2MASS Second Incremental Release Atlas Image Header Description

	The image atlas consists of a series of 512x1024 pixel (1"/pixel)
images for each scan, one FITS format file per band for each image. The 
naming convention is as follows:

	BiSSSIIII.fits

	where:

	B             - the wavelength band (j, h, or k)
	SSS           - the scan number
	IIII          - the image number within the scan
			(named for the closest frame to the image center)

	The following table gives an example of the FITS image header format.
The first line is included to show the column alignment, and is not part of
the FITS header.

1234567890123456789012345678901234567890123456789012345678901234567890123456789
BITPIX  =                  -32   / Data Values are IEEE 32 Bit Reals
NAXIS   =                    2   / # of Axes
NAXIS1  =                  512   / Number of Columns in Image
NAXIS2  =                 1024   / Number of Lines   in Image
ORDATE  = '980427  '             / Observation Ref Date (yymmdd)
DAYNUM  = '0423    '             / Observation Day Num
FN_PRFX = 'j0423049'             / .rdo and .par filename prefix
TYPE    = 'sci     '             / Scan type: dar flt sci cal tst
SCANNO  =                   49   / Scan Number
SCANDIR = 'n       '             / Scan Direction: n, s, -
COMMENT                                  (OV)
STRIP_ID=               308049   / Strip ID (OV)
POSITNID= 's121722 '             / Position ID (OV)
ORIGIN  = '2MASS   '             / 2MASS Survey Camera
CTYPE1  = 'RA---SIN'             / Orthographic Projection
CTYPE2  = 'DEC--SIN'             / Orthographic Projection
CRPIX1  =                256.5   / Column Coordinate of Grid Center
CRPIX2  =                512.5   / Line   Coordinate of Grid Center
CRVAL1  =            260.74079 /   RA  at Frame Center, J2000 (deg)
CRVAL2  =         -14.36022188 /   Dec at Frame Center, J2000 (deg)
CROTA2  =        0.01315398872 /   Image Twist +AXIS2 W of N, J2000 (deg)
CDELT1  =     -0.0002777777845 /   Axis 1 Pixel Size (degs)
CDELT2  =      0.0002777777845 /   Axis 2 Pixel Size (degs)
USXREF  =               -256.5 /   U-scan X at Grid (0,0)
USYREF  =               12766. /   U-scan Y at Grid (0,0)
SKYVAL  =          146.9015198 /   GFIND Sky Estimate   (Image DN)
SKYSIG  =         0.8133392334 /   Grid  Noise Estimate (Image DN)
MAGZP   =              20.7872 / Calibrated zero point from CALMAN
CALID   = 'y lf 0 Oct 27 1998 '/ Calibration descriptors from CALMAN
SEESH   =               1.0400 / Seeing shape parameter from SEEMAN
DXFS    =         0.5750201344 /   Cross-scan Frame Step (arcsec)
DYFS    =          82.28955841 /      In-scan Frame Step (arcsec)
PIXNAM  = 'nl.pixphot - v 980423c'
QT0227  =          145.4931641 /   2.27 Percentile (Image DN)
QT0668  =          145.8517761 /   6.68 Percentile (Image DN)
QT1586  =          146.2314911 /  15.86 Percentile (Image DN)
QT3085  =          146.6295166 /  30.85 Percentile (Image DN)
QT5000  =          147.0448303 /  50.00 Percentile (Image DN)
QT6914  =          147.4942932 /  69.14 Percentile (Image DN)
QT8413  =           148.031723 /  84.13 Percentile (Image DN)
QT9331  =          148.8986664 /  93.31 Percentile (Image DN)
QT9772  =          152.4276581 /  97.72 Percentile (Image DN)
BASE    =                    6   / Pixel Dwell (microsec)
WAVEF_P = '2massn.scn'           / Secondary waveform data file
TIMER0  =                   52   / Read1 time (millisecs)
TIMER1  =                 1298   / Read2-Read1 time (millisecs)
TIMER2  =                   51   / Secondary settling time (millisecs)
ICSVERSN= '980324  '             / ICS script pgm Version (yymmdd)
SCHEDVER= '980416  '             / Scheduler pgm Version (yymmdd)
SCRIPTFN= 'survey.sct'           / Script template filename
SCRPTVER= '980223  '             / Script template filename Versn (yymmdd)
