ObsLocTAP 1.0 Proposed Recommendation: Request for Comments


Observation Locator Table Access Protocol (ObsLocTAP) document describes the necessary data model elements and the access protocol to discover metadata about observations for a given Astronomical Observatory through a uniform interface within the VO framework. The used data model makes reference to IVOA Observation Data Model elements (Louys, et al., 2017), removing the ones associated to datasets access, as these elements are not available yet for future observations that are planned, scheduled, performed but not archived. In this way, present standard is focused on the access to metadata related to the planning of a certain observatory, more than in the access to the scientific data products of a certain observation. Also, the data model described in the present standard will be focused on metadata discovery, useful for multiwavelength coordination observations.

The latest version of ObsLocTAP can be found at:

Also, ObsLocTAP is inside the IVOA github repository at:


Reference Interoperable Implementations

Two separate reference implementations of server-side architecture exist at ESDC, through docker containers and at CFA:

1- Integral - ESDC server

The ESAC Science Data Centre (ESDC) at ESAC is creating a new version of the Integral mission Science Archive (Monica Fernandez). Following the same phylosophy like the Gaia Archive, the server side is based on TAP. For this case, the Integral SOC is producing the table of the future planned Integral observations and this table is shared using the ObsLocTAP data model.

The TAP URL location is at:

ObsLocTAP table is ivoa.obsplan. Some example queries are the following:
Discover columns for table ivoa.obsplan:
SELECT * FROM tap_schema.columns WHERE table_name = 'ivoa.obsplan'  
Discover observations for between 31/05/2020 and 08/09/2020:
SELECT * FROM ivoa.obsplan WHERE t_min > 59000 AND t_max < 59100  
Discover observations that overlaps with a circle centered on the Crab:
SELECT * FROM ivoa.obsplan WHERE 1=INTERSECTS(s_region, CIRCLE('ICRS', 83.633080, 22.014500, 0.016666 ))

Service can be tested on any TAP client application (e.g. TopCat) or directly in your browser using TapHandle:


2- Docker containers:

Two docker containers have been created (Jesus Salgado) in order to allow the creation of a ObsLocTAP server with very basic knowledge of the standard. The first one is a web server with a TAP Tuto instance. The second one is a PostgreSQL database, with a pgsphere module installed and a TAP_SCHEMA in line with ObsLocTAP datamodel.

These docker instances are explained here:

For the execution, they can be invoked by:
docker pull jsalgadodocker/pgsphere-obsplan
docker pull jsalgadodocker/tapserver
docker network create --driver=bridge db-network
docker image ls
docker run -p 8080:8080 --net=db-network --name tap <tapserver_image_id>
docker run -p 5432:5432 --net=db-network --name db  <pgsphere-obsplan_image_id>

3- Chandra CFA server:

Chandra CFA TAP server has been adapted (Michael Tibbetts and Janet Evans) to create the ObsLocTAP ivoa.obsplan table to include the future Chandra observations. The service can be found here:

  • https://cda.cfa.harvard.edu/cxctap/
This is the first X-Ray observatories service implemented (similar services are already in on development for XMM-Newton and NuStar) what will allow the preparation of coordinated observations for these three observatories in a short-term.

Similar queries to Integral TAP server could be instantiated, e.g.:

Discover observations for between 31/05/2020 and 08/09/2020:
SELECT * FROM ivoa.obsplan WHERE t_min > 59000 AND t_max < 59100  

This service has the caveat of not supporting geometrical operators yet (although this is not needed for most of the use cases)

Service can be tested on any TAP client application (e.g. TopCat) or directly in your browser using TapHandle:


4- TOBY- Client Application

Also a client has been implemented by ESA (Emilio Salazar), located at:

This graphical client application combines in a calendar view the output of ObsLocTAP servers for Integral, Chandra and the similar to ObsLocTAP servers (NuSTAR and XMM-Newton - in process of adaptation). Also, it shows the Visibility services output (ObjVisSAP) for some missions.

Comments from the IVOA Community during RFC/TCG review period: 2020-06-26 - 2020-09-01

The comments from the TCG members during the RFC/TCG review should be included in the next section.

In order to add a comment to the document, please edit this page and add your comment to the list below in the format used for the example (include your Wiki Name so that authors can contact you for further information). When the author(s) of the document have considered the comment, they will provide a response after the comment.

Additional discussion about any of the comments or responses can be conducted on the WG mailing list. However, please be sure to enter your initial comments here for full consideration in any future revisions of this document

Comments from TCG member during the RFC/TCG Review Period: TCG_start_date - TCG_end_date

WG chairs or vice chairs must read the Document, provide comments if any (including on topics not directly linked to the Group matters) or indicate that they have no comment.

IG chairs or vice chairs are also encouraged to do the same, althought their inputs are not compulsory.

TCG Chair & Vice Chair

Applications Working Group

Data Access Layer Working Group

Data Model Working Group

Grid & Web Services Working Group

Registry Working Group

Semantics Working Group

Summary response

Data Curation & Preservation Interest Group

Education Interest Group

Knowledge Discovery Interest Group

Solar System Interest Group

Theory Interest Group

Time Domain Interest Group


Standards and Processes Committee

TCG Vote : Vote_start_date - Vote_end_date

If you have minor comments (typos) on the last version of the document please indicate it in the Comments column of the table and post them in the TCG comments section above with the date.

Group Yes No Abstain Comments
Topic revision: r11 - 2020-09-07 - JesusSalgado
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