entries and changes will be tracked and time-stamped/logged. It will be frozen at the time of the first (and subsequent) call(s).  The list will be available to ESA to ensure transparancy, but will not be provided to the Community as a whole. 

A dedicated tool will be available to query the Reserved Target List. It will report back on the status of a target: if it is on the list, the title of the science theme under which the target falls along with the contact details of the theme lead on the CHEOPS Science Team will be provided to facilitate further contact. 

Targets from GO proposals that are awarded observing time on CHEOPS will be added to the Reserved Target List and similarly blocked. In all but exceptional cases, targets from the GO Programme will be removed from the Reserved Target List at the time of the next AO.