INS-DAS-26

Observation files produced by UltraDAS

Issue 2.8  2011-05-09

Richard Bassom (rab@ing.iac.es), Craige Bevil (cb@ing.iac.es), Marion Fisher (mpf@ing.iac.es), Guy Rixon, ING (gtr@ast.cam.ac.uk), Simon Rees (sgr@ing.iac.es) 


1. Introduction

Purpose of this document

The FITS files in which UltraDAS outputs its observations are described; the form of these files is a formal interface on the boundary of UltraDAS. The correctness of UltraDAS may be judged by comparing the file it produces with this specification.

This ICD supersedes the documents INT-DAS-2, JKT-DAS-1 and WHT-PDF-1.

Scope of the interface

The form of the files and the semantics of their production and consumption are defined here.  The infrastructure by which the files pass out of UltraDAS is not a part of the formal interface. The content of the FITS headers is discussed in some detail.

Changes to this document

Issue 1.1, 1998-11-16:
The original text.
Issue 2.1, 1999-11-26:
The header content is changed; details of changes are in Annex A. The system is now required to produce one image extension per channel per window when windows are enabled. Header packets for Taurus-2 and LDSS-2 are no longer specified, but the old form of these packets is retained in Annex B.
Issue 2.2, 2000-07-05:
Changes that had been agreed but not recorded were included in the specification. All files now use image extensions. The run packet is described in full. The channel packet is now specified to have only one WCS, and that WCS maps from image to detector coordinates.

Issue 2.3, 2003-01-28:
Added support for INGRID mechanism packet collection. Added placeholder for OSCA. Imported NAOMI info from WHT-NAOMI-19. Added proposals for supporting both the NAOMI USP Crate and OASIS.
Issue 2.6, 2004-12-03:
Updated TCS packet for INT and WHT, JKT TCS packet is unchanged.
Issue 2.7, 2005-11-11:
SGR: Modified USP and OASIS information to track current implementational reality. Removed Dichroic Changer information from USP crate. Added new DCHANGER packet.
Issue 2.8, 2011-05-09:
RAB: Added AF2 FITS header packets. Added UT and UT-MID header cards to integration packet. Added missing cards from camera packet.


References

  1. Command-and-status interface to DRAMA clients for UltraDAS

  2. ING document INS-DAS-27 by Guy Rixon.
     http://www.ing.iac.es/~docs/ins/das/ins-das-27/ins-das-27.html
  3. Definition of the Flexible Image Transport System (FITS)

  4. NASA standard NOST 100-2.0
     http://fits.gsfc.nasa.gov/
  5. A User's Guide for the Flexible Image Transport System

  6. NASA/GSFC Astrophysics Data Facility
  7. NOAO image-data-structure definitions

  8.  http://iraf.noao.edu/projects/ccdmosaic/imagedef/imagedef.html
  9. FITS headers for INT observations

  10. ING document INT-DAS-2 by Guy Rixon, Mike Irwin, Peter Bunclark and Jim Lewis
    (document is superseded by the current work).
  11. FITS headers for JKT observations

  12. ING document JKT-DAS-1 by Roger Edwards
    (document was never produced and is superseded by the current work).
  13. FITS headers for WHT FITS tapes

  14. ING document WHT-PDF-1 by Steve Unger and Guy Rixon
    (document is superseded by the current work).

2. Semantics of file production

UltraDAS produces FITS files on disc as its final product. The data manager, the FITS-tape writing software and the data-reduction software are consumers of these files; all these entities are outside UltraDAS.

UltraDAS produces exactly one FITS file per observation, where an "observation" is the set of integrations associated with one run number. Where two cameras are used in parallel (e.g. on ISIS blue and red arms) two observations are deemed to have taken place; two run numbers are issued and two FITS files are produced. Where one camera produces data from multiple readout-amplifiers, detectors or detector controllers, only one observation is deemed to have taken place; one run number is issued and all the pixels go into one FITS file.

Saving an observation to disc is an standard part of the observing commands such as run, bias etc. Depending on the camera in use, UltraDAS may wait to finish writing the file before the command returns or it may finish the writing during the next observation (in order to reduce the dead time between observations).

FITS files become available to the consumers only when they are complete and UltraDAS has finished with them. Consumers can write to the files after this but observatory policy is that they should not. UltraDAS does not read back its FITS files after it releases them. UltraDAS does not delete the FITS-files it outputs nor does it move them between directories; clearing old observations off the disc must be done by one of the consumer processes.

UltraDAS distinguishes archivable observations, scratch observations and glance observations. Archivable observations are to be recorded by the data manager. Scratch observations are not taken by the data manager but are recorded on disc for other consumers. Glance observations are held in memory and displayed but are not released to any consumers; if UltraDAS happens to write a glance observation to disc, it does not release the file.

Creation of a FITS file by UltraDAS takes time. UltraDAS typically starts writing the file at the start of the observation, but the consumer programmes may not depend on this as the behaviour may vary from camera to camera and between UltraDAS releases. The consumers must not attempt to use the file while UltraDAS is writing it. To enforce this, UltraDAS uses different names for the current and released observation-files. A consumer may use a released file as soon as it becomes visible in the directory structure. No file or record locking is used.

Consumers may detect the release of  observation files in two ways:

  1. Poll the observation directories for file with a modification time newer than the last sweep.
  2. Run the DRAMA client-programme udas_detect_obs in a sub-process.
The client udas_detect_obs, details of which can be found in the ICD for the client programmes [1], is notified by the camera server  when a new observation is released. It writes the name of the observation file to its standard output which the consumer programme can read through a pipe. It is important to remember that this client does not detect observations that were committed to disc before the client was started.
 

3. Use of run numbers

Each observation is given a run number and the numbers are in sequence. The numbers are never reset to zero, so a run number at a particular telescope is unique. However, the run-number streams at the three ING telescopes are independent and the same number will be issued at each telescope in due course.

Normally, there are no gaps in the sequence of run numbers. However, if an observation fails, or is aborted by the user's command, then the run number that it had been given will not be reused and there will be a gap. Run numbers are issued to all runs, even glances, at the start of the observation: this simplifies and unifies the software. Hence, taking and discarding glances leaves gaps in the run-number sequence.
 

4. Naming of observation files

5. Directory structure

Each telescope has one or more data partitions mounted (on the DAS computer) at the /obsdata mount-point. A typical set of partitions is /obsdata/inta, /obsdata/intb and /obsdata/intc. The partition name typically has only one level below /obsdata but may have more.

