API VERSION: 1.2 API SOURCE: NASA/JPL Horizons API ******************************************************************************* Revised: Oct 31, 2024 Europa Clipper (Spacecraft) / (Sun, Jupiter) -159 https://science.nasa.gov/mission/europa-clipper/ https://europa.nasa.gov/ BACKGROUND: NASA's Europa Clipper spacecraft will carry a suite of science instruments to assess habitability of Jupiter's ice-covered moon Europa (502) while confirming the existence and nature of an expected sub-surface ocean. Launched : 2024-Oct-14 16:06 UTC (SpaceX Falcon Heavy, KSC LC-39A) Mars gravity assist : 2025-Mar-01 Earth gravity assist: 2026-Dec-03 Arrival : 2030-Apr-11 (5.50 year time-of-flight) Mission length : 4.12 years (prime mission, JOI to E49) End-of-mission : 2034-Sep (directed to Ganymede impact ~30d after E49) The spacecraft is expected to orbit Jupiter 75 times and conduct 49 flybys of Europa at altitudes as low as 25 km. This will reduce exposure to the high levels of radiation Europa moves within. Gravity-assists from Europa (49), Ganymede (7), and Callisto (9) will be used to target different Europa close approach points on each flyby. SPACECRAFT: Considering solar arrays and radar antennas, Europa Clipper will be the largest spacecraft NASA has developed to-date for an interplanetary mission. When arrays are deployed, the spacecraft will span 30.5 meters. Main body (bus): 3 x 4.7 x 4 meters Dry mass (no propellant): 3241 kg Propellant: 2750 kg Solar power arrays: 2 x 14.2 x 4.1 meters SCIENCE INSTRUMENTS Europa Imaging System (EIS) Europa Thermal Emission Imaging System (E-THEMIS) Europa Ultraviolet Spectrograph (Europa-UVS) Mapping Imaging Spectrometer for Europa (MISE) Europa Clipper Magnetometer (ECM) Plasma Instrument for Magnetic Sounding (PIMS) Gravity/Radio Science Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) MAss Spectrometer for Planetary EXploration/Europa (MASPEX) SUrface Dust Analyzer (SUDA) SPACECRAFT TRAJECTORY (from JPL navigation): Segments marked by '*' below are pre-launch predictions. Based on tracking data through 2024-Oct-30, data thereafter is predicted: Trajectory files (JPL mission design/nav) Start End --------------------------------------------------- ----------- ----------- *21F31_MEGA_L241014_A300411_LP05_V7 (16:13 - 17:08) 2024-Oct-14 2024-Oct-14 trj_241014-241103-dco2410142047-postLaunch-OD001-v1 2024-Oct-14 2024-Oct-18 trj_241018-250101-dco2410291636-OD016-v1_wfimp 2024-Oct-18 2025-Jan-01 *21F31_MEGA_L241014_A300411_LP05_V7 2025-Jan-01 2031-Feb-07 ******************************************************************************* ******************************************************************************* Ephemeris / API_USER Mon Nov 4 04:18:09 2024 Pasadena, USA / Horizons ******************************************************************************* Target body name: Europa Clipper (spacecraft) (-159) {source: Europa_Clipper_merged} Center body name: Earth (399) {source: Europa_Clipper_merged} Center-site name: El Berrueco ******************************************************************************* Start time : A.D. 2024-Oct-31 00:00:00.0000 UT Stop time : A.D. 2024-Nov-01 00:00:00.0000 UT Step-size : 10 minutes ******************************************************************************* Target pole/equ : undefined Target radii : undefined Center geodetic : 356.4134, 40.8833094, 1.06361 {E-lon(deg),Lat(deg),Alt(km)} Center cylindric: 356.4134,4829.88693,4153.33056 {E-lon(deg),Dxy(km),Dz(km)} Center