******************************************************************************* Revised: Nov 16, 2022 Artemis I / Spacecraft (Earth) -1023 https://www.nasa.gov/artemis-1 BACKGROUND: NASA's 42-day unmanned Artemis I mission will test the integrated systems by - launching Orion atop the SLS rocket - operating the spacecraft in a deep space environment - orbiting the Moon in a distant retrograde orbit before returning to Earth - testing Orion's heat shield at 30,000 km/hr (2760 deg. C), and - recovering the crew module after reentry, descent, and splashdown MAJOR EVENTS: Launched November 16 @ 06:47:44 UTC from pad 39B at the Kennedy Space Center. Timings below might shift a bit if launch is delayed past the start of the reference window (Aug 29), so are approximate: launch+00h 18m 20s - Orion deploys solar arrays in Earth orbit +00h 51m 22s - Perigee raise maneuver (22 second burn) +01h 38m 03s - Trans-lunar injection burn (17m59s burn) +02h 06m 10s - Orion/ICPS separation +02h 07m 31s - Upper stage separation burn After Orion separates from the ICPS ("Interim Cryogenic Propulsion Stage"), 10 small spacecraft ("CubeSats") will be deployed to perform experiments and technology demonstrations. Each CubeSat provides its own propulsion and navigation. +07h 56m 05s - Outbound Trajectory Correction-1 burn Flight Day 02-05 - Outbound transit 06-09 - Transit to Distant Retrograde Orbit (DRO) around Moon, closest lunar approach ~97 km 10-23 - In DRO 24-34 - Exit DRO (departure burn on Day 24) 35-42 - Return transit 43 - Entry and splashdown (Pacific) ORION TEST DUMMIES (named by public contest) Commander Moonikin Campos - A suited manikin will occupy the commander's seat inside Orion to provide data on vibration, acceleration, and radiation that crew members may experience in flight. Helga and Zohar - Two additional seats in Orion will be occupied by manikin torsos manufactured from materials that mimic human bones, soft tissues, and organs. The torsos will be fitted with more than 5,600 passive sensors and 34 active radiation detectors. Zohar will wear a radiation protection vest while Helga will not. The study will provide data on radiation levels astronauts may encounter on lunar missions and evaluate the effectiveness of the protective vest. SPACECRAFT DETAILS SLS * Height : 98 meters * Mass at liftoff : 2.61 million kg * Thrust at liftoff : 39.1 million Newtons * Payload to the moon : 27,000 kg Orion module * Crew + service mod hgt: 7.92 meters * Pressurized volume : 19.6 m^3 * Mass to the Moon : 24,000 kg * Return mass at landing: 8,260 kg CUBESATS DISPENSED (independent missions and trajectories once released): Moon Lunar IceCube: Detect all forms of water & other volatiles (IR spectrometer) LunaH-Map : Higher-fidelity mapping of near-surface hydrogen in craters and other permanently shadowed regions of the lunar South Pole (neutron spectrometers) LunIR : Infrared imaging of the lunar surface OMOTENASHI : Lunar lander and studying the lunar environment Separate trajectory available in Horizons. Radiation CuSP : Measure particles & magnetic fields (space weather station) BioSentinel : Use single-celled yeast to detect, measure and compare the impact of deep-space radiation on living organisms over a long period of time EQUULEUS : Image Earth's plasmasphere for a better understanding of Earth's radiation environment from Earth-Moon LaGrange 2 point ("EM-L2", object 3012 in Horizons) Asteroid NEA Scout : Travel by solar sail to asteroid 2020 GE to image and characterize its surface in September 2024. Separate trajectory available in Horizons. Technology Demonstrations ArgoMoon : Observing interim cryogenic propulsion stage with advanced optics and software imaging system Team Miles : Demonstrating propulsion using plasma thrusters, competing in NASA's Deep Space Derby SPACECRAFT TRAJECTORY: Post-launch reconstructed Orion trajectory. Trajectory name Start (TDB) Stop (TDB) ----------------------------------------- ----------------- ----------------- Orion_OEM_20221116_1700_V0.1 2022-Nov-16 08:46 2022-Nov-26 08:46 ******************************************************************************* ******************************************************************************* Ephemeris / WWW_USER Thu Nov 17 07:12:59 2022 Pasadena, USA / Horizons ******************************************************************************* Target body name: Artemis I (spacecraft) (-1023) {source: Artemis_I_merged} Center body name: Earth (399) {source: DE441} Center-site name: (user defined site below) ******************************************************************************* Start time : A.D. 2022-Nov-17 17:00:00.0000 UT Stop time : A.D. 2022-Nov-20 17:00:00.0000 UT Step-size : 60 minutes ******************************************************************************* Target pole/equ : No model available Target radii : (unavailable) Center geodetic : 21.0833000,52.5834000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)} Center cylindric: 21.0833000,3883.60289,5042.5089 {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 (R_eq= 6378.137) km 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 EOP file : eop.221110.p230202 EOP coverage : DATA-BASED 1962-JAN-20 TO 2022-NOV-10. PREDICTS-> 2023-FEB-01 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 (NO ) 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 R.A._____(ICRF)_____DEC APmag S-brt delta deldot S-O-T /r S-T-O Sky_motion Sky_mot_PA RelVel-ANG Lun_Sky_Brt sky_SNR ****************************************************************************************************************************************************************************** $$SOE 2022-Nov-17 17:00 13 06 23.58 -05 10 08.7 n.a. n.a. 0.00161188983454 1.2999870 37.7619 /L 142.1809 24.810689 103.11984 69.601094 n.a. n.a. 2022-Nov-17 18:00 13 08 03.53 -05 15 49.4 n.a. n.a. 0.00164222503784 1.2196660 37.3877 /L 142.5545 26.109452 102.62493 66.976208 n.a. n.a. 2022-Nov-17 19:00 13 09 47.16 -05 21 36.4 n.a. n.a. 0.00167052226037 1.1312506 36.9990 /L 142.9427 26.631853 102.65845 64.573528 n.a. n.a. 2022-Nov-17 20:00 13 11 31.16 -05 27 32.4 n.a. n.a. 0.00169663568057 1.0388785 36.6082 /L 143.3331 26.348392 103.16331 62.517913 n.a. n.a. 2022-Nov-17 21:00 13 13 12.21 -05 33 38.7 n.a. n.a. 0.00172052303236 0.9469783 36.2276 /L 143.7134 25.278346 104.14758 60.961629 n.a. n.a. 2022-Nov-17 22:00 13 14 47.14 -05 39 55.6 n.a. n.a. 0.00174224961487 0.8600193 35.8689 /L 144.0719 23.487542 105.68506 60.093045 n.a. n.a. 2022-Nov-17 23:00 m 13 16 13.10 -05 46 