Within the data partitions, UltraDAS creates one directory per night of observing, named for the date on which the night began; the name has the format yyyymmdd. For example, the directory /obsdata/inta/19981112 would be used for observations from 1200hrs UTC on the 12th of November 1998 until 1200hrs on the following day.
 

6. File Syntax

Observation files are FITS files as defined by  issue 2.0 of NASA's standard [2].

All observations are stored in FITS files with image extensions, even if there is only one image per file. One image extension is produced for each contiguous raster in the output.

The primary HDU has this structure:

  1. Mandatory descriptors, such as SIMPLE and BITPIX, with NAXIS set to zero to indicate no associated image.
  2. The run packet, written by UltraDAS.
  3. Packets of descriptors from outside UltraDAS (from the CIA, ICS and TCS).
  4. A packet of descriptors detailing the timing of the integration (usually from inside UltraDAS, but may come as a packet from the ICS).
  5. A packet describing the state of the camera from inside UltraDAS.
  6. A HISTORY descriptor marking the end of the header written to file by UltraDAS.
  7. The END descriptor.
A "packet" is simply a set of adjacent descriptors from the same source.

For the INT WFC, which has a shutter driven by the ICS, the integration timing is written in one of the packets in the primary HDU.  For all other cameras, the integration timing is written in the extension HDUs.

Each image extension has this structure:

  1. Mandatory descriptors for image extension.
  2. INHERIT
  3. Channel packet.
  4. Integration packet.
  5. END
  6. Image.

  7.  
The number of image extensions depends on the number of output amplifiers used in the camera, the number of windows,
and the joining together of channels specified in the camera configuration. In the simplest case, there is one image extension per output amplifier. In some cameras, the channels may be joined together; typically, outputs from a single detetcor-chip are joined, but outputs from different chips are left separate.

This use of image extensions was developed by NOAO for the cameras at KPNO and is felt to be a de-facto standard for multi-channel cameras [3]. However, the generalization to multiple windows was devised specifically for ING.

Some keywords are provided to match the perceived conventions of IRAF and the NOAO conventions; some are traditional at ING ("traditionally" means here "in the form generated by observing system s7 at the INT and JKT".) This means that some data are duplicated.

The INHERIT keyword comes from the STScI convention on inheritence of HDUs, as described in NASA's user guide to FITS [3]. The keyword, which takes the Boolean value T, states that the extension HDU to which it applies should inherit non-conflicting descriptors from the primary HDU. Thus, if one channel of the observation is extracted to a separate file, it carries with it all the relevant information from the primary HDU. To make this scheme work, there must not be an image following the primary HDU.

Each image has a primary and secondary world co-ordinate system (WCS). The primary WCS reserves space in the header in which data-reduction software may later write celestial coordinates. The secondary WCS defines the positions of images in linear coordinates in the focal plane. The WCS arrangements are described in the channel packet. There is no "WCS packet" covering the whole camera.

The pixels may be in any FITS format. Typically, CCD pixels are recorded as signed 16-bit integers (BITPIX=16, BZERO=32768, BSCALE not present). IR images are typically stored as 32-bit floating numbers (BITPIX=-32, BZERO not present, BSCALE not present).

At the time of writing, UltraDAS does not use other FITS extensions such as tables. It may do so in later releases.

7. Contents of FITS packets

The information in this section has been adapted from earlier specifications [4], [5], [6].

The packets have formal names which form an agreement between the DAS, ICS, TCS and CIA. Both the spelling and the case of the formal names must be as given below.
 

Run packet

The run packet records the run number in various forms. These cards are written by the DAS, and the packet must never appear in a list to be collected by the HCT.
 
 

Keyword Values Data type Notes
RUN
integer Run number.
RUNSET
character Format i:n:r - see below.
IRAFNAME
character File name to be used by RFITS.

The numbers in RUN are unique among observations at a given telescope, but the same number may apppear in the observations of all telescopes. The numbers reflect the order in which observations are started. Scratch and glance observations are given run numbers too, and these numbers come into play if a scratch or glance observation is later archived.

RUNSET describes the observation's relationship to a set of runs such as a dither sequence. The run is stated to be run i of a set of n runs, starting at run number r, these numbers being formatted in a string and separated by colons: e.g. '2:10:1234567' means second run of a sequence of 10, starting at run 1234567. Both i and n are counted from 1.

IRAFNAME takes the value r<n> where n is the run number as in RUN.
 

Observation packet

The packet's formal name is observation.
 

Keyword Values Data type Notes
SYSVER   character Version number of the observing system.
ORIGIN ING La Palma   As used at the WHT.
OBSERVAT LAPALMA   Used by IRAF
OBSERVER   character Typically, this contains the observer's initials.
PROPOSAL   character This is the code for the PATT/CAT proposal.
OBJECT   character If the observer has entered a title for the observation, it appears here. Otherwise, the name of the current target should be used, or the words ARC, BIAS, FLAT, SKY etc. as appropriate.
OBSTYPE ARC, BIAS, DARK, FLASH, FLAT, FOCUS, GLANCE,  PUPIL, SCRATCH, SKY, or TARGET character The type of observation, in the format understood by the archive and associated software at IOA, Cambridge. Upper case is mandatory.
IMAGETYP arc, bias, dark, flash, flat, focus, object, object, pupil, sky or object character The type of observation in the form preferred by IRAF. The value must match the value of OBSTYPE (see the note below). Lower case is mandatory.

The lists of values for OBSTYPE and IMAGETYP are enumerations with the same ordering. If an observation takes, say, the second value (BIAS) for OPBSTYPE, then it also receives the second value (zero) for IMAGETYP. This causes the list of values for IMAGETYP to have some duplicate entries.

Telescope packet

This packet's formal name is tcs.

The tcs packet for the INT and WHT has been updated to be similar to the VAX TCS packet. The JKT packet is unchanged.

