harrispriester

namespace saltro

namespace constants

Variables

constexpr double WGS84_A_M = 6378137.0

WGS84 ellipsoid semi-major axis (equatorial radius).

Defined as \(6\,378\,137\) meters. Used for computing geodetic altitude from Earth-centered coordinates.

constexpr double WGS84_F = 1.0 / 298.257223563

WGS84 ellipsoid flattening parameter.

Defined as \(f = \frac{1}{298.257223563} \approx 3.357 \times 10^{-3}\). Characterizes Earth’s oblate spheroid shape.

constexpr double HARRIS_PRIESTER_LAG_RAD = 0.5235987755982988730771072305465838

Solar direction lag angle for Harris-Priester model.

Defines the phase lag between the spacecraft’s local solar noon and the actual peak of the atmospheric bulge. Defined as \(30°\) (≈ 0.524 radians). Accounts for the diurnal bulge offset due to atmospheric winds.

constexpr double HARRIS_PRIESTER_MIN_COS = 1e-12

Minimum cosine value threshold for Harris-Priester model.

Used to avoid division by very small numbers in the weighting function.

Set to \(10^{-12}\) for numerical stability.

constexpr double HARRIS_PRIESTER_COS_EXPONENT = 4.0

Exponent for cosine weighting in Harris-Priester model.

Controls the steepness of the day-night density transition. An exponent of 4 provides a smooth transition between minimum and maximum densities.

constexpr std::array<HarrisPriesterEntry, 50> HARRIS_PRIESTER_TABLE

Harris-Priester atmospheric density model lookup table.

Tabulated density values at 50 discrete altitudes from 100 to 1000 km. Each entry contains minimum (nightside) and maximum (dayside) density values. Interpolation or table lookup is performed during density computation to evaluate the model at arbitrary altitudes.

Reference: Harris, M. J., and W. Priester, 1962.

struct HarrisPriesterEntry

#include <harrispriester.h>

Single entry in the Harris-Priester atmospheric density table.

Each entry corresponds to a discrete altitude level and provides both minimum (nightside) and maximum (dayside) density values.

Public Members

double alt_m

Altitude above Earth surface in meters.

double rho_min_kg_m3

Minimum (nightside) density in kg/m³

double rho_max_kg_m3

Maximum (dayside) density in kg/m³