MODS FITS Headers

Updated: 2011 Jan 15 [rwp]

Below is a sample MODS science-image FITS header, divided into the various blocks of data. The example is drawn from various MODS1 image headers.

MODS science images are standard FITS format with single header and data units.

Basic FITS Data

Current FITS images are written as 16-bit integers scaled using the standard BZERO and BSCALE keywords to get all 16-bits of raw ADC data encoded. Future versions of the MODS CCD controller will create 32-bit integer headers read with an 18-bit ADC.

   SIMPLE  =                    T /
   BITPIX  =                   16 /
   NAXIS   =                    2 /
   NAXIS1  =                 8288 /
   NAXIS2  =                 3088 /
   BSCALE  =                    1 / PHYSICAL=INTEGER*BSCALE+BZERO
   BZERO   =                32768 /
   BUNIT   = 'ADU     '           / units of physical values (LBT)

Detector Information

Each MODS channel as e2v CCD231-68 8x3K CCDs (thin standard Si in the blue camera, 40um thick deep-depletion Si in the red camera). This block gives the readout configuration (binning, overscan, amplifiers, etc.) and the physical size and image scale of unbinned pixels.

   DETECTOR= 'e2v CCD231-68 Blue CCD 1'     / Detector name
   DETSIZE = '[1:8288,1:3088]'    / Unbinned size of detector full array
   NAMPS   =                    4 / Number of amplifiers in the detector
   GAINDL  =                    3 / Pixel integration time, in sequencer clocks
   PIXITIME=            1.2000E-6 / Pixel integration time, in seconds
   CCDXBIN =                    1 / CCD X-axis Binning Factor
   CCDYBIN =                    1 / CCD Y-axis Binning Factor
   OVERSCNX=                    0 /
   OVERSCNY=                    0 /
   READOUT = 'ARLBRL  '           / Amplifiers used in readout
   DISPAXIS=                    1 / Spectral Dispersion Axis
   PIXSCALE=                0.120 / Unbinned pixel scale [arcsec per pixel]
   PIXSIZE =                 15.0 / Unbinned pixel size [microns]

Observatory Information

This block gives the LBT-standard information about the LBT/MGIO observing site and the telescope focal plane

   ORIGIN  = 'MGIO-LBT'           / Location where the data was generated
   OBSERVAT= 'MGIO-LBT'           / Observatory Site
   TELESCOP= 'LBT-SX  '           / Telescope and Focus
   FOCSCALE=                 1.67 / Focal Plane Scale [arcsec per mm]
   LATITUDE=             32.70131 / Site Latitude [deg N] 
   LONGITUD=            109.88906 / Site Longitude [deg W]
   ELEVATIO=               3221.0 / Site Elevation [meters]

Observer/Partner/Project Information

This block lists the observers, partner and project IDs used by the LBT data archive, and additional information about LBTO personnel during the observing run. These data are set either by observing scripts or in the Setup screen of the MODS instrument control panel.

   OBSERVER= 'Pogge & Skillman'   / Observer(s)
   PARTNER = 'OSURC   '           / LBT Project Partner(s)
   PROPID  = 'OSU_HIIAbund'       / Observing Proposal ID
   PI_NAME = 'Pogge   '           / Project PI Name(s)
   SUPPORT = 'Pedani, Shih'       / LBT Support Scientist(s)
   TELOPS  = 'Steven Allanson'    / LBT Telescope Operator(s)

Exposure Information

This block lists information about the exposure, including the image type, object name, exposure and dark time, and the raw filename and associated acquisition identifiers.

   GROUP   =                    0 / Group identifier for related images
   IMAGETYP= 'OBJECT  '           / Type of observation 
   OBJECT  = 'Dual Prism IMCS Test PA=45 El=90' / Name of object
   EXPTIME =                  5.0 / Exposure time [seconds]
   DARKTIME=                 7.85 / Cumulative Dark Time [seconds]
   LEDFLASH=            0.0000E+0 / Time to flash lab LEDs [seconds]
   FILENAME= 'mods1b.20110113.0049' / Filename assigned by the data-taking system
   UNIQNAME= '110112M8.01c'       / Unique filename; if filename is invalid
   ACQTAG  = 'MODS1B.20110113061700' / Unique Acquisition ID Tag

The UNIQNAME keyword is protection against accidentally overwriting image files. If an image with the same name as this file is found in the raw data directory, it writes the FITS file with UNIQNAME instead.