JKT packet


Keyword JKT value Data type Meaning
TELESCOP JKT character  Common name of telescope.
LATITUDE
character Latitude of telescope corrected for polar motion.
LONGITUD
character Longitude of telescope corrected for polar motion.
HEIGHT 2369 real [m] Height of observing floor above sea-level.
SLATEL LPO1.0 character The name for the telescope as understood by the library subroutine sla_OBS().
TELSTAT   character TRACKING, GUIDING, etc.
CAT-NAME   character The name of the target as stored in the target list. May be different from the name stored under OBJECT.
CAT-RA   character Taken from the target list. In the format hh:mm:ss.ss.
CAT-DEC   character Taken from the target list. In the format sdd:mm:ss.s.
CAT-EQUI   character Equinox of the target's coordinates, taken from the target list. In the format Jnnnn.n, Bnnnn.n or A, where nnnn.n is in years AD.
CAT-EPOC   real Epoch of the target's coordinates, taken from the target list. In years AD as a decimal fraction.
PM-RA   real Proper motion in R.A. In seconds of time per year.
PM-DEC   real Proper motion in dec. In seconds of arc per year.
PARALLAX   real Half-annual parallax in seconds of arc.
RADVEL   real [km/s]Heliocentric radial velocity of the target in.
RATRACK   real Differential-tracking rate in arcsec/second in R.A.
DECTRACK   real Differential-tracking rate in arcsec/second in dec.
RA   character R.A. that the telescope is tracking. In the format hh:mm:ss.ss.
DEC   character Dec. that the telescope is tracking. In the format sdd:mm:ss.s.
EQUINOX   real Equinox of the coordinates in RA, DEC: a decimal number of years AD. Ideally, these coordinates should be given to the same equinox as CAT-RA and CAT-DEC. 
RADECSYS FK4, FK5, GAPPT
character Reference system for celestial coordinates.
STSTART   character Local sidereal time at the start of the observation. 
ST   character Same as STSTART
AZIMUTH   real [deg] Mean azimuth of telescope during observation.
ZD   real Mean zenith distance during observation. In degrees. 
AIRMASS   real Effective mean airmass during observation.
XAPOFF   real Offset from nominal pointing in `x'. In degrees.
YAPOFF   real Offset from nominal pointing in `y'. In degrees.
XAPNOM   real [degrees] Offset of nominal pointing position from the rotator centre
YAPNOM   real [degrees] Offset of nominal pointing position from the rotator centre.
ROTTRACK T   True if the instrument platform maintained constant sky PA through the observation.
ROTSKYPA   real Mean position of rotator during observation. In degrees.
PARANGLE   real Parallactic angle. In degrees.
VIGNETTE   boolean True if the mirror petals or the dome vignette the telescope's beam.
DOMEAZ   real Mean azimuth of dome during observation. In degrees.
TELFOCUS   real Position of telescope's focus drive. In metres. The sense of focus movement may vary between foci.
TEMPTUBE   real Temperature of telescope tube in degrees Celsius.

INT and WHT packet


Keyword INT value
WHT value Data type Meaning
TELESCOP INT
WHT character Common name of telescope.
LATITUDE

character Latitude of telescope corrected for polar motion
LONGITUD

character Longitude of telescope corrected for polar motion
HEIGHT 2348
2344 real [m] Height of observing floor above sea-level
SLATEL LPO2.5
LPO4.2 character The name for the telescope as understood by the library subroutine sla_OBS().
TELSTAT
  character Telescope status at start of observation, TRACKING, GUIDING, etc.
MJD-OBS
  real [days] Modified Julian date at the start of the observation.
JD
  real [days] Julian date at the start of the observation.
CAT-NAME
  character The name of the target as stored in the target list. May be different from the name stored under OBJECT.
CAT-RA
  character Taken from the target list. In the format hh:mm:ss.sss.
CAT-DEC
  character Taken from the target list. In the format sdd:mm:ss.ss.
CAT-EQUI
  character Equinox of the target's coordinates, taken from the target list. In the format Jnnnn.n, Bnnnn.n or A, where nnnn.n is in years AD.
CAT-EPOC
  real [year] Epoch of the target's coordinates, taken from the target list. In years AD as a decimal fraction.
PM-RA
  real [seconds/yr] Proper motion in R.A.
PM-DEC
  real [arcsec/yr] Proper motion in Dec.
PARALLAX
  real [arcsec] Annual parallax.
RADVEL
  real [km/s] Heliocentric radial velocity of the target .
RATRACK
  real [arcsec/s] Differential-tracking rate in R.A.
DECTRACK
  real [arcsec/s] Differential-tracking rate in Dec.
RA
  character R.A. that the telescope is tracking at the start of the observation. In the format hh:mm:ss.sss.
DEC
  character Dec. that the telescope is tracking at the start of the observation. In the format sdd:mm:ss.ss.
RADECSYS FK4, FK5, GAPPT
FK4, FK5, GAPPT character Reference system for celestial coordinates. GAPPT for Apparent coordinates.
EQUINOX
  real For RADECSYS of FK4 or FK5: equinox of the coordinates in RA, DEC: a decimal number of years AD. Ideally, these coordinates should be given to the same equinox as CAT-RA and CAT-DEC. For RADECSYS of GAPPT: current date as fraction of year.
UTOBS
  character Universal time at the start of the observation.
STSTART
  character Local sidereal time at the start of the observation.
ST
  character Same as STSTART.
AZSTART
  real [deg] Azimuth of telescope at the start of the observation.
AZEND
  real [deg] Azimuth of telescope at the end of the observation.
ZDSTART
  real [deg] Zenith distance at the start of the observation.
ZDEND

real [deg] Zenith distance at the end of the observation.
AMSTART

real Airmass at the start of the observation.
AMEND

real Airmass at the end of the observation.
AIRMASS
  real Effective mean airmass during observation.
XAPOFF
  real [deg] Total aperture offset in 'x'.
YAPOFF
  real [deg] Total aperture offset in 'y'.
XAPNOM
  real [deg] Offset of nominal pointing position from the rotator centre.
YAPNOM
  real [deg] Offset of nominal pointing position from the rotator centre.
RAOFF

real [arcsec] Positional offset parallel to RA (tangent plane).
DECOFF

real [arcsec] Positional offset in Dec (tangent plane).
ROTTRACK
  boolean True if the instrument platform maintained constant sky PA through the observation.
ROTSKYPA
  real [deg] Sky position angle at the start of the observation.
MNTPASTA

real [deg] Mount position angle at the start of the observation.
MNTPAEND

real [deg] Mount position angle at the end of the observation.
PARANSTA
  real [deg] Parallactic angle at the start of the observation.
PARANEND

real [deg] Parallactic angle at the end of the observation.
VIGNETTE

boolean True if the mirror petals or the dome vignette the telescope's beam.
DAZSTART
  real [deg] Azimuth of dome at the start of the observation.
DAZEND

real [deg] Azimuth of dome at the end of the observation.
AUTOMODE

character State of guide loop: Unlocked, Locked or Suspended.
AUTOX

real [pixel] x coord of autoguiding reference position.
AUTOY

real [pixel] y coord of autoguiding reference position.
TELFOCUS
  real [m] Position of telescope's focus drive at the start of the observation. This is the virtual focus, uncorrected for temperature, elevation, etc.
TEMPTUBE
  real [deg C] Temperature of telescope tube, ten minute running mean at the end of the observation.
FSTATION
  character Focal station of observation.
PLATESCA
  real [deg/m] Plate scale at the telescope focus.
ACTELFOC

real [m] Actual value of telescope focus encoder.
FOCUSTMP

real [mm] Focus temperature correction.
FOCUSALT

real [mm] Focus elevation correction. Currently only applied for WHT at Prime.
FOCUSFLT

real [mm] Focus correction for filter.

