Unique source identifier (unique within a particular Data Release)

radian: angular measurement of the ratio between the length on an arc
and its radius

Correlation between right ascension and proper motion in right ascension

Correlation between right ascension and proper motion in declination

Correlation between declination and proper motion in right ascension

Correlation between declination and proper motion in declination

Correlation between parallax and proper motion in right ascension

Correlation between proper motion in right ascension and proper motion in declination

Photometric quality flag. Three character flag, one character per band
[JHKs], that provides a summary of the net quality of the default
photometry in each band.  
The value for ph_qual is set for a band according to the precedence of
the table below. For example, a source that is tested and meets the
conditions for category “X” is not tested for subsequent qualities.

-   “X” - There is a detection at this location, but no valid brightness
    estimate can be extracted using any algorithm. Default magnitude is
    null.

-   “U” - Upper limit on magnitude. Source is not detected in this band,
    or it is detected, but not resolved in a consistent fashion with
    other bands. A value of ph_qual=“U” does not necessarily mean that
    there is no flux detected in this band at the location.

-   “F” - This category includes sources where a reliable estimate of
    the photometric error could not be determined. The uncertainties
    reported for these sources in [jhk]_msigcom are flags and have
    numeric values >8.0.

-   “E” - This category includes detections where the goodness-of-fit
    quality of the profile-fit photometry was very poor, or detections
    where psf fit photometry did not converge and an aperture magnitude
    is reported, or detections where the number of frames was too small
    in relation to the number of frames in which a detection was
    geometrically possible.

-   “A” - Detections in any brightness regime where valid measurements
    were made with [jhk]_snr>10 AND [jhk]_cmsig<0.10857.

-   “B” - Detections in any brightness regime where valid measurements
    were made with [jhk]_snr>7 AND [jhk]_cmsig<0.15510.

-   “C” - Detections in any brightness regime where valid measurements
    were made with [jhk]_snr>5 AND [jhk]_cmsig<0.21714.

-   “D” - Detections in any brightness regime where valid measurements
    were made with no [jhk]_snr or [jhk]_cmsig requirement.

Incremental unique numeric identifier (increasing with declination).
This is the only field which was not in the original 2MASS catalogue,
but was added for cross-match purposes.

Sexagesimal, equatorial position-based source name in the form:
hmmssss+ddmmsss[ABC...] The prefix “2MASS J” in not explicitely listed
in the designation.

Semi-major axis length of the one sigma position uncertainty ellipse

Semi-minor axis length of the one sigma position uncertainty ellipse

Position angle on the sky of the semi-major axis of the position
uncertainty ellipse (East of North)

Default J-band magnitude.  
In case of a source not detected in the J-band, it is an upper limit and
the corresponding total photometric uncertainty is NULL.  
In case of a source detected in the J-band and with no useful brightness
estimate, it is set to NULL.

Total photometric uncertainty for the default J-band magnitude. This
column is NULL if the default magnitude is a 95% confidence upper limit
(i.e. the source is not detected, or inconsistently deblended in the
J-band).

Default H-band magnitude.  
In case of a source not detected in the H-band, it is an upper limit and
In case of a source detected in the H-band and with no useful brightness

Total photometric uncertainty for the default H-band magnitude. This
H-band).

Default Ks-band magnitude.  
In case of a source not detected in the Ks-band, it is an upper limit
and the corresponding total photometric uncertainty is NULL.  
In case of a source detected in the Ks-band and with no useful
brightness estimate, it is set to NULL.

Total photometric uncertainty for the default Ks-band magnitude. This
Ks-band.

Unique identification number of the record in the XSC (2MASS Extended
Source Catalogue) that corresponds to this point source. Can be NULL if
no corresponding extended source is present in the XSC.

The Julian Date of the source measurement accurate to +30 seconds. This
value is extrapolated from the start time of the Survey scan using the
difference between the declinations of the source and the first row in
the Tile divided by the scanning rate of the telescope (approximately
5sec). The scanning rate of the two 2MASS telescopes was slightly
different because of the need to optimize the dithering of images on the
arrays.