The ACQTAG keyword is a unique identifier associated with each acquired image, used to help track activity during this acquisition in the runtime telemetry logs.

Instrument Configuration

These blocks give the configuration of the common focal plane and MODS channel (here blue) for this image

Common Focal Plane Configuration

This block lists the instrument (MODS1B = MODS1 Blue Channel), the state of the dark hatch, calibration tower, calibration lamps (Kr is lit), the slitmask, and the dichroic. This image is a dual-mode Kr lamp calibration using the 0.3-arcsec pinhole slit (test mask)

   INSTRUME= 'MODS1B '            / Instrument Name
   HATCH   = 'CLOSED  '           / Instrument Dark Hatch
   CALIB   = 'IN      '           / Calibration Tower Position
   CALLAMPS= 'KR      '           / Calibration Lamps
   VFLAT   =                  2.5 / Variable Intensity Flat Lamp Intensity
   SLITMASK=                    6 / Slit Mask Cassette position
   MASKPOS = 'IN      '           / Slit Mask Position
   MASKNAME= 'PinholeSlit'        / Slit Mask Name
   MASKINFO= '0.3 arcsec Pinhole Slit' / Slit Mask Description
   DICHROIC=                    2 / Dichroic Turret Position
   DICHNAME= 'Dual    '           / Dichroic Beam Selector position ID
   DICHINFO= 'CSIRO 575nm Dichroic Nr1' / Dichroic Beam Selector Description

Channel Configuration

This block lists the configuration of the channel used (Blue) for the collimator mirror, grating, filter, and camera focus values at the start of the exposure.

   CHANNEL = 'BLUE    '           / Channel name, Blue or Red
   COLFOCUS=                18368 / Collimator Focus (A+B+C) [microns]
   COLTTFA =                17086 / Collimator TTF actuator A [microns]
   COLTTFB =                17925 / Collimator TTF actuator B [microns]
   COLTTFC =                20092 / Collimator TTF actuator C [microns]
   GRATING =                    3 / Grating Turret Position
   GRATNAME= 'P450L   '           / Name of the Disperser at GRATING
   GRATINFO= 'FuSi+Al Double-Pass Prism Nr1' / Description of the Disperser
   GRATTILT=                19150 / Grating Tilt [microns]
   GRCENLAM= '        '           / Grating nominal central wavelength [Ang]
   GRORDER =                    0 / Grating order used
   FILTER  =                    1 / Camera Filter Wheel Position
   FILTNAME= 'Clear   '           / Camera Filter Name
   FILTINFO= 'Fused Silica Clear 128x86x6mm Nr1' / Camera Filter Description
   CAMFOCUS=                 3380 / Camera Primary Mirror Focus [microns]

Note that during an exposure the COLTTFx keywords will change as the IMCS steers the collimator to compensate for instrument flexure, but COLFOCUS will remain roughly constant (tip/tip corrections are made relative to the collimator focus vertex).

IMCS IR Laser Status

These keywords list the status of the IR laser used by the Image Motion Compensation System (IMCS)

   IRLASER = 'ON      '           / IMCS IR Laser AC Power On or Off
   IRBEAM  = 'ENABLED '           / IMCS IR Laser Beam Enabled or Disabled
   IRPSET  =                  0.3 / IMCS IR Laser Beam Power Set Point [mW]
   IRPOUT  =                  0.4 / IMCS IR Laser Beam Power Output [mW]
   IRTEMP  =                 25.4 / IMCS IR Laser Head Temperature [deg C]
   IRTSET  =                 25.5 / IMCS IR Laser Head Temp Set Point [deg C]

Target and Guide Star Coordinates

These keywords list the target and guide star coordinate information uploaded to the TCS by the preset used to point the telescope for this observation.