pole/equ : ITRF93 {East-longitude positive} Center radii : 6378.137, 6378.137, 6356.752 km {Equator_a, b, pole_c} Target primary : Earth Vis. interferer : MOON (R_eq= 1737.400) km {source: Europa_Clipper_merge Rel. light bend : Sun {source: Europa_Clipper_merge Rel. lght bnd GM: 1.3271E+11 km^3/s^2 Atmos refraction: NO (AIRLESS) RA format : HMS Time format : CAL Calendar mode : Mixed Julian/Gregorian RTS-only print : NO EOP file : eop.241101.p250128 EOP coverage : DATA-BASED 1962-JAN-20 TO 2024-NOV-01. PREDICTS-> 2025-JAN-27 Units conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s Table cut-offs 1: Elevation ( 0.0deg=YES),Airmass (>38.000=NO), Daylight (YES) Table cut-offs 2: Solar elongation ( 12.0,180.0=YES),Local Hour Angle( 0.0=NO ) Table cut-offs 3: RA/DEC angular rate ( 0.0=NO ) *************************************************************************************************************************************************************************************************************************************************** Date__(UT)__HR:MN R.A._____(ICRF)_____DEC Azi____(a-app)___Elev APmag S-brt r rdot delta deldot S-O-T /r S-T-O T-O-M/MN_Illu% RA_3sigma DEC_3sigma Sky_motion Sky_mot_PA RelVel-ANG *************************************************************************************************************************************************************************************************************************************************** $$SOE 2024-Oct-31 00:00 08 35 57.54 +30 25 21.9 64.389203 17.128424 n.a. n.a. 0.998809714878 2.1016576 0.05952767954105 5.8064582 94.0199 /L 82.5729 78.4/ 2.0496 n.a. n.a. 0.2613364 3.2493166 88.145069 2024-Oct-31 00:10 08 35 57.54 +30 25 24.5 65.770211 18.847651 n.a. n.a. 0.998818147190 2.1032771 0.05955096354495 5.8058013 94.0269 /L 82.5646 78.5/ 2.0248 n.a. n.a. 0.2611890 358.53048 88.145180 2024-Oct-31 00:20 08 35 57.53 +30 25 27.1 67.139201 20.585582 n.a. n.a. 0.998826585998 2.1048966 0.05957424608107 5.8057262 94.0340 /L 82.5562 78.6/ 2.0002 n.a. n.a. 0.2623366 353.83011 88.136285 2024-Oct-31 00:30 08 35 57.50 +30 25 29.7 68.498220 22.341080 n.a. n.a. 0.998835031301 2.1065159 0.05959752948216 5.8062325 94.0412 /L 82.5478 78.7/ 1.9759 n.a. n.a. 0.2647536 349.19402 88.118555 2024-Oct-31 00:40 08 35 57.45 +30 25 32.3 69.849410 24.113047 n.a. n.a. 0.998843483098 2.1081353 0.05962081607795 5.8073191 94.0484 /L 82.5393 78.8/ 1.9518 n.a. n.a. 0.2683876 344.66394 88.092361 2024-Oct-31 00:50 08 35 57.39 +30 25 34.8 71.195029 25.900418 n.a. n.a. 0.998851941390 2.1097545 0.05964410819043 5.8089833 94.0556 /L 82.5307 78.9/ 1.9279 n.a. n.a. 0.2731626 340.27525 88.058245 2024-Oct-31 01:00 08 35 57.31 +30 25 37.4 72.537466 27.702159 n.a. n.a. 0.998860406175 2.1113736 0.05966740812957 5.8112217 94.0630 /L 82.5221 79.0/ 1.9044 n.a. n.a. 0.2789844 336.05556 88.016883 2024-Oct-31 01:10 08 35 57.21 +30 25 39.9 73.879273 29.517259 n.a. n.a. 0.998868877454 2.1129927 0.05969071818889 5.8140295 94.0703 /L 82.5135 79.1/ 1.8811 n.a. n.a. 0.2857459 332.02431 87.969048 2024-Oct-31 01:20 08 35 57.10 +30 25 42.4 75.223184 31.344730 n.a. n.a. 0.998877355227 2.1146117 0.05971404064090 5.8174011 94.0778 /L 82.5048 79.2/ 1.8580 n.a. n.a. 0.2933318 328.19310 87.915572 2024-Oct-31 01:30 08 35 56.97 +30 25 44.9 76.572160 33.183597 n.a. n.a. 0.998885839493 2.1162307 0.05973737773296 5.8213295 94.0853 /L 82.4960 79.3/ 1.8353 n.a. n.a. 0.3016241 324.56664 87.857310 2024-Oct-31 01:40 08 35 56.83 +30 25 47.4 77.929426 