API VERSION: 1.2 API SOURCE: NASA/JPL Horizons API ******************************************************************************* Revised: Jan 16, 2025 Chandra Spacecraft (X-ray observatory) / (Earth) -151 http://xrtpub.harvard.edu/index.html Chandra X-ray Observatory: Deployment (STS-93) = July 23, 1999 Data storage = 1.8 gbs Science mission = ~5 years Length (sun shade open) = 45.3 m Orbital check-out = 2 months Length (sun shade clsd) = 38.7 m ORBITAL DATA: Inclination = 28.5 degrees Orbital period = ~64 hours Apogee altitude = ~ 86,487 km Observing time / orbit = ~55 hours Perigee altitude = ~ 5,999 km WEIGHTS & PROPULSION: Dry = 10,560 lbs Propellant = 2,153 lbs Pressurant = 10 lb Total launch weight = 12,930 lb Engines = 4 Thrust per engine = 105 lb SPACECRAFT TRAJECTORY (from CFA): Trajectory after 2026-Jan-06 is a prediction Trajectory name Start Stop ---------------------------- ----------- ----------- cxo_99219_06045 1999-Aug-07 2006-Feb-14 cxo_06002_10103 2006-Feb-03 2010-Feb-25 CXO_10056_26188 2010-Feb-25 2026-Jul-07 ******************************************************************************* ******************************************************************************* Ephemeris / API_USER Sun Jan 18 09:31:05 2026 Pasadena, USA / Horizons ******************************************************************************* Target body name: Chandra Observatory (spacecraft) (-151) {source: chandra_merged} Center body name: Earth (399) {source: chandra_merged} Center-site name: Swan Reach Imaging, Glenalta ******************************************************************************* Start time : A.D. 2025-Dec-08 00:00:00.0000 UT Stop time : A.D. 2025-Dec-22 00:00:00.0000 UT Step-size : 10 minutes ******************************************************************************* Target pole/equ : undefined Target radii : undefined Center geodetic : 139.5701, -34.5440227, .056888 {E-lon(deg),Lat(deg),Alt(km)} Center cylindric: 139.5701,5259.32258,-3596.34777 {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: chandra_merged} Rel. light bend : Sun {source: chandra_merged} 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.260116.p260414 EOP coverage : DATA-BASED 1962-JAN-20 TO 2026-JAN-16. PREDICTS-> 2026-APR-13 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 >..... Elevation Cut-off Requested .....< >..... Daylight Cut-off Requested .....< 2025-Dec-12 09:50 C 19 43 35.82 +05 18 19.2 284.748712 11.393618 n.a. n.a. 0.984315200612 1.4147288 0.00039932777037 -2.0726638 45.5626 /T 134.4205 119.3/ 44.8045 n.a. n.a. 295.66856 150.12584 -55.45040 2025-Dec-12 10:00 C 19 45 16.77 +04 34 40.2 282.894741 10.159578 n.a. n.a. 0.984320963218 1.4591614 0.00039093727584 -2.1114142 45.4169 /T 134.5666 119.6/ 44.7115 n.a. n.a. 308.98004 149.72551 -55.33580 2025-Dec-12 10:10 C 19 47 03.51 +03 49 12.4 281.047045 8.945355 n.a. n.a. 0.984326908129 1.5056625 