001 package edu.nrao.sss.astronomy;
002
003 import java.math.BigDecimal;
004 import java.util.Date;
005
006 import static edu.nrao.sss.astronomy.CelestialCoordinateSystem.*;
007 import static edu.nrao.sss.measure.ArcUnits.*;
008
009 import uk.ac.starlink.pal.AngleDR;
010 import uk.ac.starlink.pal.Galactic;
011 import uk.ac.starlink.pal.Pal;
012
013 import edu.nrao.sss.geom.EarthPosition;
014 import edu.nrao.sss.measure.Latitude;
015 import edu.nrao.sss.measure.LocalSiderealTime;
016 import edu.nrao.sss.measure.Longitude;
017
018 /**
019 * A coordinate converter based on the Positional Astronomy Library
020 * of the defunct Starlink project. This class enlists the help of their
021 * <a href="http://star-www.rl.ac.uk/starjava/javadocs/uk/ac/starlink/pal/Pal.html">
022 * Pal</a>, which is a partial implementation of their
023 * <a href="http://www.starlink.rl.ac.uk/star/docs/sun67.htx/sun67.html">
024 * SLALIB</a> software.
025 * <p>
026 * This converter handles only the J2000 Equatorial, Ecliptic, and
027 * 1958 Galactic coordinate systems.</p>
028 * <p>
029 * <b>Version Info:</b>
030 * <table style="margin-left:2em">
031 * <tr><td>$Revision: 1707 $</td></tr>
032 * <tr><td>$Date: 2008-11-14 10:23:59 -0700 (Fri, 14 Nov 2008) $</td></tr>
033 * <tr><td>$Author: dharland $ (last person to modify)</td></tr>
034 * </table></p>
035 *
036 * @author David M. Harland
037 * @since 2008-02-28
038 */
039 //In the little bit of testing done so far, the equatorial <--> galactic
040 //conversions match the HEASARC numbers extremely well. The conversions
041 //to/from ecliptic, though, are off from 1/1000 to 1/10 degree.
042 //--DMH 2/28/2008
043
044 public class StarlinkPalConverter
045 implements CelestialCoordinateConverter
046 {
047 private static final Pal STARLINK_PAL = new Pal();
048
049 public SkyPosition createFrom(SkyPosition position,
050 CelestialCoordinateSystem toSystem,
051 Epoch toEpoch,
052 EarthPosition observer,
053 LocalSiderealTime lst)
054 throws CoordinateConversionException
055 {
056 SkyPosition convertedPosition = null;
057
058 //TODO validate the from/to ccs & epoch
059 //Epoch fromEpoch = position.getEpoch();
060 CelestialCoordinateSystem fromSystem = position.getCoordinateSystem();
061
062 if (lst == null)
063 lst = new LocalSiderealTime();
064
065 switch (fromSystem)
066 {
067 case EQUATORIAL:
068 convertedPosition = convertEquatorial(position, toSystem, lst);
069 break;
070
071 case ECLIPTIC:
072 convertedPosition = convertEcliptic(position, toSystem, lst);
073 break;
074
075 case GALACTIC:
076 convertedPosition = convertGalactic(position, toSystem, lst);
077 break;
078
079 default:
080 //TODO programmer error: already handled by validation method
081 }
082
083 return convertedPosition;
084 }
085
086 //============================================================================
087 // A-to-* CONVERSIONS
088 //============================================================================
089
090 private SkyPosition convertEquatorial(SkyPosition sp,
091 CelestialCoordinateSystem ccs,
092 LocalSiderealTime lst)
093 {
094 switch (ccs)
095 {
096 case EQUATORIAL: return SimpleSkyPosition.copy(sp, lst.toDate());
097 case ECLIPTIC: return equatorialToEcliptic(sp, lst);
098 case GALACTIC: return equatorialToGalactic(sp, lst);
