Observational Data Format

This page is part of the ING manual WHT-INGRID-2: INGRID IMPB Software Operations Manual

The output files from the IMPB Observing System are FITS-compatible based on the model currently in use at the WHT , defined in the ING document WHT-PDF-1.

Note: with the introduction of ULTRADAS this model will change, with the observational data from all three ING telescopes unified into a single model.

IMPB observational data files are of 'simple' FITS type, consisting of a single FITS Header and Data Unit (HDU) of fixed length (currently 8400960 bytes).

See the following for more information:

Header Information
Detector Data Information
Example Header Data

Header Information

Header information is grouped into a number of packets, each packet providing the telemetry information for one ING subsystem (eg telescope, mechanism controller, detector controller etc).

The IMPB Observing System supports the following packets:

IMAGE - this packet contains the FITS mandatory keywords SIMPLE, BITPIX, NAXIS, NAXIS1, NAXIS2.
OBSVATON - this packet provides general information associated with the observation (eg run number, date, observatory etc).
TELESCOP - this packet provides telescope status information. It is generated by averaging the telescope status both before and after data is acquired from the detector array.
INSTINGR - this packet contains the status of the INGRID EPICS Controller. It represents the status of INGRID's mechanisms immediately before data was acquired from the detector array.
DETINGR - this packet contains the status of the INGRID SDSU Controller. It represents the status of INGRID's detector array immediately before data was acquired from it.

The actual packets which are present in any given observation depend on the type of observation, and on which of the subsystems are online (it is possible to run IMPB without the TCS or Mechanism Controller, but not without the SDSU Controller).

If the observation is of type glance then only the IMAGE packet is present. This contains the minimal information to describe the image.

If the observation is of type run, dark , flat or scratch then all the packets are potentially present, assuming the corresponding subsystems are online. If a subsystem is offline then an appropriate comment is inserted as a FITS header.

Regardless of which packets are present, the FITS Header Unit is always padded to exactly four FITS logical blocks (11520 bytes). This simplifies subsequent processing by the INGRID Real Time Display.

Detector Data Information

In addition to the header information described above, IMPB FITS files contain a data array with the following properties:

The array is of dimension 1024 x 1024 x 2 pixels.
Image plane 1 contains the pre-integration data set.
Image plane 2 contains the post-integration data set.
The pixel data type is 32-bit REAL

For MNDR observations where Nr = 1 and where frame coaveraging is off (Nc = 1) the pre-integration and post-integration data sets contain the raw pixel data (up-converted to their 32-bit real representation). For observations containing more than one read, or where a number of coaverages are present the data sets are averaged over the total number of reads which were taken.

Note: the raw pixel information provided by the SDSU Controller is quantised to 16-bits (ie a maximum of 65535 ADU).

Tips:

To view the pre-integration data using IRAF type: 'display <filename>[*,*,1]'
To view the post-integration data using IRAF type: 'display <filename>[*,*,2]
To view the subtracted data you will need to use the INGRID quick look data reduction package.

