(Note, that the symbols are only recommended, and when used as variables
in mathematical equations should be italicized)
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Symbol |
Abbreviation |
Short Definition |
Alternatives |
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1. General |
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classical |
classic equinox old |
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modern |
new polar CIO |
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2. Systems |
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Celestial systems |
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BCRS |
Barycentric Celestial Reference System |
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GCRS |
Geocentric Celestial Reference System |
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ICRS |
International Celestial Reference System |
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CIS |
celestial
intermediate system
(see question 4 b (i) for further suggestions) |
non-rotating
equatorial system (NES) celestial equatorial system (CES) |
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ted |
true
equator and equinox of date |
true
equatorial system equinoctial
equatorial system (EES) |
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med |
mean equinox and equator of date |
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Terrestrial systems |
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ITRS |
International
Terrestrial Reference System |
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TIS |
terrestrial
intermediate system (see question 4 b
(ii) for further suggestions) |
rotating
equatorial system (RES) terrestrial equatorial system (TES) |
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Symbol |
Abbreviation |
Short Definition |
Alternatives |
3. Frames |
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ICRF |
International Celestial Reference Frame |
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ITRF |
International Terrestrial Reference Frame |
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natural frame (see ASA, B26 step 3) |
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proper frame (see AsA, B26 step 4) |
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4. Origins |
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ICRS origin |
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J2000.0 origin |
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CEO |
celestial ephemeris origin |
celestial
intermediate origin (CIO) |
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s |
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CEO displacement on the CIP equator |
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TEO |
terrestrial
ephemeris origin |
terrestrial
intermediate origin (TIO) |
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s' (tiny quantity) |
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TEO displacement on CIP equator |
TIO
displacement |
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mean equinox |
mean equatorial origin |
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true equinox |
true equatorial origin |
5. Poles |
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X, Y |
CIP |
celestial intermediate pole |
celestial
ephemeris pole (CEP) conventional pole reference pole |
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Xp, Yp |
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polar motion |
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6. Meridians |
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Greenwich meridian (low precision) |
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ephemeris meridian |
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ITRF meridian |
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TEO meridian |
TIO meridian |
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Symbol |
Abbreviation |
Short Definition |
Alternatives |
7. Coordinates |
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b |
lat, LAT |
ecliptic latitude, north +ve |
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l |
long, LONG |
ecliptic longitude, east +ve |
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a |
RA |
right ascension, apparent right ascension |
(see question 5) |
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ae |
RAe |
equinox right ascension |
right
ascension w.r.t. the equinox |
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aI |
RAs |
CEO right ascension |
right
ascension w.r.t. the CEO intermediate
right ascension (RAi) longitude coordinate celestial equatorial longitude equatorial azimuth |
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d |
Dec, DEC |
declination |
intermediate declination |
8. Frame biases
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dyB, deB
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frame bias in longitude and obliquity |
offsets at J2000 |
xB, yB, zB
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frame bias in rectangular coordinates |
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da
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Frame bias in right ascension |
equinox offset at J2000 equinox correction |
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Symbol |
Abbreviation |
Short Definition |
Alternatives |
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9. UT, Sidereal time and Earth rotation |
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q
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ERA |
Earth rotation angle |
Stellar angle |
GST
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GST |
Greenwich sidereal time |
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GMST
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GMST |
Greenwich mean sidereal time |
polynomial
part of G(A)ST |
GAST
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GAST |
Greenwich apparent sidereal time |
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GHA Aries º GAST
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GHA Aries |
Greenwich hour angle Aries |
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EE = GAST - GMST
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EE |
equation of the equinoxes |
complete
equation of the equinoxes |
o = GST- q
= GAST - q
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EO |
equation of the origins |
RA
of the CEO instantaneous
origin distance |
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EqT |
equation of time |
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10. Matrices |
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B |
C2J |
frame bias matrix, ICRS to J2000.0 |
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P |
J2m |
precession matrix, J2000.0 to med |
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N |
m2t |
nutation matrix, med to ted |
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NP |
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Precession-nutation matrix, J2000.0 to ted |
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NPB |
C2t |
classical combined bias, precession, nutation matrix, ICRS to ted |
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PM(Xp, Yp, s' )
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T2I |
Polar motion matrix, terrestrial to ITRF |
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C, C(X, Y,
s)
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C2I |
ICRS (celestial) to intermediate matrix |
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C, C (X, Y,
s, q )
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C2T |
ICRS to terrestrial matrix |
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Q, Q(X, Y,
s,q )
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T2C |
terrestrial to ICRS matrix |
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Symbol |
Abbreviation |
Short Definition |
Alternatives |
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11. Classical – Pre IAU 2000 |
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GMST
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GMST |
Greenwich mean sidereal time |
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GAST= GMST + EE
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GAST |
Greenwich apparent sidereal time |
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GHA Aries = GAST
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GHA Aries |
Greenwich hour angle Aries |
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EE
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EE |
equation of the equinoxes |
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CT
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CT |
complementary terms |
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LMST = GMST + l
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LMST |
local mean sidereal time |
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LAST = GAST + l
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LAST |
local apparent sidereal time |
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LHA Aries
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LHA Aries |
local hour angle Aries |
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H = GAST - ae
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HA |
hour angle, (measured from zero long) |
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h = LAST - ae
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LHA |
local hour angle |
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12. Modern – Post IAU 2000 |
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q
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ERA |
Earth rotation angle |
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LERA = q + l
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LERA |
local Earth rotation angle |
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H = q - aI
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HA |
hour angle (measured from zero long) |
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h = q + l - aI
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LHA |
local hour angle |
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