35.032893 n.a. n.a. 0.998894330251 2.1178495 0.05976073168283 5.8258070 94.0928 /L 82.4872 79.4/ 1.8128 n.a. n.a. 0.3105049 321.14396 87.795115 2024-Oct-31 01:50 08 35 56.67 +30 25 49.7 79.298522 36.891653 n.a. n.a. 0.998902827502 2.1194683 0.05978410467451 5.8308244 94.1004 /L 82.4783 79.5/ 1.7907 n.a. n.a. 0.3198600 317.91976 87.729820 2024-Oct-31 02:00 08 35 56.49 +30 25 52.1 80.683374 38.758902 n.a. n.a. 0.998911331246 2.1210871 0.05980749885393 5.8363719 94.1080 /L 82.4694 79.6/ 1.7688 n.a. n.a. 0.3295801 314.88559 87.662215 2024-Oct-31 02:10 08 35 56.31 +30 25 54.4 82.088362 40.633652 n.a. n.a. 0.998919841481 2.1227057 0.05983091632496 5.8424384 94.1157 /L 82.4605 79.7/ 1.7473 n.a. n.a. 0.3395624 312.03096 87.593047 2024-Oct-31 02:20 08 35 56.10 +30 25 56.6 83.518423 42.514885 n.a. n.a. 0.998928358207 2.1243243 0.05985435914532 5.8490120 94.1234 /L 82.4515 79.8/ 1.7261 n.a. n.a. 0.3497110 309.34419 87.523012 2024-Oct-31 02:30 08 35 55.89 +30 25 58.8 84.979167 44.401542 n.a. n.a. 0.998936881425 2.1259428 0.05987782932259 5.8560796 94.1312 /L 82.4424 79.9/ 1.7052 n.a. n.a. 0.3599371 306.81308 87.452751 2024-Oct-31 02:40 08 35 55.66 +30 26 00.9 86.477024 46.292504 n.a. n.a. 0.998945411134 2.1275612 0.05990132881041 5.8636273 94.1390 /L 82.4333 80.0/ 1.6846 n.a. n.a. 0.3701587 304.42539 87.382854 2024-Oct-31 02:50 08 35 55.42 +30 26 03.0 88.019433 48.186577 n.a. n.a. 0.998953947333 2.1291796 0.05992485950471 5.8716402 94.1469 /L 82.4242 80.1/ 1.6644 n.a. n.a. 0.3803009 302.16916 87.313860 2024-Oct-31 03:00 08 35 55.16 +30 26 05.0 89.615077 50.082461 n.a. n.a. 0.998962490023 2.1307979 0.05994842324015 5.8801027 94.1547 /L 82.4150 80.2/ 1.6445 n.a. n.a. 0.3902947 300.03297 87.246260 2024-Oct-31 03:10 08 35 54.89 +30 26 06.9 91.274183 51.978720 n.a. n.a. 0.998971039203 2.1324161 0.05997202178636 5.8889982 94.1627 /L 82.4058 80.3/ 1.6249 n.a. n.a. 0.4000773 298.00601 87.180498 2024-Oct-31 03:20 08 35 54.61 +30 26 08.7 93.008912 53.873739 n.a. n.a. 0.998979594872 2.1340342 0.05999565684486 5.8983091 94.1706 /L 82.3966 80.4/ 1.6056 n.a. n.a. 0.4095909 296.07818 87.116979 2024-Oct-31 03:30 08 35 54.32 +30 26 10.4 94.833861 55.765672 n.a. n.a. 0.998988157031 2.1356523 0.06001933004553 5.9080173 94.1786 /L 82.3873 80.5/ 1.5867 n.a. n.a. 0.4187833 294.24011 87.056065 2024-Oct-31 03:40 08 35 54.02 +30 26 12.1 96.766722 57.652364 n.a. n.a. 0.998996725679 2.1372703 0.06004304294360 5.9181037 94.1866 /L 82.3780 80.6/ 1.5682 n.a. n.a. 0.4276064 292.48314 86.998083 2024-Oct-31 03:50 08 35 53.71 +30 26 13.7 98.829148 59.531260 n.a. n.a. 0.999005300816 2.1388882 0.06006679701664 5.9285486 94.1947 /L 82.3686 80.7/ 1.5500 n.a. n.a. 0.4360168 290.79928 86.943327 2024-Oct-31 04:00 08 35 53.39 +30 26 15.2 101.047905 61.399270 n.a. n.a. 0.999013882441 2.1405060 0.06009059366177 5.9393317 94.2027 /L 82.3593 80.8/ 1.5321 n.a. n.a. 0.4439746 289.18117 86.892059 2024-Oct-31 04:10 08 35 53.06 +30 26 16.6 103.456406 63.252584 n.a. n.a. 0.999022470555 2.1421238 0.06011443419280 5.9504318 94.2108 /L 82.3499 80.9/ 1.5146 n.a. n.a. 0.4514441 287.62203 86.844510 2024-Oct-31 04:20 08 35 52.73 +30 26 17.9 106.096756 65.086423 n.a. n.a. 0.999031065156 2.1437415 0.06013831983795 5.9618272 94.2189 /L 82.3405 81.0/ 1.4974 n.a. n.a. 0.4583926 286.11563 86.800886 2024-Oct-31 04:30 08 35 52.38 +30 26 19.1 109.022478 66.894680 n.a. n.a. 0.999039666245 2.1453591 0.06016225173728 5.9734958 94.2271 /L 82.3310 81.0/ 1.4805 n.a. n.a. 0.4647909 284.65620 86.761364 2024-Oct-31 