About the Transit and Ephemeris Service

Welcome to the Transit and Ephemeris Service

The Transit and Ephemeris Service (or "Transit Service") is a planning tool for astronomers who want to know when scientific events, such as transits and orbital phase quadratures, will be happening, and when they can be observed. The predictions are based on information contained in the NASA Exoplanet Archive from the published literature, or input by users.

A redesigned and enhanced version of the service was released in March 2018, and TESS Objects of Interest (TOIs) were added in February 2020. The current iteration accommodates several new features, including:

  • Access to more data sets, including K2 Candidates,
  • the ability to upload multiple files, each with up to 100 object names,
  • the ability to load parameters from specific references,
  • the addition of new observation planning parameters,
  • the ability to specify settings for ephemeris selection, algorithm preference, and target visibility constraints.

Support for TESS Objects of Interest (TOIs) was added in February 2020 and interactive transit visibility plots were added in July 2022.

Feature or Option Description
Input Table Selection User may select multiple data sets:
  • Planetary Systems (All, Transiting Planets, Radial Velocity Planets)
  • Kepler Objects of Interest—Cumulative (Confirmed, Candidates, and False Positives)
  • K2 Candidates (Confirmed, Candidates, and False Positives)
  • TESS Objects of Interest
Input File Upload File upload accepts multiple files, each with up to 100 object names.
Access to Published Parameter Sets All parameter sets from the literature that have been added to the archive can be browsed and loaded.
Most Precise Ephemeris Selection Users can now have the service determine which solution for a planet prediction is most precise and display only that result. This is useful for systems that have more than one orbital solution for a planet.
Prediction Algorithms

Users may specify whether to use Orbital Elements (formerly Epoch of Periastron), Transit Ephemeris, or both algorithms. Note that Transit Ephemeris is the new name for Transit Midpoint and Orbital Elements was previously known as Epoch of Periastron. The underlying algorithms have not changed. See Transit Algorithms for details.

Note the No Planet Radius option is now applied automatically, when necessary.

Altitude and Twilight Cut-offs (Target Visibility Settings) Users may specify minimum altitude (or maximum airmass) and the minimum angle of the Sun below the horizon for which the target is observable (for Civil, Nautical, or Astronomical Twilight). See Refining Transit Settings.
Ingress and Egress Times Ingress and egress times are calculated with and without padding for uncertainties. The new padded parameters are now called 1σ Event Window Start and 1σ Event Window End. See Transit Algorithms and Definitions of Transit Parameters for details.
Target Rise and Set Times

Query results include these values. See Definitions of Transit Parameters.

Approximate Twilight Start and End Times Query results include these values. See Definitions of Transit Parameters.
Duration Observable Periods Query results now include the duration of observability before, during, and outside a transit. See Definitions of Transit Parameters.
Fraction of Transit Observable; Baseline Fraction Observable Query results include these values. See Definitions of Transit Parameters.
Target Photometry Query results include these (V, J, H, Ks, Gaia), when available. See Definitions of Transit Parameters.
Transit Depths (Measured and Calculated) Query results include these values, when available. See Definitions of Transit Parameters.

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Last updated: 30 June 2022