API VERSION: 1.2 API SOURCE: NASA/JPL Horizons API ******************************************************************************* Revised: Oct 27, 2025 James Webb Space Telescope / (E-S L2) -170 https://www.jwst.nasa.gov/index.html https://www.youtube.com/watch?v=bTxLAGchWnA The James Webb Space Telescope ("JWST" or "Webb") is a space-based infrared observatory and NASA's successor to the Hubble Space Telescope. Launched by Ariane 5 booster on 2021-Dec-25 @ 12:20 UTC from the ELA-3 launch complex near Korou, French Guiana. After launch, the telescope deployed during its 30-day, 1.5 million km journey to halo orbit at the second Earth-Sun Lagrange point (E-S L2). Mission duration is nominally 5-10 years. GOALS - Search for the first galaxies or luminous objects formed after the Big Bang - Determine how galaxies evolved from their formation until now - Observe the formation of stars from the first stages to the formation of planetary systems - Measure the physical and chemical properties of planetary systems, including our own Solar System, investigating the potential for life in those systems. TELESCOPE * total launch mass : ~6200 kg (observatory, fuel, launch adaptor) * primary mirror : 25 m^2 mass : 705 kg material : beryllium coated w/48.25 grams gold (golf-ball size) segment mass : 20.1 kg, 39.48 kg for entire segment assembly No. of segments : 18 * focal length : 131.4 meters * optical resolution: 0.1 arcseconds * wavelength : 0.6 - 28.5 microns * size of sun shield: 21.197 m x 14.162 m * Sun shield layers : 1: Max temp 283K, 231 deg. F. 5: Max temp 221K, -80 F Min temp 36K, -394 F * Operating temp : < 50K (-370 deg. F) INSTRUMENTS - Near Infrared Camera (NIRCam) - Near Infrared Spectrograph (NIRSpec) - Mid Infrared Instrument (MIRI) - Fine Guidance Sensors/Near Infrared Imager & Slitless Spectrograph (FGS/NIRISS) TRAJECTORY MCC1A (65-minute engine burn) began 2021-Dec-26 12:50 UTC, completed 01:55 UTC. MCC1B (09:27 engine burn) began 2021-Dec-28 00:20 UTC, completed 00:29:27 UTC. MCC2 (04:57 engine burn) began 2022-Jan-24 19:00 UTC, completed 19:04:57 UTC. Concatenation of reconstructed trajectory solutions (as-flown) from Goddard Flight Dynamics Facility (FDF), based on tracking data through October 26, with prediction thereafter. Trajectory files Start (TDB) End (TDB) ---------------------------------------- ----------------- ----------------- DEFINITIVE_EPHEMERIS_202135913-2025292 2021-Dec-25 13:01 2025-Oct-27 00:01 28D_NOBURN_PREDICT_SK_2025300000000_02U 2025-Oct-27 00:01 2025-Nov-24 00:01 5Y_SCHEDULE_2025300000000_02U.V0.1 2025-Nov-24 00:01 2030-Oct-26 23:59 ******************************************************************************* ******************************************************************************* Ephemeris / API_USER Sun Nov 9 14:50:37 2025 Pasadena, USA / Horizons ******************************************************************************* Target body name: James Webb Space Telescope (spacecraft) (-170) {source: JWST_merged} Center body name: Earth (399) {source: DE441} Center-site name: Swan Reach Imaging, Glenalta ******************************************************************************* 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 : 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: DE441} Rel. light bend : Sun {source: DE441} 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.251107.p260203 EOP coverage : DATA-BASED 1962-JAN-20 TO 2025-NOV-07. PREDICTS-> 2026-FEB-02 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 .....