In the case of AIRMASS, the values are integrated every second to produce the effective mean airmass under the normal definition of that term.

EQUINOX should be read with RADECSYS to find out if coordinates are Besselian or Julian: FK4 coordinates are the Besselian ones. The old ING convetional of prefixing the EQUINOX value with J or B is dropped because it conflicts with the FITS standard.

The latitudes and longitudes of the telescopes can be found in the 1994 ING Observer's Guide.

This is the only packet in which the otherwise-constant values differ between telescopes.
 

Autoguider packet

This packet's formal name is autoguider.
 

Keyword Data type Meaning
AUTACQT real Integration time (in seconds) for acquisition.
AUTGUIT real Integration time (in seconds) for guiding.
AUTWINDO integer Number of autoguider window.
AUTMODE character Name of autoguider mode.
AUTXSEE real Mean FWHM (arcsec) of guide star, x-axis.
AUTYSEE real Mean FWHM (arcsec) of guide star, y-axis.
AUTXSRMS real RMS on FWHM (arcsec) of guide star, x-axis.
AUTYSRMS real RMS on FWHM (arcsec) of guide star, y-axis.
AUTMAGNI real Mean magnitude of guide star.
AUTTRANS real RMS variation of magnitude of guide star.
AUTMAGOF real Magnitude zero-point.
AUTSTATN integer Number of readings used for statistical calculations.
AUTOMODE character Mode of autoguiding.
AUTOX real Guiding position on autoguider, x-axis.
AUTOY real Guiding position on autoguider, y-axis.

The mean and RMS value above are calculated from the readings made between the start and end of each exposure.
 

Wide-field-camera packet

This packet's formal name is wfc. It describes the wide-field camera on the INT.
 

Keyword Value Data type Meaning
INSTRUME WFC character Name of instrument.
WFFPOS

integer Position-number of deployed filter
WFFBAND   character Waveband of filter, e.g. "z".
WFFPSYS   character Photometric system (e.g. Gunn).
WFFID   character Identifier for individual filter (e.g 195).
SECPPIX 0.333 real  Image scale in arcseconds per pixel.

Ideally, all headers would include the keyword SECPPIX. However, the value is only known ahead of time for an instrument that has no interchangeable optics that change the scale, has its own, unchanging detectors, and is used at exactly one focus of one telescope. Only the INT WFC meets these crtieria.
 

Meteorological packet

This packet's formal name is meteorology.
 

Keyword Data type Meaning
TEMPOUT real Temperature outside the dome, in degrees C.
TEMPDOME real Temperature inside the dome in degrees C.
TEMPMIRR real Temperature of the primary mirror in degrees C.
TEMPTUBE real Temperature of the telescope tube in degrees C.
WSPEED real Wind speed in km/h
WDIRECT real Wind direction in degrees east of north.
HUMIDITY real Relative humidity as a percentage.
PRESSURE real Atmospheric pressure in mbar.
DUSTDENS real Atmospheric extinction in magnitudes.
DEWPOINT real Dew-point temperature in degrees C. 
METMOLD real Time in seconds since measurements were obtained from the met. system.
METTOLD real Time in seconds since measurements were obtained from the TCS


IDS packet

This packet covers both IDS and FOS-1. All the descriptors are collected for each instrument even though a few are inapplicable to each. The packet's formal name is ids.
 

Keyword Value Data type Meaning
INSTRUME IDS character Name of instrument.
SLITWID   real Slit width in metres.
PSLITWID   real Slit-width projected on detector in metres.
PAOFFSET 0.0 real Slit PA - telescope's sky PA in degrees.
SLTSKYPA   real Position angle of slit on sky in degrees.
DEKKERID   character Dekker-slide name.
DEKPOS   char Name of Dekker-slide position.
BSCFILT   character Name of colour filter in the beam below the slit.
BSNDFILT   character Name of ND filter in the beam below the slit.
COLLNAME   character Name of collimator.
COLLFOC   int Collimator focus in encoder units.
HARTMANR   character State of right Hartman-shutter: `OPEN' or `SHUT'.
HARTMANL   character State of left Hartman-shutter: `OPEN' or `SHUT'.
CROSDISP   character State of cross disperser: `IN' or `OUT'.
CLINESMM   int Ruling density of cross disperser in lines per milimetre.
CDBLAZE   real Blaze of cross disperser in Āngstroms.
CAMERA   character Name of spectrograph camera: `235' or `500'.
GRATNAME   character Name of grating.
GLINESMM   int Ruling density of grating in lines per millimetre.
GRATBLAZE   real Blaze of grating nm.
GRATANGL   real Angle of grating in degrees.
GRATSHUT   character State of grating shutter: `OPEN' or `SHUT'.
CENWAVE   real Central wavelength of spectral image in nm.
DISPERSI   real Spectra dispersion in nm of wavelength per mm of length projected on the detector.
FOSMIKER   real Reading of FOS micrometer `R'.
FOSMIKEB   real Reading of FOS micrometer `B'.
FOSMIKES   real Reading of FOS micrometer `S'.


Cassegrain-A&G-box packet (INT)

The packet's formal name is agb.
 

Keyword Data type Meaning
AGTVPOSX real TV's x-position in metres.
AGTVPOSY real TV's y-position in metres.
AGTVFILT character Name of TV filter.
AGTVSHUT character State of TV shutter: `OPEN' or `SHUT'.
AGPOSX real x-position of autoguider probe in metres.
AGPOSY real y-position of autoguider probe in meters.
ASNDFILT character Name of ND filter in the beam above the slit.
ASCFILT character Name of colour filter in the beam below the slit.
FLIPMPOS character Position of `flip' mirror: `IN" or `OUT'.
AGARCLMP character Name of arc lamp in use (`NONE' if all lamps are off).
AGARCND character Name of ND filter in front of arc lamp.
COMPMPOS character Position of comparison mirror: `IN' or `OUT'.


