Public Surveys Policies

Following recommendations by STC and OPC, more than 75% of the ESO time on VST (optical) and VISTA (NIR) will be devoted to Public Surveys which will be carried out in service mode. This web page summarizes the policies and the mechanisms that ESO has developed to manage survey projects from proposal preparation, on-sky data taking, to the distribution of data products through the ESO archive.

  1. Calls for public surveys, proposal submission and evaluation process
  2. The Survey Management Plan
  3. The Survey Progress – Periodic reports
  4. ESO Survey Team: duties and responsibilities
  5. Guidelines for the Validation of Survey Data Products
  6. Policies for the submission and publication of data products

Calls for public surveys, proposal submission and evaluation process

The selection of public survey proposals is a process which takes about 11 months, from the initial expression of interest to the OPC recommendation. This activity foresees a large involvement of the ESO community, in the definition of the survey projects, via the proposal submission, and setting the standards for the survey legacy values, via the selected members of the Public Survey Panel.

ESO will issue Calls for Public Surveys periodically. The periodicity of these calls is not currently fixed, but will depend on the status of the on-going surveys according to the following criteria:

  • At no time there will be more than 2 active public surveys covering the same RA range.
  • Two active surveys will be possible only if they do not require similar observing conditions (dark time, excellent seeing, etc.).
  • ESO will issue new calls for surveys 6 months before the estimated date for completion of the current surveys.

The Public Survey Panel (PSP), composed of experts from the community, reviews the proposals submitted during the initial call. The PSP prime mandate is to review the Public Survey Proposals and elaborate a scientifically and observationally well coordinated set of Public Surveys. This process implies merging different proposals, or expanding their aims beyond the original ones e.g., in the filter set, depth, area, coordinates, etc., and the rejection of those proposals not fulfilling the legacy value of a public survey. In order to achieve these goals the PSP involves the PI’s from the selected teams which have submitted the Survey Proposals and successfully passed the first evaluation process. On the basis of the achieved coordination, the selected survey teams may decide to modify the survey proposals describing the scientific rationale, observational strategy, and data product specifications (e.g. photometric and astrometric accuracy, images, catalogs, delivery time, etc.) as agreed in the course of these activities. All PI's whose proposals were not rejected in the first evaluation process can submit their proposals for the consideration of the OPC. The PSP documentation will be available to the OPC, and the Chair of the PSP will present the PSP recommendations to the OPC.

The Calendar for the submission of and the appraisal steps for the VISTA Public Survey proposals proceeded as follows:

January 15, 2006 - Call for Proposals

March 15, 2006 - Deadline for the submission of PS proposals, 14 submitted

May 2-3 , 2006 - First meeting of the VISTA Public Surveys Panel- Chair: Duccio Macchetto - 4 proposals rejected

June 20-21, 2006 - Second meeting of the VISTA PSP with participation of PIs

Mid July, 2006 - Recommendations of the VISTA PSP communicated to PIs

September 29, 2006 - Deadline for the submission of PS proposals to OPC taking in consideration the recommendations of the VISTA PSP - 6 proposals submitted

October 31, 2006 - PSP meeting: review and final recommendations

November 20 / 24 6 public survey proposals approved with VISTA . Their scientific goals and observing strategies are presented in the science with the ESO public surveys page.

Similar steps were followed for the selection of the VST public surveys in 2005.

The proposals not selected by the PSP can still be submitted to the OPC as large projects, if appropriate, and the relevant PSP documentation will also be available to assist the OPC process. Furthermore, any time allocation for additional survey related observations (e.g. spectroscopic follow-up) at other ESO telescopes must be applied for.


The Survey Management Plan

Imaging surveys - The Principal Investigators (PIs) whose Public Survey proposal has been reviewed by the PSP and recommended by the OPC are now asked to submit their Survey Management Plan (SMP). 

~ 75% of ESO available time on VISTA (and VST) will be used for Public Surveys which will be conducted in Service Mode (SM). Therefore with respect to the standard Phase I, the SMP represents an additional form requested from the PI's, which aims at collecting the necessary information to carry out Public Surveys in SM, and allows for an efficient and timely planning of Phase II and telescope operations. The SMP must illustrate the observing strategy, the survey data calibration needs, the data reduction process, the manpower and hardware capabilities, the data quality assessment process, and the data product delivery to the Virtual Observatory (VO).

The SMP is an integral part of ESO' s appraisal of the proposal and it will be reviewed by ESO as follows:

  • The SMPs are reviewed by ESO in consultation with the Chair of the PSP. The generated Review Items are sent to the PIs for comments and revisions.
  • The revised SMPs are reviewed by a panel composed of the Head of the Data Management and Operations Division, the VLT programme scientist, and the corresponding Paranal instrument scientist. In the case of VISTA the panel will also include the VISTA Principal Investigator. The EST leader will be report on the whole review process.
  • The recommendations of the SMP review panel are sent to the Director General, for approval or further actions required.