   OBJNAME = 'M1'                 / Target Name
   OBJRA   = '05:34:30.000'       / Target RA
   OBJDEC  = '+22:01:00.00'       / Target DEC
   OBJRADEC= 'FK5'                / Target Coordinate System
   OBJEQUIN= 'J2000'              / Target Coordinate System Equinox
   OBJPMRA =                 0.00 / Target RA proper motion [mas per yr]
   OBJPMDEC=                 0.00 / Target Dec proper motion [mas per yr]
   OBJEPOCH=              2000.00 / Target Epoch
   GUINAME = 'gstar   '           / Guide Star Name
   GUIRA   = '05:34:29.449'       / Guide Star RA
   GUIDEC  = '+21:57:29.80'       / Guide Star DEC
   GUIRADEC= 'FK5'                / Guide Star Coordinate System
   GUIEQUIN= 'J2000'              / Guide Star Coord System Equinox
   GUIPMRA =                 0.00 / Guide Star RA proper motion [mas per yr]
   GUIPMDEC=                 0.00 / Guide Star Dec proper motion [mas per yr]
   GUIEPOCH=              2000.00 / Guide Star Epoch

Telescope Pointing and Rotator Information

These keywords give the telescope pointing and rotator information read from the Telescope Control System (TCS) at the start of the exposure.

   TCSLINK = 'Live    '           / TCS Communications Link Status  
   DATE-OBS= '2010-11-19T10:12:36.980' / UTC Date at start of obs
   UTC-OBS = '10:12:36.980'       / UTC Time at start of obs
   TIMESYS = 'UTC     '           / Time System
   LST-OBS = '06:46:24.101'       / Local Siderial Time at start of obs
   MJD-OBS =         55519.425428 / Modified JD=JD-2400000.5 at start of obs
   RADECSYS= 'FK5     '           / Coordinate System
   EQUINOX =               2000.0 / Equinox of coordinates
   TELRA   = '05:34:29.998'       / Telescope RA
   TELDEC  = '22:00:59.963'       / Telescope DEC
   POSANGLE=              0.00000 / Instrument Celestial Position Angle [deg]
   TELALT  =             70.96853 / Telescope Altitude at start of obs [deg]
   TELAZ   =            240.25531 / Telescope Azimuth at start of obs [deg]
   PARANGLE=             52.29008 / Parallactic Angle at start of obs [deg]
   ROTANGLE=           -100.34461 / Rotator Angle at start of obs [deg]
   ROTMODE = 'POSITION'           / Rotator Mode
   HA      = '01:12:24.101'       / Hour Angle at start of obs
   ZD      =                19.03 / Zenith Distance at start of obs [deg]
   AIRMASS =                 1.06 / Airmass (secZD) at start of obs

AGw System Configuration

These keywords list the state of the AGw (Acquisition, Guide, and Wavefront Sensing) system.

   AGWXGP  =               -4.517 / AGW Guide Probe X focal plane position [mm]
   AGWYGP  =             -138.845 / AGW Guide Probe Y focal plane position [mm]
   AGWFOCUS=                0.000 / AGW Guide Probe relative focus [mm]
   AGWFILT =                    2 / Guide Camera Filter Wheel position
   AGWFNAME= 'F525LP  '           / Guide Camera Filter Name
   AGWFINFO= 'Edmund 525nm Long-Pass Yellow 50x5mm' / Guide Camera Filter Descripti
   AGWXS   =               87.483 / AGW Stage X actuator position [mm]
   AGWYS   =               55.837 / AGW Stage Y actuator position [mm]
   AGWFS   =               47.818 / AGW Stage Focus actuator position [mm]
   AGWFS0  =               38.500 / AGW Stage Focus Zero Point [mm]

GCS and PCS Guide Star Position Data

These keywords give data from the GCS (Guiding and Collimation System) and PCS (Pointing Control System) regarding where the GCS sent the guide probe and the measured guide star positions. These are mostly for engineering/commissioning.