Example Header Data

SIMPLE =                    T /
BITPIX =                  -32 /
NAXIS   =                    3 /
NAXIS1 =                 1024 /
NAXIS2 =                 1024 /
NAXIS3 =                    2 /
ORIGIN = 'ING La Palma      ' / Origin of data
OBSERVAT= 'ING La Palma      ' / Origin of data
PDFVERSI= 'WHT-PDF-1 V2.8    ' / Headers specified by
HCTVERSI= 'IMPB ISP V2.3.1   ' / Headers collected by
TELESCOP= 'WHT               ' / Name of telescope
FSTATION= 'CASS              ' / Focal station
INSTRUME= 'INGRID            ' / Name of instrument configuration
DETECTOR= 'HAWAII-1          ' / Name of detector
OBSERVER= 'N/A               ' / Name of observer
PROPOSAL= 'N/A               ' / PATT/CAT reference
DATE-OBS= '2000/10/08        ' / Date of UT at start of observation
RUN     =               363699 / Run number of observation
OBJECT = 'AD-4/8: Ori04_14 ' / Title of observation
OBSTYPE = 'RUN               ' / Type of observation
IMAGETYP= 'RUN               ' / Type of observation
CTYPE1 = 'LINEAR            ' / Units of x axis
CRPIX1 =                  1.0 / Reference pixel is 1
CRVAL1 =                  1.0 / Axis value at reference pixel
CDELT1 =                  TBD / Interval between pixel centres
CTYPE2 = 'LINEAR            ' / Units of y axis
CRPIX2 =                  1.0 / Reference pixel is 1
CRVAL2 =                  1.0 / Axis value at reference pixel
CDELT2 =                  TBD / Interval between pixel centres
DISPAXIS=                    1 / Axis in dispersion direction
INGMCHID= 'v1-18_mdcb_28/06/0' / INGRID EPICS IOC Software Id
INGPSCAL=                 13.5 / INGRID Plate Scale (arcsec/mm)
INGPSPOS=                    4 / Pupil Stop Position
INGPSNAM= 'cs                ' / Pupil Stop Name
INGF1POS=                   10 / Filter 1 Position
INGF1NAM= 'h                 ' / Filter 1 Name
INGF2POS=                    9 / Filter 2 Position
INGF2NAM= 'clear             ' / Filter 2 Name
INGPISTA= 'OUT_OF_SERVICE    ' / Pupil Imager Status
INGFOCUS= '-50.00            ' / Focus (um)
LATITUDE=            28.760583 / Telescope latitude (degrees), +28:45:38.1
LONGITUD=            17.881639 / Telescope longitude (degrees), +17:52:53.9
HEIGHT =                 2344 / [m] Height above sea level.
SLATEL = 'LPO4.2 '           / Telescope name known to SLALIB
TELESCOP= 'WHT     '           / 4.2m William Herschel Telescope
TELSTAT = 'TRACKING'           / Telescope status: TRACKING or GUIDING normally.
RA      = ' 5:39:48.797'      / RA ( 84.9533198119190300 degrees)
DEC     = '-02:12:26.96'       / DEC ( -2.2074889087706970 degrees)
EQUINOX = 'J2000.00'           / Equinox of coordinates
RADECSYS= 'FK5     '           / mean place new (after the 1976 IAU) system
XAPNOM =         0.0000000000 / nominal aperture in x (0.00 arcsec)
YAPNOM =         0.0000000000 / nominal aperture in y (0.00 arcsec)
XAPOFF =         0.0000000000 / total aperture offset in x (0.00 arcsec)
YAPOFF =        -0.0019444445 / total aperture offset in y (-7.00 arcsec)
MJD-OBS =        51825.1950983 / Modified Julian Date of midtime of observation
JD      =      2451825.6950983 / Julian Date of midtime of observation
STSTART = ' 4:37:43.0'        / Local sidereal time at start of observation
ST      = ' 4:37:43.0'        / Local sidereal time at start of observation
AZIMUTH =           151.779207 / Mean azimuth of observation (degrees)
ZD      =            34.342662 / Mean zenith-distance of observation (degrees)
FSTATION= 'CASSEGRAIN'         / Focal station of observation
PLATESCA=             1.238735 / [d/m] Platescale ( 4.46arcsec/mm)
TELFOCUS=             0.098100 / Telescope focus (metres)
ROTTRACK=                    T / Rotator always tracks sky on equatorial mount
ROTSKYPA=             0.000000 / demmand SKY position angle (degrees)
PARANGLE=           335.501979 / Parallactic angle at observation midpoint
VIGNETTE=                    F / Can we see out?
DOMEAZ =           150.919778 / Mean dome azimuth during observation
AIRMASS =             1.210532 / Effective mean airmass
TEMPTUBE=            10.765206 / Truss Temperature (degrees Celsius)
CAT-NAME= 'ORI04_14'           / Target input-catalogue name
CAT-RA = ' 5:39:48.800'      / Target Right Ascension
CAT-DEC = '-02:12:27.00'       / Target Declination
CAT-EQUI= 'J2000.00'           / Equinox of target coordinates
CAT-EPOC=              2000.00 / Target epoch of proper motions
PM-RA   =             0.000000 / Target proper-motion RA (sec time/year)
PM-DEC =             0.000000 / Target proper-motion (sec arc/year)
PARALLAX=             0.000000 / Target Parallax (arcsec)
RADVEL =             0.000000 / Target radial velocity (km/s)
RATRACK =             0.000000 / Differential-tracking rate RA (arcsec/sec)
DECTRACK=             0.000000 / Differential-tracking rate Dec (arcsec/sec)
INGDETIR= 'HAWAII-1          ' / Detector Name eg HAWAII-1
INGSWID = '3.1-3.1-3.1-3.1   ' / Detector Controller Software Identifier
INGRDTIM=                0.600 / Array Read Time (s)
INGSTMP =                  0.0 / Array Set Temperature (K)
INGATMP =                 71.8 / Array Actual Temperature (K)
READNOIS=                 25.0 / Detector Readout Noise (e- rms)
BUNIT   = 'ADU               ' / Physical Units of data array
GAIN    =                  3.6 / Electrons per ADU conversion factor
INGBIASV=                3.400 / Detector array bias voltage
INGRSTV =                0.550 / Detector array reset voltage
INGRDMOD= 'MNDR              ' / Array Read Mode
INGNR   =                    1 / Number of Reads in MNDR
INGNC   =                    2 / Number of Coadds
INGNM   =                    1 / Total Number of images in multirun sequence
INGIM   =                    1 / Index within multirun sequence (1..INGNM)
INGXSIZE=                 1024 / X dimension of digitized frame
INGYSIZE=                 1024 / Y dimension of digitized frame
INGXIMSI=                 1024 / X dimension of useful image area
INGYIMSI=                 1024 / Y dimension of useful image area
INGWMODE=                    F / Windowing enabled ? [T or F]
INGWXO1 =                    0 / X offset of Window 1
INGWYO1 =                    0 / Y offset of Window 1
INGWXO2 =                    0 / X offset of Window 2
INGWYO2 =                    0 / Y offset of Window 2
INGWXO3 =                    0 / X offset of Window 3
INGWYO3 =                    0 / Y offset of Window 3
INGWXO4 =                    0 / X offset of Window 4
INGWYO4 =                    0 / Y offset of Window 4
UTSTART = '04:40:42          ' / UT at start of observation
INGSMODE= 'OPEN              ' / Shutter Mode
INGITIM =                    8 / Integration Time (secs)
EXPOSED =                    8 / On-sky Exposure Time (secs)
EXPTIM =                    8 / On-sky Exposure Time (secs)
INGTEMP1=                 71.8 / Temperature Monitoring Point 1 (K)
INGTEMP2=                 92.9 / Temperature Monitoring Point 2 (K)
INGTEMP3=                 69.8 / Temperature Monitoring Point 3 (K)
HISTORY This is the end of the packets written by the observing system.
COMMENT There now follows blanks to pad to the end of the 4th logical record.

END