Cassegrain-A&G-box packet (WHT)

The packet's formal name is cagb.
 

Keyword Data type Meaning
AGTVPOSX real TV's x-position in metres.
AGTVPOSY real TV's y-position in metres.
AGTVFILT character Name of TV filter.
AGTVSHUT character State of TV shutter: `OPEN' or `SHUT'.
AGPOSR real r-position of autoguider probe in metres.
AGPOST real theta-position of autoguider probe in degrees.
ASNDFILT character Name of ND filter in the beam above the slit.
ASCFILT character Name of colour filter in the beam above the slit.
MAINMPOS character Name of mirror that directs the main beam.
AGARCLMP character Name of arc lamp in use (`NONE' if all lamps are off).
AGARCND character Name of ND filter in front of arc lamp.
AGARCC character Name of colour filter in front of arc lamp.
COMPMPOS character Position of comparison mirror: `IN' or `OUT'.


ISIS packet

The packet's formal name is isis.
 
 

Keyword Values Variable type Meaning
INSTRUME ISIS

CENWAVE   real Central wavelength in nm.
GLINESMM   real Ruling density of the grating in lines/mm.
DISPERSI   real Spectra dispersion in nm of wavelength per mm of length projected on the detector.
ISIHWAVE   real Position of half-wave polarizer.
ISIQWAVE   real Position of quarter-wave polarizer.
DEKPOS   character Name of dekker-slide position.
ISISLITU LONG, MULTI or FIBRE character Name of slit-unit position: LONG, MULTI or FIBRE.
SLITWID   real Slit width in metres.
PAOFFSET 90.2 real Slit pa. - mount p.a. in degrees.
ISIFCP FIELD-LENS, CALCITES, POLAROID or CLEAR character Choice of polarizer.
ISIBFOLD   character Position of blue fold.
ISIRFOLD   character Position of red fold.
ISIFILTA   character Name of filter A in ISIS arm.
ISISFILTB   character Name of filter B in ISIS arm.
ISIHART   character Configuration of hartmann shutter
COLFOC   character Collimator focus in metres.
GRATNAME   character Name of grating.
GRATANGL   character Position of grating in degrees.
ISITIGHT T or F boolean Is the spectrograph light tight?
ISISDOOR   character State of slit door.
ISIGDOOR   character State of grating door.
ISILID   character State of ISIS' lid.
ISICELL   character State of grating clamps.


PFIP packet (WHT prime-focus imaging)

The formal name of the packet is pfip.
 

Keyword Values Data type Meaning
INSTRUME Prime Imaging
character Name of instrument (not included when PFIP used with AF2)
PFADCSTA   real Angle of ADC at start of observation in degrees.
PFADCEND   real Angle of ADC at end of observation in degrees.
PFMFBAND   character Passband of main-beam filter (e.g. V) from filter database.
PFMFPSYS   character Photometric system of main-beam filter (e.g. Harris) from filter database.
PFMFNAME   character Id-code of main-beam filter from filter database.
PFMFPOS   integer Position of main filter-wheel.
PFAFBAND   character Passband of autoguider filter from filter database.
PFAFPSYS   character Photometric system of autoguider filter from filter database.
PFAFILT   character Id-code of autoguider filter from filter database.
PFAGX   real x-position of autoguider in microns.
PFAGY   real y-position of autoguider in microns.
PFTEMP   real Temperature in centigrade
PFHUM   real Relative humidity as a percentage.
PFAPOS

integer
Filter position of autoguider
PFADCACT

character
State of ADC automatic updates
PFAUTFOC

character
State of automatic telescope focus updates
PFFOCOFF

real
Last focus offset applied to telescope to compensate for main filter optical characteristics

The id-code of a filter is the unique and permanent ID of a particular filter. It is not the position of a filter in the wheel.


PFIP packet (With AF2)

This is the PFIP packet which is written when the PFIP is being used in conjunction with the AF2 instrument.

Keyword
Values
DataType
Meaning
PFADCACT
character State of ADC automatic updates
PFADCSTA
real Angle of ADC at start of observation in degrees.
PFADCEND
real Angle of ADC at end of observation in degrees.


AF2 (AUTOFIB-2) packet

The packet's formal name is af2.

This is the AF2 main packet.

Keyword
Values
DataType
Meaning
AF2FLDDC
character Field Dec as defined in CONFIGURE
AF2FLDNM
character Field name as defined in CONFIGURE
AF2FLDRA
character Field RA as defined in CONFIGURE
AF2MODUL
character AF2 Module ID
AF2NDIS
integer Total number of fibres disabled
AF2NFIB
integer Total number of fibres in this module
AF2NFID
integer Total number of fiducial positions
AF2NOBJ
integer Total number of fibres configured on objects
AF2NONPE
real Non-perpendicularity term in distortion map
AF2PLATE
real Plate scale term in distortion map
AF2RADIA
real Radial distortion term in distortion map
AF2RMS
integer Overall positioning error RMS (microns)
AF2TEMP
real AF2 temperature


This is the AF2 packet which is written for the AF2 instrument for each of the fibres.

Keyword
Values
DataType
Meaning
F<Fibre-number>CMNT
character Comment
F<Fibre-number>DEC
character Fibre Dec
F<Fibre-number>FIBT
integer Fibre theta angle
F<Fibre-number>FIBX
integer Fibre x position (microns)
F<Fibre-number>FIBY
integer Fibre y position (microns)
F<Fibre-number>FPVX
integer Fibre pivot x position (microns)
F<Fibre-number>FPVY
integer Fibre pivot y position (microns)
F<Fibre-number>ID
integer Object ID code
F<Fibre-number>MAGN
character Object magnitude
F<Fibre-number>NAME
character Object name
F<Fibre-number>PEX
integer Fibre x position error (microns)
F<Fibre-number>PEY
integer Fibre y position error (microns)
F<Fibre-number>RA
character Fibre RA
F<Fibre-number>STAT
integer Fibre status
F<Fibre-number>TYPE
character Object type
F<Fibre-number>WT
real Fibre weighting


INGRIDCASS packet

This packet was written when INGRID was located in its cassegrain configuration.  Since May 2004 the instrument is no longer offered in this configuration. The information presented below is retained purely for documentation purposes.

The packet's formal name is ingridcass.

