Below is the prose describing the new photometric quality flag. The acutal query is here

It is proposed that the new photometric
quality column ph_qual replace the cat column in the public release.
ph_qual is a char(3) column with bands JHK per the usual convention
for band dependent columns.

	For each band a photometric quality is assigned according to
the following prescription:

A	snr > 10 ... or corresponding msig condition (but not ghost
		rejects (use_src=0 and dup_src=0)
B	snr >  7 ... or corresponding msig condition and rows that
		would have been A but were downgraded by ghosts
		(use_src=0 and dup_src=0)
C	snr >  5 ... or corresponding msig condition
D	no snr or msig condition
E	not a valid detection or an upper limit
	to be a valid detection the rd_flg must be 1,2,or 3
	and if 2, psf_chi < 10.0 and ndet conditions apply for brighter
	sources on a band by band basis.

	What we previously called the catalog (cat='C') is replaced by
any row in which ph_qual is A in at least one band.

The table below shows color-color/mag diagrams for various selections of flags. Unless otherwise specified the underlying assumptions are abs(glat)>20. and prox>8.0 and cc_flg='000'.

AAA	Contains A (no E's)	Contains B (no E's)
Contains C (no E's)	Contains D (no E's)	Contains E
EEE (use_src=1)	< BBB (402K)	between BBB and DDD (158K)
AAA (abs(glat)<20.) (510K)