04:40 08 35 52.03 +30 26 20.2 112.302085 68.669407 n.a. n.a. 0.999048273821 2.1469767 0.06018623094061 5.9854147 94.2352 /L 82.3216 81.1/ 1.4640 n.a. n.a. 0.4706128 283.23840 86.726099 2024-Oct-31 04:50 08 35 51.67 +30 26 21.3 116.023611 70.400087 n.a. n.a. 0.999056887884 2.1485942 0.06021025840547 5.9975608 94.2434 /L 82.3121 81.2/ 1.4479 n.a. n.a. 0.4758351 281.85726 86.695223 2024-Oct-31 05:00 08 35 51.31 +30 26 22.2 120.299936 72.072593 n.a. n.a. 0.999065508434 2.1502116 0.06023433499527 6.0099102 94.2515 /L 82.3027 81.3/ 1.4321 n.a. n.a. 0.4804370 280.50814 86.668846 2024-Oct-31 05:10 08 35 50.94 +30 26 23.0 125.273943 73.667730 n.a. n.a. 0.999074135470 2.1518289 0.06025846147757 6.0224390 94.2597 /L 82.2932 81.4/ 1.4166 n.a. n.a. 0.4844009 279.18669 86.647056 2024-Oct-31 05:20 A 08 35 50.57 +30 26 23.7 131.120558 75.159279 n.a. n.a. 0.999082768993 2.1534462 0.06028263852274 6.0351227 94.2679 /L 82.2837 81.5/ 1.4014 n.a. n.a. 0.4877113 277.88880 86.629925 2024-Oct-31 05:30 A 08 35 50.20 +30 26 24.3 138.038525 76.511669 n.a. n.a. 0.999091409001 2.1550634 0.06030686670253 6.0479366 94.2761 /L 82.2742 81.6/ 1.3866 n.a. n.a. 0.4903556 276.61057 86.617502 2024-Oct-31 05:40 Am 08 35 49.82 +30 26 24.8 146.217801 77.677954 n.a. n.a. 0.999100055494 2.1566805 0.06033114648906 6.0608558 94.2842 /L 82.2647 81.6/ 1.3721 n.a. n.a. 0.4923233 275.34824 86.609821 2024-Oct-31 05:50 Nm 08 35 49.44 +30 26 25.2 155.763230 78.599988 n.a. n.a. 0.999108708473 2.1582975 0.06035547825388 6.0738549 94.2924 /L 82.2552 81.7/ 1.3579 n.a. n.a. 0.4936066 274.09822 86.606898 2024-Oct-31 06:00 Nm 08 35 49.06 +30 26 25.5 166.570338 79.214274 n.a. n.a. 0.999117367937 2.1599145 0.06037986226719 6.0869088 94.3006 /L 82.2457 81.8/ 1.3441 n.a. n.a. 0.4941997 272.85699 86.608733 2024-Oct-31 06:10 Nm 08 35 48.67 +30 26 25.7 178.212573 79.466405 n.a. n.a. 0.999126033885 2.1615314 0.06040429869749 6.0999920 94.3087 /L 82.2362 81.9/ 1.3305 n.a. n.a. 0.4940993 271.62111 86.615309 2024-Oct-31 06:20 Ct 08 35 48.29 +30 26 25.7 189.974703 79.330509 n.a. n.a. 0.999134706318 2.1631482 0.06042878761111 6.1130789 94.3169 /L 82.2267 82.0/ 1.3173 n.a. n.a. 0.4933045 270.38717 86.626595 2024-Oct-31 06:30 Cm 08 35 47.91 +30 26 25.7 201.094873 78.820814 n.a. n.a. 0.999143385234 2.1647649 0.06045332897209 6.1261442 94.3250 /L 82.2172 82.0/ 1.3044 n.a. n.a. 0.4918165 269.15176 86.642544 >..... Daylight Cut-off Requested .....< >..... Elevation Cut-off Requested .....< 2024-Oct-31 22:10 08 35 54.52 +30 25 18.5 48.536446 0.390694 n.a. n.a. 0.999988112769 2.3164011 0.06279114471972 5.8171442 94.9350 /L 81.4794 88.9/ 0.4031 n.a. n.a. 0.3013870 42.851663 87.748037 2024-Oct-31 22:20 08 35 54.67 +30 25 20.7 50.152637 1.828641 n.a. n.a. 0.999997406327 2.3180106 0.06281445976908 5.8105838 94.9415 /L 81.4717 89.0/ 0.3927 n.a. n.a. 0.2930240 39.621876 87.807181 2024-Oct-31 22:30 08 35 54.81 +30 25 23.0 51.739284 3.300557 n.a. n.a. 1.000006706341 2.3196200 0.06283774954220 5.8045404 94.9480 /L 81.4639 89.1/ 0.3824 n.a. n.a. 0.2850916 36.199170 87.863476 2024-Oct-31 22:40 08 35 54.93 +30 25 25.3 53.297730 4.804714 n.a. n.a. 1.000016012810 2.3212294 0.06286101613509 5.7990252 94.9546 /L 81.4560 89.2/ 0.3722 n.a. n.a. 0.2776971 32.579022 87.916094 2024-Oct-31 22:50 08 35 55.04 +30 25 27.7 54.829394 6.339446 n.a. n.a. 1.000025325733 2.3228386 0.06288426168652 5.7940483 94.9613 /L 81.4481 89.3/ 0.3622 n.a. n.a. 0.2709508 28.761237 87.964180 2024-Oct-31 23:00 08 35 55.13 +30 25 30.1 56.335763 7.903153 n.a. n.a. 