   GPREQ_X =                4.961 / GCS Requested guide probe PCS X [mm]
   GPREQ_Y =             -138.929 / GCS Requested guide probe PCS Y [mm]
   GPACT_X =                4.960 / GCS Actual guide probe PCS X [mm]
   GPACT_Y =             -138.926 / GCS Actual guide probe PCX Y [mm]
   GSPRED_X=                4.591 / PCS Predicted guide star X position [mm]
   GSPRED_Y=             -125.829 / PCS Predicted guide star Y position [mm]
   GSMEAS_X=                3.818 / GCS Measured guide star X position [mm]
   GSMEAS_Y=             -124.538 / GCS Measured guide star Y position [mm]
   GSDELTAX=              192.541 / GCS cumulative X guide update position [mm]
   GSDELTAY=               71.543 / GCS cumulative Y guide update position [mm]

Instrument Environmental Monitoring Data

CCD Head Electronics Box Sensor Data

These keywords list the temperatures, pressures, and voltages measured in the CCD detector head electronics box at the start of the exposure.

   DEWPRES = '9.4700E-06'         / Dewar Pressure [torr]
   DEWTEMP =              -198.16 / Dewar LN2 Reservoir Temperature [deg C]
   CCDTEMP =              -113.78 / CCD Mount Temperature [deg C]
   HEBTEMP =                17.09 / HEB Air Temperature [deg C]
   HSTEMP  =                 3.24 / HEB Post Heat Sink Air Temperature [deg C]
   CTEMPIN =                 0.90 / HEB Coolant Input Temperature [deg C]
   CTEMPOUT=                 2.13 / HEB Coolant Output Temperature [deg C]
   TEDPOWER= 'ON      '           / HEB Thermoelectric Device Power State
   LEDPOWER= 'OFF     '           / HEB External LED Power State
   IGPOWER = 'ON      '           / Dewar Vacuum Ion Gauge Power State
   HEB3V   =                 3.31 / HEB +3V Power Supply [VDC]
   HEBFANV =                11.86 / HEB Fan Power Supply [VDC]
   HEB15V  =               -15.04 / HEB -15V Power Supply [VDC]
   HEB5V   =                 4.93 / HEB +5V Power Supply [VDC]
   HEB24V  =                23.16 / HEB +24V Power Supply [VDC]
   BOGHTRV =                 1.99 / Dewar boil-off gas heater voltage

Of particular interest to observers are the dewar temperature and pressure and the CCD temperature. If the LN2 reservoir has run dry, DEWTEMP and DEWPRES will rise above the nominal values depicted above. CCDTEMP is the temperature of the CCD detector mount. If the detector is warming up and producing high dark counts or other warm-detector artifacts, this number will be warmer than the nominal value shown above.

Instrument Temperature Sensor Data

These keywords report the values of various instrument temperature sensors in the instrument at the start of the exposure. Sensors are located inside the instrument electronics boxes (Mechanism controller and utility boxes), on the instrument main structural truss, and sampling the air temperature inside the instrument.

   AMBTEMP =                  0.3 / Outside Ambient Air Temperature [deg C]
   TAIRTOP =                  1.6 / MODS Inside Air Temp at Top [deg C]
   TAIRBOT =                  0.5 / MODS Inside Air Temp at Bottom [deg C]
   TCOLLTOP=                  2.1 / Collimator Truss Tube Top Temp [deg C]
   TCOLLBOT=                  0.8 / Collimator Truss Tube Bottom Temp [deg C]
   IEBTEMPB=                  4.1 / Blue IEB Air Temperature [deg C]
   IEBGRT_B=                  0.0 / Blue IEB Glycol Return Temperature [deg C]
   IEBTEMPR=                  2.5 / Red IEB Air Temperature [deg C]
   IEBGRT_R=                 -0.2 / Red IEB Glycol Return Temperature [deg C]
   IUBTAIR =                  1.4 / Utility Box Air Temperature [deg C]
   AGHSTEMP=                  0.0 / AGw Controller Heat Sink Temp [deg C]

Glycol Cooling Sensor Data

These keywords report the glycol coolant supply and return temperatures and pressures at the start of the observation.

