ProcessNoise

Struct ProcessNoise 

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pub struct ProcessNoise<A: DimName>{
    pub start_time: Option<Epoch>,
    pub local_frame: Option<LocalFrame>,
    pub disable_time: Duration,
    pub init_epoch: Option<Epoch>,
    pub prev_epoch: Option<Epoch>,
    /* private fields */
}

Fields§

§start_time: Option<Epoch>

Time at which this SNC starts to become applicable

§local_frame: Option<LocalFrame>

Specify the local frame of this SNC

§disable_time: Duration

Enables state noise compensation (process noise) only be applied if the time between measurements is less than the disable_time

§init_epoch: Option<Epoch>§prev_epoch: Option<Epoch>

Implementations§

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impl<A: DimName> ProcessNoise<A>

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pub fn from_diagonal(disable_time: Duration, values: &[f64]) -> Self

Initialize a state noise compensation structure from the diagonal values

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pub fn with_start_time( disable_time: Duration, values: &[f64], start_time: Epoch, ) -> Self

Initialize an SNC with a time at which it should start

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pub fn with_decay( disable_time: Duration, initial_snc: &[f64], decay_constants_s: &[f64], ) -> Self

Initialize an exponentially decaying SNC with initial SNC and decay constants. Decay constants in seconds since start of the tracking pass.

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pub fn to_matrix(&self, epoch: Epoch) -> Option<OMatrix<f64, A, A>>

Returns the SNC matrix (not incl. Gamma matrix approximation) at the provided Epoch. May be None if:

  1. Start time of this matrix is after epoch
  2. Time between epoch and previous epoch (set in the Kalman filter!) is longer than disabling time
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impl ProcessNoise<Const<3>>

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pub fn from_velocity_km_s( velocity_noise: &[f64; 3], noise_duration: Duration, disable_time: Duration, local_frame: Option<LocalFrame>, ) -> Self