1.000034645110 2.3244478 0.06290748837390 5.7896188 94.9680 /L 81.4401 89.4/ 0.3523 n.a. n.a. 0.2649631 24.751168 88.006875 2024-Oct-31 23:10 08 35 55.21 +30 25 32.5 57.818386 9.494296 n.a. n.a. 1.000043970941 2.3260569 0.06293069840925 5.7857448 94.9747 /L 81.4321 89.5/ 0.3425 n.a. n.a. 0.2598416 20.560843 88.043341 2024-Oct-31 23:20 08 35 55.27 +30 25 34.9 59.278869 11.111398 n.a. n.a. 1.000053303226 2.3276659 0.06295389403484 5.7824334 94.9816 /L 81.4240 89.6/ 0.3329 n.a. n.a. 0.2556864 16.209774 88.072796 2024-Oct-31 23:30 08 35 55.32 +30 25 37.4 60.718880 12.753042 n.a. n.a. 1.000062641963 2.3292748 0.06297707751897 5.7796905 94.9884 /L 81.4159 89.7/ 0.3234 n.a. n.a. 0.2525852 11.725219 88.094549 2024-Oct-31 23:40 08 35 55.35 +30 25 39.9 62.140138 14.417867 n.a. n.a. 1.000071987154 2.3308837 0.06300025115161 5.7775210 94.9954 /L 81.4077 89.8/ 0.3141 n.a. n.a. 0.2506094 7.1416832 88.108039 2024-Oct-31 23:50 08 35 55.37 +30 25 42.4 63.544424 16.104567 n.a. n.a. 1.000081338797 2.3324925 0.06302341724004 5.7759286 95.0023 /L 81.3995 89.9/ 0.3050 n.a. n.a. 0.2498085 2.4995508 88.112869 2024-Nov-01 00:00 08 35 55.37 +30 25 44.9 64.933584 17.811885 n.a. n.a. 1.000090696892 2.3341011 0.06304657810439 5.7749160 95.0094 /L 81.3912 90.0/ 0.2960 n.a. n.a. 0.2502076 357.84291 88.108830 $$EOE *************************************************************************************************************************************************************************************************************************************************** Column meaning: TIME Times PRIOR to 1962 are UT1, a mean-solar time closely related to the prior but now-deprecated GMT. Times AFTER 1962 are in UTC, the current civil or "wall-clock" time-scale. UTC is kept within 0.9 seconds of UT1 using integer leap-seconds for 1972 and later years. Conversion from the internal Barycentric Dynamical Time (TDB) of solar system dynamics to the non-uniform civil UT time-scale requested for output has not been determined for UTC times after the next July or January 1st. Therefore, the last known leap-second is used as a constant over future intervals. Time tags refer to the UT time-scale conversion from TDB on Earth regardless of observer location within the solar system, although clock rates may differ due to the local gravity field and no analog to "UT" may be defined for that location. Any 'b' symbol in the 1st-column denotes a B.C. date. First-column blank (" ") denotes an A.D. date. CALENDAR SYSTEM Mixed calendar mode was active such that calendar dates after AD 1582-Oct-15 (if any) are in the modern Gregorian system. Dates prior to 1582-Oct-5 (if any) are in the Julian calendar system, which is automatically extended for dates prior to its adoption on 45-Jan-1 BC. The Julian calendar is useful for matching historical dates. The Gregorian calendar more accurately corresponds to the Earth's orbital motion and seasons. A "Gregorian-only" calendar mode is available if such physical events are the primary interest. NOTE: "n.a." in output means quantity "not available" at the print-time. SOLAR PRESENCE (OBSERVING SITE) Time tag is followed by a blank, then a solar-presence condition code: '*' Daylight (refracted solar upper-limb on or above apparent horizon) 'C' Civil twilight/dawn 'N' Nautical twilight/dawn 'A' Astronomical twilight/dawn ' ' Night OR geocentric ephemeris LUNAR PRESENCE WITH TARGET RISE/TRANSIT/SET EVENT MARKER (OBSERVING SITE) The solar-presence code column is