< 2024-Oct-31 11:40 04 28 09.30 +23 36 18.4 60.917254 -0.096982 n.a. n.a. 1.001380111782 -0.3580766 0.01007738341679 -0.2372230 149.0962 /L 30.6078 137.2/ 1.1098 n.a. n.a. 1.7077593 75.839020 -48.74924 2024-Oct-31 11:50 04 28 10.46 +23 36 22.5 59.483225 1.690682 n.a. n.a. 1.001378675711 -0.3580335 0.01007644161382 -0.2323341 149.0986 /L 30.6054 137.3/ 1.0916 n.a. n.a. 1.5767911 75.303476 -50.41943 2024-Oct-31 12:00 04 28 11.52 +23 36 26.4 58.015245 3.452136 n.a. n.a. 1.001377239813 -0.3579904 0.01007552068153 -0.2268168 149.1014 /L 30.6026 137.4/ 1.0733 n.a. n.a. 1.4473229 74.778597 -52.14545 2024-Oct-31 12:10 04 28 12.49 +23 36 30.2 56.510928 5.185559 n.a. n.a. 1.001375804088 -0.3579473 0.01007462312023 -0.2206812 149.1046 /L 30.5995 137.5/ 1.0552 n.a. n.a. 1.3195601 74.270642 -53.93674 2024-Oct-31 12:20 04 28 13.36 +23 36 33.6 54.967885 6.889017 n.a. n.a. 1.001374368535 -0.3579042 0.01007375138661 -0.2139389 149.1081 /L 30.5961 137.6/ 1.0371 n.a. n.a. 1.1937043 73.788542 -55.80492 2024-Oct-31 12:30 04 28 14.15 +23 36 36.9 53.383732 8.560455 n.a. n.a. 1.001372933156 -0.3578611 0.01007290788900 -0.2066025 149.1120 /L 30.5923 137.7/ 1.0190 n.a. n.a. 1.0699530 73.345298 -57.76431 2024-Oct-31 12:40 04 28 14.86 +23 36 39.8 51.756104 10.197694 n.a. n.a. 1.001371497949 -0.3578180 0.01007209498273 -0.1986858 149.1162 /L 30.5881 137.8/ 1.0010 n.a. n.a. 0.9485005 72.960312 -59.83281 2024-Oct-31 12:50 04 28 15.47 +23 36 42.5 50.082671 11.798425 n.a. n.a. 1.001370062915 -0.3577748 0.01007131496560 -0.1902038 149.1207 /L 30.5836 137.9/ 0.9832 n.a. n.a. 0.8295392 72.663515 -62.03288 2024-Oct-31 13:00 04 28 16.01 +23 36 44.8 48.361157 13.360206 n.a. n.a. 1.001368628055 -0.3577317 0.01007057007333 -0.1811724 149.1256 /L 30.5788 138.0/ 0.9654 n.a. n.a. 0.7132638 72.503096 -64.39305 2024-Oct-31 13:10 04 28 16.46 +23 36 46.8 46.589372 14.880460 n.a. n.a. 1.001367193367 -0.3576886 0.01006986247530 -0.1716087 149.1308 /L 30.5737 138.1/ 0.9477 n.a. n.a. 0.5998782 72.561119 -66.94964 2024-Oct-31 13:20 04 28 16.84 +23 36 48.4 44.765240 16.356471 n.a. n.a. 1.001365758852 -0.3576455 0.01006919427030 -0.1615308 149.1363 /L 30.5683 138.2/ 0.9302 n.a. n.a. 0.4896149 72.988220 -69.74891 2024-Oct-31 13:30 04 28 17.14 +23 36 49.7 42.886834 17.785390 n.a. n.a. 1.001364324510 -0.3576024 0.01006856748243 -0.1509578 149.1421 /L 30.5625 138.3/ 0.9128 n.a. n.a. 0.3827826 74.091248 -72.84870 2024-Oct-31 13:40 04 28 17.38 +23 36 50.5 40.952426 19.164237 n.a. n.a. 1.001362890342 -0.3575592 0.01006798405715 -0.1399099 149.1482 /L 30.5565 138.5/ 0.8955 n.a. n.a. 0.2799140 76.597568 -76.31548 2024-Oct-31 13:50 04 28 17.54 +23 36 51.0 38.960532 20.489906 n.a. n.a. 1.001361456346 -0.3575161 0.01006744585744 -0.1284081 149.1545 /L 30.5502 138.6/ 0.8784 n.a. n.a. 0.1823661 82.692431 -80.19427 2024-Oct-31 14:00 04 28 17.64 +23 36 51.0 36.909968 21.759179 n.a. n.a. 1.001360022523 -0.3574730 0.01006695466026 -0.1164742 149.1612 /L 30.5436 138.7/ 0.8614 n.a. n.a. 0.0961945 102.03157 -84.26098 2024-Oct-31 14:10 04 28 17.68 +23 36 50.6 34.799908 22.968740 n.a. n.a. 1.001358588874 -0.3574299 0.01006651215296 -0.1041311 149.1681 /L 30.5368 138.8/ 0.8446 n.a. n.a. 0.0658909 169.46325 -85.59709 2024-Oct-31 14:20 04 28 17.66 +23 36 49.7 32.629953 24.115194 n.a. n.a. 1.001357155397 -0.3573867 0.01006611993004 -0.0914022 149.1752 /L 30.5297 138.9/ 0.8280 n.a. n.a. 0.1285730 210.39470 -80.28741 2024-Oct-31 14:30 04 28 17.59 +23 36 48.3 30.400187 25.195090 n.a. n.a. 1.001355722094 -0.3573436 0.01006577948999 -0.0783119 149.1826 /L 30.5225 139.0/ 0.8116 n.a. n.a. 0.2094205 220.88415 -71.97661 2024-Oct-31 14:40 04 28 17.46 +23 36 46.5 28.111253 26.204955 n.a. n.a. 1.001354288963 -0.3573005 0.01006549223236 -0.0648851 149.1902 /L 30.5149 139.1/ 0.7954 n.a. n.a. 0.2905170 224.56796 -61.42085 2024-Oct-31 14:50 04 28 17.29 +23 36 44.2 25.764403 27.141326 n.a. n.a. 1.001352856006 -0.3572574 0.01006525945500 -0.0511477 149.1979 /L 30.5072 139.2/ 0.7793 n.a. n.a. 0.3691947 225.94275 -48.71153 2024-Oct-31 15:00 04 28 17.08 +23 36 41.4 23.361566 28.000793 n.a. n.a. 1.001351423221 -0.3572142 0.01006508235148 -0.0371259 149.2059 /L 30.4993 139.3/ 0.7635 n.a. n.a. 0.4447423 226.25596 -34.45768 2024-Oct-31 15:10 04 28 16.83 +23 36 38.0 20.905379 28.780043 n.a. n.a. 1.001349990610 -0.3571711 0.01006496200878 -0.0228465 149.2141 /L 30.4913 139.5/ 0.7479 n.a. n.a. 0.5169097 225.97808 -19.96875 2024-Oct-31 15:20 04 28 16.54 +23 36 34.2 18.399228 29.475911 n.a. n.a. 1.001348558171 -0.3571280 0.01006489940511 -0.0083369 149.2224 /L 30.4830 139.6/ 0.7325 n.a. n.a. 0.5856104 225.32312 -6.678032 2024-Oct-31 15:30 04 28 16.22 +23 36 29.8 15.847252 30.085433 n.a. n.a. 1.001347125905 -0.3570849 0.01006489540801 0.0063750 149.2308 /L 30.4746 139.7/ 0.7173 n.a. n.a. 0.6508376 224.40101 4.5990212 2024-Oct-31 15:40 04 28 15.88 +23 36 24.8 13.254334 30.605898 n.a. n.a. 1.001345693813 -0.3570418 0.01006495077265 0.0212611 149.2394 /L 30.4661 139.8/ 0.7023 n.a. n.a. 0.7126342 223.27311 13.774589 2024-Oct-31 15:50 04 28 15.52 +23 36 19.4 10.626061 31.034905 n.a. n.a. 1.001344261893 -0.3569987 0.01006506614025 0.0362928 149.2481 /L 30.4575 139.9/ 0.6876 n.a. n.a. 0.7710812 221.97563 21.146155 2024-Oct-31 16:00 04 28 15.13 +23 36 13.3 7.968665 31.370410 n.a. n.a. 1.001342830147 -0.3569556 0.01006524203691 0.0514412 149.2569 /L 30.4488 140.0/ 0.6732 n.a. n.a. 0.8262926 220.53078 27.095233 2024-Oct-31 16:10 04 28 14.74 +23 36 06.8 5.288931 31.610771 n.a. n.a. 1.001341398573 -0.3569125 0.01006547887248 0.0666772 149.2657 /L 30.4400 140.1/ 0.6589 n.a. n.a. 0.8784134 218.95254 31.956224 2024-Oct-31 16:20 04 28 14.33 +23 35 59.7 2.594079 31.754792 n.a. n.a. 1.001339967173 -0.3568694 0.01006577693983 0.0819716 149.2747 /L 30.4311 140.2/ 0.6450 n.a. n.a. 0.9276189 217.24988 35.987424 2024-Oct-31 16:30 t 04 28 13.93 +23 35 52.0 359.891637 31.801743 n.a. n.a. 1.001338535945 -0.3568263 0.01006613641424 0.0972951 149.2837 /L 30.4222 140.3/ 0.6312 n.a. n.a. 0.9741144 215.42867 39.379139 2024-Oct-31 16:40 04 28 13.52 +23 35 43.7 357.189282 31.751385 n.a. n.a. 1.001337104890 -0.3567831 0.01006655735300 0.1126181 149.2927 /L 30.4133 140.4/ 0.6178 n.a. n.a. 1.0181350 213.49295 42.269595 2024-Oct-31 16:50 04 28 13.11 +23 35 35.0 354.494692 31.603974 n.a. n.a. 1.001335674008 -0.3567400 0.01006703969534 0.1279112 149.3017 /L 30.4043 140.6/ 0.6045 n.a. n.a. 1.0599453 211.44571 44.759226 2024-Oct-31 17:00 04 28 12.72 +23 35 25.6 351.815385 31.360252 n.a. n.a. 1.001334243299 -0.3566969 0.01006758326257 0.1431451 149.3107 /L 30.3954 140.7/ 0.5916 