Initialize the process noise from velocity errors over time

Examples found in repository?
examples/04_lro_od/main.rs (lines 268-273)
34fn main() -> Result<(), Box<dyn Error>> {
35    pel::init();
36
37    // ====================== //
38    // === ALMANAC SET UP === //
39    // ====================== //
40
41    // Dynamics models require planetary constants and ephemerides to be defined.
42    // Let's start by grabbing those by using ANISE's MetaAlmanac.
43
44    let data_folder: PathBuf = [env!("CARGO_MANIFEST_DIR"), "examples", "04_lro_od"]
45        .iter()
46        .collect();
47
48    let meta = data_folder.join("lro-dynamics.dhall");
49
50    // Load this ephem in the general Almanac we're using for this analysis.
51    let mut almanac = MetaAlmanac::new(meta.to_string_lossy().to_string())
52        .map_err(Box::new)?
53        .process(true)
54        .map_err(Box::new)?;
55
56    let mut moon_pc = almanac.planetary_data.get_by_id(MOON)?;
57    moon_pc.mu_km3_s2 = 4902.74987;
58    almanac.planetary_data.set_by_id(MOON, moon_pc)?;
59
60    let mut earth_pc = almanac.planetary_data.get_by_id(EARTH)?;
61    earth_pc.mu_km3_s2 = 398600.436;
62    almanac.planetary_data.set_by_id(EARTH, earth_pc)?;
63
64    // Save this new kernel for reuse.
65    // In an operational context, this would be part of the "Lock" process, and should not change throughout the mission.
66    almanac
67        .planetary_data
68        .save_as(&data_folder.join("lro-specific.pca"), true)?;
69
70    // Lock the almanac (an Arc is a read only structure).
71    let almanac = Arc::new(almanac);
72
73    // Orbit determination requires a Trajectory structure, which can be saved as parquet file.
74    // In our case, the trajectory comes from the BSP file, so we need to build a Trajectory from the almanac directly.
75    // To query the Almanac, we need to build the LRO frame in the J2000 orientation in our case.
76    // Inspecting the LRO BSP in the ANISE GUI shows us that NASA has assigned ID -85 to LRO.
77    let lro_frame = Frame::from_ephem_j2000(-85);
78
79    // To build the trajectory we need to provide a spacecraft template.
80    let sc_template = Spacecraft::builder()
81        .mass(Mass::from_dry_and_prop_masses(1018.0, 900.0)) // Launch masses
82        .srp(SRPData {
83            // SRP configuration is arbitrary, but we will be estimating it anyway.
84            area_m2: 3.9 * 2.7,
85            coeff_reflectivity: 0.96,
86        })
87        .orbit(Orbit::zero(MOON_J2000)) // Setting a zero orbit here because it's just a template
88        .build();
89    // Now we can build the trajectory from the BSP file.
90    // We'll arbitrarily set the tracking arc to 24 hours with a five second time step.
91    let traj_as_flown = Traj::from_bsp(
92        lro_frame,
93        MOON_J2000,
94        almanac.clone(),
95        sc_template,
96        5.seconds(),
97        Some(Epoch::from_str("2024-01-01 00:00:00 UTC")?),
98        Some(Epoch::from_str("2024-01-02 00:00:00 UTC")?),
99        Aberration::LT,
100        Some("LRO".to_string()),
101    )?;
102
103    println!("{traj_as_flown}");
104
105    // ====================== //
106    // === MODEL MATCHING === //
107    // ====================== //
108
109    // Set up the spacecraft dynamics.
110
111    // Specify that the orbital dynamics must account for the graviational pull of the Earth and the Sun.
112    // The gravity of the Moon will also be accounted for since the spaceraft in a lunar orbit.
113    let mut orbital_dyn = OrbitalDynamics::point_masses(vec![EARTH, SUN, JUPITER_BARYCENTER]);
114
115    // We want to include the spherical harmonics, so let's download the gravitational data from the Nyx Cloud.
116    // We're using the GRAIL JGGRX model.
117    let mut jggrx_meta = MetaFile {
118        uri: "http://public-data.nyxspace.com/nyx/models/Luna_jggrx_1500e_sha.tab.gz".to_string(),
119        crc32: Some(0x6bcacda8), // Specifying the CRC32 avoids redownloading it if it's cached.
120    };
121    // And let's download it if we don't have it yet.
122    jggrx_meta.process(true)?;
123
124    // Build the spherical harmonics.
125    // The harmonics must be computed in the body fixed frame.
126    // We're using the long term prediction of the Moon principal axes frame.
127    let moon_pa_frame = MOON_PA_FRAME.with_orient(31008);
128    let sph_harmonics = Harmonics::from_stor(
129        almanac.frame_from_uid(moon_pa_frame)?,
130        HarmonicsMem::from_shadr(&jggrx_meta.uri, 80, 80, true)?,
131    );
132
133    // Include the spherical harmonics into the orbital dynamics.
134    orbital_dyn.accel_models.push(sph_harmonics);
135
136    // We define the solar radiation pressure, using the default solar flux and accounting only
137    // for the eclipsing caused by the Earth and Moon.
138    // Note that by default, enabling the SolarPressure model will also enable the estimation of the coefficient of reflectivity.
139    let srp_dyn = SolarPressure::new(vec![EARTH_J2000, MOON_J2000], almanac.clone())?;
140
141    // Finalize setting up the dynamics, specifying the force models (orbital_dyn) separately from the
142    // acceleration models (SRP in this case). Use `from_models` to specify multiple accel models.
143    let dynamics = SpacecraftDynamics::from_model(orbital_dyn, srp_dyn);
144
145    println!("{dynamics}");
146
147    // Now we can build the propagator.
148    let setup = Propagator::default_dp78(dynamics.clone());
149
150    // For reference, let's build the trajectory with Nyx's models from that LRO state.
151    let (sim_final, traj_as_sim) = setup
152        .with(*traj_as_flown.first(), almanac.clone())
153        .until_epoch_with_traj(traj_as_flown.last().epoch())?;
154
155    println!("SIM INIT:  {:x}", traj_as_flown.first());
156    println!("SIM FINAL: {sim_final:x}");
157    // Compute RIC difference between SIM and LRO ephem
158    let sim_lro_delta = sim_final
159        .orbit
160        .ric_difference(&traj_as_flown.last().orbit)?;
161    println!("{traj_as_sim}");
162    println!(
163        "SIM v LRO - RIC Position (m): {:.3}",
164        sim_lro_delta.radius_km * 1e3
165    );
166    println!(
167        "SIM v LRO - RIC Velocity (m/s): {:.3}",
168        sim_lro_delta.velocity_km_s * 1e3
169    );
170
171    traj_as_sim.ric_diff_to_parquet(
172        &traj_as_flown,
173        "./04_lro_sim_truth_error.parquet",
174        ExportCfg::default(),
175    )?;
176
177    // ==================== //
