moira

Frame-Specific Positions Backend Standard

Version: 0.1 Date: 2026-06-14 Status: implemented backend standard for P-GAP-01 REST admission Scope: heliocentric, planetocentric, SSB, and received-light position products

This standard governs the non-geocentric position products that are public in the Python engine, Moira facade, and admitted P-GAP-01 REST routes:

• moira.planets.heliocentric_planet_at
• moira.planets.all_heliocentric_at
• moira.planetocentric.planetocentric_at
• moira.planetocentric.all_planetocentric_at
• moira.ssb.ssb_position_at
• moira.ssb.all_ssb_positions_at
• moira.light_cone.received_light_at
• moira.light_cone.all_received_light_at

The existing /v1/positions/* REST family is geocentric/topocentric and sky projection oriented. It must not be silently stretched to mean all possible position centers. P-GAP-01 exists because these frame-specific products have different centers, correction semantics, and result vessels.

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1. Governing Objects

Frame-specific position transport must preserve four distinct governing objects.

Heliocentric Position

Owned by:

• moira.planets.HeliocentricData
• moira.planets.heliocentric_planet_at
• moira.planets.all_heliocentric_at

Meaning:

• body position measured from the Sun
• true-of-date ecliptic orientation
• precession and nutation applied
• no geocentric observer
• not meaningful for Sun or Moon

Admitted result fields:

• name
• longitude
• latitude
• distance
• distance_au
• speed
• retrograde
• sign
• sign_symbol
• sign_degree

Planetocentric Position

Owned by:

• moira.planetocentric.PlanetocentricData
• moira.planetocentric.planetocentric_at
• moira.planetocentric.all_planetocentric_at

Meaning:

• target position measured from the center of a named observer body
• geometric ecliptic position
• true-of-date ecliptic orientation
• precession and nutation applied
• light-time not corrected
• observer and target must differ

Admitted result fields:

• observer
• name
• longitude
• latitude
• distance
• distance_au
• speed
• retrograde
• sign
• sign_symbol
• sign_degree

SSB Position

Owned by:

• moira.ssb.SSBPosition
• moira.ssb.ssb_position_at
• moira.ssb.all_ssb_positions_at

Meaning:

• body position measured from the Solar System Barycenter
• BCRS/SSB-origin product projected into true-of-date ecliptic orientation
• geometric product
• light-time not corrected
• Sun has non-zero SSB position

Admitted result fields:

• name
• longitude
• latitude
• distance
• distance_au
• speed
• retrograde
• sign
• sign_symbol
• sign_degree

Received-Light Position

Owned by:

• moira.light_cone.ReceivedLightPosition
• moira.light_cone.received_light_at
• moira.light_cone.all_received_light_at

Meaning:

• explicit light-cone comparison at Earth receipt time
• apparent ecliptic position from the ordinary apparent pipeline
• geometric ecliptic position at the same JD
• light-travel duration and emission JD preserved
• physical bodies only

Admitted result fields:

• name
• apparent_longitude
• apparent_latitude
• geometric_longitude
• geometric_latitude
• longitude_displacement
• distance_km
• distance_au
• light_travel_days
• light_travel_minutes
• emission_jd
• speed
• retrograde
• sign
• sign_symbol
• sign_degree

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2. Body Admission

REST transport must preserve each engine surface’s native body policy.

Heliocentric:

• default body list excludes Sun and Moon
• requests for Sun or Moon must be rejected

Planetocentric:

• observer must be in VALID_OBSERVER_BODIES
• target must be in VALID_OBSERVER_BODIES
• observer and target must differ
• default target list excludes the observer

SSB:

• body must be in SSB_BODIES
• Sun and Earth are meaningful products here when kernel support exists

Received light:

• body must be in RECEIVED_LIGHT_BODIES
• computed points such as nodes and Lilith are not admitted

Transport must cap bulk requests. Initial REST admission should allow at most 12 bodies per request, matching the existing server tendency for bounded chart/position products.

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3. Time And Reader Policy

All P-GAP-01 requests must use timezone-aware datetimes at the REST boundary.

Transport must report:

• requested datetime
• normalized UTC datetime
• jd_ut
• jd_tt
• delta_t_seconds
• source module
• engine entrypoint
• reader owner

The server should use the existing engine reader binding from the application dependency context. It must not create a new global kernel state or mutate kernel paths.

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4. Frame And Correction Truth

Every response must state its center and correction semantics.

Heliocentric:

• center: sun
• frame: true_of_date_ecliptic
• correction model: geometric_heliocentric_precession_nutation
• light-time corrected: false
• apparent-sky corrected: false

Planetocentric:

• center: requested observer body
• frame: true_of_date_ecliptic
• correction model: geometric_planetocentric_precession_nutation
• light-time corrected: false
• apparent-sky corrected: false

SSB:

• center: solar_system_barycenter
• frame: true_of_date_ecliptic
• correction model: geometric_barycentric_precession_nutation
• light-time corrected: false
• apparent-sky corrected: false

Received light:

• center: earth
• frame: true_of_date_ecliptic
• correction model: apparent_received_light_compared_to_same_time_geometric
• light-time corrected: true
• apparent-sky corrected: true for apparent fields
• geometric comparison included: true

Transport must not describe heliocentric, planetocentric, or SSB products as observed/apparent positions. Transport must not describe received-light output as simply “geometric” because its primary apparent fields come from the ordinary apparent pipeline.

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5. Route Admission Boundary

P-GAP-01 admits a bounded synchronous REST family under:

• /v1/positions/frame/*

The route family should include:

• POST /v1/positions/frame/heliocentric
• POST /v1/positions/frame/planetocentric
• POST /v1/positions/frame/ssb
• POST /v1/positions/frame/received-light

Each route should accept:

• one timezone-aware datetime
• optional bounded body list, except planetocentric also requires observer
• output controls limited to fields that do not change computation semantics

Route names must not imply that these are replacements for:

• /v1/positions/planet
• /v1/positions/sky
• /v1/chart

They are specialized frame products.

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6. Non-Goals

P-GAP-01 does not admit:

• arbitrary centers beyond the named engine support
• topocentric planetocentric observation
• light-time iteration for planetocentric products
• occultation/eclipsing products from non-Earth observers
• rendered charts
• dense ephemeris tables
• transit/search products such as heliocentric conjunctions
• kernel path mutation or manifest loading
• small-body expansion beyond what the owning engine functions support

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7. Verification Requirements

Before REST admission, tests must cover:

• route registration
• successful heliocentric request
• successful planetocentric request
• successful SSB request
• successful received-light request
• bulk body cap
• timezone-aware datetime rejection for all routes
• heliocentric rejection of Sun and Moon
• planetocentric rejection of invalid observer
• planetocentric rejection of observer equal to target
• SSB rejection of unsupported body
• received-light rejection of nodes or nonphysical points
• provenance and frame/correction truth for every route
• no hidden kernel mutation

At least one test should assert that received-light output preserves both apparent and geometric longitudes and the light-travel fields.

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8. Admission Decision

P-GAP-01 is admitted through the bounded /v1/positions/frame/* REST family.

Recommended status:

• admitted

Reason:

• the engine surfaces are already explicit and facade-visible
• the computational vessels preserve center/frame truth
• the main risk is transport semantic collapse, not missing computation

The transport implementation is named in docs/architecture/P-GAP-01_FRAME_SPECIFIC_POSITIONS_TRANSPORT_DESIGN.md. It remains a server adapter over existing engine/facade computations.

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