0.00038238707458 -2.1523133 45.2838 /T 134.7001 120.0/ 44.6188 n.a. n.a. 323.36409 149.33457 -55.22305 2025-Dec-12 10:20 N 19 48 56.48 +03 01 46.6 279.202001 7.756303 n.a. n.a. 0.984333043975 1.5544014 0.00037366831005 -2.1954812 45.1651 /T 134.8191 120.4/ 44.5264 n.a. n.a. 338.95482 148.95374 -55.11116 2025-Dec-12 10:30 N 19 50 56.22 +02 12 12.8 277.355977 6.598166 n.a. n.a. 0.984339380101 1.6055663 0.00036477162229 -2.2410490 45.0630 /T 134.9216 120.8/ 44.4344 n.a. n.a. 355.90906 148.58358 -54.99901 2025-Dec-12 10:40 N 19 53 03.32 +01 20 19.4 275.505336 5.477160 n.a. n.a. 0.984345926652 1.6593672 0.00035568710031 -2.2891607 44.9800 /T 135.0051 121.3/ 44.3428 n.a. n.a. 374.41129 148.22449 -54.88536 2025-Dec-12 10:50 N 19 55 18.46 +00 25 53.4 273.646451 4.400076 n.a. n.a. 0.984352694661 1.7160386 0.00034640422807 -2.3399743 44.9188 /T 135.0667 121.8/ 44.2517 n.a. n.a. 394.67982 147.87663 -54.76880 2025-Dec-12 11:00 A 19 57 42.44 -00 31 20.5 271.775708 3.374394 n.a. n.a. 0.984359696158 1.7758431 0.00033691182269 -2.3936645 44.8827 /T 135.1031 122.3/ 44.1610 n.a. n.a. 416.97476 147.53992 -54.64774 2025-Dec-12 11:10 A 20 00 16.16 -01 31 39.4 269.889524 2.408433 n.a. n.a. 0.984366944289 1.8390754 0.00032719796497 -2.4504241 44.8758 /T 135.1104 122.8/ 44.0709 n.a. n.a. 441.60822 147.21397 -54.52038 2025-Dec-12 11:20 A 20 03 00.69 -02 35 23.4 267.984360 1.511520 n.a. n.a. 0.984374453454 1.9060665 0.00031724992084 -2.5104670 44.9025 /T 135.0841 123.4/ 43.9814 n.a. n.a. 468.95759 146.89803 -54.38469 2025-Dec-12 11:30 A 20 05 57.30 -03 42 56.0 266.056740 0.694215 n.a. n.a. 0.984382239459 1.9771884 0.00030705405378 -2.5740296 44.9683 /T 135.0187 124.0/ 43.8924 n.a. n.a. 499.48309 146.59088 -54.23830 2025-Dec-12 11:40 20 09 07.50 -04 54 44.3 264.103273 -0.031418 n.a. n.a. 0.984390319695 2.0528594 0.00029659572851 -2.6413737 45.0798 /T 134.9076 124.6/ 43.8042 n.a. n.a. 533.75106 146.29073 -54.07849 >..... Elevation Cut-off Requested .....< 2025-Dec-12 13:00 r 20 48 27.32 -18 36 48.3 247.182014 -0.183476 n.a. n.a. 0.984468329604 2.8896100 0.00020132081393 -3.3540315 49.0760 /T 130.9148 131.0/ 43.1250 n.a. n.a. 1087.3314 143.49888 -51.72991 2025-Dec-12 13:10 20 56 37.38 -21 11 24.5 244.863512 1.013970 n.a. n.a. 0.984480202793 3.0326398 0.00018763997886 -3.4682831 50.3144 /T 129.6768 131.9/ 43.0440 n.a. n.a. 1231.4120 142.89118 -51.15556 2025-Dec-12 13:20 21 06 15.69 -24 06 00.4 242.487790 2.691446 n.a. n.a. 0.984492669014 3.1852013 0.00017349186036 -3.5866741 51.8721 /T 128.1196 132.7/ 42.9639 n.a. n.a. 1412.5849 142.10405 -50.44549 2025-Dec-12 13:30 21 17 55.18 -27 25 19.3 240.046172 4.973563 n.a. n.a. 0.984505764056 3.3458067 0.00015886538255 -3.7060415 53.8453 /T 126.1469 133.5/ 42.8847 n.a. n.a. 1645.6589 141.03710 -49.54519 2025-Dec-12 13:40 21 32 29.08 -31 15 29.5 237.522868 8.035798 n.a. n.a. 0.984519513680 3.5107167 0.00014376844812 -3.8196853 56.3712 /T 123.6215 