   GSPRES  =                 27.0 / Glycol Supply Pressure [psi-g]
   GSTEMP  =                 -0.2 / Glycol Supply Temperature [deg C]
   GRPRES  =                 24.7 / Glycol Return Pressure [psi-g]
   GRTEMP  =                  0.0 / Glycol Return Temperature [deg C]

Telescope Telemetry

These keywords are read from the various telescope subsystems to provide basic telemetry on the telescope configuration and environmental sensors

LBT Telescope Primary and Secondary Mirror Collimation State

These keywords list the primary and secondary mirror collimation parameters at the start of the exposure.

   M1POSX  =                0.504 / Primary Mirror X Position [mm]
   M1POSY  =               -1.111 / Primary Mirror Y Position [mm]
   M1POSZ  =               -0.226 / Primary Mirror Z Position [mm]
   M1ROTX  =              -30.721 / Primary Mirror RX Rotation [arcsec]
   M1ROTY  =                4.298 / Primary Mirror RY Rotation [arcsec]
   M1ROTZ  =                0.000 / Primary Mirror RZ Rotation [arcsec]
   M1CTEMP =                 4.50 / Primary Mirror Temperature [deg C]
   M1ATEMP =                 0.67 / Primary Mirror Ambient Air Temp [deg C]
   M2POSX  =               -4.010 / Secondary Mirror X Position [mm]
   M2POSY  =               -0.317 / Secondary Mirror Y Position [mm]
   M2POSZ  =                0.000 / Secondary Mirror Z Position [mm]
   M2ROTX  =              148.650 / Secondary Mirror RX Rotation [arcsec]
   M2ROTY  =              181.800 / Secondary Mirror RY Rotation [arcsec]
   M2ROTZ  =                0.000 / Secondary Mirror RZ Rotation [arcsec]
   M2CTEMP =                 4.50 / Secondary Mirror Temperature [deg C]

Telescope Temperature Sensor Data

These keywords report the readings from temperature sensors on the telescope at the start of the exposure.

   TTEMP201=                1.614 / Channel 201 Temperature [deg C]
   TTEMP202=                0.939 / Channel 202 Temperature [deg C]
   TTEMP203=                0.969 / Channel 203 Temperature [deg C]
   TTEMP204=                0.568 / Channel 204 Temperature [deg C]
   TTEMP205=                0.731 / Channel 205 Temperature [deg C]
   TTEMP206=                0.672 / Channel 206 Temperature [deg C]
   TTEMP207=                0.051 / Channel 207 Temperature [deg C]
   TTEMP208=                0.499 / Channel 208 Temperature [deg C]
   TTEMP209=                1.072 / Channel 209 Temperature [deg C]
   TTEMP210=                1.011 / Channel 210 Temperature [deg C]
   TTEMP301=                0.540 / Channel 301 Temperature [deg C]
   TTEMP302=                0.476 / Channel 302 Temperature [deg C]
   TTEMP303=                1.351 / Channel 303 Temperature [deg C]
   TTEMP304=                0.734 / Channel 304 Temperature [deg C]
   TTEMP305=                1.028 / Channel 305 Temperature [deg C]
   TTEMP306=                0.361 / Channel 306 Temperature [deg C]
   TTEMP307=                0.282 / Channel 307 Temperature [deg C]
   TTEMP308=                0.548 / Channel 308 Temperature [deg C]
   TTEMP309=                1.080 / Channel 309 Temperature [deg C]
   TTEMP310=                0.320 / Channel 310 Temperature [deg C]

Weather Data

These keywords report weather conditions at the start of the exposure as read from the LBT weather station located on the roof. At present we only report ambient temperature, pressure, relative humidity, and dewpoint temperature.

   LBTWLINK= 'Up      '           / LBT Weather Station Link State
   LBTPRES =               692.70 / LBT Ambient Pressure [hPa]
   LBTTEMP =                 0.20 / LBT Ambient Temperature [deg C]
   LBTHUM  =                36.80 / LBT Relative Humidity [percent]
   LBTDWPT =               -12.90 / LBT Dew Point [deg C]

-- RichardPogge - 16 Jan 2011