nyx_space/od/interlink/
trk_device.rs

1/*
2    Nyx, blazing fast astrodynamics
3    Copyright (C) 2018-onwards Christopher Rabotin <christopher.rabotin@gmail.com>
4
5    This program is free software: you can redistribute it and/or modify
6    it under the terms of the GNU Affero General Public License as published
7    by the Free Software Foundation, either version 3 of the License, or
8    (at your option) any later version.
9
10    This program is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13    GNU Affero General Public License for more details.
14
15    You should have received a copy of the GNU Affero General Public License
16    along with this program.  If not, see <https://www.gnu.org/licenses/>.
17*/
18use anise::almanac::Almanac;
19use anise::astro::Aberration;
20use anise::errors::AlmanacResult;
21use anise::prelude::{Frame, Orbit};
22use hifitime::{Duration, Epoch, TimeUnits};
23use indexmap::{IndexMap, IndexSet};
24use rand_pcg::Pcg64Mcg;
25use serde::{Deserialize, Serialize};
26use snafu::{ensure, ResultExt};
27
28use crate::io::ConfigRepr;
29use crate::md::prelude::Traj;
30use crate::md::Trajectory;
31use crate::od::msr::MeasurementType;
32use crate::od::noise::StochasticNoise;
33use crate::od::prelude::{Measurement, NoiseNotConfiguredSnafu, ODError};
34use crate::od::TrackingDevice;
35use crate::od::{ODAlmanacSnafu, ODTrajSnafu};
36use crate::Spacecraft;
37use crate::State;
38
39use std::sync::Arc;
40
41// Defines a (transmitter) spacecraft capable of inter-satellite links.
42// NOTE: There is _no_ `InterlinkRxSpacecraft`, instead you must independently build their trajectories and provide them to the InterlinkArcSim.
43#[derive(Clone, Debug)]
44pub struct InterlinkTxSpacecraft {
45    /// Trajectory of the transmitter spacercaft
46    pub traj: Trajectory,
47    /// Measurement types supported by the link
48    pub measurement_types: IndexSet<MeasurementType>,
49    /// Integration time used to generate the measurement.
50    pub integration_time: Option<Duration>,
51    pub timestamp_noise_s: Option<StochasticNoise>,
52    pub stochastic_noises: Option<IndexMap<MeasurementType, StochasticNoise>>,
53    /// Aberration correction used in the interlink
54    pub ab_corr: Option<Aberration>,
55}
56
57impl InterlinkTxSpacecraft {
58    /// Returns the noises for all measurement types configured for this ground station at the provided epoch, timestamp noise is the first entry.
59    fn noises(&mut self, epoch: Epoch, rng: Option<&mut Pcg64Mcg>) -> Result<Vec<f64>, ODError> {
60        let mut noises = vec![0.0; self.measurement_types.len() + 1];
61
62        if let Some(rng) = rng {
63            ensure!(
64                self.stochastic_noises.is_some(),
65                NoiseNotConfiguredSnafu {
66                    kind: "ground station stochastics".to_string(),
67                }
68            );
69            // Add the timestamp noise first
70
71            if let Some(mut timestamp_noise) = self.timestamp_noise_s {
72                noises[0] = timestamp_noise.sample(epoch, rng);
73            }
74
75            let stochastics = self.stochastic_noises.as_mut().unwrap();
76
77            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
78                noises[ii + 1] = stochastics
79                    .get_mut(msr_type)
80                    .ok_or(ODError::NoiseNotConfigured {
81                        kind: format!("{msr_type:?}"),
82                    })?
83                    .sample(epoch, rng);
84            }
85        }
86
87        Ok(noises)
88    }
89}
90
91impl TrackingDevice<Spacecraft> for InterlinkTxSpacecraft {
92    fn name(&self) -> String {
93        self.traj.name.clone().unwrap_or("unnamed".to_string())
94    }
95
96    fn measurement_types(&self) -> &IndexSet<MeasurementType> {
97        &self.measurement_types
98    }
99
100    fn location(&self, epoch: Epoch, frame: Frame, almanac: Arc<Almanac>) -> AlmanacResult<Orbit> {
101        almanac.transform_to(self.traj.at(epoch).unwrap().orbit, frame, self.ab_corr)
102    }
103
104    fn measure(
105        &mut self,
106        epoch: Epoch,
107        traj: &Traj<Spacecraft>,
108        rng: Option<&mut Pcg64Mcg>,
109        almanac: Arc<Almanac>,
110    ) -> Result<Option<Measurement>, ODError> {
111        match self.integration_time {
112            Some(integration_time) => {
113                // TODO: This should support measurement alignment
114                // If out of traj bounds, return None, else the whole strand is rejected.
115                let rx_0 = match traj.at(epoch - integration_time).context(ODTrajSnafu {
116                    details: format!(
117                        "fetching state {epoch} at start of ground station integration time {integration_time}"
118                    ),
119                }) {
120                    Ok(rx) => rx,
121                    Err(_) => return Ok(None),
122                };
123
124                let rx_1 = match traj.at(epoch).context(ODTrajSnafu {
125                    details: format!(
126                        "fetching state {epoch} at end of ground station integration time"
127                    ),
128                }) {
129                    Ok(rx) => rx,
130                    Err(_) => return Ok(None),
131                };
132
133                // Start of integration time
134                let msr_t0_opt = self.measure_instantaneous(rx_0, None, almanac.clone())?;
135
136                // End of integration time
137                let msr_t1_opt = self.measure_instantaneous(rx_1, None, almanac.clone())?;
138
139                if let Some(msr_t0) = msr_t0_opt {
140                    if let Some(msr_t1) = msr_t1_opt {
141                        // Line of sight in both cases
142
143                        // Noises are computed at the midpoint of the integration time.