134.0/ 42.8066 n.a. n.a. 1953.7077 139.51852 -48.36665 2025-Dec-12 13:50 21 51 29.68 -35 44 14.4 234.887325 12.134229 n.a. n.a. 0.984533921271 3.6721280 0.00012824840129 -3.9138181 59.6517 /T 120.3414 134.0/ 42.7294 n.a. n.a. 2374.0046 137.23417 -46.76109 2025-Dec-12 14:00 22 17 51.12 -41 00 00.1 232.076609 17.656996 n.a. n.a. 0.984548946106 3.8152606 0.00011243341704 -3.9602143 63.9938 /T 115.9999 133.2/ 42.6532 n.a. n.a. 2968.6715 133.56149 -44.46595 2025-Dec-12 14:10 22 57 35.23 -47 06 05.0 228.949224 25.212321 n.a. n.a. 0.984564467613 3.9143668 0.00009661734014 -3.9009837 69.8758 /T 110.1184 131.0/ 42.5781 n.a. n.a. 3841.8147 127.15117 -41.00356 2025-Dec-12 14:20 00 04 04.01 -53 32 39.8 225.138239 35.757570 n.a. n.a. 0.984580233710 3.9293144 0.00008143210463 -3.6190556 78.0365 /T 101.9583 126.2/ 42.5041 n.a. n.a. 5152.2427 114.91858 -35.50980 2025-Dec-12 14:30 02 00 24.48 -57 28 42.2 219.409220 50.636271 n.a. n.a. 0.984595805199 3.8084297 0.00006816685909 -2.8985576 89.4520 /T 90.5435 117.2/ 42.4311 n.a. n.a. 7028.8255 91.482705 -26.58355 2025-Dec-12 14:40 04 32 38.01 -51 44 33.1 204.333717 70.544245 n.a. n.a. 0.984610540280 3.5071840 0.00005913398137 -1.4757081 104.4938 /T 75.5024 102.6/ 42.3591 n.a. n.a. 9058.8307 60.692652 -12.83407 2025-Dec-12 14:50 t 06 25 35.39 -34 34 32.3 93.939114 79.294193 n.a. n.a. 0.984623690367 3.0228691 0.00005715328917 0.5311349 120.1735 /L 59.8234 83.9/ 42.2883 n.a. n.a. 9648.5787 41.419243 4.5602813 2025-Dec-12 15:00 07 32 51.05 -14 40 58.0 58.047026 58.385793 n.a. n.a. 0.984634621710 2.4153130 0.00006308360335 2.3210515 129.9347 /L 50.0626 66.8/ 42.2185 n.a. n.a. 8106.4624 34.639037 20.583485 2025-Dec-12 15:10 m 08 16 47.71 +01 35 35.0 50.630532 40.695227 n.a. n.a. 0.984643028050 1.7796699 0.00007476325139 3.3835894 131.7649 /L 48.2324 55.3/ 42.1498 n.a. n.a. 6028.4356 33.645344 31.844765 2025-Dec-12 15:20 m 08 49 20.63 +13 31 34.7 46.883728 27.896921 n.a. n.a. 0.984648967248 1.1949186 0.00008944735153 3.8670625 129.3339 /L 50.6628 48.8/ 42.0822 n.a. n.a. 4434.5503 34.875106 38.887798 2025-Dec-12 15:30 m 09 15 41.85 +22 14 09.5 44.353940 18.654637 n.a. n.a. 0.984652733354 0.6990875 0.00010535981951 4.0321623 125.6986 /L 54.2973 45.7/ 42.0157 n.a. n.a. 3361.6808 36.940125 43.283516 2025-Dec-12 15:40 m 09 38 16.45 +28 45 27.5 42.416332 11.801041 n.a. n.a. 0.984654701205 0.2972202 0.00012158324449 4.0412478 122.0535 /L 57.9413 44.6/ 41.9503 n.a. n.a. 2640.4674 39.315392 46.161438 2025-Dec-12 15:50 m 09 58 18.63 +33 46 53.8 40.834057 6.574481 n.a. n.a. 0.984655228500 -0.0217204 0.00013767771175 3.9772638 118.7350 /L 61.2588 44.6/ 41.8860 n.a. n.a. 2139.3860 41.790934 48.165026 2025-Dec-12 16:00 m 10 16 29.80 +37 44 50.5 39.493723 2.495293 n.a. n.a. 0.984654617135 -0.2731782 0.00015344141500 3.8808844 115.7963 /L 64.1965 45.1/ 41.8228 n.a. n.a. 1777.9016 44.275537 49.644831 >..... Elevation Cut-off Requested .....