ephemeris

Target and system membership

Record authoritative target identifiers and whether each target denotes an individual body, spacecraft or barycentre.

1. Which identifiers resolve the represented targets, and does each denote a body centre, spacecraft or system barycentre? definition
2. Which requested targets could be confused with these identifiers but are not represented? boundary

Origin, observer and quantities

Record the state origin or observer, its defining information, and the available state quantities.

1. Relative to which centre or observer are position, velocity, direction and distance expressed? definition
2. If an observer-specific result is requested, which site coordinates or observer trajectory must be supplied? action

Epoch semantics

Record how epochs identify instants and whether reported times refer to observation, emission or another declared event.

1. Which time scale and encoding define an input epoch, and what instant does an output timestamp denote? definition
2. Which conversion data or conventions are required to interpret a user's requested time correctly? action

Supported evaluation domain

Record coverage per target and quantity, gaps, evaluator requirements and the treatment of interval boundaries.

1. What intervals are supported for each target and quantity, including gaps and endpoint inclusion? boundary
2. How are intermediate epochs evaluated, and what response is required when a request would extrapolate beyond coverage? action

Reference frame definition

Record frame identity, coordinate representation, units and any time-dependent orientation conventions.

1. Which frame, axes, coordinate representation and units define each reported quantity? definition
2. Which orientation data and epoch conventions are necessary to transform these states into the requested frame? action

Correction chain

Record the meaning of apparent quantities and the individual corrections already applied.

1. Are the quantities geometric or apparent, and which light-time, aberration, deflection or atmospheric corrections are declared? definition
2. Which corrections must an agent apply or avoid applying again for the intended observer and use? action

Underlying solution

Record documented derivation and distinguish fitted, predicted and transformed content where the provider supports that distinction.

1. Which named solution, observations or upstream ephemeris produced these states, and where is that derivation documented? provenance
2. Which intervals or targets have different derivation assumptions or prediction status? boundary

Reproducible state request

Record release identity, evaluator and dependency versions, query settings and any supersession notice.

1. Which artifact or service release, evaluator, dependencies and query settings identify the result reproducibly? provenance
2. Has the provider superseded or withdrawn this solution, and which uses require migration rather than historical reproduction? action

Qualified error claims

Record accuracy evidence with its target, interval, quantity, reference and statistical interpretation.

1. What error bounds, uncertainty estimates or validation residuals are documented, with which units and statistical meaning? measurement
2. Which targets, intervals and quantities do those claims cover, and do they include interpolation and transformation effects? boundary

Request fitness and disposition

Record the requested tolerance and decide whether to proceed, qualify the result or obtain another ephemeris.

1. What position, angular or timing tolerance does the proposed use require, and can the available evidence support it? measurement
2. When coverage, conventions or accuracy evidence are insufficient, should the agent reject the request, return an explicitly qualified result or select another ephemeris? action

Kinds and varieties

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Fundamental (dynamical) planetary ephemeris - a numerically integrated, self-consistent solar-system solution (JPL DE, IMCCE INPOP, IAA RAS EPM) from which other products are derived.
• Analytical series ephemeris - closed-form trigonometric expansions of coordinates (VSOP, Éphéméride Lunaire Parisienne).
• Apparent or astrometric observational ephemeris - right ascension, declination and related quantities for a stated equinox, as used by observers and printed almanacs.
• GNSS broadcast ephemeris - satellite-specific orbital and clock parameters in the real-time navigation message, valid only for a few hours.
• Precise GNSS orbit and clock product - post-processed or real-time precise ephemerides (for example IGS), used instead of the broadcast message.
• Celestial-navigation almanac ephemeris - tabulated Sun, Moon, planet and star data in the Nautical Almanac and Air Almanac.
• Operational spacecraft/satellite ephemeris - binary state files or propagator products (SPICE SPK, mission kernels) used for pointing and navigation.
• Astrological ephemeris - daily tropical or sidereal longitudes of planets and nodes for chart calculation.

1. Which of these kinds and varieties hold for the sense of ephemeris this model covers, and on what evidence? provenance

Identifiers and schemes

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Wikidata item - Q134286 - Concept item for ephemeris as a table or model of celestial positions over time.
• JPL Development Ephemeris designation - DE{nnn} or DE{nnn}/LE{nnn} (for example DE440, DE441, DE405/LE405) - NASA JPL labels for successive numerically integrated planetary and lunar ephemerides.
• IMCCE planetary ephemeris designation - INPOP{version} (for example INPOP10e, INPOP17a) - Paris Observatory / IMCCE numerical planetary ephemeris series.
• IAA RAS planetary ephemeris designation - EPM{year or version} - Institute of Applied Astronomy, Russian Academy of Sciences, Ephemerides of Planets and the Moon.
• GPS navigation-message keys - IODE (Issue of Data, Ephemeris) with toe (time of ephemeris) and GPS week - Identify a specific broadcast-ephemeris fit on a given satellite; mismatch means the set must not be used.
• RINEX navigation file - RINEX navigation/ephemeris files (historically .yyN; mixed GNSS NAV) - International GNSS Service exchange format for broadcast ephemerides recovered from receivers.