n.a. n.a. 1.0998391 209.28957 46.921508 2024-Oct-31 17:10 04 28 12.34 +23 35 15.8 349.158570 31.021433 n.a. n.a. 1.001332812764 -0.3566538 0.01006818775836 0.1582904 149.3197 /L 30.3864 140.8/ 0.5789 n.a. n.a. 1.1381379 207.02721 48.810703 2024-Oct-31 17:20 04 28 11.97 +23 35 05.3 346.531012 30.589169 n.a. n.a. 1.001331382401 -0.3566107 0.01006885276937 0.1733182 149.3287 /L 30.3775 140.9/ 0.5665 n.a. n.a. 1.1751895 204.66176 50.467287 2024-Oct-31 17:30 04 28 11.63 +23 34 54.4 343.938923 30.065517 n.a. n.a. 1.001329952211 -0.3565676 0.01006957776604 0.1881996 149.3376 /L 30.3687 141.0/ 0.5543 n.a. n.a. 1.2113652 202.19715 51.921766 2024-Oct-31 17:40 04 28 11.31 +23 34 42.9 341.387868 29.452889 n.a. n.a. 1.001328522194 -0.3565245 0.01007036210365 0.2029059 149.3464 /L 30.3599 141.1/ 0.5424 n.a. n.a. 1.2470565 199.63835 53.197363 2024-Oct-31 17:50 04 28 11.02 +23 34 30.9 338.882703 28.754004 n.a. n.a. 1.001327092349 -0.3564814 0.01007120502357 0.2174090 149.3552 /L 30.3512 141.2/ 0.5308 n.a. n.a. 1.2826706 196.99156 54.311951 2024-Oct-31 18:00 04 28 10.77 +23 34 18.3 336.427541 27.971833 n.a. n.a. 1.001325662678 -0.3564383 0.01007210565475 0.2316810 149.3639 /L 30.3426 141.3/ 0.5194 n.a. n.a. 1.3186253 194.26438 55.279461 2024-Oct-31 18:10 A 04 28 10.56 +23 34 05.3 334.025740 27.109547 n.a. n.a. 1.001324233180 -0.3563952 0.01007306301545 0.2456946 149.3724 /L 30.3341 141.4/ 0.5083 n.a. n.a. 1.3553422 191.46585 56.110919 2024-Oct-31 18:20 A 04 28 10.38 +23 33 51.8 331.679913 26.170462 n.a. n.a. 1.001322803855 -0.3563521 0.01007407601517 0.2594229 149.3808 /L 30.3257 141.5/ 0.4975 n.a. n.a. 1.3932403 188.60644 56.815234 2024-Oct-31 18:30 A 04 28 10.26 +23 33 37.7 329.391961 25.157991 n.a. n.a. 1.001321374702 -0.3563090 0.01007514345678 0.2728396 149.3891 /L 30.3175 141.6/ 0.4869 n.a. n.a. 1.4327276 185.69795 57.399785 2024-Oct-31 18:40 A 04 28 10.18 +23 33 23.2 327.163115 24.075596 n.a. n.a. 1.001319945723 -0.3562659 0.01007626403887 0.2859190 149.3972 /L 30.3094 141.7/ 0.4766 n.a. n.a. 1.4741940 182.75328 57.870881 2024-Oct-31 18:50 N 04 28 10.16 +23 33 08.3 324.993992 22.926751 n.a. n.a. 1.001318516916 -0.3562228 0.01007743635832 0.2986361 149.4051 /L 30.3015 141.8/ 0.4666 n.a. n.a. 1.5180033 179.78617 58.234104 2024-Oct-31 19:00 N 04 28 10.20 +23 32 52.9 322.884659 21.714906 n.a. n.a. 1.001317088283 -0.3561797 0.01007865891303 0.3109665 149.4128 /L 30.2938 141.9/ 0.4568 n.a. n.a. 1.5644859 176.81083 58.494569 2024-Oct-31 19:10 N 04 28 10.30 +23 32 37.1 320.834696 20.443452 n.a. n.a. 1.001315659822 -0.3561366 0.01007993010491 0.3228868 149.4203 /L 30.2863 142.0/ 0.4473 n.a. n.a. 1.6139327 173.84160 58.657113 2024-Oct-31 19:20 Cm 04 28 10.46 +23 32 20.8 318.843261 19.115704 n.a. n.a. 1.001314231535 -0.3560935 0.01008124824294 0.3343741 149.4277 /L 30.2791 142.0/ 0.4380 n.a. n.a. 1.6665903 170.89247 58.726424 2024-Oct-31 19:30 Cm 04 28 10.69 +23 32 04.2 316.909155 17.734877 n.a. n.a. 1.001312803420 -0.3560504 0.01008261154658 0.3454066 149.4347 /L 30.2720 142.1/ 0.4290 n.a. n.a. 1.7226572 167.97677 58.707128 >..... 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 ***************************************************************************************************************************************************************************************************************************************************