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Added visibility status to struct predict_observation. #36

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Oct 5, 2015
Merged

Added visibility status to struct predict_observation. #36

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e4b72b2
Added visibility status to struct predict_observation.
bjorgan Oct 4, 2015
391c50b
Correction in visibility check: Checks should be against the elevatio…
bjorgan Oct 4, 2015
a41ccb8
Elaboration of code comment on 'visible'.
bjorgan Oct 5, 2015
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2 changes: 2 additions & 0 deletions include/predict/predict.h.in
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Original file line number Diff line number Diff line change
Expand Up @@ -287,6 +287,8 @@ struct predict_observation {
double range_x, range_y, range_z;
///Range velocity (km/s)
double range_rate;
///Visibility status, whether satellite can be seen through optical means
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My understanding: The satellite is "visible" if all of these apply:

  • The satellite is in sunlight
  • The satellite is above the horizon
  • The sun is low enough to make the sky so dark that the satellite is visible (this obviously depends on a definition of darkness)

The short description of the variable is OK, but I'd like to see a longer description containing all the details.

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I've written a longer comment (commit a41ccb8).

bool visible;
};

/**
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10 changes: 10 additions & 0 deletions src/observer.c
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Expand Up @@ -29,6 +29,9 @@ void predict_destroy_observer(predict_observer_t *obs)
}
}


#define VISIBILITY_SUN_ELE_UPPER_THRESH -12.0
#define VISIBILITY_ORBIT_ELE_LOWER_THRESH 0.0
/**
* \brief Calculates range, azimuth, elevation and relative velocity.
*
Expand All @@ -43,6 +46,13 @@ void predict_observe_orbit(const predict_observer_t *observer, const predict_orb

observer_calculate(observer, julTime, orbit->position, orbit->velocity, obs);

// Calculate visibility status of the orbit: Orbit is visible if sun elevation is low enough and the orbit is above the horizon, but still in sunlight.
obs->visible = false;
struct predict_observation sun_obs;
predict_observe_sun(observer, orbit->time, &sun_obs);
if (!(orbit->eclipsed) && (sun_obs.elevation*180.0/M_PI < VISIBILITY_SUN_ELE_UPPER_THRESH) && (obs->elevation*180.0/M_PI > VISIBILITY_ORBIT_ELE_LOWER_THRESH)) {
obs->visible = true;
}
}

void observer_calculate(const predict_observer_t *observer, double time, const double pos[3], const double vel[3], struct predict_observation *result)
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