******************************************************************************* Revised: Dec 23, 2021 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. Launch is by Ariane 5 booster no earlier than 2021-Dec-25 @ 12:20 UTC from the ELA-3 launch complex near Korou, French Guiana. After launch, the telescope will deploy 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 Pre-launch planning trajectory for beginning of launch window Trajectory files Start (TDB) End (TDB) ---------------------------------------- ----------------- ----------- BURN_TTF_01_2021359124800_01U.OEM.V0.3 2021-Dec-25 12:50 2022-Jan-22 ******************************************************************************* Ephemeris / WWW_USER Fri Dec 24 00:49:50 2021 Pasadena, USA / Horizons ******************************************************************************* Target body name: James Webb Space Telescope (spacecraft) (-170) {source: JWST_prelaunch_merged} Center body name: Earth (399) {source: DE441} Center-site name: (user defined site below) ******************************************************************************* Start time : A.D. 2021-Dec-25 18:00:00.0000 UT Stop time : A.D. 2022-Jan-01 00:00:00.0000 UT Step-size : 60 minutes ******************************************************************************* Target pole/equ : No model available Target radii : (unavailable) Center geodetic : 0.17000000,52.1900000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)} Center cylindric: 0.17000000,3918.27947,5015.7915 {E-lon(deg),Dxy(km),Dz(km)} Center pole/equ : ITRF93 {East-longitude positive} Center radii : 6378.1 x 6378.1 x 6356.8 km {Equator, meridian, pole} Target primary : Earth Vis. interferer : MOON (R_eq= 1737.400) km {source: DE441} Rel. light bend : Sun, EARTH {source: DE441} Rel. lght bnd GM: 1.3271E+11, 3.9860E+05 km^3/s^2 Atmos refraction: NO (AIRLESS) RA format : HMS Time format : CAL EOP file : eop.211222.p220317 EOP coverage : DATA-BASED 1962-JAN-20 TO 2021-DEC-22. PREDICTS-> 2022-MAR-16 Units conversion: 1 au= 149597870.700 km, c= 299792.458 km/s, 1 day= 86400.0 s Table cut-offs 1: Elevation (-90.0deg=NO ),Airmass (>38.000=NO), Daylight (YES) Table cut-offs 2: Solar elongation ( 0.0,180.0=NO ),Local Hour Angle( 0.0=NO ) Table cut-offs 3: RA/DEC angular rate ( 0.0=NO ) *********************************************************************************************************************************************** Date__(UT)__HR:MN:SS R.A.__(a-apparent)__DEC delta deldot Cnst Sky_motion Sky_mot_PA RelVel-ANG Lun_Sky_Brt sky_SNR *********************************************************************************************************************************************** $$SOE 2021-Dec-25 18:00:00 04 45 15.80 -05 07 44.6 0.00052389130477 2.6628171 Eri 111.20264 71.192027 75.186881 n.a. n.a. 2021-Dec-25 19:00:00 04 51 16.69 -04 36 19.6 0.00058612560725 2.5182798 Eri 81.289321 70.138684 77.118158 n.a. n.a. 2021-Dec-25 20:00:00 04 55 41.90 -04 11 33.6 0.00064547066212 2.4204584 Eri 61.197642 68.662646 78.840696 n.a. n.a. 2021-Dec-25 21:00:00 04 59 02.38 -03 51 14.7 0.00070290478433 