wiki:CommonVocabulary

Version 6 (modified by jbecla, 11 years ago) (diff)

fixed tai taiObs duplicate

Common Vocabulary

LSST Data Management

This document defines common vocabulary that should be used when naming columns in database schema and variables in transient classes. It also defines units and types.

Names for columns/attributes defining errors were omitted. To build them, append "Err" after columns' name (eg raErr, declErr). All error columns use the same units as the columns, for which the error is defined.

used name unit type full name comments
Position related
ra degrees int64 right ascension
decl degrees int64 declination dec is a reserved word in most DBMSes
uErrA arcsec float Large dimension of the position error ellipse, assuming gaussian scatter for u filter
uErrB arcsec float Small dimension of the position error ellipse, assuming gaussian scatter for u filter
uErrTheta degrees float Orientation of the position error ellipse for u filter
WCS related
radesys string(5) Type of WCS used Obsolete in ICRS
equinox float Equinox of the WCS Obsolete in ICRS
equinox int32 equinox of World Coordinate System (different type than previous)
ctype1 string(20) Coordinate projection type, axis 1
ctype2 string(20) Coordinate projection type, axis 2
crpix1 float Coordinate reference pixel, axis 1
crpix2 float Coordinate reference pixel, axis 2
crval1 double Coordinate value 1 @reference pixel
crval2 double Coordinate value 2 @reference pixel
cunit1 varchar(10) X axis units
cunit2 varchar(10) Y axis units
cdelt1 float Obsolete by cd_xx terms?
cdelt2 float Obsolete by cd_xx terms?
cd11 float First derivative of coordinate 1 w.r.t. axis 1
cd21 float First derivative of coordinate 2 w.r.t. axis 1
cd12 float First derivative of coordinate 1 w.r.t. axis 2
cd22 float First derivative of coordinate 2 w.r.t. axis 2
ra_ll degrees double ra for the low-left corner probably something more fancy needed
decl_ll degrees double decl for the low-left corner probably something more fancy needed
ra_lr degrees double ra for the low-right corner probably something more fancy needed
decl_lr degrees double decl for the low-right corner probably something more fancy needed
ra_ul degrees double ra for the upper-left corner probably something more fancy needed
decl_ul degrees double decl for the upper-left corner probably something more fancy needed
ra_ur degrees double ra for the upper-right corner probably something more fancy needed
decl_ur degrees double decl for the upper-right corner probably something more fancy needed
Time related
dateObs datetime Date/Time? of observation start (UTC)
taiObs datetime time of shutter open international atomic time
mjdObs double MJD of observation start
expTime float Duration of exposure
darkTime float Total elapsed time from exposure start to end of read
taiDark double time of shutter closed during the exposure, if there was such an occasion; see Kem Cook for details. International atomic time. There also could be a situation when the shutter was closed and reopened multiple times during the exposure. In this case, a more complicated data structure is needed?
tDark float Dark time length during exposure (clouds, etc). Since this can happen multiple times (see comment for MJDdark attribute), a more complex data structure may be needed
texp float Exposure time for this particular element, eg Amplifier, CCD
Observation related
zd float Zenith distance at observation mid-point
airmass float Airmass value for the Amp reference pixel preferably center, but not guaranteed
temperature celsius float
wavelength float wavelength
telAngle degrees float Orientation angle of the telescope w.r.t sky This is different from camera orientation w.r.t sky (encapsulated in WCS), since telescope is on alt-az mount
azimuth degrees float Azimuth of observation preferably at center of exposure at center of image and including refraction correction, but none of this is guaranteed
alt degrees float Altitude of observation preferably at center of observation at center of image and including refraction correction, but none of this is guaranteed
elevation degrees float same as alt?
zpt double Photometric zero point magnitude
PSF related
psf_nstar int32 Number of stars used for PSF measurement
psf_apcorr float Photometric error due to imperfect PSF model (aperture correction)
psf_sigma1 float Inner Gaussian sigma for the composite fit (XXX)
psf_sigma2 float Outer Gaussian sigma for the composite fit (XXX)
psf_b float Ratio of inner PSF to outer PSF (XXX)
psf_b_2G float Ratio of Gaussian 2 to Gaussian 1 at origin (XXX)
psf_p0 float The value of the power law at the origin (XXX)
psf_beta float The slope of the power law (XXX)
psf_sigmap float Width parameter for the power law (XXX)
psf_nprof float Number of profile bins (XXX)
fwhm float Effective PSF width
sigma_x float
sigma_y float
posAngle float psf related
peak float psf related
x0 float psf related
x1 float psf related
Magnitudes and shapes
uMagnitude double magnitude (weighted average) for u filter
uPetroMag double petrosian magnitude for u filter
uApMag double aperture magnitude for u filter
uIxx float Adaptive second moment for u filter
uIyy float Adaptive second moment for u filter
uIxy float Adaptive second moment for u filter
Variability
uAmplitude float amplitude of magnitude variations for u filter
uPeriod float period of magnitude variations for u filter
primaryPeriod float Average period across all filters
uTimescale days float timescale of flux variations for u filter
uNumObs - int32 number of measurements in the lightcurve for u filter
uVarProb % int16 probability of variability. 100% = variable object for u filter
Calibration related
bias float Bias level for the calibrated image
gain float Gain value for the amplifier
rdNoise electrons float Read noise value for this particular element, eg AmpExposure
sky float The average sky level in the frame
skySig float Sigma of distribution of sky values
u_fringeTime datetime Time when corresponding CMFringeExposure was processed for u filter
u_flatTime datetime Time when corresponding CMFlatExposure was processed for u filter
Image pixel array properties
binX int16 binning in X-coordinate
binY int16 binning in Y-coordinate
sizeX int16 Size of the image in X-direction (along rows; binned pixels) Ignores overscan but includes regions that may be considered outside of the data portion of the image
sizeY int16 Size of the image in Y-direction (along columns; binned pixels) Ignores overscan but includes regions that may be considered outside of the data portion of the image
averPixelValue float average pixel value
stdevPixelValue float standard deviation of average pixel value
uncategorized
url - string logical url of the corresponding FITS file
nCombine - int32 Number of images co-added to create a deeper image
probability % int8 Probability that given object is of given type
sizeRa float size of ra this appears in postage stamp table
sizeDecl float size of decl this appears in postage stamp table
mops related
a float semi-major axis of the orbit (AU)
incl degrees float inclination of the orbit
e float eccentricity of the orbit
periTAI float TAI of the perihelion passage (comets)
periDist float Perihelion distance (AU)
omega float argument of perihelion
node float longitude of the ascending node
meanAnom float mean anomaly of the orbit
qual float measure of the accuracy of the derived orbit, classification, etc. can be more than one. Placeholder
various ids
alertId - int32 Id of an Alert
amplifierId - int16 Id of an Amplifier
ccExposureId - int64 Id of CCD Exposure
filterId - int8 Id of a Filter
objectId - int64 Id of an Astronomical Object
movingObjectId - int64 Id of a Moving Object
visitId - int32 Id of a Visit
flatExposureId - int32 Id of a Flat Exposure
biasExposureId - int32 Id of a Bias Exposure
darkExposureId - int32 Id of a Dark Exposure
cmFlatExposureId - int32 Id of a Calibrated Master Flat Exposure
subtractedExposureId - int32 Id of a Subtracted Exposure
varianceExposureId - int32 Id of a Variance Exposure