1. Which of these identifiers and schemes hold for the sense of ephemeris this model covers, and on what evidence? provenance

Standards and regulation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• IERS Conventions (2010), Technical Note 36 - International Earth Rotation and Reference Systems Service: conventional celestial and terrestrial frames, time scales and relativistic models used with high-precision ephemerides.
• IAU resolutions on time scales and the International Celestial Reference System - International Astronomical Union: TDB as independent argument of barycentric ephemerides; ICRS/ICRF as the reference frame for modern planetary ephemerides.
• IS-GPS-200 (Navstar GPS Space Segment/Navigation User Interfaces) - U.S. Space Force / GPS directorate: binary layout, fit interval and user algorithms for the GPS broadcast ephemeris (and the distinct almanac).
• Corresponding GNSS interface control documents - European Union (Galileo OS SIS ICD), Russian Federation (GLONASS ICD), China (BeiDou ICD), Japan (QZSS): each constellation's broadcast-ephemeris message.
• The Astronomical Almanac / former American Ephemeris and Nautical Almanac conventions - U.S. Naval Observatory with HM Nautical Almanac Office (UK): official apparent ephemerides of Sun, Moon and planets; based on JPL DE200 (1984-2002), DE405 (from 2003), DE440 (by 2024).
• IERS recommendation of JPL DE405 (IERS Conventions 2003 era) - IERS: DE405 as a recommended fundamental ephemeris, without an IAU resolution adopting any single DE.
• RINEX (Receiver Independent Exchange Format) - International GNSS Service: standard files for exchanging recovered broadcast ephemerides.
• NASA NAIF SPICE SPK - NASA Navigation and Ancillary Information Facility: operational kernel format for spacecraft and natural-body ephemerides.

1. Which of these standards and regulation hold for the sense of ephemeris this model covers, and on what evidence? provenance

Real-world use

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• A GNSS receiver decodes each satellite's broadcast ephemeris from subframes 1-3 and computes that satellite's Earth-fixed position and clock at signal time in order to form a position-velocity-time solution.
• Mission navigators and astronomers query JPL HORIZONS or load a DE440/SPK kernel to obtain barycentric states of planets, the Moon and many small bodies.
• The Astronomical Almanac, Connaissance des Temps, Nautical Almanac and Air Almanac publish apparent places used for telescope scheduling, reduction of observations, and backup celestial navigation.
• Spacecraft trajectory design and in-flight navigation are integrated against a chosen fundamental ephemeris (DE, INPOP or EPM); the three are treated as comparably valid.
• Surveyors and geodesists apply precise IGS orbit/clock products rather than broadcast ephemerides when millimetre-to-centimetre positioning is required.
• Astrologers still read daily tropical longitudes from printed or Swiss-Ephemeris-class tables, even though chart software has replaced most hand calculation.
• Printed tables remain a fall-back when electronic computation is unavailable, which is why nautical and astronomical almanacs are still issued.

1. Which of these real-world use hold for the sense of ephemeris this model covers, and on what evidence? provenance

Typical measurements

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• GNSS broadcast-ephemeris fit / validity interval - about 2 hours before and after time of ephemeris (toe); GPS ephemeris commonly treated as valid ~4 hours, versus almanac days to ~90 days - hour
• Broadcast GNSS orbit accuracy (modern GPS) - roughly 1 to 2 - metre
• Broadcast GNSS satellite-clock error - a few - nanosecond
• Fundamental planetary-ephemeris time span (examples) - DE405 about 1600-2201; DE440 file linux_p1550p2650.440 about 1550-2650; DE441 longer for historical work - year (Julian/Gregorian civil)
• Independent time argument of a barycentric planetary ephemeris - TDB or equivalent IAU coordinate time along the integration; historical products used ephemeris time (ET) - second (SI) on the stated scale
• Observer-frame sky position - right ascension 0-24; declination −90 to +90, plus distance when given - hour and degree (plus astronomical unit or kilometre)
• Tabulation step of a printed ephemeris - hours to a month, set by how fast the coordinates change (Moon finer than outer planets) - day