2.3577971 Eri 47.639264 67.056899 80.258912 n.a. n.a. 2021-Dec-25 22:00:00 05 01 39.80 -03 34 05.1 0.00075915889232 2.3209477 Ori 38.738353 65.796482 81.292120 n.a. n.a. 2021-Dec-25 23:00:00 m 05 03 50.23 -03 19 16.1 0.00081475342264 2.3017008 Ori 33.276730 65.434157 81.896457 0.722 0.000 2021-Dec-26 00:00:00 m 05 05 45.85 -03 06 16.5 0.00087002106972 2.2925914 Ori 30.391625 66.315254 82.063423 0.833 0.000 2021-Dec-26 01:00:00 m 05 07 35.85 -02 54 45.3 0.00092512984010 2.2900632 Ori 29.507257 68.347176 81.800802 0.928 0.000 2021-Dec-26 02:00:00 m 05 09 27.83 -02 44 24.1 0.00098037127063 2.2987542 Ori 30.277934 71.048337 81.128449 0.997 0.000 2021-Dec-26 03:00:00 m 05 11 25.67 -02 35 05.1 0.00103552885808 2.2837707 Ori 31.581786 73.779160 80.179606 1.063 0.000 2021-Dec-26 04:00:00 m 05 13 31.25 -02 26 43.2 0.00109020362950 2.2581434 Ori 33.398015 76.269014 78.971161 1.149 0.000 2021-Dec-26 05:00:00 m 05 15 45.53 -02 19 11.9 0.00114410949534 2.2195573 Ori 35.349057 78.367779 77.578832 n.a. n.a. 2021-Dec-26 06:00:00 m 05 18 08.13 -02 12 26.3 0.00119691864611 2.1669558 Ori 37.120036 80.059798 76.080592 n.a. n.a. 2021-Dec-26 07:00:00 Nm 05 20 37.61 -02 06 21.6 0.00124829339011 2.1004999 Ori 38.463509 81.388746 74.554539 n.a. n.a. 2021-Dec-26 08:00:00 Cm 05 23 11.72 -02 00 53.9 0.00129791435525 2.0214699 Ori 39.198083 82.412761 73.079478 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-26 16:00:00 C 05 40 31.94 -01 32 30.0 0.00161536520625 1.3266529 Ori 19.413524 82.730068 74.053813 n.a. n.a. 2021-Dec-26 17:00:00 N 05 41 40.28 -01 30 06.8 0.00164679128700 1.2882924 Ori 15.087911 81.146899 76.877196 n.a. n.a. 2021-Dec-26 18:00:00 05 42 31.48 -01 27 50.6 0.00167752749899 1.2694874 Ori 10.958734 78.300879 80.071397 n.a. n.a. 2021-Dec-26 19:00:00 05 43 06.68 -01 25 39.6 0.00170804839381 1.2702419 Ori 7.2652555 72.771764 83.265198 n.a. n.a. 2021-Dec-26 20:00:00 05 43 27.80 -01 23 32.0 0.00173881073778 1.2892400 Ori 4.2812171 60.544526 86.007443 n.a. n.a. 2021-Dec-26 21:00:00 05 43 37.50 -01 21 26.6 0.00177022497843 1.3239355 Ori 2.4270632 31.195681 87.753580 n.a. n.a. 2021-Dec-26 22:00:00 05 43 39.00 -01 19 22.6 0.00180262778179 1.3706396 Ori 2.0891298 350.04940 88.097781 n.a. n.a. 2021-Dec-26 23:00:00 05 43 35.83 -01 17 19.6 0.00183625367448 1.4248251 Ori 2.3088616 332.26543 87.940061 n.a. n.a. 2021-Dec-27 00:00:00 m 05 43 31.60 -01 15 17.4 0.00187122337429 1.4814485 Ori 2.2170141 336.17198 88.061285 0.517 0.000 2021-Dec-27 01:00:00 m 05 43 29.75 -01 13 16.4 0.00190753323121 1.5353125 Ori 2.0088155 2.8758546 88.271954 0.593 0.000 2021-Dec-27 02:00:00 m 05 43 33.32 -01 11 16.9 0.00194505578134 1.5815109 Ori 2.6625249 42.118486 87.733282 0.682 0.000 2021-Dec-27 03:00:00 m 05 43 44.73 -01 09 19.6 0.00198355441131 1.6157701 Ori 4.4320470 64.154865 86.237184 0.750 0.000 2021-Dec-27 04:00:00 m 05 44 05.66 -01 07 25.3 0.00202269938615 1.6347244 Ori 6.7798460 73.925845 84.209819 0.821 0.000 2021-Dec-27 05:00:00 m 05 44 37.01 -01 05 34.6 0.00206209248706 1.6361705 Ori 9.3371587 78.816491 81.904266 0.897 0.000 2021-Dec-27 06:00:00 m 05 45 18.84 -01 03 48.2 0.00210129879934 1.6191587 