21.9 n.a. n.a. 0.00176198617623 0.7822532 35.5429 /L 144.3976 21.086786 107.93490 60.137168 n.a. n.a. 2022-Nov-18 00:00 m 13 17 27.73 -05 52 55.5 n.a. n.a. 0.00178000056635 0.7174563 35.2587 /L 144.6817 18.231034 111.18921 61.331497 n.a. n.a. 2022-Nov-18 01:00 m 13 18 29.30 -05 59 32.8 n.a. n.a. 0.00179664325858 0.6686795 35.0230 /L 144.9171 15.120084 115.97046 63.844632 n.a. n.a. 2022-Nov-18 02:00 m 13 19 16.84 -06 06 09.6 n.a. n.a. 0.00181232713495 0.6380243 34.8402 /L 145.0998 12.003235 123.21171 67.600727 n.a. n.a. 2022-Nov-18 03:00 m 13 19 50.15 -06 12 40.9 n.a. n.a. 0.00182750232444 0.6264593 34.7113 /L 145.2283 9.1914507 134.48887 72.041342 0.977 n.a. 2022-Nov-18 04:00 m 13 20 09.94 -06 19 01.3 n.a. n.a. 0.00184262736477 0.6337011 34.6346 /L 145.3047 7.0630654 151.69227 76.057773 0.923 n.a. 2022-Nov-18 05:00 Nm 13 20 17.71 -06 25 05.7 n.a. n.a. 0.00185813846971 0.6581797 34.6049 /L 145.3339 5.9436804 174.02655 78.534009 n.a. n.a. 2022-Nov-18 06:00 Cm 13 20 15.75 -06 30 49.3 n.a. n.a. 0.00187441913507 0.6971034 34.6144 /L 145.3238 5.7232908 194.83939 79.462156 n.a. n.a. 2022-Nov-18 07:00 *m 13 20 06.91 -06 36 08.4 n.a. n.a. 0.00189177259459 0.7466301 34.6527 /L 145.2849 5.8083926 208.58060 79.912804 n.a. n.a. 2022-Nov-18 08:00 *m 13 19 54.47 -06 41 00.6 n.a. n.a. 0.00191039963016 0.8021390 34.7079 /L 145.2291 5.6664018 215.01876 80.735039 n.a. n.a. 2022-Nov-18 09:00 *m 13 19 41.83 -06 45 25.0 n.a. n.a. 0.00193038388667 0.8585779 34.7671 /L 145.1691 5.0754603 214.55724 82.146235 n.a. n.a. 2022-Nov-18 10:00 *m 13 19 32.32 -06 49 22.5 n.a. n.a. 0.00195168615147 0.9108542 34.8177 /L 145.1177 4.1217951 204.63279 83.906355 n.a. n.a. 2022-Nov-18 11:00 *m 13 19 28.88 -06 52 55.5 n.a. n.a. 0.00197414813104 0.9542262 34.8482 /L 145.0864 3.3685469 178.00106 85.184741 n.a. n.a. 2022-Nov-18 12:00 *m 13 19 33.94 -06 56 08.0 n.a. n.a. 0.00199750525720 0.9846560 34.8490 /L 145.0848 3.9321075 141.10470 84.492394 n.a. n.a. 2022-Nov-18 13:00 * 13 19 49.20 -06 59 04.8 n.a. n.a. 0.00202140716242 0.9990898 34.8131 /L 145.1200 5.8813096 118.90775 81.814761 n.a. n.a. 2022-Nov-18 14:00 * 13 20 15.59 -07 01 51.5 n.a. n.a. 0.00204544382226 0.9956462 34.7363 /L 145.1962 8.4079583 108.89249 78.206114 n.a. n.a. 2022-Nov-18 15:00 C 13 20 53.21 -07 04 34.1 n.a. n.a. 0.00206917504147 0.9737058 34.6175 /L 145.3143 11.025316 104.17298 74.186968 n.a. n.a. 2022-Nov-18 16:00 A 13 21 41.40 -07 07 18.3 n.a. n.a. 0.00209216094589 0.9339067 34.4587 /L 145.4726 13.457201 101.87447 69.976991 n.a. n.a. 2022-Nov-18 17:00 13 22 38.81 -07 10 09.2 n.a. n.a. 0.00211399136317 0.8780593 34.2645 /L 145.6664 15.512945 100.85100 65.701768 n.a. n.a. 2022-Nov-18 18:00 13 23 43.50 -07 13 11.4 n.a. n.a. 0.00213431233032 0.8089955 34.0416 /L 145.8890 17.054561 100.60533 61.458134 n.a. n.a. 2022-Nov-18 19:00 13 24 53.12 -07 16 28.3 n.a. n.a. 0.00215284836303 0.7303698 33.7987 /L 146.1318 17.988902 100.91511 57.340772 n.a. n.a. 2022-Nov-18 20:00 13 26 05.03 -07 20 02.4 n.a. n.a. 0.00216941949374 0.6464255 33.5454 /L 146.3850 18.265759 101.69624 53.460271 n.a. n.a. 2022-Nov-18 21:00 13 27 16.45 -07 23 54.5 n.a. n.a. 0.00218395239856 0.5617389 33.2920 /L 146.6384 17.877205 102.95338 49.962690 n.a. n.a. 2022-Nov-18 22:00 13 28 24.66 -07 28 04.6 n.a. n.a. 0.00219648518752 0.4809501 