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136 lines
6.1 KiB
Plaintext
136 lines
6.1 KiB
Plaintext
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Revised: Apr 21, 2022 Gaia Observatory -139479
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http://sci.esa.int/gaia/
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BACKGROUND:
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Gaia is designed and operated by the European Space Agency. It launched
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December 19, 2013 @ 09:12 UTC on a Soyuz launcher from Kourou, French Guiana.
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On 2014-Jan-08, it arrived at its operational Lissajous orbit around the
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gravitationally stable Earth-Sun Lagrange-point L2, roughly 1.5 million km
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from Earth in the direction opposite the Sun. The orbit is not shadowed by
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Earth eclipses. The orbit period is about 180 days; the size of the orbit
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is typically 340,000 x 90,000 km.
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MISSION:
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Gaia's 5-year primary mission is to ...
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* Measure the positions of ~1 billion stars both in our Galaxy and other
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members of the Local Group, with an accuracy down to 24 uas
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* Perform spectral and photometric measurements of all objects
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* Derive space velocities of the Galaxy's constituent stars using the
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stellar distances and motions
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* Create a three-dimensional structural map of the Galaxy
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Additional expected results include extrasolar planet detection, brown dwarf
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detection, solar system asteroid discoveries, supernova early detection, and
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testing of Einstein's general relativity.
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GAIA SPACECRAFT:
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Spacecraft dry mass total 1392 kg
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Propellant 237 kg
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Total launch mass 2029 kg
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Power: 12.8 m^2 solar array provides up to 1910 Watts
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SCIENCE INSTRUMENTS:
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Single integrated instrument that comprises three major functions:
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astrometry, photometry (320-1000 nm) and spectrometry (846-874 nm).
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The three functions use two common telescopes and a shared focal plane,
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with each function having a dedicated area on the large 0.5m x 1m CCD
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detector array.
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SPACECRAFT TRAJECTORY (from ESA 2022-Apr-19, predicts thereafter)
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Trajectory name Start Stop
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-------------------------------------------- ----------- -----------
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ORB1_20220419_000001 2013-Dec-19 2026-Sep-14
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*******************************************************************************
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*******************************************************************************
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Ephemeris / API_USER Mon May 23 05:28:00 2022 Pasadena, USA / Horizons
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*******************************************************************************
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Target body name: Gaia (spacecraft) (-139479) {source: gaia_merged}
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Center body name: Earth-Moon Barycenter (3) {source: gaia_merged}
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Center-site name: BODY CENTER
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*******************************************************************************
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Start time : A.D. 2022-May-22 00:00:00.0000 TDB
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Stop time : A.D. 2022-May-23 00:00:00.0000 TDB
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Step-size : 720 minutes
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*******************************************************************************
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Center geodetic : 0.00000000,0.00000000,0.0000000 {E-lon(deg),Lat(deg),Alt(km)}
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Center cylindric: 0.00000000,0.00000000,0.0000000 {E-lon(deg),Dxy(km),Dz(km)}
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Center radii : (undefined)
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Output units : KM-S
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Output type : GEOMETRIC cartesian states
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Output format : 1 (position only)
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Reference frame : Ecliptic of J2000.0
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*******************************************************************************
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JDTDB
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X Y Z
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*******************************************************************************
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$$SOE
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2459721.500000000 = A.D. 2022-May-22 00:00:00.0000 TDB
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-1.005869741260714E+06 -1.229636409807553E+06 5.553741267973231E+04
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2459722.000000000 = A.D. 2022-May-22 12:00:00.0000 TDB
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-9.976647219177654E+05 -1.235095646685846E+06 5.296169462755765E+04
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2459722.500000000 = A.D. 2022-May-23 00:00:00.0000 TDB
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-9.893621107980320E+05 -1.240524898186224E+06 5.037219698871591E+04
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$$EOE
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TIME
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Barycentric Dynamical Time ("TDB" or T_eph) output was requested. This
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continuous relativistic coordinate time is equivalent to the relativistic
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proper time of a clock at rest in a reference frame comoving with the
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solar system barycenter but outside the system's gravity well. It is the
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independent variable in the solar system relativistic equations of motion.
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TDB runs at a uniform rate of one SI second per second and is independent
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of irregularities in Earth's rotation.
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Calendar dates prior to 1582-Oct-15 are in the Julian calendar system.
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Later calendar dates are in the Gregorian system.
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REFERENCE FRAME AND COORDINATES
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Ecliptic at the standard reference epoch
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Reference epoch: J2000.0
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X-Y plane: adopted Earth orbital plane at the reference epoch
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Note: IAU76 obliquity of 84381.448 arcseconds wrt ICRF X-Y plane
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X-axis : ICRF
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Z-axis : perpendicular to the X-Y plane in the directional (+ or -) sense
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of Earth's north pole at the reference epoch.
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Symbol meaning:
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JDTDB Julian Day Number, Barycentric Dynamical Time
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X X-component of position vector (km)
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Y Y-component of position vector (km)
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Z Z-component of position vector (km)
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ABERRATIONS AND CORRECTIONS
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Geometric state vectors have NO corrections or aberrations applied.
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Computations by ...
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Solar System Dynamics Group, Horizons On-Line Ephemeris System
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4800 Oak Grove Drive, Jet Propulsion Laboratory
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Pasadena, CA 91109 USA
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General site: https://ssd.jpl.nasa.gov/
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Mailing list: https://ssd.jpl.nasa.gov/email_list.html
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System news : https://ssd.jpl.nasa.gov/horizons/news.html
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User Guide : https://ssd.jpl.nasa.gov/horizons/manual.html
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Connect : browser https://ssd.jpl.nasa.gov/horizons/app.html#/x
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API https://ssd-api.jpl.nasa.gov/doc/horizons.html
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command-line telnet ssd.jpl.nasa.gov 6775
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e-mail/batch https://ssd.jpl.nasa.gov/ftp/ssd/hrzn_batch.txt
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scripts https://ssd.jpl.nasa.gov/ftp/ssd/SCRIPTS
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Author : Jon.D.Giorgini@jpl.nasa.gov
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*******************************************************************************
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