< >..... Daylight Cut-off Requested .....< >..... Elevation Cut-off Requested .....< >..... Elevation Cut-off Requested .....< >..... Elevation Cut-off Requested .....< >..... Elevation Cut-off Requested .....< >..... Elevation Cut-off Requested .....< >..... Elevation Cut-off Requested .....< 2025-Dec-20 10:00 Cm 20 07 50.82 -04 54 02.3 273.689214 13.834059 n.a. n.a. 0.983657247643 2.2247769 0.00029087583522 -2.6115678 37.3861 /T 142.6033 36.6/ 0.2038 n.a. n.a. 526.49525 149.30402 -54.67012 2025-Dec-20 10:10 Cm 20 10 57.43 -06 12 10.4 271.588848 13.145573 n.a. n.a. 0.983666350608 2.3154869 0.00028027083049 -2.6770357 37.3440 /T 142.6458 36.3/ 0.2069 n.a. n.a. 564.98870 149.01135 -54.43557 2025-Dec-20 10:20 Cm 20 14 20.32 -07 35 56.3 269.459148 12.558329 n.a. n.a. 0.983675830152 2.4126730 0.00026939504587 -2.7466248 37.3633 /T 142.6269 36.0/ 0.2103 n.a. n.a. 608.78579 148.72361 -54.17979 2025-Dec-20 10:30 N 20 18 02.02 -09 06 07.7 267.292701 12.090408 n.a. n.a. 0.983685713681 2.5170641 0.00025823139351 -2.8206134 37.4576 /T 142.5329 35.7/ 0.2138 n.a. n.a. 659.00732 148.43785 -53.89752 2025-Dec-20 10:40 N 20 22 05.68 -10 43 42.7 265.081185 11.763327 n.a. n.a. 0.983696031708 2.6294809 0.00024676166912 -2.8992770 37.6440 /T 142.3470 35.5/ 0.2176 n.a. n.a. 717.09898 148.14967 -53.58219 2025-Dec-20 10:50 N 20 26 35.33 -12 29 52.5 262.815035 11.603045 n.a. n.a. 0.983706818228 2.7508389 0.00023496660410 -2.9828655 37.9437 /T 142.0476 35.5/ 0.2215 n.a. n.a. 784.95347 147.85261 -53.22543 2025-Dec-20 11:00 A 20 31 36.20 -14 26 05.1 260.482926 11.641354 n.a. n.a. 0.983718111088 2.8821424 0.00022282604479 -3.0715612 38.3840 /T 141.6077 35.5/ 0.2257 n.a. n.a. 865.09049 147.53720 -52.81637 2025-Dec-20 11:10 A 20 37 15.24 -16 34 11.3 258.070978 11.917833 n.a. n.a. 0.983729952308 3.0244604 0.00021031936293 -3.1654016 38.9994 /T 140.9927 35.7/ 0.2301 n.a. n.a. 960.92741 147.18942 -52.34054 2025-Dec-20 11:20 A 20 43 41.95 -18 56 31.9 255.561480 12.482640 n.a. n.a. 0.983742388235 3.1788680 0.00019742628459 -3.2641421 39.8347 /T 140.1576 36.1/ 0.2347 n.a. n.a. 1077.1972 146.78817 -51.77817 2025-Dec-20 11:30 A 20 51 09.71 -21 36 08.8 252.930785 13.400617 n.a. n.a. 0.983755469346 3.3463211 0.00018412847942 -3.3670025 40.9492 /T 139.0435 36.8/ 0.2396 n.a. n.a. 1220.6104 146.30088 -51.10141 2025-Dec-20 11:40 20 59 58.16 -24 36 59.7 250.145670 14.757454 n.a. n.a. 0.983769249332 3.5274100 0.00017041254947 -3.4721995 42.4219 /T 137.5711 37.8/ 0.2447 n.a. n.a. 1400.9348 145.67552 -50.26968 2025-Dec-20 11:50 21 10 37.40 -28 04 20.0 247.156750 16.669200 n.a. n.a. 0.983783782783 3.7218886 0.00015627563870 -3.5760616 44.3610 /T 135.6323 39.4/ 0.2500 n.a. n.a. 1632.8058 144.82533 -49.22175 2025-Dec-20 12:00 21 23 56.46 -32 05 09.8 243.885798 19.297226 n.a. n.a. 0.983799120262 3.9278015 0.00014173605753 -3.6713184 46.9188 /T 133.0749 41.6/ 0.2556 n.a. n.a. 1938.8388 143.59757 -47.86151 2025-Dec-20 