099
100 default:
101 //TODO programmer error: already handled by validation method
102 return null;
103 }
104 }
105
106
107 private SkyPosition convertEcliptic(SkyPosition sp,
108 CelestialCoordinateSystem ccs,
109 LocalSiderealTime lst)
110 {
111 switch (ccs)
112 {
113 case EQUATORIAL: return eclipticToEquatorial(sp, lst);
114 case ECLIPTIC: return SimpleSkyPosition.copy(sp, lst.toDate());
115 case GALACTIC: return eclipticToGalactic(sp, lst);
116
117 default:
118 //TODO programmer error: already handled by validation method
119 return null;
120 }
121 }
122
123
124 private SkyPosition convertGalactic(SkyPosition sp,
125 CelestialCoordinateSystem ccs,
126 LocalSiderealTime lst)
127 {
128 switch (ccs)
129 {
130 case EQUATORIAL: return galacticToEquatorial(sp, lst);
131 case ECLIPTIC: return galacticToEcliptic(sp, lst);
132 case GALACTIC: return SimpleSkyPosition.copy(sp, lst.toDate());
133
134 default:
135 //TODO programmer error: already handled by validation method
136 return null;
137 }
138 }
139
140 //============================================================================
141 // A-to-B CONVERSIONS
142 //============================================================================
143
144 private SkyPosition equatorialToEcliptic(SkyPosition origPos,
145 LocalSiderealTime lst)
146 {
147 AngleDR raDec = toAngleDR(origPos, lst);
148 AngleDR eclip =
149 STARLINK_PAL.Eqecl(raDec,
150 lst.toJulianDate().modifiedValue().doubleValue());
151
152 return toSkyPos(eclip, ECLIPTIC);
153 }
154
155
156 private SkyPosition eclipticToEquatorial(SkyPosition origPos,
157 LocalSiderealTime lst)
158 {
159 AngleDR eclip = toAngleDR(origPos, lst);
160 AngleDR raDec =
161 STARLINK_PAL.Ecleq(eclip,
162 lst.toJulianDate().modifiedValue().doubleValue());
163
164 return toSkyPos(raDec, EQUATORIAL);
165 }
166
167
168 private SkyPosition equatorialToGalactic(SkyPosition origPos,
169 LocalSiderealTime lst)
170 {
171 AngleDR raDec = toAngleDR(origPos, lst);
172 Galactic galactic = STARLINK_PAL.Eqgal(raDec);
173
174 return toSkyPos(galactic);
175 }
176
177
178 private SkyPosition galacticToEquatorial(SkyPosition origPos,
179 LocalSiderealTime lst)
180 {
181 Galactic galactic = toGalactic(origPos, lst);
182 AngleDR raDec = STARLINK_PAL.Galeq(galactic);
183
184 return toSkyPos(raDec, EQUATORIAL);
185 }
186
187
188 private SkyPosition eclipticToGalactic(SkyPosition origPos,
189 LocalSiderealTime lst)
190 {
191 AngleDR eclip = toAngleDR(origPos, lst);
192 AngleDR raDec =
193 STARLINK_PAL.Ecleq(eclip,
194 lst.toJulianDate().modifiedValue().doubleValue());
195
196 Galactic galactic = STARLINK_PAL.Eqgal(raDec);
197
198 return toSkyPos(galactic);
199 }
200
201
202 private SkyPosition galacticToEcliptic(SkyPosition origPos,
203 LocalSiderealTime lst)
204 {
205 Galactic galactic = toGalactic(origPos, lst);
206 AngleDR raDec = STARLINK_PAL.Galeq(galactic);
207
208 AngleDR eclip =
209 STARLINK_PAL.Eqecl(raDec,
210 lst.toJulianDate().modifiedValue().doubleValue());
211
212 return toSkyPos(eclip, ECLIPTIC);
213 }
214
215 //============================================================================
216 // STARLINK <---> SSS CONVERSIONS
217 //============================================================================
218
219 private AngleDR toAngleDR(SkyPosition sp, LocalSiderealTime lst)
