nyx_space/od/ground_station/
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*/
18
19use super::{ODAlmanacSnafu, ODError, ODTrajSnafu, TrackingDevice};
20use crate::md::prelude::{Interpolatable, Traj};
21use crate::od::msr::measurement::Measurement;
22use crate::od::msr::MeasurementType;
23use crate::time::Epoch;
24use crate::Spacecraft;
25use anise::errors::AlmanacResult;
26use anise::frames::Frame;
27use anise::prelude::{Almanac, Orbit};
28use hifitime::TimeUnits;
29use indexmap::IndexSet;
30use log::debug;
31use rand_pcg::Pcg64Mcg;
32use snafu::ResultExt;
33use std::sync::Arc;
34
35use super::GroundStation;
36
37impl TrackingDevice<Spacecraft> for GroundStation {
38    fn measurement_types(&self) -> &IndexSet<MeasurementType> {
39        &self.measurement_types
40    }
41
42    /// Perform a measurement from the ground station to the receiver (rx).
43    fn measure(
44        &mut self,
45        epoch: Epoch,
46        traj: &Traj<Spacecraft>,
47        rng: Option<&mut Pcg64Mcg>,
48        almanac: Arc<Almanac>,
49    ) -> Result<Option<Measurement>, ODError> {
50        match self.integration_time {
51            Some(integration_time) => {
52                // TODO: This should support measurement alignment
53                // If out of traj bounds, return None, else the whole strand is rejected.
54                let rx_0 = match traj.at(epoch - integration_time).context(ODTrajSnafu {
55                    details: format!(
56                        "fetching state {epoch} at start of ground station integration time {integration_time}"
57                    ),
58                }) {
59                    Ok(rx) => rx,
60                    Err(_) => return Ok(None),
61                };
62
63                let rx_1 = match traj.at(epoch).context(ODTrajSnafu {
64                    details: format!(
65                        "fetching state {epoch} at end of ground station integration time"
66                    ),
67                }) {
68                    Ok(rx) => rx,
69                    Err(_) => return Ok(None),
70                };
71
72                let obstructing_body = if !self.frame.ephem_origin_match(rx_0.frame()) {
73                    Some(rx_0.frame())
74                } else {
75                    None
76                };
77
78                let aer_t0 = self
79                    .azimuth_elevation_of(rx_0.orbit, obstructing_body, &almanac)
80                    .context(ODAlmanacSnafu {
81                        action: "computing AER",
82                    })?;
83                let aer_t1 = self
84                    .azimuth_elevation_of(rx_1.orbit, obstructing_body, &almanac)
85                    .context(ODAlmanacSnafu {
86                        action: "computing AER",
87                    })?;
88
89                if aer_t0.elevation_deg < self.elevation_mask_deg
90                    || aer_t1.elevation_deg < self.elevation_mask_deg
91                {
92                    debug!(
93                        "{} (el. mask {:.3} deg) but object moves from {:.3} to {:.3} deg -- no measurement",
94                        self.name, self.elevation_mask_deg, aer_t0.elevation_deg, aer_t1.elevation_deg
95                    );
96                    return Ok(None);
97                } else if aer_t0.is_obstructed() || aer_t1.is_obstructed() {
98                    debug!(
99                        "{} obstruction at t0={}, t1={} -- no measurement",
100                        self.name,
101                        aer_t0.is_obstructed(),
102                        aer_t1.is_obstructed()
103                    );
104                    return Ok(None);
105                }
106
107                // Noises are computed at the midpoint of the integration time.
108                let noises = self.noises(epoch - integration_time * 0.5, rng)?;
109
110                let mut msr = Measurement::new(self.name.clone(), epoch + noises[0].seconds());
111
112                for (ii, msr_type) in self.measurement_types.iter().enumerate() {
113                    let msr_value = msr_type.compute_two_way(aer_t0, aer_t1, noises[ii + 1])?;
114                    msr.push(*msr_type, msr_value);
115                }
116
117                Ok(Some(msr))
118            }
119            None => self.measure_instantaneous(
120                traj.at(epoch).context(ODTrajSnafu {
121                    details: "fetching state for instantaneous measurement".to_string(),
122                })?,
123                rng,
124                almanac,
125            ),
126        }
127    }
128
129    fn name(&self) -> String {
130        self.name.clone()
131    }
132
133    fn location(&self, epoch: Epoch, frame: Frame, almanac: Arc<Almanac>) -> AlmanacResult<Orbit> {
134        almanac.transform_to(self.to_orbit(epoch, &almanac).unwrap(), frame, None)
135    }
136
137    fn measure_instantaneous(
138        &mut self,
139        rx: Spacecraft,
140        rng: Option<&mut Pcg64Mcg>,
141        almanac: Arc<Almanac>,
142    ) -> Result<Option<Measurement>, ODError> {
143        let obstructing_body = if !self.frame.ephem_origin_match(rx.frame()) {
144            Some(rx.frame())
145        } else {
146            None
147        };
148
149        let aer = self
150            .azimuth_elevation_of(rx.orbit, obstructing_body, &almanac)
151            .context(ODAlmanacSnafu {
152                action: "computing AER",
153            })?;
154
155        if aer.elevation_deg >= self.elevation_mask_deg && !aer.is_obstructed() {
156            // Only update the noises if the measurement is valid.
157            let noises = self.noises(rx.orbit.epoch, rng)?;
158
159            let mut msr = Measurement::new(self.name.clone(), rx.orbit.epoch + noises[0].seconds());
160
161            for (ii, msr_type) in self.measurement_types.iter().enumerate() {
162                let msr_value = msr_type.compute_one_way(aer, noises[ii + 1])?;
163                msr.push(*msr_type, msr_value);
164            }
165
166            Ok(Some(msr))
167        } else {
168            debug!(
169                "{} {} (el. mask {:.3} deg), object at {:.3} deg -- no measurement",
170                self.name, rx.orbit.epoch, self.elevation_mask_deg, aer.elevation_deg
171            );
172            Ok(None)
173        }
174    }
175
176    /// Returns the measurement noise of this ground station.
177    ///
178    /// # Methodology
179    /// Noises are modeled using a [StochasticNoise] process, defined by the sigma on the turn-on bias and on the steady state noise.
180    /// The measurement noise is computed assuming that all measurements are independent variables, i.e. the measurement matrix is
181    /// 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
182    /// second item is the Doppler noise (in km/s), set to the square of the steady state sigma of that Gauss Markov process.
183    fn measurement_covar(&self, msr_type: MeasurementType, epoch: Epoch) -> Result<f64, ODError> {
184        let stochastics = self.stochastic_noises.as_ref().unwrap();
185
186        Ok(stochastics
187            .get(&msr_type)
188            .ok_or(ODError::NoiseNotConfigured {
189                kind: format!("{msr_type:?}"),
190            })?
191            .covariance(epoch))
192    }
193
194    fn measurement_bias(&self, msr_type: MeasurementType, _epoch: Epoch) -> Result<f64, ODError> {
195        let stochastics = self.stochastic_noises.as_ref().unwrap();
196
197        if let Some(gm) = stochastics
198            .get(&msr_type)
199            .ok_or(ODError::NoiseNotConfigured {
200                kind: format!("{msr_type:?}"),
201            })?
202            .bias
203        {
204            Ok(gm.constant.unwrap_or(0.0))
205        } else {
206            Ok(0.0)
207        }
208    }
209}
nyx_space/od/ground_station/trk_device.rs

nyx_space/od/ground_station/
trk_device.rs