immediately followed by another marker: 'm' Refracted upper-limb of Moon on or above apparent horizon ' ' Refracted upper-limb of Moon below apparent horizon OR geocentric The lunar presence marker (an ongoing state) can be over-ridden by a target event marker if an event has occurred since the last output step: 'r' Rise (target body on or went above cut-off RTS elevation) 'e' Elevation max (target body maximum elevation angle has occurred) 't' Transit (target body at or passed through observer meridian) 's' Set (target body on or went below cut-off RTS elevation) RTS MARKERS (TVH) Rise and set are with respect to the reference ellipsoid true visual horizon defined by the elevation cut-off angle. Horizon dip and yellow-light refraction (Earth only) are considered. Accuracy is < or = to twice the requested search step-size. 'R.A._____(ICRF)_____DEC' = Astrometric right ascension and declination of the target center with respect to the observing site (coordinate origin) in the reference frame of the planetary ephemeris (ICRF). Compensated for down-leg light-time delay aberration. Units: RA in hours-minutes-seconds of time, HH MM SS.ff{ffff} DEC in degrees-minutes-seconds of arc, sDD MN SC.f{ffff} 'Azi____(a-app)___Elev' = Airless apparent azimuth and elevation of target center. Compensated for light-time, the gravitational deflection of light, stellar aberration, precession and nutation. Azimuth is measured clockwise from north: North(0) -> East(90) -> South(180) -> West(270) -> North (360) Elevation angle is with respect to a plane perpendicular to the reference surface local zenith direction. TOPOCENTRIC ONLY. Units: DEGREES 'APmag S-brt' = The targets' approximate apparent visual magnitude and surface brightness. For planets and natural satellites, output is restricted to solar phase angles covered by observational data. Outside the observed phase angle range, "n.a." may be output to avoid extrapolation beyond the limit of model validity. For Earth-based observers, the estimated dimming due to atmospheric absorption (extinction) is available as a separate, requestable quantity. Surface brightness is the average airless visual magnitude of a square-arcsecond of the illuminated portion of the apparent disk. It is computed only if the target radius is known. Units: MAGNITUDES & MAGNITUDES PER SQUARE ARCSECOND 'r rdot' = The Sun's apparent range ("r", light-time aberrated) and range-rate ("rdot") relative to the target center, as seen by the observer. A positive "rdot" means the target center was moving away from the Sun, negative means moving toward the Sun. Units: AU and KM/S 'delta deldot' = Apparent range ("delta", light-time aberrated) and range-rate ("delta-dot") of the target center relative to the observer. A positive "deldot" means the target center is moving away from the observer, negative indicates movement toward the observer. Units: AU and KM/S 'S-O-T /r' = Sun-Observer-Target apparent SOLAR ELONGATION ANGLE seen from the observers' location at print-time. The '/r' column provides a code indicating the targets' apparent position relative to the Sun in the observers' sky, as described below: Case A: For an observing location on the surface of a rotating body, that body rotational sense is considered: /T indicates target TRAILS Sun (evening sky: rises and sets AFTER Sun) /L indicates target LEADS Sun (morning sky: rises and sets BEFORE Sun) Case B: For an observing point that does not have a rotational model (such as a