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pub use super::{Cosm, Frame, LTCorr, Orbit, Spacecraft};
use crate::md::EventEvaluator;
use crate::time::{Duration, TimeUnit};
use std::cmp::{Eq, Ord, Ordering, PartialOrd};
use std::fmt;
use std::sync::Arc;
#[derive(Clone, Copy, Debug, PartialEq)]
pub enum EclipseState {
Umbra,
Penumbra(f64),
Visibilis,
}
impl EclipseState {
pub fn as_f64(self) -> f64 {
match self {
Self::Umbra => 0.0,
Self::Visibilis => 1.0,
Self::Penumbra(val) => val,
}
}
}
impl Eq for EclipseState {}
impl Ord for EclipseState {
fn cmp(&self, other: &Self) -> Ordering {
match *self {
EclipseState::Umbra => {
if *other == EclipseState::Umbra {
Ordering::Equal
} else {
Ordering::Greater
}
}
EclipseState::Visibilis => {
if *other == EclipseState::Visibilis {
Ordering::Equal
} else {
Ordering::Less
}
}
EclipseState::Penumbra(s) => match *other {
EclipseState::Penumbra(o) => {
if s > o {
Ordering::Greater
} else {
Ordering::Less
}
}
EclipseState::Visibilis => Ordering::Greater,
EclipseState::Umbra => Ordering::Less,
},
}
}
}
impl PartialOrd for EclipseState {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
Some(self.cmp(other))
}
}
impl fmt::Display for EclipseState {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
match *self {
Self::Umbra => write!(f, "Umbra"),
Self::Visibilis => write!(f, "Visibilis"),
Self::Penumbra(v) => write!(f, "Penumbra {:.2}%", v * 100.0),
}
}
}
#[derive(Clone)]
pub struct EclipseLocator {
pub light_source: Frame,
pub shadow_bodies: Vec<Frame>,
pub cosm: Arc<Cosm>,
}
impl fmt::Display for EclipseLocator {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
let shadow_bodies = self
.shadow_bodies
.iter()
.map(|b| format!("{} ", b))
.collect::<String>();
write!(
f,
"light-source: {}\tshadows casted by: {})",
self.light_source, shadow_bodies
)
}
}
impl EclipseLocator {
pub fn compute(&self, observer: &Orbit) -> EclipseState {
let mut state = EclipseState::Visibilis;
for eclipsing_body in &self.shadow_bodies {
let this_state =
eclipse_state(observer, self.light_source, *eclipsing_body, &self.cosm);
if this_state > state {
state = this_state;
}
}
state
}
pub fn to_umbra_event(&self) -> UmbraEvent {
UmbraEvent {
e_loc: self.clone(),
}
}
pub fn to_penumbra_event(&self) -> PenumbraEvent {
PenumbraEvent {
e_loc: self.clone(),
}
}
}
pub struct UmbraEvent {
e_loc: EclipseLocator,
}
impl fmt::Display for UmbraEvent {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "umbra event {}", self.e_loc)
}
}
impl EventEvaluator<Orbit> for UmbraEvent {
fn eval(&self, observer: &Orbit) -> f64 {
match self.e_loc.compute(observer) {
EclipseState::Umbra => 0.0,
EclipseState::Visibilis => 1.0,
EclipseState::Penumbra(val) => val,
}
}
fn epoch_precision(&self) -> Duration {
0.1 * TimeUnit::Second
}
fn value_precision(&self) -> f64 {
