nyx_space/od/groundpnt/
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::ephemerides::EphemerisError;
20use anise::errors::{AlmanacError, AlmanacResult};
21use anise::math::interpolation::InterpolationError;
22use anise::prelude::{Frame, Orbit};
23use hifitime::{Epoch, TimeUnits};
24use indexmap::IndexSet;
25use rand_pcg::Pcg64Mcg;
26use snafu::ResultExt;
27
28use crate::State;
29use crate::md::prelude::Traj;
30use crate::od::TrackingDevice;
31use crate::od::groundpnt::GroundAsset;
32use crate::od::interlink::InterlinkTxSpacecraft;
33use crate::od::msr::MeasurementType;
34use crate::od::prelude::{Measurement, ODError};
35use crate::od::{ODAlmanacSnafu, ODTrajSnafu};
36
37impl TrackingDevice<GroundAsset> for InterlinkTxSpacecraft {
38    fn name(&self) -> String {
39        self.traj.name.clone().unwrap_or("unnamed".to_string())
40    }
41
42    fn measurement_types(&self) -> &IndexSet<MeasurementType> {
43        &self.measurement_types
44    }
45
46    fn location(&self, epoch: Epoch, frame: Frame, almanac: &Almanac) -> AlmanacResult<Orbit> {
47        match self.traj.at(epoch) {
48            Ok(state) => almanac.transform_to(state.orbit, frame, self.ab_corr),
49            Err(_) => Err(AlmanacError::Ephemeris {
50                action: "computing location from Interlink",
51                source: Box::new(EphemerisError::EphemInterpolation {
52                    source: InterpolationError::MissingInterpolationData { epoch },
53                }),
54            }),
55        }
56    }
57
58    fn measure(
59        &mut self,
60        epoch: Epoch,
61        traj: &Traj<GroundAsset>,
62        rng: Option<&mut Pcg64Mcg>,
63        almanac: &Almanac,
64    ) -> Result<Option<Measurement>, ODError> {
65        match self.integration_time {
66            Some(integration_time) => {
67                // TODO: This should support measurement alignment
68                // If out of traj bounds, return None, else the whole strand is rejected.
69                let rx_0 = match traj.at(epoch - integration_time).context(ODTrajSnafu {
70                    details: format!(
71                        "fetching state {epoch} at start of ground station integration time {integration_time}"
72                    ),
73                }) {
74                    Ok(rx) => rx,
75                    Err(_) => return Ok(None),
76                };
77
78                let rx_1 = match traj.at(epoch).context(ODTrajSnafu {
79                    details: format!(
80                        "fetching state {epoch} at end of ground station integration time"
81                    ),
82                }) {
83                    Ok(rx) => rx,
84                    Err(_) => return Ok(None),
85                };
86
87                // Start of integration time
88                let msr_t0_opt = self.measure_instantaneous(rx_0, None, almanac)?;
89
90                // End of integration time
91                let msr_t1_opt = self.measure_instantaneous(rx_1, None, almanac)?;
92
93                if let Some(msr_t0) = msr_t0_opt {
94                    if let Some(msr_t1) = msr_t1_opt {
95                        // Line of sight in both cases
96
97                        // Noises are computed at the midpoint of the integration time.
98                        let noises = self.noises(epoch - integration_time * 0.5, rng)?;
99
100                        let mut msr = Measurement::new(
101                            "GroundAsset".to_string(),
102                            epoch + noises[0].seconds(),
103                        );
104
105                        for (ii, msr_type) in self.measurement_types.iter().enumerate() {
106                            let msr_value_0 = msr_t0.data[msr_type];
107                            let msr_value_1 = msr_t1.data[msr_type];
108
109                            let msr_value =
110                                (msr_value_1 + msr_value_0) * 0.5 + noises[ii + 1] / 2.0_f64.sqrt();
111                            msr.push(*msr_type, msr_value);
112                        }
113
114                        Ok(Some(msr))
115                    } else {
116                        Ok(None)
117                    }
118                } else {
119                    Ok(None)
120                }
121            }
122            None => self.measure_instantaneous(
123                traj.at(epoch).context(ODTrajSnafu {
124                    details: "fetching state for instantaneous measurement".to_string(),
125                })?,
126                rng,
127                almanac,
128            ),
129        }
130    }
131
132    /// Returns the Range and Doppler from pnt vehicle to ground asset (i.e. the opposed AER range and doppler data.)
133    fn measure_instantaneous(
134        &mut self,
135        rx: GroundAsset,
136        rng: Option<&mut Pcg64Mcg>,
137        almanac: &Almanac,
138    ) -> Result<Option<Measurement>, ODError> {
139        let pnt_veh = self.traj.at(rx.epoch()).context(ODTrajSnafu {
140            details: format!("fetching state {} for interlink", rx.epoch()),
141        })?;
142
143        let asset_loc = rx.to_location();
144
145        let aer = almanac
146            .azimuth_elevation_range_sez_from_location(pnt_veh.orbit, asset_loc, None, None)
147            .context(ODAlmanacSnafu {
148                action: "transforming receiver to transmitter frame",
149            })?;
150
151        if aer.elevation_above_mask_deg() < 0.0 {
152            Ok(None)
153        } else {
154            let noises = self.noises(rx.epoch, rng)?;
155
156            let mut msr =
157                Measurement::new("GroundAsset".to_string(), rx.epoch + noises[0].seconds());
158
159            // Range is a norm, so we don't flip the sign. But the rate depends on the direction of travel, so we do indeed flip its sign.
160            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
161                let msr_value = match *msr_type {
162                    MeasurementType::Range => aer.range_km,
163                    MeasurementType::Doppler => aer.range_rate_km_s,
164                    // Or return an error for unsupported types
165                    _ => unreachable!("unsupported measurement type for interlink: {:?}", msr_type),
166                } + noises[ii + 1];
167                msr.push(*msr_type, msr_value);
168            }
169
170            Ok(Some(msr))
171        }
172    }
173
174    /// Returns the measurement noise of this ground station.
175    ///
176    /// # Methodology
177    /// Noises are modeled using a [StochasticNoise] process, defined by the sigma on the turn-on bias and on the steady state noise.
178    /// The measurement noise is computed assuming that all measurements are independent variables, i.e. the measurement matrix is
179    /// 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
180    /// second item is the Doppler noise (in km/s), set to the square of the steady state sigma of that Gauss Markov process.
181    fn measurement_covar(&self, msr_type: MeasurementType, epoch: Epoch) -> Result<f64, ODError> {
182        let stochastics =
183            self.stochastic_noises
184                .as_ref()
185                .ok_or_else(|| ODError::NoiseNotConfigured {
186                    kind: "stochastic noises for interlink transmitter".to_string(),
187                })?;
188
189        Ok(stochastics
190            .get(&msr_type)
191            .ok_or(ODError::NoiseNotConfigured {
192                kind: format!("{msr_type:?}"),
193            })?
194            .covariance(epoch))
195    }
196
197    fn measurement_bias(&self, msr_type: MeasurementType, _epoch: Epoch) -> Result<f64, ODError> {
198        let stochastics = self.stochastic_noises.as_ref().unwrap();
199
200        if let Some(gm) = stochastics
201            .get(&msr_type)
202            .ok_or(ODError::NoiseNotConfigured {
203                kind: format!("{msr_type:?}"),
204            })?
205            .bias
206        {
207            Ok(gm.constant.unwrap_or(0.0))
208        } else {
209            Ok(0.0)
210        }
211    }
212}
nyx_space/od/groundpnt/trk_device.rs

nyx_space/od/groundpnt/
trk_device.rs