Ori 11.854083 81.583778 79.465893 n.a. n.a. 2021-Dec-27 07:00:00 Nm 05 46 10.49 -01 02 06.5 0.00213987604177 1.5839892 Ori 14.132641 83.288702 77.004776 n.a. n.a. 2021-Dec-27 08:00:00 Cm 05 47 10.60 -01 00 30.1 0.00217740231181 1.5321888 Ori 16.013513 84.396771 74.619781 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-27 16:00:00 C 05 55 45.94 -00 50 35.6 0.00241424903579 0.9573340 Ori 10.296313 84.485754 72.575018 n.a. n.a. 2021-Dec-27 17:00:00 N 05 56 21.71 -00 49 37.2 0.00243689397493 0.9278276 Ori 7.6788871 82.826453 76.299414 n.a. n.a. 2021-Dec-27 18:00:00 05 56 46.89 -00 48 40.3 0.00245905850837 0.9174855 Ori 5.0663443 79.318660 80.678759 n.a. n.a. 2021-Dec-27 19:00:00 05 57 01.76 -00 47 44.3 0.00248120783150 0.9264748 Ori 2.6596579 69.561167 85.078995 n.a. n.a. 2021-Dec-27 20:00:00 05 57 07.25 -00 46 48.7 0.00250379567264 0.9536469 Ori 0.9789130 18.817038 88.220545 n.a. n.a. 2021-Dec-27 21:00:00 05 57 04.89 -00 45 53.0 0.00252723276617 0.9965760 Ori 1.6934073 303.33266 87.028469 n.a. n.a. 2021-Dec-27 22:00:00 05 56 56.67 -00 44 57.0 0.00255185765208 1.0517038 Ori 2.7589412 289.88266 85.373684 n.a. n.a. 2021-Dec-27 23:00:00 05 56 44.95 -00 44 00.4 0.00257791216963 1.1145831 Ori 3.2972116 286.70077 84.733133 n.a. n.a. 2021-Dec-28 00:00:00 05 56 32.25 -00 43 03.3 0.00260552382625 1.1802020 Ori 3.2308432 287.20947 85.072153 n.a. n.a. 2021-Dec-28 01:00:00 05 56 21.11 -00 42 05.7 0.00263473095838 1.2458400 Ori 2.5800602 291.93796 86.226454 n.a. n.a. 2021-Dec-28 02:00:00 m 05 56 13.80 -00 41 07.8 0.00266540154260 1.3015326 Ori 1.5207907 309.37207 87.844019 0.403 0.000 2021-Dec-28 03:00:00 m 05 56 12.27 -00 40 10.1 0.00269727746834 1.3453450 Ori 1.0696956 26.189283 88.515001 0.482 0.000 2021-Dec-28 04:00:00 m 05 56 17.97 -00 39 12.8 0.00273002844797 1.3737409 Ori 2.5959290 68.560045 86.431692 0.555 0.000 2021-Dec-28 05:00:00 m 05 56 31.79 -00 38 16.3 0.00276325174962 1.3843060 Ori 4.6037192 78.323328 83.661488 0.631 0.000 2021-Dec-28 06:00:00 m 05 56 54.03 -00 37 21.1 0.00279650166466 1.3758892 Ori 6.6591834 82.154672 80.708482 n.a. n.a. 2021-Dec-28 07:00:00 Nm 05 57 24.37 -00 36 27.4 0.00282932104186 1.3486479 Ori 8.5825889 84.105055 77.721540 n.a. n.a. 2021-Dec-28 08:00:00 Cm 05 58 01.95 -00 35 35.4 0.00286127142558 1.3039877 Ori 10.236815 85.234822 74.809752 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-28 16:00:00 C 06 03 58.19 -00 29 47.9 0.00305787490139 0.7619011 Ori 7.1760109 85.009576 70.805592 n.a. n.a. 2021-Dec-28 17:00:00 N 06 04 22.80 -00 29 10.9 0.00307584837760 0.7349652 Ori 5.1732999 83.198281 75.334591 n.a. n.a. 2021-Dec-28 18:00:00 06 04 39.24 -00 28 34.3 0.00309340214393 0.7271663 Ori 3.1429549 78.884049 80.819496 n.a. n.a. 2021-Dec-28 19:00:00 06 04 47.60 -00 27 58.1 0.00311100205489 0.7387263 Ori 1.2755571 61.758940 86.284848 n.a. n.a. 2021-Dec-28 20:00:00 06 04 48.53 -00 27 21.8 0.00312910334538 0.7685416 Ori 0.8626835 314.52033 87.568824 n.a. n.a. 2021-Dec-28 21:00:00 06 04 43.14 -00 26 45.4 0.00314811906889 0.8142270 Ori 2.1078041 286.79290 84.373831 n.a. n.a. 2021-Dec-28 22:00:00 06 04 32.96 -00 26 08.7 0.00316839086488 0.8722628 Ori 