UT_OFF1 =   7.427007299270E-01   / UT Offset (IC),SOS to frm#1 Cntr (secs)
XS_OFF1 =   7.500000000000E-01   / X-Scan Offset (IN),SOS to f#1 RA Cntr (ASec)
IS_OFF1 =   3.745100000000E+02   / In-Scan Offset (IN),SOS to f#1 Dec Cntr(ASec)
XS_OFF2 =   1.230000000000E+00   / X-Scan Offset(IN),EOS to End Frm RA Ctr(ASec)
IS_OFF2 =  -1.149400000000E+02   / In-Scan Offset(IN),EOS to End Frm Dec Ctr(AS)
FOCUS   =                 1045   / Focus Setting
NUMFRMS =                  274   / Total Number of Frames in this Scan
SKIPRDOS=                    0   / Total Number of SOS junk RDOs skipped (IC)
TELNAME = 'CTIO    '             / Telescope -30.165/+70.815 lat/lon degs
FILTER  = 'j       '             / Band: j, h, k
UT_DATE = '980427  '             / UT Date of Frame (IC) (yymmdd)
UT      = '06:33:55.89'          / Time of Frame (IC) (sxgsml)
AMASS_FC=       1.08769238E+00   / Airmass (aprox) at this Frame (IC) (unitless)
GRP2_SOS= 'SOS     '             / Bgn Group#2 .par params at SOS
DATE_SOS= '980427  '             / Date at SOS  (yymmdd)
EQUINOX =   2.000000000000E+03   / Equinox at SOS
AM_SOS  =       1.07000005E+00   / Airmass at SOS (unitless)
ZD_SOS  =       2.10000000E+01   / Zenith Distance at SOS (degs)
HA_SOS  = '-01:15:58.00'         / Hour Angle at SOS (sxgsml)
UT_SOS  = '06:29:56.00'          / Scan Reference UT  (SOS) (sxgsml)
ST_SOS  = '16:06:53.00'          / Sidereal time at SOS  (sxgsml)
RA_SOS  = '17:22:57.61'          / Scan Reference RA at SOS ,epoch 2000 (sxgsml)
DEC_SOS = '-18:09:09.9'          / Scan Reference Dec at SOS,epoch 2000 (sxgsml)
WSPD_SOS=                    0   / Wind Speed at SOS, see WARNING below
WDIR_SOS=                    0   / Wind Direction at SOS, see WARNING below
HUM_SOS =                   62   / Humidity at SOS, 0-100%
SEE_SOS =       0.00000000E+00   / Seeing at SOS, see WARNING below
BAR_SOS =       2.97000008E+01   / Barometer at SOS (inches of Hg)
AIRT_SOS=       4.19999981E+00   / Air temperature at SOS, degs Celsius
TELT_SOS=       4.59999990E+00   / Telescope Temp at SOS, degs Celsius
ARYT_SOS=      -1.90000000E+02   / Temperature of array, see WARNING below
GRP2_EOS= 'EOS     '             / Bgn Group#2 .par params at EOS
DATE_EOS= '980427  '             / Date at EOS (yymmdd)
AM_EOS  =       1.10000002E+00   / Airmass at EOS (unitless)
ZD_EOS  =       2.42999992E+01   / Zenith Distance at EOS (degs)
HA_EOS  = '-01:09:10.00'         / Hour Angle at EOS (sxgsml)
UT_EOS  = '06:36:43.00'          / UT  at EOS (sxgsml)
ST_EOS  = '16:13:41.00'          / ST  at EOS (sxgsml)
RA_EOS  = '17:22:57.40'          / RA  at EOS, epoch 2000 (sxgsml)
DEC_EOS = '-11:45:55.9'          / Dec at EOS, epoch 2000 (sxgsml)
WSPD_EOS=                    0   / Wind Speed at SOS, see WARNING below
WDIR_EOS=                    0   / Wind Direction at EOS, see WARNING below
HUM_EOS =                   65   / Humidity at EOS, 0-100%
SEE_EOS =       0.00000000E+00   / Seeing at EOS, see WARNING below
BAR_EOS =       2.97000008E+01   / Barometer at EOS (inches of Hg)
AIRT_EOS=       4.00000000E+00   / Air temperature at EOS, degs Celsius
TELT_EOS=       4.59999990E+00   / Telescope Temp at EOS, degs Celsius
ARYT_EOS=      -1.90000000E+02   / Temperature of array, see WARNING below
COMMENT *** WARNING *** indicated parameter not measured, dummy only
COMMENT src keys: (IK)=IPAC Konstant; (IC)=IPAC cmptd; (IN)=IPAC namelist
COMMENT           (OV)=Obsrvtry .par file variable
COMMENT   Group 2 parms are ALL from the Obs .par file
COMMENT   non-Group 2 parms w/o (xx) are usually fm Obs
RF_NLID = 'norot sat s 980730'   / Rdframe namelist version id
HISTORY * Rdframe version= 980423     jhw.  Bgn Xeq = 98-10-26 18:47:55
HISTORY * DFlat  vsn1.95 980924  Run on 10/26/98 at 18:43:58
HISTORY > Image Created by pixphot - version 980709c
HISTORY >         Gene Kopan  IPAC/ Caltech