178    // === OD SIMULATOR === //
179    // ==================== //
180
181    // After quite some time trying to exactly match the model, we still end up with an oscillatory difference on the order of 150 meters between the propagated state
182    // and the truth LRO state.
183
184    // Therefore, we will actually run an estimation from a dispersed LRO state.
185    // The sc_seed is the true LRO state from the BSP.
186    let sc_seed = *traj_as_flown.first();
187
188    // Load the Deep Space Network ground stations.
189    // Nyx allows you to build these at runtime but it's pretty static so we can just load them from YAML.
190    let ground_station_file: PathBuf = [
191        env!("CARGO_MANIFEST_DIR"),
192        "examples",
193        "04_lro_od",
194        "dsn-network.yaml",
195    ]
196    .iter()
197    .collect();
198
199    let devices = GroundStation::load_named(ground_station_file)?;
200
201    let mut proc_devices = devices.clone();
202
203    // Increase the noise in the devices to accept more measurements.
204    for gs in proc_devices.values_mut() {
205        if let Some(noise) = &mut gs
206            .stochastic_noises
207            .as_mut()
208            .unwrap()
209            .get_mut(&MeasurementType::Range)
210        {
211            *noise.white_noise.as_mut().unwrap() *= 3.0;
212        }
213    }
214
215    // Typical OD software requires that you specify your own tracking schedule or you'll have overlapping measurements.
216    // Nyx can build a tracking schedule for you based on the first station with access.
217    let trkconfg_yaml: PathBuf = [
218        env!("CARGO_MANIFEST_DIR"),
219        "examples",
220        "04_lro_od",
221        "tracking-cfg.yaml",
222    ]
223    .iter()
224    .collect();
225
226    let configs: BTreeMap<String, TrkConfig> = TrkConfig::load_named(trkconfg_yaml)?;
227
228    // Build the tracking arc simulation to generate a "standard measurement".
229    let mut trk = TrackingArcSim::<Spacecraft, GroundStation>::with_seed(
230        devices.clone(),
231        traj_as_flown.clone(),
232        configs,
233        123, // Set a seed for reproducibility
234    )?;
235
236    trk.build_schedule(almanac.clone())?;
237    let arc = trk.generate_measurements(almanac.clone())?;
238    // Save the simulated tracking data
239    arc.to_parquet_simple("./04_lro_simulated_tracking.parquet")?;
240
241    // We'll note that in our case, we have continuous coverage of LRO when the vehicle is not behind the Moon.
242    println!("{arc}");
243
244    // Now that we have simulated measurements, we'll run the orbit determination.
245
246    // ===================== //
247    // === OD ESTIMATION === //
248    // ===================== //
249
250    let sc = SpacecraftUncertainty::builder()
251        .nominal(sc_seed)
252        .frame(LocalFrame::RIC)
253        .x_km(0.5)
254        .y_km(0.5)
255        .z_km(0.5)
256        .vx_km_s(5e-3)
257        .vy_km_s(5e-3)
258        .vz_km_s(5e-3)
259        .build();
260
261    // Build the filter initial estimate, which we will reuse in the filter.
262    let mut initial_estimate = sc.to_estimate()?;
263    initial_estimate.covar *= 3.0;
264
265    println!("== FILTER STATE ==\n{sc_seed:x}\n{initial_estimate}");
266
267    // Build the SNC in the Moon J2000 frame, specified as a velocity noise over time.
268    let process_noise = ProcessNoise3D::from_velocity_km_s(
269        &[1e-10, 1e-10, 1e-10],
270        1 * Unit::Hour,
271        10 * Unit::Minute,
272        None,
273    );
274
275    println!("{process_noise}");
276
277    // We'll set up the OD process to reject measurements whose residuals are move than 3 sigmas away from what we expect.
278    let odp = SpacecraftKalmanOD::new(
279        setup,
280        KalmanVariant::ReferenceUpdate,
281        Some(ResidRejectCrit::default()),
282        proc_devices,
283        almanac.clone(),
284    )
285    .with_process_noise(process_noise);
286
287    let od_sol = odp.process_arc(initial_estimate, &arc)?;
288
289    let final_est = od_sol.estimates.last().unwrap();
290
291    println!("{final_est}");
292
293    let ric_err = traj_as_flown
294        .at(final_est.epoch())?
295        .orbit
296        .ric_difference(&final_est.orbital_state())?;
297    println!("== RIC at end ==");
298    println!("RIC Position (m): {:.3}", ric_err.radius_km * 1e3);
299    println!("RIC Velocity (m/s): {:.3}", ric_err.velocity_km_s * 1e3);
300
301    println!(
302        "Num residuals rejected: #{}",
303        od_sol.rejected_residuals().len()
304    );
305    println!(
306        "Percentage within +/-3: {}",
307        od_sol.residual_ratio_within_threshold(3.0).unwrap()
308    );
309    println!("Ratios normal? {}", od_sol.is_normal(None).unwrap());
310
311    od_sol.to_parquet("./04_lro_od_results.parquet", ExportCfg::default())?;
312
313    // In our case, we have the truth trajectory from NASA.
314    // So we can compute the RIC state difference between the real LRO ephem and what we've just estimated.
315    // Export the OD trajectory first.
316    let od_trajectory = od_sol.to_traj()?;
317    // Build the RIC difference.
318    od_trajectory.ric_diff_to_parquet(
319        &traj_as_flown,
320        "./04_lro_od_truth_error.parquet",
321        ExportCfg::default(),
322    )?;
323
324    Ok(())
325}

Trait Implementations§

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impl<A: Clone + DimName> Clone for ProcessNoise<A>

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fn clone(&self) -> ProcessNoise<A>

Returns a duplicate of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<A> Debug for ProcessNoise<A>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more
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impl<A> Display for ProcessNoise<A>

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<A> !Freeze for ProcessNoise<A>

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impl<A> !RefUnwindSafe for ProcessNoise<A>

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impl<A> !Send for ProcessNoise<A>

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impl<A> !Sync for ProcessNoise<A>

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impl<A> !Unpin for ProcessNoise<A>

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impl<A> !UnwindSafe for ProcessNoise<A>

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impl<T> Any for T
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