Implement IAU1980 nutation (#23)

Implements nutation calculation for the IAU 1980 model, and provides the skeleton to calculate nutation for any given model, pending their implementation.

Cargo.toml

@@ -15,7 +15,5 @@ authors = ["Helge Eichhorn and the lox-space contributors"]
 
 [workspace.dependencies]
 lox_core = { path = "./crates/lox_core" }
-lox_io = { path = "./crates/lox_io" }
-lox_py = { path = "./crates/lox_py" }
 thiserror = "1.0"
 

crates/lox-space/examples/iss.rs

@@ -16,7 +16,10 @@ fn main() {
     let velocity = DVec3::new(-660.415582, 5495.938726, -5303.093233) * 1e-3;
     let iss = Cartesian::new(epoch, Earth, position, velocity);
 
-    println!("ISS Orbit for Julian Day {}", iss.epoch().j2000());
+    println!(
+        "ISS Orbit for Julian Day {}",
+        iss.epoch().days_since_j2000(),
+    );
     println!("=============================");
     println!("Semi-major axis: {:.3} km", iss.semi_major());
     println!("Eccentricity: {:.6}", iss.eccentricity());

crates/lox_core/src/bodies.rs

@@ -15,6 +15,7 @@ mod generated;
 pub use generated::*;
 
 pub mod fundamental;
+pub mod nutation;
 
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[repr(transparent)]