0.02
}
}
impl EventEvaluator<Spacecraft> for UmbraEvent {
fn eval(&self, sc: &Spacecraft) -> f64 {
match self.e_loc.compute(&sc.orbit) {
EclipseState::Umbra => 0.0,
EclipseState::Visibilis => 1.0,
EclipseState::Penumbra(val) => val,
}
}
fn epoch_precision(&self) -> Duration {
0.1 * TimeUnit::Second
}
fn value_precision(&self) -> f64 {
0.02
}
}
pub struct PenumbraEvent {
e_loc: EclipseLocator,
}
impl fmt::Display for PenumbraEvent {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "penumbra event {}", self.e_loc)
}
}
impl EventEvaluator<Orbit> for PenumbraEvent {
fn eval(&self, observer: &Orbit) -> f64 {
match self.e_loc.compute(observer) {
EclipseState::Umbra => 0.0,
EclipseState::Visibilis => 1.0,
EclipseState::Penumbra(val) => val - 1.0,
}
}
fn epoch_precision(&self) -> Duration {
0.1 * TimeUnit::Second
}
fn value_precision(&self) -> f64 {
0.02
}
}
impl EventEvaluator<Spacecraft> for PenumbraEvent {
fn eval(&self, sc: &Spacecraft) -> f64 {
match self.e_loc.compute(&sc.orbit) {
EclipseState::Umbra => 0.0,
EclipseState::Visibilis => 1.0,
EclipseState::Penumbra(val) => val - 1.0,
}
}
fn epoch_precision(&self) -> Duration {
0.1 * TimeUnit::Second
}
fn value_precision(&self) -> f64 {
0.02
}
}
pub fn eclipse_state(
observer: &Orbit,
light_source: Frame,
eclipsing_body: Frame,
cosm: &Cosm,
) -> EclipseState {
assert!(light_source.is_geoid() || light_source.is_celestial());
assert!(eclipsing_body.is_geoid());
if light_source.equatorial_radius() < std::f64::EPSILON {
let observed = cosm.celestial_state(
&light_source.ephem_path(),
observer.dt,
observer.frame,
LTCorr::None,
);
return line_of_sight(observer, &observed, eclipsing_body, &cosm);
}
let r_eb = cosm.frame_chg(observer, eclipsing_body).radius();
let r_ls = -cosm.frame_chg(observer, light_source).radius();
let r_ls_prime = if light_source.equatorial_radius() >= r_ls.norm() {
light_source.equatorial_radius()
} else {
(light_source.equatorial_radius() / r_ls.norm()).asin()
};
let r_eb_prime = if eclipsing_body.equatorial_radius() >= r_eb.norm() {
eclipsing_body.equatorial_radius()
} else {
(eclipsing_body.equatorial_radius() / r_eb.norm()).asin()
};
let d_prime = (-(r_ls.dot(&r_eb)) / (r_eb.norm() * r_ls.norm())).acos();
if d_prime - r_ls_prime > r_eb_prime {
EclipseState::Visibilis
} else if r_eb_prime > d_prime + r_ls_prime {
EclipseState::Umbra
} else if (r_ls_prime - r_eb_prime).abs() < d_prime && d_prime < r_ls_prime + r_eb_prime {
let d1 = (d_prime.powi(2) - r_ls_prime.powi(2) + r_eb_prime.powi(2)) / (2.0 * d_prime);
let d2 = (d_prime.powi(2) + r_ls_prime.powi(2) - r_eb_prime.powi(2)) / (2.0 * d_prime);
let shadow_area = circ_seg_area(r_eb_prime, d1) + circ_seg_area(r_ls_prime, d2);
if shadow_area.is_nan() {
warn!(
"Shadow area is NaN! Please file a bug with initial states, eclipsing bodies, etc."