Spectroscopic surveys - The spectroscopic public surveys will be carried out in VISITOR mode, and  given the large investment in observing time the SMP is instrumental to provide the support to the survey teams for the whole durations of the surveys. The SMP is an integral part of the Public Survey proposal and the proposal is offcially approved only after the SMP is and the contract signed between the ESO Director General and the Public Survey PI. The SMPs will be reviewed by the ESO Survey Team in consultation with the Spectroscopic Public Survey Panel Chair and the VLT programme scientist. The recommendation will be presented to the ESO Director General, for approval or further actions.

  • SMP latex template - PIs are asked to download the SMP template from the ESO web pages dedicated to public surveys. The guidelines are included in the template so that the form is self-explanatory. The SMP template is available here (tex file) and here (pdf version).
  • SMP submission deadline - PIs are asked to submit the SMPs for their survey projects at the earliest convenience, and no later than September 15, 2011, by email. Such deadline will allow the EST review and the submission of RIXes, for the final recommendation to the ESO DG by the  OPC meeting in November 2011.
  • SMP publication - Once the Spectroscopic Public Survey SMP will be accepted by the ESO DG, the approved SMPs and Public Survey proposals will be made public, via the ESO Public Surveys web pages, so that observing strategies and the planned observations become  accesible by the community at large, in order to avoid duplication of targets in open time proposals, and to support the community scientific usage of  the data products from the public spectroscopic surveys.


The Survey Progress – Periodic reports

The PSP Chair and the PSP members are asked to serve as independent referees of the progress and achievements of the public surveys. The PSP will receive a yearly report by the ESO Survey Team, in written form, with the information on the basic monitoring of the progress for each ESO public survey. This report shall describe:

  • the data transfer from the Observatory to the teams,
  • the percentage of PHASE II OBs completed in each semester, and
  • the delivery of data products from the Survey Teams to the ESO archive, in terms of keeping to the agreed upon delivery schedule, product types and quantity.

Following the PSP evaluation, the PSP Chair will participate in an annual review with the appropriate ESO staff to evaluate whether the survey teams are carrying out the survey project in a manner consistent with the survey goals and produce the results and products that are expected from each survey, according to their specific survey management plan. The first progress review will be carried out one year after the ESO public surveys have begun, and then on once per year, untill the completion of each survey. The EST leader, after consultation with the PSP Chair, will report to the OPC on the status of advancement of the ESO public surveys. These reports will be the basis for the OPC determination to continue or curtail the allocation of observing time to the surveys.


ESO Survey Team: duties and responsibilities

The ESO survey team follows the implementation of the ESO policies for Public Surveys . The ESO Survey Team members are Magda Arnaboldi (team leader), Evanthia Hatziminaoglou, Wolfgang Hummel, Gaitee Hussain, Mark Neeser and Marina Rejkuba. In the framework set by the current policies, the ESO Survey Team (EST) has a role which is similar to that of an Audit group, which supports the teams during their observations at the Survey telescopes, VST and VISTA, monitors the progress of the surveys, and perform a data quality assessment of the PS products submitted for ingestion into the ESO archive, based on the quality control parameters and technical reports provided by the Survey Teams. The current responsibilities of the ESO survey team are the following:

Reviewing the Survey Management Plan in all its dimensions. To assess in detail the resources available in the Survey Teams (manpower, expertise, hardware, and software), and whether they are adequate to the demands of their proposed survey. The EST also evaluates the proposed data products to be delivered to ESO and whether they are suitable to fulfil the goal of serving a broad community.

Taking part in the science verification of VST/VISTA and collaborating to finalise PHASE II tools (SADT, P2PP and OT upgrade, etc.).

Participation to the definition of the ESO standard calibration plan of OmegaCAM and VISTA, as well as the configuration of the QC parameters in the DFO pipeline.

Support the PI's to optimize the scheduling of the observations (Phase II). To ensure that the survey strategy (dither size and pattern, tiling, field selection, sky conditions, moon phase, etc.) is compatible with the attributes of OmegaCAM and VISTA, and with the goals of the respective survey.

Basic monitoring the progress of the public surveys. To oversee the data transfer from the Observatory to the teams, to monitor the percentage of PHASE II OBs completed in each semester, and to monitor the delivery of data products from the Survey Teams to the ESO archive, in terms of keeping to the agreed upon delivery schedule, product types, and quantity.

Validating Survey Data Products. The EST will act as a referee and will base its assessment of the data quality of the survey products, on the quality control parameters, and the detailed reports provided by the survey teams. These quality control parameters are described in the Survey Management Plan, and the EST will ensure that the PS teams comply with these quality control standards. In the case of a disagreement, the EST may carry out independent checks on a subset of data products delivered by the PIs, using standard tools and consolidated criteria. The expected frequency of the validation checks is to be determined, but we can anticipate that it will be driven by the main releases of the data products from PS to the ESO archive and VO.

Issuing and updating guidelines and ESO standards for ingestion and digestion of data products by the ESO archive.


Guidelines for the Validation of Survey Data Products

These guidelines are intended to describe the reports and tests which will be requested by the EST from the Survey Teams in order to verify the declared accuracy/uniformity of the data products from PS before their acceptance and ingestion into the ESO archive.