33.0487 /L 146.8817 16.857117 104.77116 47.056671 n.a. n.a. 2022-Nov-18 23:00 13 29 27.14 -07 32 31.1 n.a. n.a. 0.00220716564582 0.4084890 32.8253 /L 147.1051 15.280815 107.33601 45.053651 n.a. n.a. 2022-Nov-19 00:00 m 13 30 21.68 -07 37 11.3 n.a. n.a. 0.00221624292049 0.3483064 32.6303 /L 147.3003 13.265303 110.99953 44.422219 n.a. n.a. 2022-Nov-19 01:00 m 13 31 06.58 -07 42 01.3 n.a. n.a. 0.00222405288095 0.3036189 32.4705 /L 147.4602 10.971820 116.42030 45.825795 n.a. n.a. 2022-Nov-19 02:00 m 13 31 40.71 -07 46 56.4 n.a. n.a. 0.00223099767538 0.2766842 32.3507 /L 147.5800 8.6154235 124.85967 49.976824 n.a. n.a. 2022-Nov-19 03:00 m 13 32 03.60 -07 51 51.0 n.a. n.a. 0.00223752036860 0.2686201 32.2731 /L 147.6575 6.4916094 138.63934 56.829016 0.761 n.a. 2022-Nov-19 04:00 m 13 32 15.53 -07 56 39.6 n.a. n.a. 0.00224407597321 0.2792886 32.2377 /L 147.6928 5.0095172 160.55978 64.054080 0.742 n.a. 2022-Nov-19 05:00 Nm 13 32 17.48 -08 01 16.2 n.a. n.a. 0.00225110063092 0.3072613 32.2411 /L 147.6891 4.5268984 187.91288 68.153967 n.a. n.a. 2022-Nov-19 06:00 Cm 13 32 11.12 -08 05 36.0 n.a. n.a. 0.00225898109246 0.3498800 32.2779 /L 147.6520 4.8199973 210.23788 69.385083 n.a. n.a. 2022-Nov-19 07:00 *m 13 31 58.66 -08 09 34.5 n.a. n.a. 0.00226802688792 0.4034202 32.3402 /L 147.5894 5.2392560 223.75768 70.402010 n.a. n.a. 2022-Nov-19 08:00 *m 13 31 42.73 -08 13 09.0 n.a. n.a. 0.00227844758253 0.4633480 32.4184 /L 147.5107 5.3327253 230.83080 72.412717 n.a. n.a. 2022-Nov-19 09:00 *m 13 31 26.18 -08 16 18.1 n.a. n.a. 0.00229033721340 0.5246559 32.5018 /L 147.4268 4.9135311 233.18607 75.464637 n.a. n.a. 2022-Nov-19 10:00 *m 13 31 11.84 -08 19 02.3 n.a. n.a. 0.00230366740071 0.5822421 32.5797 /L 147.3484 3.9690213 230.19081 79.251908 n.a. n.a. 2022-Nov-19 11:00 *m 13 31 02.33 -08 21 23.7 n.a. n.a. 0.00231828979125 0.6313001 32.6418 /L 147.2856 2.6840885 215.48390 83.205511 n.a. n.a. 2022-Nov-19 12:00 *m 13 30 59.88 -08 23 25.9 n.a. n.a. 0.00233394755725 0.6676758 32.6794 /L 147.2475 1.9459654 167.58859 85.299350 n.a. n.a. 2022-Nov-19 13:00 *m 13 31 06.15 -08 25 13.6 n.a. n.a. 0.00235029479463 0.6881620 32.6855 /L 147.2408 3.2156632 121.96822 82.437829 n.a. n.a. 2022-Nov-19 14:00 * 13 31 22.15 -08 26 52.4 n.a. n.a. 0.00236692198328 0.6907050 32.6559 /L 147.2700 5.4422341 107.11437 77.295770 n.a. n.a. 2022-Nov-19 15:00 C 13 31 48.19 -08 28 28.3 n.a. n.a. 0.00238338527087 0.6745151 32.5885 /L 147.3369 7.8289322 101.79407 71.510066 n.a. n.a. 2022-Nov-19 16:00 A 13 32 23.89 -08 30 07.1 n.a. n.a. 0.00239923723482 0.6400800 32.4844 /L 147.4408 10.091847 99.665833 65.426684 n.a. n.a. 2022-Nov-19 17:00 13 33 08.21 -08 31 54.3 n.a. n.a. 0.00241405691806 0.5890933 32.3467 /L 147.5782 12.053985 98.945672 59.157552 n.a. n.a. 2022-Nov-19 18:00 13 33 59.59 -08 33 54.6 n.a. n.a. 0.00242747724014 0.5243104 32.1811 /L 147.7438 13.584282 99.001097 52.754592 n.a. n.a. 2022-Nov-19 19:00 13 34 56.01 -08 36 11.8 n.a. n.a. 0.00243920826797 0.4493512 31.9947 /L 147.9302 14.589137 99.583730 46.247881 n.a. n.a. 2022-Nov-19 20:00 13 35 55.16 -08 38 48.2 n.a. n.a. 0.00244905521930 0.3684624 31.7960 /L 148.1290 15.012080 100.61111 39.659114 n.a. n.a. 2022-Nov-19 21:00 13 36 54.56 -08 41 45.2 n.a. n.a. 0.00245693042212 0.2862543 31.5943 /L 148.3309 14.834545 102.09832 