Triple

Target class: Hipparcos catalog entry
Context triple: [HIP 21421, instanceOf, Hipparcos catalog entry]

• A. astronomical catalogue chosen
  An astronomical catalogue is a systematically organized list of celestial objects, typically including their positions, brightness, and other observational properties for scientific reference and study.
• B. deep-sky object catalogue
  A deep-sky object catalogue is a systematically organized list of non-stellar astronomical objects—such as galaxies, nebulae, and star clusters—typically including their positions, classifications, and observational properties.
• C. phase of the Optical Gravitational Lensing Experiment
  A phase of the Optical Gravitational Lensing Experiment is a distinct operational period of the long-term sky survey characterized by specific instrumentation, observational strategies, and scientific objectives for detecting and studying gravitational microlensing and variable astronomical objects.
• D. celestial coordinate system
  A celestial coordinate system is a framework for specifying the positions of objects in the sky using angular measurements relative to defined reference planes and points, such as the celestial equator and poles.
• E. astronomical data archive
  An astronomical data archive is a curated repository that stores, organizes, and provides access to observational and simulated data from astronomical instruments and surveys for scientific analysis and long-term preservation.
• F. None of above.