3.0559800 281.60572 82.357542 n.a. n.a. 2021-Dec-28 23:00:00 06 04 19.84 -00 25 31.7 0.00319016431389 0.9382334 Ori 3.5363986 280.11714 81.729903 n.a. n.a. 2021-Dec-29 00:00:00 06 04 05.80 -00 24 54.2 0.00321357108629 1.0071452 Ori 3.5134839 280.28197 82.282551 n.a. n.a. 2021-Dec-29 01:00:00 06 03 52.85 -00 24 16.5 0.00323861942958 1.0737943 Ori 3.0008062 282.14986 83.756482 n.a. n.a. 2021-Dec-29 02:00:00 06 03 42.92 -00 23 38.5 0.00326519358973 1.1331544 Ori 2.0601632 287.91628 85.895574 n.a. n.a. 2021-Dec-29 03:00:00 m 06 03 37.66 -00 23 00.5 0.00329306280875 1.1807480 Ori 0.8845368 315.70829 88.291942 0.259 0.000 2021-Dec-29 04:00:00 m 06 03 38.33 -00 22 22.6 0.00332189875962 1.2129566 Ori 1.1727896 57.539106 87.776621 0.319 0.000 2021-Dec-29 05:00:00 m 06 03 45.76 -00 21 45.0 0.00335129835226 1.2272726 Ori 2.8115558 77.203669 84.697943 0.390 0.000 2021-Dec-29 06:00:00 m 06 04 00.29 -00 21 07.9 0.00338081326407 1.2224494 Ori 4.5548884 82.263616 81.342152 n.a. n.a. 2021-Dec-29 07:00:00 Nm 06 04 21.73 -00 20 31.5 0.00340998104176 1.1985578 Ori 6.2116860 84.445770 77.941705 n.a. n.a. 2021-Dec-29 08:00:00 Cm 06 04 49.46 -00 19 55.8 0.00343835656361 1.1569513 Ori 7.6605811 85.601826 74.613558 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-29 16:00:00 C 06 09 27.84 -00 15 40.9 0.00360829361347 0.6298346 Ori 5.5767324 84.981381 68.884534 n.a. n.a. 2021-Dec-29 17:00:00 N 06 09 46.74 -00 15 11.8 0.00362310490236 0.6042768 Ori 3.9041377 82.888729 74.201232 n.a. n.a. 2021-Dec-29 18:00:00 A 06 09 58.78 -00 14 42.9 0.00363753059148 0.5978729 Ori 2.1987719 77.365529 80.814565 n.a. n.a. 2021-Dec-29 19:00:00 06 10 04.00 -00 14 14.1 0.00365203635741 0.6108504 Ori 0.6821559 45.226193 87.177703 n.a. n.a. 2021-Dec-29 20:00:00 06 10 02.90 -00 13 45.2 0.00366707802578 0.6421158 Ori 1.1085037 295.74407 85.624042 n.a. n.a. 2021-Dec-29 21:00:00 06 09 56.39 -00 13 16.3 0.00368306945946 0.6892923 Ori 2.2553634 282.38100 81.711863 n.a. n.a. 2021-Dec-29 22:00:00 06 09 45.76 -00 12 47.2 0.00370035331454 0.7488694 Ori 3.0870092 279.06223 79.552703 n.a. n.a. 2021-Dec-29 23:00:00 06 09 32.56 -00 12 17.9 0.00371917645965 0.8164418 Ori 3.5144774 277.99665 79.047161 n.a. n.a. 2021-Dec-30 00:00:00 06 09 18.51 -00 11 48.5 0.00373967209303 0.8870235 Ori 3.5082790 278.04805 79.863051 n.a. n.a. 2021-Dec-30 01:00:00 06 09 05.35 -00 11 19.0 0.00376185008811 0.9554125 Ori 3.0759008 279.21525 81.671118 n.a. n.a. 2021-Dec-30 02:00:00 06 08 54.74 -00 10 49.5 0.00378559667404 1.0165790 Ori 2.2607793 282.59212 84.189214 n.a. n.a. 2021-Dec-30 03:00:00 06 08 48.13 -00 10 19.9 0.00381068270768 1.0660127 Ori 1.1599482 295.08922 87.130611 n.a. n.a. 2021-Dec-30 04:00:00 m 06 08 46.65 -00 09 50.5 0.00383677969727 1.1000683 Ori 0.5980335 35.064615 88.555719 0.157 0.000 2021-Dec-30 05:00:00 m 06 08 51.05 -00 09 21.2 0.00386348445740 1.1161988 Ori 1.9355451 75.461613 85.370197 0.189 0.000 2021-Dec-30 06:00:00 m 06 09 01.67 -00 08 52.2 0.00389034745394 1.1131164 Ori 3.4644373 82.016188 81.673293 n.a. n.a. 2021-Dec-30 07:00:00 Nm 06 09 18.39 -00 08 23.5 0.00391690406268 1.0908561 Ori 4.9312615 84.464504 77.919287 