Keyword Values Variable type Meaning
INSTRUME INGRIDCASS character "Name of Instrument"
INGPSCAL  12.9 real "INGRID Plate Scale (arcsec/mm)"
INGPSPOS  1-11 integer "Pupil Stop Position"
INGPSNAM <pupil stop name> character "Pupil Stop Name"
The pupil stop names are defined in the EPICS configuration file "pupil.dat".
INGF1POS 1-11 integer "Filter 1 Position"
INGF1NAM <fwheel1 name> character "Filter 1 Name"
The filter names are defined in the EPICS configuration file "fwheel1.dat".
INGF2POS 1-11 integer "Filter 2 Position"
INGF2NAM <fwheel1 name> character "Filter 2 Name"
The filter names are defined in the EPICS configuration file "fwheel2.dat".
INGPISTA IN, OUT character "Pupil Imager Status"
INGFOCUS <focus_position> character "Focus (um)"

INGRID packet

This packet is written when INGRID is located in its Nasmyth configuration with NAOMI. The packet's formal name is ingrid.
 

Keyword Values Variable type Meaning
INGPSCAL  2.17 real "INGRID Plate Scale (arcsec/mm)"
INGPSPOS  1-11 integer "Pupil Stop Position"
INGPSNAM <pupil stop name> character "Pupil Stop Name"
The pupil stop names are defined in the EPICS configuration file "pupil.dat".
INGF1POS 1-11 integer "Filter 1 Position"
INGF1NAM <fwheel1 name> character "Filter 1 Name"
The filter names are defined in the EPICS configuration file "fwheel1.dat".
INGF2POS 1-11 integer "Filter 2 Position"
INGF2NAM <fwheel1 name> character "Filter 2 Name"
The filter names are defined in the EPICS configuration file "fwheel2.dat".
INGPISTA IN, OUT character "Pupil Imager Status"
INGFOCUS <focus_position> character "Focus (um)"

NAOMI USP (Universal Science Port) packet

This packet is written to reflect the status of mechanisms controlled by NAOMI's Universal Science Port EPICS crate. Additionally, the crate controls some other functions such as the state of the NAOMI Bench and the new Calibration Unit

The packet's formal name is usp.  

Keyword Values Variable type Meaning
AOBENCH FIXED, FLOATING or UNKNOWN character "State of NAOMI Optical Bench"
AOSLSTA NOT_INITIALISED,
NOT_IN_POSITION,
MOVING,
SCIENCE,
OSCA_PINHOLE,
SPECTRAL_CALIB,
WHITE_BRIGHT_CALIB,
WHITE_DIM_CALIB,
ERROR
character "State of NCU Slide"
AOSLPOS <current_position> real "Position of NCU Slide"
 
AOLAMPHE ON, OFF, or ERROR character "State of Helium Lamp within NCU"
AOLAMPNE ON, OFF, or ERROR character "State of Neon Lamp within NCU"
AOLAMPNS ON, OFF, or ERROR character "State of Naomi Simplex Lamp within NCU"
AOLAMPOC ON, OFF, WARMING_UP, COOLING_DOWN or ERROR character "State of Oasis Continuum Lamp within NCU"
AOINTSP <light_intensity> integer "Intensity of Spectral Iris"
This value reflects the setting of the spectral iris within the NCU. Intensity will be represented in terms of a percentage (0-100) of the max possible light flux through the iris.
AOINTNS <light_intensity> integer "Intensity of Naomi Simplex Lamp Iris"
This value reflects the setting of the white-dim iris within the NCU. Intensity will be represented in terms of a percentage (0-100) of the max possible light flux through the iris.
AOINTOC <light_intensity> integer "Intensity of Oasis Continuum Lamp Iris"
This value reflects the setting of the white-bright iris within the NCU. Intensity will be represented in terms of a percentage (0-100) of the max possible light flux through the iris.
AOADCDS IN, OUT, MOVING, UNKNOWN or ERROR character "State of ADC Deployment System"
AOADCAX <correction_axis> real "Correction axis of ADC (degrees)"

Specifies the axis on which the ADC is providing its applied correction. The value will be stated in degrees, relative to some agreed reference position.

AOADCCOR <applied_correction> real "Degree of correction being applied by ADC"

Specifies the amount of correction being applied by the ADC in degrees.

AOOFLAT IN, OUT, MOVING, UNKNOWN or ERROR character "Deployment State of OASIS Flat"
AOSFLAT IN, OUT, MOVING, UNKNOWN or ERROR character "Deployment State of Simplexing Flat"
AOFCORSTA NOT_INITIALISED, NOT_IN_POSITION, MOVING, IN_POSITION, ERROR character "State of Filter Focus Correction Mechanism"
AOFCORPOS <current_position> real "Configuration of  Filter Focus Correction Mechanism"

This field only returns valid data if the AOCORSTA field reports IN_POSITION.
 

NAOMI DCHANGER (Dichroic Changer) packet

The packet's formal name is dchanger


Keyword
 
Values Data Type Meaning
AODCHPOS <position_code>

0-10
integer Position of dichroic changer: 0 = Parked; 1-10 = Dichroic Positions 1-10.

In the case of an error condition this field may contain negative values. Consult ING engineering for further information.

AODCHNAM <dichroic>

eg "IR", "50/50", "#1", "#2", "#3", "#4", "#5".
character Name of the dichroic currently deployed by the dichroic changer.

In the cases of an error condition the field will contain a string saying "ERROR: <n>".Consult ING engineering for further information.

OASIS packet

The packet's formal name is oasis.
 

Keyword
 
Values Data Type Meaning
INSTRUME OASIS character "Name of instrument"
OAPSCAL Value to be determined ? character "OASIS Imaging Plate Scale (microns/arcsec)"
OACONFIG eg "LR10_33" character "Configuration Name"
OAFOCPL eg "clear aperture" character "Focal Plane Id"
OAENLRGE eg "clear aperture" character "Enlarger Id"
OAFILTER eg "oasis_MR_6, 
7686-8452,7625-8537,5350,4900,-5.90"
character "Filter Id"
OAIMAGER eg "62mm (#1/2) , 2.1" character "Imaging Id"
OASAMPLE eg "145mm (#3/3) & 62mm (#2/2) " character "Sampler Id"
OAWDGSL eg "0" character "Wedge Slide Id"
OAWDGAN eg "14.510000" character "Wedge Angle"
OAGRISM eg "clear aperture" character "Grism Id"
CAMERA_P eg "-5.900000" real "Camera Position"
OAFCLASS eg 25 integer "File Class - used by Data Reduction"

NAOMI packet

The information presented below comes from document WHT-NAOMI-19.  The format is different from the format shown for other packets. Further work will be required to convert it to the appropriate format. Additionally, some of the information must change - eg the info shown for the NCU is only relevant to the OLD NCU - this is being replaced.
 