220 {
221 Date time = lst.toDate();
222
223 return new AngleDR(sp.getLongitude(time).toUnits(RADIAN).doubleValue(),
224 sp.getLatitude(time).toUnits(RADIAN).doubleValue());
225
226 }
227
228
229 private Galactic toGalactic(SkyPosition sp, LocalSiderealTime lst)
230 {
231 Date time = lst.toDate();
232
233 return new Galactic(sp.getLongitude(time).toUnits(RADIAN).doubleValue(),
234 sp.getLatitude(time).toUnits(RADIAN).doubleValue());
235
236 }
237
238
239 private SkyPosition toSkyPos(AngleDR angleDR, CelestialCoordinateSystem ccs)
240 {
241 SimpleSkyPosition sp = new SimpleSkyPosition(ccs, Epoch.J2000);
242
243 sp.setLongitude(new Longitude(new BigDecimal(angleDR.getAlpha()), RADIAN));
244 sp.setLatitude(new Latitude(new BigDecimal(angleDR.getDelta()), RADIAN));
245
246 return sp;
247 }
248
249
250 private SkyPosition toSkyPos(Galactic galactic)
251 {
252 SimpleSkyPosition sp = new SimpleSkyPosition(GALACTIC, Epoch.J2000);
253
254 sp.setLongitude(new Longitude(new BigDecimal(galactic.getLongitude()), RADIAN));
255 sp.setLatitude(new Latitude(new BigDecimal(galactic.getLatitude()), RADIAN));
256
257 return sp;
258 }
259
260 //============================================================================
261 //
262 //============================================================================
263 /*
264 public static void main(String... args) throws Exception
265 {
266 //RA/Dec J2000 positions
267 SimpleSkyPosition eq = new SimpleSkyPosition(EQUATORIAL, Epoch.J2000);
268 eq.setLongitude(new Longitude(266.404996)); //10.684625));
269 eq.setLatitude(new Latitude(-28.936172)); //41.269278));
270
271 System.out.println("J2000: " + eq.getLongitude().toUnits(DEGREE) +
272 ", " + eq.getLatitude().toUnits(DEGREE));
273
274 StarlinkPalConverter converter = new StarlinkPalConverter();
275 LocalSiderealTime lst = new LocalSiderealTime();
276
277 SkyPosition ecliptic = converter.createFrom(eq, ECLIPTIC, Epoch.J2000, null, lst);
278 System.out.println("\nEcliptic: " + ecliptic.getLongitude().toUnits(DEGREE) +
279 ", " + ecliptic.getLatitude().toUnits(DEGREE));
280
281 SkyPosition galactic = converter.createFrom(eq, GALACTIC, Epoch.J2000, null, lst);
282 System.out.println("\nGalactic: " + galactic.getLongitude().toUnits(DEGREE) +
283 ", " + galactic.getLatitude().toUnits(DEGREE));
284 }
285 */
286 /*
287 public static void main(String... args) throws Exception
288 {
289 //Galactic positions
290 SimpleSkyPosition g = new SimpleSkyPosition(GALACTIC, Epoch.J2000);
291 g.setLongitude(new Longitude(0.0));
292 g.setLatitude(new Latitude(0.0));
293
294 System.out.println("Galactic: " + g.getLongitude().toUnits(DEGREE) +
295 ", " + g.getLatitude().toUnits(DEGREE));
296
297 StarlinkPalConverter converter = new StarlinkPalConverter();
298 LocalSiderealTime lst = new LocalSiderealTime();
299
300 SkyPosition ecliptic = converter.createFrom(g, ECLIPTIC, Epoch.J2000, null, lst);
301 System.out.println("\nEcliptic: " + ecliptic.getLongitude().toUnits(DEGREE) +
302 ", " + ecliptic.getLatitude().toUnits(DEGREE));
303
304 SkyPosition j2000 = converter.createFrom(g, EQUATORIAL, Epoch.J2000, null, lst);
305 System.out.println("\nJ2000: " + j2000.getLongitude().toUnits(DEGREE) +
306 ", " + j2000.getLatitude().toUnits(DEGREE));
307 }
308 */
309 }