1. Which of these typical measurements hold for the sense of ephemeris this model covers, and on what evidence? provenance

Failure modes and hazards

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• Using a GNSS broadcast ephemeris outside its fit interval, or mixing records with mismatched IODE/toe, yields metre-to-worse satellite positions and a false PVT fix.
• Treating the coarse almanac as an ephemeris in the navigation solution produces kilometre-scale satellite-position error.
• Evaluating a planetary ephemeris on the wrong time scale (UT1 or UTC instead of TT/TDB, or GPS time without leap-second handling) shifts the body by an amount that grows with its angular rate - critical for the Moon and for spacecraft.
• Applying a geometric barycentric state as an apparent geocentric or topocentric place, or using the wrong equinox (B1950, J2000, of-date), mispoints telescopes and misreduces observations.
• For the Moon and near-Earth asteroids, a geocentric ephemeris used as if it were topocentric is geometrically wrong by a large fraction of a degree.
• Secular error from poorly known asteroid masses limits how far a planetary ephemeris can be trusted, which is why DE/INPOP/EPM are re-fit as new data arrive.
• Interpolating a printed table whose step is too coarse relative to the motion introduces errors larger than the underlying theory.
• An unhealthy satellite flag or stale upload left in the broadcast message can be used by a receiver that does not check health, corrupting the navigation solution.
• Celestial-navigation position-line error follows directly from a wrong almanac year, assumed-position interpolation mistake, or outdated v correction.

1. Which of these failure modes and hazards hold for the sense of ephemeris this model covers, and on what evidence? provenance

Regional variation

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• English-language official products are the joint US/UK Astronomical Almanac and the Nautical/Air Almanacs; the underlying dynamical ephemeris has long been a JPL DE.
• In French, éphémérides is the technical term (IMCCE, Connaissance des Temps, INPOP), while éphéméride in ordinary usage also means the day's notable events, unrelated to celestial positions.
• Russia maintains an independent numerical theory (EPM at IAA RAS) and a distinct GLONASS broadcast-ephemeris ICD; France maintains INPOP in parallel with JPL DE.
• Historical Islamic practice named the same kind of table a zīj; Chinese official tables and the Mayan Dresden Codex are independent tabular traditions.
• Each GNSS operator (GPS, Galileo, GLONASS, BeiDou, QZSS, NavIC) broadcasts ephemerides in its own message layout and time scale, even though RINEX is used to archive them in a common form.
• Astrology still publishes national 'ephemerides' (for example Raphael's, Swiss Ephemeris) whose longitudes are not the ICRS apparent places of the Astronomical Almanac.

1. Which of these regional variation hold for the sense of ephemeris this model covers, and on what evidence? provenance

Neighbouring kinds and how to tell them apart

Reported by the breadth pass; each item needs checking against its source before it becomes normative.

• GNSS almanac - The almanac is a coarse, constellation-wide orbit and health set valid for days to months and used only to acquire satellites; the ephemeris is satellite-specific, metre-class, and required for the PVT solution, with a validity of a few hours.
• Orbital elements (Keplerian or osculating) - Six (or a few more) parameters describe an orbit at an epoch; an ephemeris is the time series of states, or a fit that can be evaluated as a function of time, generated from such a theory plus perturbations.
• Two-line element set (TLE) - A TLE is a mean-element card for the SGP4/SDP4 propagator, typically kilometre-class for many objects; a high-precision ephemeris is a numerically integrated or GNSS-fitted state in a stated inertial or ECEF frame.
• Ephemeris time (ET) - ET is a historical uniform time scale (IAU 1952, used as the independent argument of ephemerides until the 1970s-84) and is not the table or model itself; modern arguments are TDB/TCB/TT.
• Star catalogue - A catalogue gives mean places of stars (with proper motion and parallax) at a catalogue epoch; an ephemeris gives the changing position of a solar-system body or satellite. An astrometric ephemeris is deliberately made comparable to an updated catalogue place.
• Nautical or astronomical almanac (the book) - The almanac is a publication that contains ephemerides plus phenomena, sight-reduction data and explanations; the ephemeris is the position-versus-time content inside it.
• Apparent place versus geometric barycentric state - A fundamental ephemeris yields geometric states in the solar-system barycentric frame; an apparent ephemeris has been reduced for light-time, aberration, precession-nutation and the observer's location.
• Ephemera - Ephemera are transient printed items collected as objects; the shared Greek root (daily) is etymological only and does not make a handbill an astronomical ephemeris.

1. Which of these neighbouring kinds and how to tell them apart hold for the sense of ephemeris this model covers, and on what evidence? provenance