);
return EclipseState::Umbra;
}
let nominal_area = std::f64::consts::PI * r_ls_prime.powi(2);
EclipseState::Penumbra((nominal_area - shadow_area) / nominal_area)
} else {
EclipseState::Penumbra(1.0 - r_eb_prime.powi(2) / r_ls_prime.powi(2))
}
}
fn circ_seg_area(r: f64, d: f64) -> f64 {
r.powi(2) * (d / r).acos() - d * (r.powi(2) - d.powi(2)).sqrt()
}
pub fn line_of_sight(
observer: &Orbit,
observed: &Orbit,
eclipsing_body: Frame,
cosm: &Cosm,
) -> EclipseState {
if observer == observed {
return EclipseState::Visibilis;
}
let r1 = &cosm.frame_chg(observed, eclipsing_body).radius();
let r2 = &cosm.frame_chg(observer, eclipsing_body).radius();
let r1sq = r1.dot(&r1);
let r2sq = r2.dot(&r2);
let r1dotr2 = r1.dot(&r2);
let tau = (r1sq - r1dotr2) / (r1sq + r2sq - 2.0 * r1dotr2);
if !(0.0..=1.0).contains(&tau)
|| (1.0 - tau) * r1sq + r1dotr2 * tau > eclipsing_body.equatorial_radius().powi(2)
{
EclipseState::Visibilis
} else {
EclipseState::Umbra
}
}
#[cfg(test)]
mod tests {
use super::*;
use hifitime::Epoch;
#[test]
fn los_edge_case() {
let cosm = Cosm::de438();
let eme2k = cosm.frame("EME2000");
let luna = cosm.frame("Luna");
let dt1 = Epoch::from_gregorian_tai(2020, 1, 1, 6, 7, 40, 0);
let dt2 = Epoch::from_gregorian_tai(2020, 1, 1, 6, 7, 50, 0);
let dt3 = Epoch::from_gregorian_tai(2020, 1, 1, 6, 8, 0, 0);
let xmtr1 = Orbit::cartesian(
397_477.494_485,
-57_258.902_156,
-62_857.909_437,
0.230_482,
2.331_362,
0.615_501,
dt1,
eme2k,
);
let rcvr1 = Orbit::cartesian(
338_335.467_589,
-55_439.526_977,
-13_327.354_273,
0.197_141,
0.944_261,
0.337_407,
dt1,
eme2k,
);
let xmtr2 = Orbit::cartesian(
397_479.756_900,
-57_235.586_465,
-62_851.758_851,
0.222_000,
2.331_768,
0.614_614,
dt2,
eme2k,
);
let rcvr2 = Orbit::cartesian(
338_337.438_860,
-55_430.084_340,
-13_323.980_229,
0.197_113,
0.944_266,
0.337_402,
dt2,
eme2k,
);
let xmtr3 = Orbit::cartesian(
397_481.934_480,
-57_212.266_970,
-62_845.617_185,
0.213_516,
2.332_122,
0.613_717,
dt3,
eme2k,
);
let rcvr3 = Orbit::cartesian(
338_339.409_858,
-55_420.641_651,
-13_320.606_228,
0.197_086,
0.944_272,
0.337_398,
dt3,
eme2k,
);
assert_eq!(
line_of_sight(&xmtr1, &rcvr1, luna, &cosm),
EclipseState::Umbra
);
assert_eq!(
line_of_sight(&xmtr2, &rcvr2, luna, &cosm),
EclipseState::Umbra
);
assert_eq!(
line_of_sight(&xmtr3, &rcvr3, luna, &cosm),
EclipseState::Umbra
);
assert_eq!(
line_of_sight(&rcvr1, &xmtr1, luna, &cosm),
EclipseState::Umbra
);
assert_eq!(
line_of_sight(&rcvr2, &xmtr2, luna, &cosm),
EclipseState::Umbra
);
assert_eq!(
line_of_sight(&rcvr3, &xmtr3, luna, &cosm),
EclipseState::Umbra
);
}
#[test]
fn los_earth_eclipse() {
let cosm = Cosm::de438();
let eme2k = cosm.frame("EME2000");
let dt = Epoch::from_gregorian_tai_at_midnight(2020, 1, 1);
let sma = eme2k.equatorial_radius() + 300.0;
let sc1 = Orbit::keplerian(sma, 0.001, 0.1, 90.0, 75.0, 0.0, dt, eme2k);
let sc2 = Orbit::keplerian(sma + 1.0, 0.001, 0.1, 90.0, 75.0, 0.0, dt, eme2k);
let sc3 = Orbit::keplerian(sma, 0.001, 0.1, 90.0, 75.0, 180.0, dt, eme2k);
assert_eq!(line_of_sight(&sc1, &sc3, eme2k, &cosm), EclipseState::Umbra);
assert_eq!(
line_of_sight(&sc2, &sc1, eme2k, &cosm),
EclipseState::Visibilis
);
assert_eq!(
line_of_sight(&sc1, &sc2, eme2k, &cosm),
EclipseState::Visibilis
);
}
}