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JWST Ephemeris

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 Revised: Dec 26, 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. 


 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 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

 Post-launch trajectory, data through ~16:00 UTC Dec 26, predicts thereafter.


 Trajectory files                              Start (TDB)        End (TDB) 

 --------------------------------------   -----------------  -----------------

 BURN_TTF_01_2021359124800_02U.OEM.V0.3   2021-Dec-25 12:50  2021-Dec-25 20:01

 BURN_MCC_1A_2021359200000_04U.OEM.V0.1   2021-Dec-25 20:01  2021-Dec-26 15:01

 BURN_MCC_1B_2021360150000_01U.OEM.V0.1   2021-Dec-26 15:01  2022-Jan-23 15:01

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Ephemeris / WWW_USER Sun Dec 26 23:15:38 2021 Pasadena, USA      / Horizons    

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Target body name: James Webb Space Telescope (spacecraft) (-170) {source: JWST_merged}

Center body name: Earth (399)                     {source: DE441}

Center-site name: GEOCENTRIC

*******************************************************************************

Start time      : A.D. 2021-Dec-27 00:00:00.0000 UT      

Stop  time      : A.D. 2022-Jan-06 00:00:00.0000 UT      

Step-size       : 1440 minutes

*******************************************************************************

Target pole/equ : No model available

Target radii    : (unavailable)                                                

Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}

Center cylindric: 0.00000000,0.00000000,0.0000000 {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.211223.p220318                                           

EOP coverage    : DATA-BASED 1962-JAN-20 TO 2021-DEC-23. PREDICTS-> 2022-MAR-17

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

 2021-Dec-27 00:00     05 42 56.05 -00 14 08.9     n.a.    n.a.  0.00189650825362   1.4329090  154.5580 /T   25.3947   11.270798   85.786121   79.778541         n.a.     n.a.

 2021-Dec-28 00:00     05 55 42.00 +00 00 53.3     n.a.    n.a.  0.00263108791411   1.1421249  155.5285 /T   24.4082   5.8167451   85.383588   80.799510         n.a.     n.a.

 2021-Dec-29 00:00     06 03 10.35 +00 10 47.7     n.a.    n.a.  0.00323933913676   0.9735787  155.9536 /T   23.9697   3.8092629   84.638866   81.289811         n.a.     n.a.

 2021-Dec-30 00:00     06 08 20.68 +00 18 56.5     n.a.    n.a.  0.00376557033050   0.8549440  156.1911 /T   23.7206   2.7907352   83.482081   81.548935         n.a.     n.a.

 2021-Dec-31 00:00     06 12 15.68 +00 26 32.2     n.a.    n.a.  0.00423247214568   0.7656768  156.3416 /T   23.5598   2.1938176   81.892340   81.660644         n.a.     n.a.

 2022-Jan-01 00:00     06 15 24.37 +00 34 08.6     n.a.    n.a.  0.00465356508162   0.6950406  156.4432 /T   23.4490   1.8150387   79.908666   81.643353         n.a.     n.a.

 2022-Jan-02 00:00     06 18 02.68 +00 42 03.0     n.a.    n.a.  0.00503775953544   0.6371579  156.5128 /T   23.3708   1.5653284   77.644898   81.491514         n.a.     n.a.

 2022-Jan-03 00:00     06 20 20.43 +00 50 24.3     n.a.    n.a.  0.00539130042008   0.5884046  156.5590 /T   23.3167   1.3988900   75.272915   81.193020         n.a.     n.a.

 2022-Jan-04 00:00     06 22 24.10 +00 59 15.9     n.a.    n.a.  0.00571872660429   0.5463952  156.5863 /T   23.2820   1.2887235   72.978480   80.739962         n.a.     n.a.

 2022-Jan-05 00:00     06 24 18.14 +01 08 37.9     n.a.    n.a.  0.00602341794849   0.5094458  156.5973 /T   23.2641   1.2171913   70.911712   80.131656         n.a.     n.a.

 2022-Jan-06 00:00     06 26 05.69 +01 18 28.4     n.a.    n.a.  0.00630793626558   0.4763691  156.5933 /T   23.2616   1.1720598   69.154412   79.374752         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.

 

 '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#/

                  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


******************************************************************************************************************************************************************************


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