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::{ResultExt, ensure};
27
28use crate::Spacecraft;
29use crate::State;
30use crate::io::ConfigRepr;
31use crate::md::Trajectory;
32use crate::md::prelude::Traj;
33use crate::od::TrackingDevice;
34use crate::od::msr::MeasurementType;
35use crate::od::noise::StochasticNoise;
36use crate::od::prelude::{Measurement, NoiseNotConfiguredSnafu, ODError};
37use crate::od::{ODAlmanacSnafu, ODTrajSnafu};
38
39// Defines a (transmitter) spacecraft capable of inter-satellite links.
40// NOTE: There is _no_ `InterlinkRxSpacecraft`, instead you must independently build their trajectories and provide them to the InterlinkArcSim.
41#[derive(Clone, Debug)]
42pub struct InterlinkTxSpacecraft {
43    /// Trajectory of the transmitter spacercaft
44    pub traj: Trajectory,
45    /// Measurement types supported by the link
46    pub measurement_types: IndexSet<MeasurementType>,
47    /// Integration time used to generate the measurement.
48    pub integration_time: Option<Duration>,
49    pub timestamp_noise_s: Option<StochasticNoise>,
50    pub stochastic_noises: Option<IndexMap<MeasurementType, StochasticNoise>>,
51    /// Aberration correction used in the interlink
52    pub ab_corr: Option<Aberration>,
53}
54
55impl InterlinkTxSpacecraft {
56    /// Returns the noises for all measurement types configured for this ground station at the provided epoch, timestamp noise is the first entry.
57    pub fn noises(
58        &mut self,
59        epoch: Epoch,
60        rng: Option<&mut Pcg64Mcg>,
61    ) -> Result<Vec<f64>, ODError> {
62        let mut noises = vec![0.0; self.measurement_types.len() + 1];
63
64        if let Some(rng) = rng {
65            ensure!(
66                self.stochastic_noises.is_some(),
67                NoiseNotConfiguredSnafu {
68                    kind: "ground station stochastics".to_string(),
69                }
70            );
71            // Add the timestamp noise first
72
73            if let Some(mut timestamp_noise) = self.timestamp_noise_s {
74                noises[0] = timestamp_noise.sample(epoch, rng);
75            }
76
77            let stochastics = self.stochastic_noises.as_mut().unwrap();
78
79            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
80                noises[ii + 1] = stochastics
81                    .get_mut(msr_type)
82                    .ok_or(ODError::NoiseNotConfigured {
83                        kind: format!("{msr_type:?}"),
84                    })?
85                    .sample(epoch, rng);
86            }
87        }
88
89        Ok(noises)
90    }
91}
92
93impl TrackingDevice<Spacecraft> for InterlinkTxSpacecraft {
94    fn name(&self) -> String {
95        self.traj.name.clone().unwrap_or("unnamed".to_string())
96    }
97
98    fn measurement_types(&self) -> &IndexSet<MeasurementType> {
99        &self.measurement_types
100    }
101
102    fn location(&self, epoch: Epoch, frame: Frame, almanac: &Almanac) -> AlmanacResult<Orbit> {
103        almanac.transform_to(self.traj.at(epoch).unwrap().orbit, frame, self.ab_corr)
104    }
105
106    fn measure(
107        &mut self,
108        epoch: Epoch,
109        traj: &Traj<Spacecraft>,
110        rng: Option<&mut Pcg64Mcg>,
111        almanac: &Almanac,
112    ) -> Result<Option<Measurement>, ODError> {
113        match self.integration_time {
114            Some(integration_time) => {
115                // TODO: This should support measurement alignment
116                // If out of traj bounds, return None, else the whole strand is rejected.
117                let rx_0 = match traj.at(epoch - integration_time).context(ODTrajSnafu {
118                    details: format!(
119                        "fetching state {epoch} at start of ground station integration time {integration_time}"
120                    ),
121                }) {
122                    Ok(rx) => rx,
123                    Err(_) => return Ok(None),
124                };
125
126                let rx_1 = match traj.at(epoch).context(ODTrajSnafu {
127                    details: format!(
128                        "fetching state {epoch} at end of ground station integration time"
129                    ),
130                }) {
131                    Ok(rx) => rx,
132                    Err(_) => return Ok(None),
133                };
134
135                // Start of integration time
136                let msr_t0_opt = self.measure_instantaneous(rx_0, None, almanac)?;
137
138                // End of integration time
139                let msr_t1_opt = self.measure_instantaneous(rx_1, None, almanac)?;
140
141                if let Some(msr_t0) = msr_t0_opt {
142                    if let Some(msr_t1) = msr_t1_opt {
143                        // Line of sight in both cases
144
145                        // Noises are computed at the midpoint of the integration time.
