Collaborative Occultation Resources and Archive (CORA)

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Information and Credits

Codes and Abbreviations: CORA

The CORA (Collaborative Occultation Resources and Archive) system is maintained by Mike Kretlow (IAA-CSIC). CORA provides predictions of stellar occultations by solar system objects / small bodies. Occultation observations are archived here and are also provided with some visualizing and analyzing capabilities. For more details refer to this presentation.

Usage and Tips
Note that some functionalities (e.g. display of station coordinates or download of observations etc.) requires to login with a Cora account with the right permissions for that functionality

Data Sources and Credits
Data and services used here are (from): CDS, MPC, JPL, Lowell Observatory, Gaia collaboration, USNO, ARI Heidelberg, ESA, IERS, DAMIT, SiMDA, 3D Asteroid Catalogue.

This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Occultation observations: We acknowledge the contributions of several thousands observers who have provided the observations in the data set. Most of those observers are affiliated with one or more of (i) European Asteroidal Occultation Network (EAON) · (ii) International Occultation Timing Association (IOTA) · (iii) International Occultation Timing Association - European Section (IOTA-ES) · (iv) Japanese Occultation Information Network (JOIN) · (v) Trans Tasman Occultation Alliance (TTOA).

We acknowledge the tremendous work by many local and global data collectors and validators and the Occult software by Dave Herald often used for this work (see also Herald et al. 2020), and for providing the observation data (1958-) to the community.

We acknowledge the data collection and validation of European observations (1997-2022) by Eric Frappa (, and for providing the observation data to the community.

Additional references:
  • Herald, D. et al. (2020), Precise astrometry and diameters of asteroids from occultations - a data set of observations and their interpretation. MNRAS, 499, 3, ADS: 2020MNRAS.499.4570H.
  • Ďurech, J. et al. (2010), DAMIT: a database of asteroid models, A&A, 513, A46, ADS Bibcode: 2010A&A...513A..46D.
  • Gaia Collaboration et al. (2018): Gaia Data Release 2. Summary of the contents and survey properties. ADS Bibcode: 2018A&A...616A...1G
  • Mignard et al. (2018): Gaia Data Release 2. The celestial reference frame (Gaia-CRF2). ADS Bibcode: 2018A&A...616A..14G
  • Gaia Collaboration et al. (2021): Gaia Early Data Release 3. Summary of the contents and survey properties. ADS Bibcode: 2021A&A...649A...1G
Software used : Python, NumPy, SciPy, Pandas, Astropy, Matplotlib, Django, JavaScript, SQLite, Leaflet and Plugins, OpenStreetMap, NOVAS, SOFA, Linux, Git, GNU Fortran, Povray, and some more open source projects and contributions.

List of codes / abbreviations used by CORA

WGS84Geod.Datumlon,lat,alt in WGS84 system
WSGeod.Datumlon,lat,alt in WGS84 system
CCDMethodCCD or CMOS (digital) imaging
VIDMethodVideo (analog) recording
VISMethodVisual observation
PHGMethodPhotographic recording
PHMMethodPhotometer recording
DRSMethodDrift-Scan Method
O+ObservationOccultation detection positive. Secondary / multiple events : O+1, O+2, ...
O-ObservationOccultation detection negative
O?ObservationOccultation detection unknown or uncertain. Secondary / multiple events : O?1, O?2, ...
NDObservationNo data obtained (weather, technical problems, etc.)
MOpticsMirror optics
LOpticsLens optics
EOpticsNaked Eye
TOpticsTelescope (not further specified)
TSRCTime SourceTime Source
GPSTime SourceGPS receiver (no more info and/or see comments, e.g. for 1PPS)
NTPTime SourceNetwork Time Protocol (no more info and/or see comments)
PHONETime SourcePhone time signal (wired phone)
RADTime SourceRadio time signal (no more info or intermittent radio controled clock)
LACTime SourceLocal atomic clock
UT1TimingsStart of Observation
UT2TimingsTime of Disappearance D
UT2ETimingsError (sigma) of UT2
UT3TimingsTime of Reappearance R
UT3ETimingsError (sigma) of UT3
UT4TimingsEnd of Observation