wiki:CommonVocabulary
Last modified 9 years ago Last modified on 03/11/2008 01:30:57 PM

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 [Is this fair to assume?]

First moments seem to be missing, should they be added?

A columns called probability have table-specific meaning, for example in PhotoZ table it means probability that given object has a photo z.

name unit type ucd description comments
Position related
ra degrees double Right ascension
decl degrees double Declination dec is a reserved word in most DBMSes
muRa arcsec/year double Derived proper motion mu_alpha*cos(decl)
muDecl arcsec/year double Derived proper motion mu_delta
uPosErrA arcsec float Large dimension of the position error ellipse, assuming gaussian scatter for u filter
uPosErrB arcsec float Small dimension of the position error ellipse, assuming gaussian scatter for u filter
uPosErrTheta degrees float Orientation of the position error ellipse for u filter
parallax float Derived parallax for the object
WCS related
radesys string(5) Type of WCS used Obsolete in ICRS
equinox float Equinox of the WCS Obsolete in ICRS
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 for this particular element, eg Amplifier, CCD
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?
taiMidPoint double If a DIASource corresponds to a single exposure, taiMidPoint represents tai time of the middle of exposure. For multiple exposures, this is middle of beginning-of-first-exposure to end-of-last-exposure.
taiRange float If a DIASource corresponds to a single exposure, taiRange equals to exposure length. If DIASoure corresponds to multiple exposures, its taiRange equals to end-of-last-exposure minus beginning-of-first-exposure.
earliestObsTime datetime Time of the first observation of given object
latestObsTime datetime Time of the last observation of given object
timeGenerated datetime Date/time when alert was generated
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
apDia pixels float Diameter of aperture
photoFlam float Inverse sensitivity
photoZP float System photometric zero-point
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)
psf_fwhm float Effective PSF width
psf_sigma_x float
psf_sigma_y float
psf_posAngle float
psf_peak float
psf_x0 float
psf_x1 float
chi2 float Chi-square value for the PSF fit
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
uApMag double aperture magnitude for u filter
psfMag double PSF magnitude of the object
apMag double Aperture magnitude
modelMag double Model magnitude (adaptive 2D gauss)
uIxx float Adaptive second moment for u filter
uIyy float Adaptive second moment for u filter
uIxy float Adaptive second moment for u filter
fwhmA float Size of the object along major axis (pixels)
fwhmB float Size of the object along minor axis (pixels)
fwhmTheta degrees float Position angle of the major axis w.r.t. X-axis
flux float Measured DIA flux for the source (ADUs)
snr - float Signal-to-Noise ratio
ugColor double Precalculated color: difference between u and g)
grColor double Precalculated color: difference between g and r)
riColor double Precalculated color: difference between r and i)
izColor double Precalculated color: difference between i and z)
zyColor double Precalculated color: difference between z and y)
moment0 float Sum of all flux of all pixels that belong to a source placeholder
moment1_x float Center of light - x component placeholder
moment1_y float Center of light - y component placeholder
moment2_xx float Standard deviation about center of light - xx component placeholder
moment2_xy float Standard deviation about center of light - xy component placeholder
moment2_yy float Standard deviation about center of light - yy component placeholder
moment3_xxx float Skewness of the profile - xxx component placeholder
moment3_xxy float Skewness of the profile - xxy component placeholder
moment3_xyy float Skewness of the profile - xyy component placeholder
moment3_yyy float Skewness of the profile - yyy component placeholder
moment4_xxxx float Kurtosis - xxxx component placeholder
moment4_xxxy float Kurtosis - xxxy component placeholder
moment4_xxyy float Kurtosis - xxyy component placeholder
moment4_xyyy float Kurtosis - xyyy component placeholder
moment4_yyyy float Kurtosis - yyyy component placeholder
splitPercentage % int8 percentage of the split all for a given source must add up to 100%
Redshifts
redshift float Photometric redshift
photoZ1 float
photoZ2 float
photoZ1Outlier float
photoZ2Outlier float
probability int8 Probability that given object has photo-z
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
Rectilinear coordinates
row double Pixel coordinate (Y) of the source centroid
col double Pixel coordinate (X) of the source centroid
cx double x-component of the (RA,Dec) unit vector
cy double y-component of the (RA,Dec) unit vector
cz double z-component of the (RA,Dec) unit vector
flags
flag - [varies] Flag to indicate a problem/special condition
flag4association - int16 Flag to indicate a problem/special condition related to Association Pipeline
flag4detection - int16 Flag to indicate a problem/special condition related to Detection Pipeline
flag4wcs - int16 Flag to indicate a problem/special condition related to WCS
isProvisional bool If this is set to true it indicates that the object was created at the base camp. If set to false, it means it was created by Deep Detection
uncategorized
url - string logical url of the corresponding FITS file
imagePStampURL string(255) Logical URL describing where the image postamp associated with the alert is located
templatePStampURL string(255) Logical URL of the postagestamp of the template image related to given alert
alertURL string(255) Logical URL to the actual alert sent
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