Guides

Guides show how to use the common DiffOrb APIs for one task at a time. Use them when you want concrete examples for creating objects, loading data, propagating orbits, generating ephemerides, or running solvers.

Concepts explain the models behind those tasks. Workflows show full runs.

Time And Epochs

• Configure Earth Orientation Data: check the local EOP file, refresh it when network access is available, and verify one modern epoch.
• Create And Convert Time Objects: build Time objects from calendar dates or split Julian dates, inspect their fields, batch them, and shift them by uniform intervals.
• Convert Between UTC, TT, TDB, UT1: derive the main time-scale views from one epoch, measure offsets, and apply the topocentric TDB - TT correction.

Ephemerides And Bodies

• Load SPK Kernels And Query Major Bodies: configure the default ephemeris, inspect available body names, and query major-body states.
• Create And Convert Keplerian Elements: build KepElement objects, convert them to Cartesian states, and round-trip them back to elements.
• Create A SmallBody From State Or Elements: initialize SmallBody objects from Cartesian states or Keplerian elements and verify the stored canonical orbit.

States And Frames

• Build State From Cartesian Data: create a State from canonical Cartesian data and inspect its stacked array form.
• Transform State Between Frames: convert a State between reference frames and roundtrip the result.

Observer Geometry

• Get Earth Rotation Quantities And Matrices: read polar-motion coordinates, the Earth Rotation Angle, the CIO-based matrices, and the equinox-based matrices from one Time object.
• Create A Ground Site And Get Its GCRS State: create a ground observer from codes, geodetic coordinates, or geocentric constants and evaluate it in canonical GCRS.
• Create A Space Site And Reuse Its GCRS State: create a space observer from a canonical GCRS state and reuse it through the site API.

Dynamics And Propagation

• Configure Force Models And Dynamic Systems: build the standard major-body system, the extended system with asteroid perturbers, or one custom ForceModel with explicit gravity and non-gravitational terms.
• Propagate A SmallBody And Evaluate Dense Trajectories: propagate one SmallBody, check trajectory coverage, and query interpolated BCRS states inside the solved interval.

Observation Products

• Get Optical Outputs In Observer And Vector Modes: sample observer-mode optical outputs and vector-mode relative states from one propagated target, one observer, and one observation-time grid.
• Get Radar Outputs In Monostatic And Bistatic Geometry: sample 2025 BC10 radar delay and Doppler predictions at DSS-14 and compare them with JPL radar astrometry records.

Observation Preparation

• Load Online Observations From MPC And JPL: fetch online observations and save them to a local ADES PSV file.
• Load Local ADES Observations: reopen that PSV file or another local ADES PSV file and inspect the mixed rows.
• Choose And Override Observation Weights: compare VFCC17 with reported ADES uncertainties and add row-level overrides.
• Inspect Optical Debias Corrections: run the Eggl model and inspect row-level optical corrections.

Orbit Determination

• Solve Initial Orbit From Optical Observations: run IODSolver on optical observations and inspect the initial guess.
• Configure Outlier Rejection For Orbit Determination: configure automatic chi-square rejection and manual inlier/outlier settings.
• Run Differential Correction From An Initial Orbit: run one DCSolver solve from an initial guess and inspect convergence.
• Run Integrated Orbit Determination With ODSolver: run IOD and staged differential correction through one solver, including IODStrategy and DCStrategy.
• Inspect Differential Correction Results: read the fitted orbit, RMS, covariance status, and inlier counts.
• Analyze Residuals By Station And Tracklet: join residuals back to observations and analyze station or tracklet diagnostics.
• Estimate Nongravitational Parameters In Differential Correction: add estimated force-model parameters and read them from DCResult.
• Estimate A Comet Photocenter Offset In Differential Correction: estimate a global optical S0 parameter and read it from DCResult.

Shared Patterns

• Use Batch Inputs Across DiffOrb APIs: build batched objects, inspect batch shapes, slice rows, and choose point-wise or grid calls.

When To Leave The Guides

• Go back to Concepts when you need the rules behind a task.
• Move forward to Workflows when you need a multi-stage workflow such as ephemeris generation or orbit determination.
• Use the API pages when you need exact arguments and return fields.