From c5d3ec8dbcb279f8dd4cdb0a547707ed05a7a6e9 Mon Sep 17 00:00:00 2001
From: Christopher Rabotin <christopher.rabotin@gmail.com>
Date: Tue, 14 Jan 2025 15:06:58 -0600
Subject: [PATCH] Impl Mul and MulAssign for stochastic noise

---
 src/od/noise/gauss_markov.rs           | 22 +++++++++++++---------
 src/od/noise/mod.rs                    | 22 ++++++++++++++++++++++
 src/od/noise/white.rs                  | 18 ++++++++++++++++++
 tests/orbit_determination/simulator.rs | 10 +++++++++-
 4 files changed, 62 insertions(+), 10 deletions(-)

diff --git a/src/od/noise/gauss_markov.rs b/src/od/noise/gauss_markov.rs
index 96b51b63..26433b02 100644
--- a/src/od/noise/gauss_markov.rs
+++ b/src/od/noise/gauss_markov.rs
@@ -23,7 +23,7 @@ use rand::Rng;
 use rand_distr::Normal;
 use serde_derive::{Deserialize, Serialize};
 use std::fmt;
-use std::ops::Mul;
+use std::ops::{Mul, MulAssign};
 
 use super::Stochastics;
 
@@ -153,14 +153,18 @@ impl Mul<f64> for GaussMarkov {
     type Output = Self;
 
     /// Scale the Gauss Markov process by a constant, maintaining the same time constant.
-    fn mul(self, rhs: f64) -> Self::Output {
-        Self {
-            tau: self.tau,
-            process_noise: self.process_noise * rhs,
-            constant: None,
-            init_sample: None,
-            prev_epoch: None,
-        }
+    fn mul(mut self, rhs: f64) -> Self::Output {
+        self.process_noise *= rhs;
+        self.constant = None;
+        self.init_sample = None;
+        self.prev_epoch = None;
+        self
+    }
+}
+
+impl MulAssign<f64> for GaussMarkov {
+    fn mul_assign(&mut self, rhs: f64) {
+        *self = *self * rhs;
     }
 }
 
diff --git a/src/od/noise/mod.rs b/src/od/noise/mod.rs
index b32d7332..ed78a417 100644
--- a/src/od/noise/mod.rs
+++ b/src/od/noise/mod.rs
@@ -27,6 +27,7 @@ use rand_pcg::Pcg64Mcg;
 use serde_derive::{Deserialize, Serialize};
 use std::error::Error;
 use std::fs::File;
+use std::ops::{Mul, MulAssign};
 use std::path::Path;
 use std::sync::Arc;
 
@@ -212,6 +213,27 @@ impl StochasticNoise {
     }
 }
 
+impl Mul<f64> for StochasticNoise {
+    type Output = Self;
+
+    fn mul(mut self, rhs: f64) -> Self::Output {
+        if let Some(mut wn) = &mut self.white_noise {
+            wn *= rhs;
+        }
+        if let Some(mut gm) = &mut self.bias {
+            gm *= rhs;
+        }
+
+        self
+    }
+}
+
+impl MulAssign<f64> for StochasticNoise {
+    fn mul_assign(&mut self, rhs: f64) {
+        *self = *self * rhs;
+    }
+}
+
 pub struct StochasticState {
     pub run: u32,
     pub dt_s: f64,
diff --git a/src/od/noise/white.rs b/src/od/noise/white.rs
index 305d1189..a8cea983 100644
--- a/src/od/noise/white.rs
+++ b/src/od/noise/white.rs
@@ -16,6 +16,8 @@
     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */
 
+use std::ops::{Mul, MulAssign};
+
 use anise::constants::SPEED_OF_LIGHT_KM_S;
 use hifitime::{Duration, Epoch};
 use rand::Rng;
@@ -77,6 +79,22 @@ impl Stochastics for WhiteNoise {
     }
 }
 
+impl Mul<f64> for WhiteNoise {
+    type Output = Self;
+
+    /// Scale the white noise sigmas by a constant.
+    fn mul(mut self, rhs: f64) -> Self::Output {
+        self.sigma *= rhs;
+        self
+    }
+}
+
+impl MulAssign<f64> for WhiteNoise {
+    fn mul_assign(&mut self, rhs: f64) {
+        *self = *self * rhs;
+    }
+}
+
 #[cfg(test)]
 mod ut_wn {
     use hifitime::{Epoch, TimeUnits};
diff --git a/tests/orbit_determination/simulator.rs b/tests/orbit_determination/simulator.rs
index b03d1d73..277702a8 100644
--- a/tests/orbit_determination/simulator.rs
+++ b/tests/orbit_determination/simulator.rs
@@ -216,7 +216,7 @@ fn continuous_tracking_cov_test(tracking_data: TrackingDataArc) {
 fn od_with_modulus_cov_test(
     spacecraft: Spacecraft,
     tracking_data: TrackingDataArc,
-    devices: BTreeMap<String, GroundStation>,
+    mut devices: BTreeMap<String, GroundStation>,
     trajectory: Trajectory,
     almanac: Arc<Almanac>,
 ) {
@@ -227,6 +227,14 @@ fn od_with_modulus_cov_test(
     arc.set_moduli(MeasurementType::Range, jpl_dsn_code_length_km);
     arc.apply_moduli();
 
+    // Increase the noise on the OD process
+    // Set a bias instead of assuming a modulus.
+    for (_, device) in &mut devices {
+        for (_, stochastics) in device.stochastic_noises.as_mut().unwrap().iter_mut() {
+            *stochastics *= 2.0;
+        }
+    }
+
     let uncertainty = SpacecraftUncertainty::builder()
         .nominal(spacecraft)
         .frame(LocalFrame::RIC)