Keyword EPM Process Variable Name FITS Data Type Collection Time Description
AOSYS  AoSystem String Write  This is the name of the adaptive optics unit. 
AODFM DMtype  String  Write  The deformable mirror that is in use
AOLENSLT LensletName String  Write  Name of lenslet used.
AOWFILT FilterNumber Integer Write  The filter number that was used.
AOWEXP WFSintegrationTime Real Write  The length of the WFS integration in millisecs.
AOWBIN WFSbinningMode Integer Write  Binning mode used  by the WFS
AOGAIN GainGlobal  Real  Write  Global gain in centroid units
AOWOFF WFSoffsets String  Write  WFS Offsets
AOLOOP NaomiLoopState  String Write  AO loop state
AOFOCOFF  FocusOffloadState String  Write  Focus offload state
AOOPTALG  OptAlgorithm  String  Write  AO optical algorithm
AORECON  ReconAlgorithm String  Write  Reconstructor algorithm
AOCAMSYN CameraSyncState String  Write  Camera sync state
AOGDX  PickoffPosnX  Real Write  WFS pickoff x position (arcsec)
AOGDY PickoffPosnY Real Write  WFS pickoff y position (arcsec)
AODMX DMstagePosnX Real Write  DM stage x position (mm)
AODMY DMstagePosnY  Real Write    DM stage y position (mm)
AODMTMP1 TempDM  Real Write  DM temperature 1 (C)
AODMTMP2 Temp2  Real Write  DM temperature 2 (C)
AOLAMP NCUlampState  String Write  NCU lamp state
AOLMPINT NCUlampIntensity Real Write  NCU lamp intensity
AOMASK NCUmaskState String Write  NCU mask state
AOBSPLIT  NCUbeamsplitState  String Write  NCU beamsplitter state
AOSEGLIM SegTiltLimit  Real Write  Segment tip tilt limit

OSCA packet

Information regarding the OSCA packet should be written here.
 

Integration packet

These descriptors are usually generated inside UltraDAS. For the INT WFC, they are sent by the ICS as packet with the formal name integration.
 

Keyword Data type Meaning
DATE-OBS character Date of observation in the FITS-approved format.
UT character UTC of start of observation. In the format hh:mm:ss.s.
UTSTART character UTC of start of observation. In the format hh:mm:ss.s.
UT-MID character UTC at the middle of the exposure. In the format hh:mm:ss.s.
ELAPSED real Length of exposure, including pauses, from end of clearing to start of readout. In seconds.
DARKTIME real Same as ELAPSED.
EXPOSED real Length of exposure, excluding pauses, from the first opening of the shutter to its final closing. In seconds.
EXPTIME real Same as EXPOSED.

DATE-OBS is the UT date and changes at 0000hrs UTC. It has the format yyyy-mm-dd.DATE-OBS and UTSTART must be derived from the same time-stamp. It is an error for UTSTART and DATE-OBS to refer to instants on opposite side of the date-change at midnight.

Camera packet

The camera packet describes aspects of the camera that apply equally to all channels.
 

Keyword
Value
Data Type
Meaning
DETECTOR   character Name of the camera, e.g. EEV13.
CCDSPEED FAST or SLOW character Name of the readout speed. Upper case is mandatory.
CCDXBIN   real Binning factor in the x or serial direction of the amplifier frame.
CCDYBIN   real Binning factor in the y or parallel direction of the amplifier frame.
CCDSUM   character Both binning factors, x given first, with no punctuation, e.g. "2 4"
NWINDOWS   integer Number of readout windows in this observation.
CCDTEMP   real [K] Cryostat temperature.
CCDTEMP2

real [K] Monitor pt 1 temperature
CCDTEMP2

real [K] Monitor pt 2 temperature
READMODE

character Readout mode
STORMODE

character Store mode
NUMREADS

integer Number of reads
COAVERAG

integer Number of cycles coaveraged

The binning is given in the amplifier frame because that's how the observing system applies the two factors. Some detectors (or detector segments) in a mosaic may have rotations and reflections between the amplifier frame and the detector frame in which all the pixels of the camera can be mosaicked together. The reflections don't affect the binning, but if there are relative rotations through an odd number of right angles, then the sense of binning differs between channels.

NWINDOWS is the number of readout windows of non-zero extent anywhere on the camera in the current observation; it can change from run to run. A window of zero extent (one or both size parameters set to zero) is "turned off" and is ignored by the system. The camera may have windows of non-zero extent defined, but may also have windowing disabled. When windowing is disabled, NWINDOWS is set to zero.
NWINDOWS partly determines the number of image extensions in the observation file.
 

Channel packet

A channel packet is traditionally a small, fast steamship carrying mails, news media and passengers between the south coast of England and the French and Belgian ports. Like UltraDAS, it moves high-value data en bloc and with some style, but the cycle time is a worry.

Inside UltraDAS, the channel FITS-header packet describes the arrangement of the data from one readout channel. The formal name of the packet is channel.
 
 

Keyword Value Data type Meaning
IMAGEID   integer Number of the image in the file.
DASCHAN   integer Number of readout channel (1+).
WINNO   integer Number of window (1+).
CHIPNAME   character Name of detector chip.
CCDNAME   character Same as CHIPNAME.
CCDTYPE   character Type of detector, e.g. EEV42.
CCDXPIXE   real [m] Size of pixels in the x axis of the CCD frame.
CCDYPIXE   real [m] Size of pixels in the y axis of the CCD frame.
AMPNAME   character Name of readout amplifier
GAIN   real Gain of amplifier in electrons per ADU
READNOIS   real Readout noise of amplifier in electrons
SATURATE   real [ADU] Highest data value that is good data.
MAXBIAS
real [ADU] Highest data value that is good data for a bias observation.
BIASSEC   character Image section in image coordinates holding only bias values
TRIMSEC   character Image section in image coordinates that excludes all bias areas and includes all illuminated areas
RTDATSEC

character Location in d-space for RTD
CTYPE1  X character Type of world coordinate for 1st axis in primary WCS.
CTYPE2  Y character Type of world coordinate for  2nd axis in primary WCS.
CRPIX1   real Reference pixel on 1st axis in primary WCS.
CRPIX2   real Reference pixel on 2nd axis in primary WCS.
CRVAL1   real Value at reference pixel on 1st axis in primary WCS.
CRVAL2   real Value at reference pixel on 2nd axis in primary WCS.
CUNIT1 pixel character Units of 1st axis in primary WCS.
CUNIT2 pixel character Units of 2nd axis in primary WCS.
CD1_1   real Transformation matrix from image coordinates to primary WCS.
CD1_2   real Transformation matrix from image coordinates to primary WCS.
CD2_1   real Transformation matrix from image coordinates to primary WCS.
CD2_2   real Transformation matrix from image coordinates to primary WCS.
PROJP1
real Projection coefficient for primary WCS: linear term.
PROJP3
real Projection coefficient for primary WCS: cubic term.
PV1_1
real Projection coefficient for primary WCS: linear term.
PV1_2
real Projection coefficient for primary WCS: cubic term.
PV2_1
real Projection coefficient for primary WCS: linear term.
PV2_2
real Projection coefficient for primary WCS: cubic term.

