EarthStandardAtmosphereRefraction.java
- /* Copyright 2013 Applied Defense Solutions, Inc.
- * Licensed to CS Communication & Systèmes (CS) under one or more
- * contributor license agreements. See the NOTICE file distributed with
- * this work for additional information regarding copyright ownership.
- * CS licenses this file to You under the Apache License, Version 2.0
- * (the "License"); you may not use this file except in compliance with
- * the License. You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
- package org.orekit.models.earth;
- import org.hipparchus.util.FastMath;
- import org.orekit.models.AtmosphericRefractionModel;
- /** Implementation of refraction model for Earth standard atmosphere.
- * <p>Refraction angle is 0 at zenith, about 1 arcminute at 45°, and 34 arcminutes at the
- * horizon for optical wavelengths.</p>
- * <p>Refraction angle is computed according to Saemundssen formula quoted by Meeus.
- * For reference, see <b>Astronomical Algorithms</b> (1998), 2nd ed,
- * (ISBN 0-943396-61-1), chap. 15.</p>
- * <p>This formula is about 30 arcseconds of accuracy very close to the horizon, as
- * variable atmospheric effects become very important.</p>
- * <p>Local pressure and temperature can be set to correct refraction at the viewpoint.</p>
- * @since 6.1
- */
- public class EarthStandardAtmosphereRefraction implements AtmosphericRefractionModel {
- /** Default correction factor value. */
- public static final double DEFAULT_CORRECTION_FACTOR = 1.0;
- /** Default local pressure at viewpoint (Pa). */
- public static final double DEFAULT_PRESSURE = 101000.0;
- /** Default local temperature at viewpoint (K). */
- public static final double DEFAULT_TEMPERATURE = 283.0;
- /** NIST standard atmospheric pressure (Pa). */
- public static final double STANDARD_ATM_PRESSURE = 101325.0;
- /** NIST standard atmospheric temperature (K). */
- public static final double STANDARD_ATM_TEMPERATURE = 293.15;
- /** Elevation min value to compute refraction (under the horizon). */
- private static final double MIN_ELEVATION = -2.0;
- /** Elevation max value to compute refraction (zenithal). */
- private static final double MAX_ELEVATION = 89.89;
- /** Serializable UID. */
- private static final long serialVersionUID = 6001744143210742620L;
- /** Refraction correction from local pressure and temperature. */
- private double correfrac;
- /** Local pressure. */
- private double pressure;
- /** Local temperature. */
- private double temperature;
- /**
- * Creates a new default instance.
- */
- public EarthStandardAtmosphereRefraction() {
- correfrac = DEFAULT_CORRECTION_FACTOR;
- pressure = DEFAULT_PRESSURE;
- temperature = DEFAULT_TEMPERATURE;
- }
- /**
- * Creates an instance given a specific pressure and temperature.
- * @param pressure in Pascals (Pa)
- * @param temperature in Kelvin (K)
- */
- public EarthStandardAtmosphereRefraction(final double pressure, final double temperature) {
- setTemperature(temperature);
- setPressure(pressure);
- }
- /** Get the local pressure at the evaluation location.
- * @return the pressure (Pa)
- */
- public double getPressure() {
- return pressure;
- }
- /** Set the local pressure at the evaluation location
- * <p>Otherwise the default value for the local pressure is set to {@link #DEFAULT_PRESSURE}.</p>
- * @param pressure the pressure to set (Pa)
- */
- public void setPressure(final double pressure) {
- this.pressure = pressure;
- this.correfrac = (pressure / DEFAULT_PRESSURE) * (DEFAULT_TEMPERATURE / temperature);
- }
- /** Get the local temperature at the evaluation location.
- * @return the temperature (K)
- */
- public double getTemperature() {
- return temperature;
- }
- /** Set the local temperature at the evaluation location
- * <p>Otherwise the default value for the local temperature is set to {@link #DEFAULT_TEMPERATURE}.</p>
- * @param temperature the temperature to set (K)
- */
- public void setTemperature(final double temperature) {
- this.temperature = temperature;
- this.correfrac = (pressure / DEFAULT_PRESSURE) * (DEFAULT_TEMPERATURE / temperature);
- }
- @Override
- /** {@inheritDoc} */
- public double getRefraction(final double trueElevation) {
- double refraction = 0.0;
- final double eld = FastMath.toDegrees(trueElevation);
- if (eld > MIN_ELEVATION && eld < MAX_ELEVATION) {
- final double tmp = eld + 10.3 / (eld + 5.11);
- final double ref = 1.02 / FastMath.tan(FastMath.toRadians(tmp)) / 60.;
- refraction = FastMath.toRadians(correfrac * ref);
- }
- return refraction;
- }
- }