33.009747 n.a. n.a. 2022-Nov-19 22:00 13 37 51.71 -08 45 02.6 n.a. n.a. 0.00246285875194 0.2074240 31.3988 /L 148.5266 14.076500 104.14678 26.329934 n.a. n.a. 2022-Nov-19 23:00 13 38 44.26 -08 48 38.8 n.a. n.a. 0.00246697632600 0.1364736 31.2188 /L 148.7069 12.796992 106.97169 19.673903 n.a. n.a. 2022-Nov-20 00:00 13 39 30.13 -08 52 31.0 n.a. n.a. 0.00246952247341 0.0774344 31.0622 /L 148.8637 11.095399 110.98297 13.154248 n.a. n.a. 2022-Nov-20 01:00 13 40 07.63 -08 56 35.1 n.a. n.a. 0.00247082525552 0.0336090 30.9360 /L 148.9902 9.1158247 116.97582 7.0323775 n.a. n.a. 2022-Nov-20 02:00 m 13 40 35.60 -09 00 46.2 n.a. n.a. 0.00247128110791 0.0073432 30.8449 /L 149.0814 7.0618671 126.56076 1.9888879 n.a. n.a. 2022-Nov-20 03:00 m 13 40 53.47 -09 04 58.5 n.a. n.a. 0.00247132952851 -0.0001553 30.7919 /L 149.1345 5.2396278 142.88678 -0.060976 n.a. n.a. 2022-Nov-20 04:00 m 13 41 01.33 -09 09 05.9 n.a. n.a. 0.00247142413952 0.0110665 30.7773 /L 149.1493 4.1175587 169.40339 5.1382584 0.550 n.a. 2022-Nov-20 05:00 Nm 13 40 59.94 -09 13 02.3 n.a. n.a. 0.00247200186651 0.0396693 30.7988 /L 149.1277 4.0592268 199.85170 18.110242 n.a. n.a. 2022-Nov-20 06:00 Cm 13 40 50.69 -09 16 42.2 n.a. n.a. 0.00247345234361 0.0830794 30.8519 /L 149.0744 4.6761198 221.49882 30.721372 n.a. n.a. 2022-Nov-20 07:00 *m 13 40 35.52 -09 20 00.9 n.a. n.a. 0.00247608988411 0.1376446 30.9297 /L 148.9963 5.2987297 233.93684 40.956389 n.a. n.a. 2022-Nov-20 08:00 *m 13 40 16.77 -09 22 55.2 n.a. n.a. 0.00248013036591 0.1988846 31.0238 /L 148.9019 5.5497909 240.96115 50.086662 n.a. n.a. 2022-Nov-20 09:00 *m 13 39 57.04 -09 25 23.4 n.a. n.a. 0.00248567510981 0.2618179 31.1246 /L 148.8008 5.2758776 244.69645 58.807476 n.a. n.a. 2022-Nov-20 10:00 *m 13 39 38.94 -09 27 25.6 n.a. n.a. 0.00249270327125 0.3213368 31.2219 /L 148.7031 4.4454037 245.65474 67.372135 n.a. n.a. 2022-Nov-20 11:00 *m 13 39 24.96 -09 29 03.8 n.a. n.a. 0.00250107347560 0.3725947 31.3062 /L 148.6183 3.1158966 242.16161 75.811655 n.a. n.a. 2022-Nov-20 12:00 *m 13 39 17.22 -09 30 21.3 n.a. n.a. 0.00251053452449 0.4113665 31.3691 /L 148.5550 1.5144057 220.76732 83.625404 n.a. n.a. 2022-Nov-20 13:00 *m 13 39 17.38 -09 31 23.1 n.a. n.a. 0.00252074412947 0.4343500 31.4037 /L 148.5200 1.4485148 129.77404 84.197718 n.a. n.a. 2022-Nov-20 14:00 * 13 39 26.49 -09 32 14.7 n.a. n.a. 0.00253129392697 0.4393841 31.4054 /L 148.5180 3.4893926 103.34749 76.341861 n.a. n.a. 2022-Nov-20 15:00 C 13 39 44.94 -09 33 02.2 n.a. n.a. 0.00254173858684 0.4255696 31.3721 /L 148.5510 5.7468455 97.872896 67.465952 n.a. n.a. 2022-Nov-20 16:00 A 13 40 12.47 -09 33 51.7 n.a. n.a. 0.00255162667045 0.3932943 31.3042 /L 148.6187 7.8937120 96.313080 58.238860 n.a. n.a. 2022-Nov-20 17:00 13 40 48.19 -09 34 49.0 n.a. n.a. 0.00256053099155 0.3441687 31.2045 /L 148.7184 9.7639124 96.102241 48.712366 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._____(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} '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 '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 '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 ******************************************************************************************************************************************************************************