n.a. n.a. 2021-Dec-30 08:00:00 Cm 06 09 40.69 -00 07 55.2 0.00394270623940 1.0507474 Ori 6.2248864 85.672969 74.233780 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-30 16:00:00 C 06 13 32.86 -00 04 20.0 0.00409307669382 0.5322489 Ori 4.6019431 84.582872 66.840375 n.a. n.a. 2021-Dec-30 17:00:00 N 06 13 48.28 -00 03 53.9 0.00410555256828 0.5077212 Ori 3.1396295 82.064318 72.940093 n.a. n.a. 2021-Dec-30 18:00:00 A 06 13 57.68 -00 03 28.0 0.00411766717435 0.5023717 Ori 1.6487022 74.772057 80.722853 n.a. n.a. 2021-Dec-30 19:00:00 06 14 01.09 -00 03 02.0 0.00412988737032 0.5164225 Ori 0.4512044 16.325450 87.502518 n.a. n.a. 2021-Dec-30 20:00:00 06 13 58.91 -00 02 36.0 0.00414266930694 0.5487632 Ori 1.2601742 290.10332 83.440074 n.a. n.a. 2021-Dec-30 21:00:00 06 13 51.95 -00 02 10.0 0.00415642683149 0.5970047 Ori 2.2920649 280.89488 79.081884 n.a. n.a. 2021-Dec-30 22:00:00 06 13 41.33 -00 01 44.0 0.00417150231571 0.6576282 Ori 3.0338726 278.20648 76.904115 n.a. n.a. 2021-Dec-30 23:00:00 06 13 28.42 -00 01 18.1 0.00418814217093 0.7262255 Ori 3.4170703 277.27166 76.601180 n.a. n.a. 2021-Dec-31 00:00:00 06 13 14.74 -00 00 52.2 0.00420647911351 0.7978112 Ori 3.4150028 277.25881 77.720811 n.a. n.a. 2021-Dec-31 01:00:00 06 13 01.83 -00 00 26.3 0.00422652254008 0.8671856 Ori 3.0324617 278.15138 79.870502 n.a. n.a. 2021-Dec-31 02:00:00 06 12 51.19 -00 00 00.6 0.00424815795077 0.9293143 Ori 2.3048529 280.70136 82.741839 n.a. n.a. 2021-Dec-31 03:00:00 06 12 44.10 +00 00 25.0 0.00427115538492 0.9796930 Ori 1.3051687 289.03362 86.065287 n.a. n.a. 2021-Dec-31 04:00:00 06 12 41.60 +00 00 50.5 0.00429518611580 1.0146670 Ori 0.4233162 1.8845054 88.759128 n.a. n.a. 2021-Dec-31 05:00:00 06 12 44.38 +00 01 15.8 0.00431984627534 1.0316791 Ori 1.4501715 73.144612 85.802085 n.a. n.a. 2021-Dec-31 06:00:00 m 06 12 52.74 +00 01 40.9 0.00434468535821 1.0294310 Ori 2.8221853 81.481852 81.807095 n.a. n.a. 2021-Dec-31 07:00:00 Nm 06 13 06.61 +00 02 05.9 0.00436923754976 1.0079507 Ori 4.1479498 84.245671 77.738035 n.a. n.a. 2021-Dec-31 08:00:00 Cm 06 13 25.54 +00 02 30.8 0.00439305348243 0.9685665 Ori 5.3225723 85.536689 73.732406 n.a. n.a. >..... Daylight Cut-off Requested .....< 2021-Dec-31 16:00:00 C 06 16 47.15 +00 05 49.8 0.00452812007196 0.4557518 Ori 3.9468341 83.903345 64.639622 n.a. n.a. 2021-Dec-31 17:00:00 N 06 17 00.23 +00 06 14.9 0.00453876602459 0.4321412 Ori 2.6324746 80.812251 71.520186 n.a. n.a. 2021-Dec-31 18:00:00 A 06 17 07.89 +00 06 40.2 0.00454907317268 0.4277397 Ori 1.2987332 71.087946 80.521473 n.a. n.a. 2021-Dec-31 19:00:00 06 17 10.14 +00 07 05.4 0.00455950880773 0.4427433 Ori 0.4310902 347.48311 86.928219 n.a. n.a. 2021-Dec-31 20:00:00 06 17 07.34 +00 07 30.6 0.00457052891737 0.4760153 Ori 1.3447829 288.19534 81.128726 n.a. n.a. 2021-Dec-31 21:00:00 06 17 00.21 +00 07 55.8 0.00458254655129 0.5251406 Ori 2.2812902 280.56086 76.469493 n.a. n.a. 2021-Dec-31 22:00:00 06 16 49.78 +00 08 20.8 0.00459590265800 0.5865828 Ori 2.9520863 278.09040 74.379189 n.a. n.a. 2021-Dec-31 23:00:00 06 16 37.28 +00 08 45.6 0.00461084193466 0.6559226 Ori 3.2977364 277.17831 74.345867 n.a. n.a. 2022-Jan-01 00:00:00 06 16 24.08 +00 09 10.2 0.00462749520289 0.7281717 Ori 3.2936603 277.11840 75.801134 n.a. n.a. $$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 dates prior to 1582-Oct-15 are in the Julian calendar system. Later calendar dates are in the Gregorian system. 