*******************************************************************************
 Revised: Apr 21, 2022             Gaia Observatory                     -139479
                               http://sci.esa.int/gaia/

 BACKGROUND:
  Gaia is designed and operated by the European Space Agency. It launched
  December 19, 2013 @ 09:12 UTC on a Soyuz launcher from Kourou, French Guiana.

  On 2014-Jan-08, it arrived at its operational Lissajous orbit around the 
  gravitationally stable Earth-Sun Lagrange-point L2, roughly 1.5 million km 
  from Earth in the direction opposite the Sun.  The orbit is not shadowed by 
  Earth eclipses. The orbit period is about 180 days; the size of the orbit 
  is typically 340,000 x 90,000 km. 
 
 MISSION:
  Gaia's 5-year primary mission is to ... 

    * Measure the positions of ~1 billion stars both in our Galaxy and other 
       members of the Local Group, with an accuracy down to 24 uas 
    * Perform spectral and photometric measurements of all objects 
    * Derive space velocities of the Galaxy's constituent stars using the 
       stellar distances and motions
    * Create a three-dimensional structural map of the Galaxy

  Additional expected results include extrasolar planet detection, brown dwarf 
  detection, solar system asteroid discoveries, supernova early detection, and 
  testing of Einstein's general relativity.
 
 GAIA SPACECRAFT: 
  Spacecraft dry mass total       1392 kg
  Propellant                       237 kg
  Total launch mass               2029 kg
  Power: 12.8 m^2 solar array provides up to 1910 Watts

 SCIENCE INSTRUMENTS:
  Single integrated instrument that comprises three major functions: 
  astrometry, photometry (320-1000 nm) and spectrometry (846-874 nm). 

  The three functions use two common telescopes and a shared focal plane, 
  with each function having a dedicated area on the large 0.5m x 1m CCD 
  detector array.

 SPACECRAFT TRAJECTORY (from ESA 2022-Apr-19, predicts thereafter)
  Trajectory name                                    Start         Stop
  --------------------------------------------    -----------   -----------
  ORB1_20220419_000001                            2013-Dec-19   2026-Sep-14 
*******************************************************************************


*******************************************************************************
Ephemeris / API_USER Mon May 23 05:28:00 2022 Pasadena, USA      / Horizons
*******************************************************************************
Target body name: Gaia (spacecraft) (-139479)     {source: gaia_merged}
Center body name: Earth-Moon Barycenter (3)       {source: gaia_merged}
Center-site name: BODY CENTER
*******************************************************************************
Start time      : A.D. 2022-May-22 00:00:00.0000 TDB
Stop  time      : A.D. 2022-May-23 00:00:00.0000 TDB
Step-size       : 720 minutes
*******************************************************************************
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 radii    : (undefined)                                                  
Output units    : KM-S
Output type     : GEOMETRIC cartesian states
Output format   : 1 (position only)
Reference frame : Ecliptic of J2000.0
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JDTDB
   X     Y     Z
*******************************************************************************
$$SOE
2459721.500000000 = A.D. 2022-May-22 00:00:00.0000 TDB 
  -1.005869741260714E+06 -1.229636409807553E+06  5.553741267973231E+04
2459722.000000000 = A.D. 2022-May-22 12:00:00.0000 TDB 
  -9.976647219177654E+05 -1.235095646685846E+06  5.296169462755765E+04
2459722.500000000 = A.D. 2022-May-23 00:00:00.0000 TDB 
  -9.893621107980320E+05 -1.240524898186224E+06  5.037219698871591E+04
$$EOE
*******************************************************************************
 
TIME

  Barycentric Dynamical Time ("TDB" or T_eph) output was requested. This
continuous relativistic coordinate time is equivalent to the relativistic
proper time of a clock at rest in a reference frame comoving with the
solar system barycenter but outside the system's gravity well. It is the
independent variable in the solar system relativistic equations of motion.

  TDB runs at a uniform rate of one SI second per second and is independent
of irregularities in Earth's rotation.

  Calendar dates prior to 1582-Oct-15 are in the Julian calendar system.
Later calendar dates are in the Gregorian system.

REFERENCE FRAME AND COORDINATES

  Ecliptic at the standard reference epoch

    Reference epoch: J2000.0
    X-Y plane: adopted Earth orbital plane at the reference epoch
               Note: IAU76 obliquity of 84381.448 arcseconds wrt ICRF X-Y plane
    X-axis   : ICRF
    Z-axis   : perpendicular to the X-Y plane in the directional (+ or -) sense
               of Earth's north pole at the reference epoch.

  Symbol meaning:

    JDTDB    Julian Day Number, Barycentric Dynamical Time
      X      X-component of position vector (km)
      Y      Y-component of position vector (km)
      Z      Z-component of position vector (km)

ABERRATIONS AND CORRECTIONS

 Geometric state vectors have NO corrections or aberrations applied.

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
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