12:10 21 41 21.30 -36 48 40.9 240.199451 22.872027 n.a. n.a. 0.983815298596 4.1399165 0.00012685373311 -3.7437150 50.3150 /T 129.6790 44.7/ 0.2614 n.a. n.a. 2355.0397 141.70422 -46.03212 2025-Dec-20 12:20 22 05 37.32 -42 25 58.7 235.849032 27.730060 n.a. n.a. 0.983832322816 4.3470500 0.00011177030376 -3.7651995 54.8778 /T 125.1166 49.0/ 0.2675 n.a. n.a. 2939.9231 138.55356 -43.46836 2025-Dec-20 12:30 22 42 41.74 -49 05 30.8 230.313995 34.361879 n.a. n.a. 0.983850134531 4.5279600 0.00009678870856 -3.6803181 61.1071 /T 118.8876 55.1/ 0.2738 n.a. n.a. 3787.2961 132.79773 -39.71150 2025-Dec-20 12:40 23 46 53.10 -56 27 30.3 222.316982 43.418890 n.a. n.a. 0.983868561647 4.6464294 0.00008252871753 -3.3813856 69.7529 /T 110.2422 63.9/ 0.2804 n.a. n.a. 5028.6126 121.07264 -33.98034 2025-Dec-20 12:50 01 47 57.05 -61 49 07.6 207.939571 55.304762 n.a. n.a. 0.983887252193 4.6493115 0.00007019806033 -2.6801464 81.7776 /T 98.2179 76.2/ 0.2872 n.a. n.a. 6741.1986 96.256052 -25.10233 2025-Dec-20 13:00 t 04 35 35.43 -57 17 52.1 172.926916 67.038856 n.a. n.a. 0.983905620909 4.4767801 0.00006186478599 -1.3633320 97.6294 /T 82.3666 92.9/ 0.2942 n.a. n.a. 8531.6297 61.091672 -12.05809 2025-Dec-20 13:10 e 06 33 03.09 -40 51 34.9 113.646623 64.035032 n.a. n.a. 0.983922877987 4.0933764 0.00005997867478 0.4646712 115.0642 /L 64.9324 111.8/ 0.3016 n.a. n.a. 9122.2247 39.732880 4.0230903 2025-Dec-20 13:20 07 38 24.18 -21 17 11.4 84.240539 47.726099 n.a. n.a. 0.983938205360 3.5248405 0.00006539239164 2.1524133 128.5251 /L 51.4719 127.5/ 0.3091 n.a. n.a. 7907.4881 32.370398 19.004832 2025-Dec-20 13:30 08 20 02.38 -04 42 19.4 71.819154 32.085161 n.a. n.a. 0.983951020048 2.8577631 0.00007638995660 3.2239616 134.5561 /L 45.4411 136.3/ 0.3169 n.a. n.a. 6080.9633 31.141782 29.864719 2025-Dec-20 13:40 08 50 47.56 +07 49 39.3 64.831760 20.063933 n.a. n.a. 0.983961131702 2.1916664 0.00009051854937 3.7503740 134.8305 /L 45.1664 138.8/ 0.3250 n.a. n.a. 4577.5617 32.309758 36.826269 2025-Dec-20 13:50 09 15 49.41 +17 09 53.8 60.110837 11.129078 n.a. n.a. 0.983968692954 1.5934151 0.00010604187172 3.9527821 132.4308 /L 47.5654 137.8/ 0.3333 n.a. n.a. 3519.2646 34.400571 41.226831 2025-Dec-20 14:00 09 37 25.46 +24 15 00.8 56.571196 4.409652 n.a. n.a. 0.983974039338 1.0886896 0.00012200230297 3.9876736 129.2073 /L 50.7880 135.3/ 0.3418 n.a. n.a. 2787.8321 36.832751 44.125402 >..... Elevation Cut-off Requested .....< >..... Daylight Cut-off Requested .....< >..... Elevation Cut-off Requested .....< $$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/horizons_batch.txt scripts https://ssd.jpl.nasa.gov/ftp/ssd/SCRIPTS Author : Jon.D.Giorgini@jpl.nasa.gov ***************************************************************************************************************************************************************************************************************************************************