144                        let noises = self.noises(epoch - integration_time * 0.5, rng)?;
145
146                        let mut msr = Measurement::new(self.name(), epoch + noises[0].seconds());
147
148                        for (ii, msr_type) in self.measurement_types.iter().enumerate() {
149                            let msr_value_0 = msr_t0.data[msr_type];
150                            let msr_value_1 = msr_t1.data[msr_type];
151
152                            let msr_value =
153                                (msr_value_1 + msr_value_0) * 0.5 + noises[ii + 1] / 2.0_f64.sqrt();
154                            msr.push(*msr_type, msr_value);
155                        }
156
157                        Ok(Some(msr))
158                    } else {
159                        Ok(None)
160                    }
161                } else {
162                    Ok(None)
163                }
164            }
165            None => self.measure_instantaneous(
166                traj.at(epoch).context(ODTrajSnafu {
167                    details: "fetching state for instantaneous measurement".to_string(),
168                })?,
169                rng,
170                almanac,
171            ),
172        }
173    }
174
175    fn measure_instantaneous(
176        &mut self,
177        rx: Spacecraft,
178        rng: Option<&mut Pcg64Mcg>,
179        almanac: Arc<Almanac>,
180    ) -> Result<Option<Measurement>, ODError> {
181        let observer = self.traj.at(rx.epoch()).context(ODTrajSnafu {
182            details: format!("fetching state {} for interlink", rx.epoch()),
183        })?;
184
185        let is_obstructed = almanac
186            .line_of_sight_obstructed(observer.orbit, rx.orbit, observer.orbit.frame, self.ab_corr)
187            .context(ODAlmanacSnafu {
188                action: "computing line of sight",
189            })?;
190
191        if is_obstructed {
192            Ok(None)
193        } else {
194            // Convert the receiver into the body fixed transmitter frame.
195            let rx_in_tx_frame = almanac
196                .transform_to(rx.orbit, observer.orbit.frame, self.ab_corr)
197                .context(ODAlmanacSnafu {
198                    action: "transforming receiver to transmitter frame",
199                })?;
200
201            let rho_tx_frame = rx_in_tx_frame.radius_km - observer.orbit.radius_km;
202
203            // Compute the range-rate \dot ρ. Note that rx_in_tx_frame is already the relative velocity of rx wrt tx!
204            let range_rate_km_s =
205                rho_tx_frame.dot(&rx_in_tx_frame.velocity_km_s) / rho_tx_frame.norm();
206
207            let noises = self.noises(observer.epoch(), rng)?;
208
209            let mut msr = Measurement::new(self.name(), rx.orbit.epoch + noises[0].seconds());
210
211            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
212                let msr_value = match *msr_type {
213                    MeasurementType::Range => rho_tx_frame.norm(),
214                    MeasurementType::Doppler => range_rate_km_s,
215                    // Or return an error for unsupported types
216                    _ => unreachable!("unsupported measurement type for interlink: {:?}", msr_type),
217                } + noises[ii + 1];
218                msr.push(*msr_type, msr_value);
219            }
220
221            Ok(Some(msr))
222        }
223    }
224
225    /// Returns the measurement noise of this ground station.
226    ///
227    /// # Methodology
228    /// Noises are modeled using a [StochasticNoise] process, defined by the sigma on the turn-on bias and on the steady state noise.
229    /// The measurement noise is computed assuming that all measurements are independent variables, i.e. the measurement matrix is
230    /// a diagonal matrix. The first item in the diagonal is the range noise (in km), set to the square of the steady state sigma. The
231    /// second item is the Doppler noise (in km/s), set to the square of the steady state sigma of that Gauss Markov process.
232    fn measurement_covar(&self, msr_type: MeasurementType, epoch: Epoch) -> Result<f64, ODError> {
233        let stochastics = self.stochastic_noises.as_ref().unwrap();
234
235        Ok(stochastics
236            .get(&msr_type)
237            .ok_or(ODError::NoiseNotConfigured {
238                kind: format!("{msr_type:?}"),
239            })?
240            .covariance(epoch))
241    }
242
243    fn measurement_bias(&self, msr_type: MeasurementType, _epoch: Epoch) -> Result<f64, ODError> {
244        let stochastics = self.stochastic_noises.as_ref().unwrap();
245
246        if let Some(gm) = stochastics
247            .get(&msr_type)
248            .ok_or(ODError::NoiseNotConfigured {
249                kind: format!("{msr_type:?}"),
250            })?
251            .bias
252        {
253            Ok(gm.constant.unwrap_or(0.0))
254        } else {
255            Ok(0.0)
256        }
257    }
258}
259
260impl Serialize for InterlinkTxSpacecraft {
261    fn serialize<S>(&self, _serializer: S) -> Result<S::Ok, S::Error>
262    where
263        S: serde::Serializer,
264    {
265        unimplemented!("interlink spacecraft cannot be serialized")
266    }
267}
268
269impl<'de> Deserialize<'de> for InterlinkTxSpacecraft {
270    fn deserialize<D>(_deserializer: D) -> Result<Self, D::Error>
271    where
272        D: serde::Deserializer<'de>,
273    {
274        unimplemented!("interlink spacecraft cannot be deserialized")
275    }
276}
277
278impl ConfigRepr for InterlinkTxSpacecraft {}
nyx_space/od/interlink/trk_device.rs

nyx_space/od/interlink/
trk_device.rs