146                        let noises = self.noises(epoch - integration_time * 0.5, rng)?;
147
148                        let mut msr = Measurement::new(
149                            <InterlinkTxSpacecraft as TrackingDevice<Spacecraft>>::name(self),
150                            epoch + noises[0].seconds(),
151                        );
152
153                        for (ii, msr_type) in self.measurement_types.iter().enumerate() {
154                            let msr_value_0 = msr_t0.data[msr_type];
155                            let msr_value_1 = msr_t1.data[msr_type];
156
157                            let msr_value =
158                                (msr_value_1 + msr_value_0) * 0.5 + noises[ii + 1] / 2.0_f64.sqrt();
159                            msr.push(*msr_type, msr_value);
160                        }
161
162                        Ok(Some(msr))
163                    } else {
164                        Ok(None)
165                    }
166                } else {
167                    Ok(None)
168                }
169            }
170            None => self.measure_instantaneous(
171                traj.at(epoch).context(ODTrajSnafu {
172                    details: "fetching state for instantaneous measurement".to_string(),
173                })?,
174                rng,
175                almanac,
176            ),
177        }
178    }
179
180    fn measure_instantaneous(
181        &mut self,
182        rx: Spacecraft,
183        rng: Option<&mut Pcg64Mcg>,
184        almanac: &Almanac,
185    ) -> Result<Option<Measurement>, ODError> {
186        let observer = self.traj.at(rx.epoch()).context(ODTrajSnafu {
187            details: format!("fetching state {} for interlink", rx.epoch()),
188        })?;
189
190        let is_obstructed = almanac
191            .line_of_sight_obstructed(observer.orbit, rx.orbit, observer.orbit.frame, self.ab_corr)
192            .context(ODAlmanacSnafu {
193                action: "computing line of sight",
194            })?;
195
196        if is_obstructed {
197            Ok(None)
198        } else {
199            // Convert the receiver into the body fixed transmitter frame.
200            let rx_in_tx_frame = almanac
201                .transform_to(rx.orbit, observer.orbit.frame, self.ab_corr)
202                .context(ODAlmanacSnafu {
203                    action: "transforming receiver to transmitter frame",
204                })?;
205
206            let rho_tx_frame = rx_in_tx_frame.radius_km - observer.orbit.radius_km;
207
208            // Compute the range-rate \dot ρ. Note that rx_in_tx_frame is already the relative velocity of rx wrt tx!
209            let range_rate_km_s =
210                rho_tx_frame.dot(&rx_in_tx_frame.velocity_km_s) / rho_tx_frame.norm();
211
212            let noises = self.noises(observer.epoch(), rng)?;
213
214            let mut msr = Measurement::new(
215                <InterlinkTxSpacecraft as TrackingDevice<Spacecraft>>::name(self),
216                rx.orbit.epoch + noises[0].seconds(),
217            );
218
219            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
220                let msr_value = match *msr_type {
221                    MeasurementType::Range => rho_tx_frame.norm(),
222                    MeasurementType::Doppler => range_rate_km_s,
223                    // Or return an error for unsupported types
224                    _ => unreachable!("unsupported measurement type for interlink: {:?}", msr_type),
225                } + noises[ii + 1];
226                msr.push(*msr_type, msr_value);
227            }
228
229            Ok(Some(msr))
230        }
231    }
232
233    /// Returns the measurement noise of this ground station.
234    ///
235    /// # Methodology
236    /// Noises are modeled using a [StochasticNoise] process, defined by the sigma on the turn-on bias and on the steady state noise.
237    /// The measurement noise is computed assuming that all measurements are independent variables, i.e. the measurement matrix is
238    /// 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
239    /// second item is the Doppler noise (in km/s), set to the square of the steady state sigma of that Gauss Markov process.
240    fn measurement_covar(&self, msr_type: MeasurementType, epoch: Epoch) -> Result<f64, ODError> {
241        let stochastics = self.stochastic_noises.as_ref().unwrap();
242
243        Ok(stochastics
244            .get(&msr_type)
245            .ok_or(ODError::NoiseNotConfigured {
246                kind: format!("{msr_type:?}"),
247            })?
248            .covariance(epoch))
249    }
250
251    fn measurement_bias(&self, msr_type: MeasurementType, _epoch: Epoch) -> Result<f64, ODError> {
252        let stochastics = self.stochastic_noises.as_ref().unwrap();
253
254        if let Some(gm) = stochastics
255            .get(&msr_type)
256            .ok_or(ODError::NoiseNotConfigured {
257                kind: format!("{msr_type:?}"),
258            })?
259            .bias
260        {
261            Ok(gm.constant.unwrap_or(0.0))
262        } else {
263            Ok(0.0)
264        }
265    }
266}
267
268impl Serialize for InterlinkTxSpacecraft {
269    fn serialize<S>(&self, _serializer: S) -> Result<S::Ok, S::Error>
270    where
271        S: serde::Serializer,
272    {
273        unimplemented!("interlink spacecraft cannot be serialized")
274    }
275}
276
277impl<'de> Deserialize<'de> for InterlinkTxSpacecraft {
278    fn deserialize<D>(_deserializer: D) -> Result<Self, D::Error>
279    where
280        D: serde::Deserializer<'de>,
281    {
282        unimplemented!("interlink spacecraft cannot be deserialized")
283    }
284}
285
286impl ConfigRepr for InterlinkTxSpacecraft {}
nyx_space/od/interlink/trk_device.rs

nyx_space/od/interlink/
trk_device.rs