IMAGEID is an NOAO convention. It numbers the imagw extensions in the order that they appear in the file, counting from one. This keyword is useful if one image extension is extracted from its original file.
DASCHAN and WINNO are an ING convention that supports multiple readout-windows.

CCDNAME is the IRAFicated version of CHIPNAME. The two keywords take the same value. This value must identify a particular device, typically by reference to the silicon wafer on which it was made (e.g. A1708-2) rather than a cryostat (e.g. WFC) or a position in a mosaic (e.g. WFC-2).

RDNOISE is the IRAFicated version of READNOIS.

Each channel packet carries a world-coordinate system (WCS).  The primary WCS is initially set by UltraDAS to "detector coordinates". That is:

The keywords of this WCS are provided mainly as placeholders; typically, a celestial WCS is written over the CCD WCS by data-reduction software. In unreduced data, the chance is taken to record how the recorded rasters relate to the silicon, which avoids the need to write this under other keywords; in reduced data, this information is of little use anyway.When the default primary WCS is replaced by celestial coordinates, a tangent-plane (or gnomonic) project is used. The prime-focus cameras at ING add to this projection a distortion that is cubic with distance from the optical axis. The default primary WCS includes enough keywords for this projection to be written in without reformatting the header, but the values with the keywords actually apply no projection (axis types of X and Y instead of RA-TAN and DEC-TAN; linear term of distortion set to unity; cubicterm set to zero). Two encoding for the distortion correction are given: PROJP1 and PROJP3 are the old (IRAF) convention in polar coordinates; PVi_j are the emerging standard in cartesian coordinates.
 

8. Derivation of the packet definitions

The observation IDS, AGB, telescope, autoguider, wfc and meteorology packets were taken from  the previous packet-list for the INT [4]. The latitudes and longitudes of the telescopes were copied from the La Palma Observer's guide.

The specification for the WFC packet was changed to use the encoding for main-beam filters suggested by Jim lewis for the Astronomical Data Centre, Cambridge. This encoding has been in use in the observing system for WFC for some months.

No specification exists for the JKT instrument-packets.

The details of the WHT instrument packets were copied from the packet list for the old (ADAM) WHT DAS [6]. That packet list gives different details for the telescope and observation packets but the INT's specification, which is new, is presumed to supersede this. The INT form of the headers is a better match to modern data-reduction software.

Some details of the ISIS, LDSS and TAURUS packets were altered to fit the style adopted for the IDS packet.
The channel packet draw on the examples in NOAO's document [3] but has more differences than similarities. The RRxx keywords are specific to ING and replace NOAO's description of transformations. The WINxSWCn and DISJOINT keywords do not appear in NOAO's header. NOAO appear to copy into the extension header many data that apply equally to all channels: these data are not present in the ING channel-packet, being covered in the primary HDU.
 

Annex A: detailed changes from issue 1 to issue 2

First draft: Second draft: Third draft:

Annex B: packets for withdrawn instruments

ING no longer supports the use of Taurus-2 or LDSS-2 and the header packets for those instruments are no longer a formal part of this ICD. The old definitions of the packets are retained here to avoid losing the information.
 

Taurus packet

The formal name of the packet is taurus.
 

Keyword Values Data type Meaning
INSTRUME TAURUS character Name of instrument.
TAUCAMER F/2 or F/4 character Name of spectrograph camera.
TAUFRAT 2.11 or 3.96 real Focal ratio of spectrograph camera.
TAUSCALE 23.25 or 12.40 real Image scale in arcsec/mm.
TAUMASK   character Name of aperture mask.
TAUFFILT   character Name of focal-plane filter.
TAUIRIS   real Diameter of iris in meters.
TAUPFILT   character Name of pupil-plane filter.
TAUETALON   character Name of etalon.
TAUFOCUS   real Camera focus in metres.
TAUDOORS   character State of access doors.
TAUTEMP1   real Temperature at focal plane in kelvin.
TAUTEMP2   real Temperature at etalon in kelvin.
TAUTEMP3   real External temperature in kelvin.
TAUPRES1   real Pressure at etalon cavity in mbar.
TAUPRES2   real External pressure in mbar.
TAUIVL   character State of N2 inlet valve.
TAUOVL   character State of N2 outlet valve.
CSCEXT T or F boolean CS100 external control enabled?
CSCINT T or F boolean CS100 integration enabled?
CSCGAIN   real CS100 servo-gain.
CSCTICO   real CS100 time-constant.
CSCLOOP   character State of CS100 servo-loop.
CSCXOFF   real CS100 x-offset.
CSCYOFF   real CS100 y-offset.
CSCZOFF   real CS100 z-offset.
CSCZSTAR   real Start position for etalon scan.
CSCZSTEP   real Step size for etalon scan.
CSCNSTEP   integer Number of steps in etalon scan.
CSCRAMP SINGLE or DOUBLE character Single or double-sized ramp?
TAUFPSTE   integer Number of detector frames per step.
PAOFFSET   real Instrument p.a. - mount p.a. in degrees.

LDSS packet

The formal name of the packet is ldss.
 

Keyword Values Data type Meaning
INSTRUME LDSS character Name of instrument.
LDSMASK   character Name of aperture mask.
LDSFILTE   character Name of filter.
LDSGRISM   character Name of grism.
LDSFOCUS   real Camera focus in metres.
LDSDOORS   character Status of access hatches.
LDSFRAT   real Focal ratio of camera.
LDSSCALE   real Image scale in arcsec/mm.
PAOFFSET   real Instrument p.a. - mount p.a. in degrees.