Six months after receiving the complete (on a tile-by-tile basis) data and the associated calibrations, the corresponding data products should be delivered to the ESO archive. They consist of:

  • Instrumentally corrected, stacked (as appropriate) frames in all the relevant bands of the survey, with photometric and astrometric calibrations in the headers.
  • Confidence maps
  • Object catalogues including multi-band photometric, astrometric and morphological measurements.

These data should be calibrated using standard night-by-night calibration procedures and there are no requirements on the global uniformity of these calibrations at this stage. Major data releases with uniform photometric and astrometric calibrations should be made at least once per year, with the first delivery expected no later than 18 moths after the beginning of the observations.

A final release with a global photometric and astrometric calibration should be made upon completion of the survey. It will be highly desirable if high-level science products (for example photometric redshifts, shapelets, etc.) were delivered at some point to the ESO archive in order to enhance the legacy value of the data. The delivery of the above data products by the survey teams must be supported by the following documentation:

  • the data acquisition: the general image quality according to the standard QC parameters based on the camera standard calibration plan, seeing distribution, transparency, moon illumination, dithering pattern (% of overlap between frames), etc.
  • the pre-reduction: mostly the instrumental signature removal, i.e. bias properties, strategy for optimal flat-fielding in the adopted bands, tests for presence of scattered light, removal of fringing patterns, etc..
  • Regarding the NIR, there is the need to test for and correct linearity effects, possible cross-talk, and bad pixel masking (particularly for VIRCAM'S detector #16 which has a large 200 bad pixel area).

Astrometry : The astrometric solution must be computed using both an external astrometric catalogue (e.g. USNO in the optical; 2MASS for the near-infrared bands, as examples) and an internal catalogue generated from matched objects in overlapping CCDs (i.e. global astrometry). Specify whether astrometric solutions are computed before or after co-addition of frames. Survey teams must provide plots of astrometric residuals for un-saturated point-like sources over the whole area covered by the dataset being submitted for ingestion into the ESO database. These residual plots will illustrate the accuracy of the absolute astrometry and the relative astrometric solution within the current survey area.

Photometry : This should include two steps: 1) obtain the absolute calibration based on observations of standard star fields relevant to the observed wavelengths; 2) combine the absolute calibration with a relative calibration based on the catalogues of overlapping sources. This allows a determination of the scaling factors to be applied during the co-addition, and will provide a uniform zero point across the whole survey area. A description of the co-addition process must be provided: whether it is performed after the image is re-sampled, the flux scaling applied, and the algorithm adopted for its execution.

Catalogue Preparation: The Survey Teams must provide a report on the tests on the PSF uniformity across the co-added images; tests for the optimisation of the extraction parameters for the object detection algorithm. Particularly important here is the selection of an optimal photometric aperture; in case of the multi-band surveys, the Survey Teams must describe the strategy adopted , i.e. whether a particular band is used for the master catalogue, or a χ2 image is produced as the detection image; discuss point-like (unresolved) vs. extended (resolved) classification. The Survey Teams must describe their procedure for the evaluation of the limiting magnitude of the co-added frames and provide these values. They should specify whether the magnitude limit refers to point-like sources and/or tests were carried out for surface brightness selection effects.

Data quality assessment : It is in the Survey Team's best interest to certify the data quality of their survey products and carry out all the tests needed to certify the quoted accuracy and the absence of (the most obvious) systematic effects in their data. We list here a number of tests aimed at certifying the uniformity of the photometry, image quality and limiting magnitude across the whole survey area. Depending on the scientific aim of the surveys, the Survey Teams are requested to provide the results of these tests to the EST, to certify their survey products.

Stellar colours - Distribution of stars in colour-colour space as a function of magnitude : to be carried out on point-like bright objects (depending on the limiting magnitude of the survey). This test is aimed at establishing a consistent photometric system and rule out systematic effects due to incorrect matching of multi-band catalogues or residual colour-terms. This is relevant for both galactic and extragalactic surveys.

Effect of crowding : These tests should quantify the effect on the photometry of point-sources from overlapping PSFs. Relevant for galactic surveys.

Field galaxy colours - Distribution of galaxies in colour-colour space as a function of magnitude: This test is aimed at establishing a consistent photometric system and rule out systematic effects due to incorrect matching of multi-band catalogues for extended sources or residual colour-terms. Relevant mostly for extragalactic surveys and photometric redshift determination.

Galaxy number counts : tests on galaxy number counts will provide independent evidence for the magnitude limits across the whole area of the survey, and certify its completeness up to that magnitude. Most relevant for extragalactic surveys.

Clustering properties of extended sources : these tests are most relevant for extragalactic surveys.


Policies for the submission and publication of data products

  • The raw data from the public surveys with VST-OmegaCAM and VISTA-VIRCAM will be immediately made public worldwide from the ESO archive, with public users being able to download limited volumes.
  • Science-ready data products from the ESO public surveys will be available from the ESO archive.

Information on the preparation of reduced data products and the submission to ESO is provided on the ESO Phase 3 web pages, including an overview of the survey deliverables, their timelines, a description of the specific data formats (ESO External Data Products standard) and a user guide to the submission process.

Data products from VISTA public surveys will be available also from the Wide Field Astronomy Unit at the Royal Observatory Edinburgh.