dahlend · dahlend · Mar 9, 2026 · Mar 2, 2026 · Mar 2, 2026 · Mar 3, 2026
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -6,6 +6,13 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
+## [Unreleased]
+
+### Added
+
+- Added orbit determination, including Initial Orbit Determination (IOD), State
+  Transition Matrices, and support for non-gravitational parameter fitting.
+
 ## [v2.1.6]
 
 ### Added

diff --git a/Cargo.toml b/Cargo.toml
@@ -12,8 +12,8 @@ license.workspace = true
 repository.workspace = true
 
 [workspace]
-members = ["src/kete_core", "src/kete_stats"]
-default-members = ["src/kete_core", "src/kete_stats"]
+members = ["src/kete_core", "src/kete_stats", "src/kete_fitting"]
+default-members = ["src/kete_core", "src/kete_stats", "src/kete_fitting"]
 
 [workspace.package]
 version = "2.1.6"
@@ -26,9 +26,12 @@ repository = "https://github.com/dahlend/kete"
 [dependencies]
 kete_core = { version = "*", path = "src/kete_core", features=["pyo3", "polars"]}
 kete_stats = {version = "*", path = "src/kete_stats"}
+kete_fitting = {version = "*", path = "src/kete_fitting"}
 pyo3 = { version =  "^0.25.0", features = ["extension-module", "abi3-py39"] }
 serde = { version = "^1.0.203", features = ["derive"] }
 nalgebra = {version = "^0.33.0", features = ["rayon"]}
+rand = "^0.10.0"
+rand_distr = "^0.6.0"
 itertools = "^0.14.0"
 rayon = "^1.10.0"
 sgp4 = "2.2.0"

diff --git a/README.md b/README.md
@@ -13,11 +13,12 @@ See the [arXiv paper](http://arxiv.org/abs/2509.04666).
 [![arXiv](https://img.shields.io/badge/arXiv-2509.04666-00ff00.svg)](http://arxiv.org/abs/2509.04666)
 
 The kete tools are intended to enable the simulation of all-sky surveys of minor
-planets. This includes multi-body physics orbital dynamics, thermal and optical modeling
-of the objects, as well as field of view and light delay corrections. These tools in
-conjunction with the Minor Planet Centers (MPC) database of known asteroids can be used
-to not only plan surveys but can also be used to predict what objects are visible for
-existing or past surveys.
+planets. This includes multi-body physics orbital dynamics, orbit determination and
+fitting (IOD, differential correction, and MCMC posterior sampling), thermal and optical
+modeling of the objects, as well as field of view and light delay corrections. These
+tools in conjunction with the Minor Planet Centers (MPC) database of known asteroids can
+be used to not only plan surveys but can also be used to predict what objects are visible
+for existing or past surveys.
 
 The primary goal for kete is to enable a set of tools that can operate on the entire
 MPC catalog at once, without having to do queries on specific objects. It has been

diff --git a/docs/api/api.rst b/docs/api/api.rst
@@ -11,6 +11,7 @@ API
 
    cache
    conversion
+   fitting
    flux
    fov
    interface

diff --git a/docs/api/fitting.rst b/docs/api/fitting.rst
@@ -0,0 +1,6 @@
+Fitting
+=======
+
+.. automodule:: kete.fitting
+   :members:
+   :inherited-members:
diff --git a/docs/api/observatory.rst b/docs/api/observatory.rst
@@ -25,3 +25,9 @@ PTF
 .. automodule:: kete.ptf
    :members:
    :inherited-members:
+
+SPHEREx
+-------
+.. automodule:: kete.spherex
+   :members:
+   :inherited-members:
diff --git a/docs/api/vector.rst b/docs/api/vector.rst
@@ -6,5 +6,5 @@ Units used throughout kete are distance in au, and time in Days TDB scaled.
 Coordinate frames match the coordinate frames used by cSPICE.
 
 .. automodule:: kete.vector
-   :members: Vector
+   :members:
    :inherited-members:
diff --git a/docs/code_structure.rst b/docs/code_structure.rst
@@ -68,16 +68,33 @@ benefit from orbit computation can be written without having to have Python inst
 It is important to note that if performance is a concern, then removing the Python is an
 important step to get the maximum possible performance.
 
+Kete Fitting
+~~~~~~~~~~~~
+The `kete_fitting` crate contains orbit determination and fitting algorithms, all
+written in Rust without reference to Python. This includes:
+
+- **Initial Orbit Determination (IOD)** -- Statistical ranging over observation
+  pairs followed by two-body scoring to produce candidate orbits from short arcs.
+- **Orbit Fitting** -- Batch least-squares with Levenberg--Marquardt
+  damping, progressive arc expansion, and optional chi-squared outlier rejection.
+- **MCMC Orbit Sampling** -- No-U-Turn Sampler for posterior orbit characterization
+  on short arcs where the Gaussian approximation breaks down.
+- **Lambert Solver** -- Universal-variable Stumpff-function solver for single-
+  revolution Keplerian transfers.
+- **Observation Types** -- Optical (RA/Dec), radar range, and radar range-rate.
+
+Like `kete_core`, this crate can be used from pure Rust without Python.
+
 Core Python Wrapper
 ~~~~~~~~~~~~~~~~~~~
-The Rust library described above then has Python wrappers written over it, allowing
-users to call these compiled tools inside of Python. In order to do this, some
-boiler-plate code is required to glue these independent parts together. This is where
-the `rust` folder inside of kete comes from. Inside of this folder there are rust
-files which are mostly a one-to-one mapping to their respective counterparts inside of
-the `kete_core`. Ideally there should be no 'business' logic contained within these
-wrappers, and they should largely exist to provide convenient mappings from the Python
-concepts to the Rust internal organization.
+The Rust libraries described above then have Python wrappers written over them,
+allowing users to call these compiled tools inside of Python. In order to do this,
+some boiler-plate code is required to glue these independent parts together. This is
+where the `rust` folder inside of kete comes from. Inside of this folder there are
+rust files which are mostly a one-to-one mapping to their respective counterparts
+inside of `kete_core` and `kete_fitting`. Ideally there should be no 'business' logic
+contained within these wrappers, and they should largely exist to provide convenient
+mappings from the Python concepts to the Rust internal organization.
 
 Kete Python
 ~~~~~~~~~~~

diff --git a/docs/data/mcmc_miss_distance.png b/docs/data/mcmc_miss_distance.png
diff --git a/docs/data/mcmc_posterior.png b/docs/data/mcmc_posterior.png
diff --git a/docs/data/mcmc_sky_track.png b/docs/data/mcmc_sky_track.png
diff --git a/docs/index.rst b/docs/index.rst
@@ -6,6 +6,8 @@ surveys of minor planets. Included here are:
 
    - Orbit propagation code capable of accurately calculating the orbits for many
      thousands of minor planets over decades on a laptop.
+   - Orbit determination and fitting, including initial orbit determination (IOD),
+     batch least-squares differential correction, and MCMC posterior sampling.
    - Thermal modeling, including NEATM (Near Earth Asteroid Thermal Model) and the FRM
      (Fast Rotator Model) for asteroids. Including support for non-spherical asteroids.
    - Optical modeling.

diff --git a/docs/tutorials/index.rst b/docs/tutorials/index.rst
@@ -12,5 +12,6 @@ These are more in-depth worked examples.
    neatm
    palomar
    kona
+   mcmc_near_miss
    spherex
    wise
-Original file line number
+Diff line change
@@ Expand Up / @@ -11,6 +11,7 @@ API @@
        cache
        conversion
+       fitting
        flux
        fov
        interface
@@ Expand Down @@