spacecraft), the "leading" and "trailing" condition is defined by the observers' heliocentric ORBITAL motion: * If continuing in the observers' current direction of heliocentric motion would encounter the targets' apparent longitude first, followed by the Sun's, the target LEADS the Sun as seen by the observer. * If the Sun's apparent longitude would be encountered first, followed by the targets', the target TRAILS the Sun. Two other codes can be output: /* indicates observer is Sun-centered (undefined) /? Target is aligned with Sun center (no lead or trail) The S-O-T solar elongation angle is numerically the minimum separation angle of the Sun and target in the sky in any direction. It does NOT indicate the amount of separation in the leading or trailing directions, which would be defined along the equator of a spherical coordinate system. Units: DEGREES 'S-T-O' = The Sun-Target-Observer angle; the interior vertex angle at target center formed by a vector from the target to the apparent center of the Sun (at reflection time on the target) and the apparent vector from target to the observer at print-time. Slightly different from true PHASE ANGLE (requestable separately) at the few arcsecond level in that it includes stellar aberration on the down-leg from target to observer. Units: DEGREES 'T-O-M/MN_Illu%' = Target-Observer-Moon LUNAR ELONGATION angle and illuminated percentage. The apparent lunar elongation angle between target body center and Moon center, seen from the observing site, along with fraction of the lunar disk illuminated by the Sun. A negative lunar elongation angle indicates the target center is behind the Moon. Units: DEGREES & PERCENT 'RA_3sigma DEC_3sigma' = Uncertainty in Right-Ascension and Declination. Output values are the formal +/- 3 standard-deviations (sigmas) around nominal position. Units: ARCSECONDS 'Sky_motion Sky_mot_PA RelVel-ANG' = Total apparent angular rate of the target in the plane-of-sky. "Sky_mot_PA" is the position angle of the target's direction of motion in the plane-of-sky, measured counter-clockwise from the apparent of-date north pole direction. "RelVel-ANG" is the flight path angle of the target's relative motion with respect to the observer's line-of-sight, in the range [-90,+90], where positive values indicate motion away from the observer, negative values are toward the observer: -90 = target is moving directly toward the observer 0 = target is moving at right angles to the observer's line-of-sight +90 = target is moving directly away from the observer UNITS: ARCSECONDS/MINUTE, DEGREES, DEGREES Computations by ... Solar System Dynamics Group, Horizons On-Line Ephemeris System 4800 Oak Grove Drive, Jet Propulsion Laboratory Pasadena, CA 91109 USA General site: https://ssd.jpl.nasa.gov/ Mailing list: https://ssd.jpl.nasa.gov/email_list.html System news : https://ssd.jpl.nasa.gov/horizons/news.html User Guide : https://ssd.jpl.nasa.gov/horizons/manual.html Connect : browser https://ssd.jpl.nasa.gov/horizons/app.html#/x API https://ssd-api.jpl.nasa.gov/doc/horizons.html command-line telnet ssd.jpl.nasa.gov 6775 e-mail/batch https://ssd.jpl.nasa.gov/ftp/ssd/hrzn_batch.txt scripts https://ssd.jpl.nasa.gov/ftp/ssd/SCRIPTS Author : Jon.D.Giorgini@jpl.nasa.gov ***************************************************************************************************************************************************************************************************************************************************