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 symbol: '*' 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 (OBSERVING SITE) The solar-presence symbol is immediately followed by a lunar-presence symbol: 'm' Refracted upper-limb of Moon on or above apparent horizon ' ' Refracted upper-limb of Moon below apparent horizon OR geocentric ephemeris 'R.A.__(a-apparent)__DEC' = Airless apparent right ascension and declination of the target center with respect to an instantaneous reference frame defined by the Earth equator of-dat (z-axis) and meridian containing the Earth equinox of-date (x-axis, EOP-correct IAU76/80). Compensated for down-leg light-time delay, gravitational deflection of light, stellar aberration, precession & nutation. Note: equinox (RA origin) is offset -53 mas from the of-date frame defined by the IAU06/00a P & N system. 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} '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 'Cnst' = Constellation ID; the 3-letter abbreviation for the name of the constellation containing the target centers' astrometric position, as defined by IAU (1930) boundary delineation. See documentation for list of abbreviations. '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 'Lun_Sky_Brt sky_SNR' = Sky brightness due to moonlight scattered by Earth's atmosphere at the target's position in the sky. "sky_SNR" is the visual signal-to-noise ratio (SNR) of the target's surface brightness relative to background sky. Output only for topocentric Earth observers when both the Moon and target are above the local horizon and the Sun is in astronomical twilight (or further) below the horizon, and the target is not the Moon or Sun. If all conditions are not met, "n.a." is output. Galactic brightness, local sky light-pollution and weather are NOT considered. Lunar opposition surge is considered. The value returned is accurate under ideal conditions at the approximately 8-23% level, so is a useful but not definitive value. If the target-body radius is also known, "sky_SNR" is output. This is the approximate visual signal-to-noise ratio of the target's brightness divided by lunar sky brightness. When sky_SNR < 1, the target is dimmer than the ideal moonlight-scattering background sky, so unlikely to be detectable at visual wavelengths. In practice, visibility requires sky_SNR > 1 and a detector sensitive enough to reach the target's magnitude, even if it isn't washed out by moonlight. When relating magnitudes and brightness values, keep in mind their logarithmic relationship m2-m1 = -2.5*log_10(b2/b1). UNITS: VISUAL MAGNITUDES / ARCSECOND^2, and unitless ratio 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 ***********************************************************************************************************************************************