DD Variables useful for Instrument UIs and Image Headers
Below is a list of TCS Data Dictionary (DD) variables that instruments may find useful, along with suggested FITS header keyword matchings for them where appropriate. Some of the values will be of interest for display on the instrument User's Interface (UI), while others are purely intended for telescope engineering purposes at this time. Note that all of the sided examples below are listed as "S_". This means there is a "L_" for left side and "R_" for the right side.Archive-specific header keywords are listed on this link for
Archive Keywords.
Parameters sent from instrument to position the telescope:
This section includes observation configuration information supplied by the user. Some of it gets copied into the DD for use by the TCS, but everything in this section should be available to the instrument without reading it back from the DD.
DD variable name |
FITS Keyword |
Description |
|
OBJNAME |
Name of the Target |
|
OBJECT |
Identifier observation title |
|
OBJDEC |
Requested Dec. in degrees (given by OB). Should use info instrument sent |
|
OBJRA |
Requested R.A. in hours (given by OB). Should use info instrument sent |
|
OBJPMRA |
Proper motion for R.A. in mas/yr |
|
OBJPMDEC |
Proper motion for DEC. in mas/yr |
|
OBJEPOCH |
Coordinates epoch of OBJRA and OBJDEC |
|
OBJPA |
Requested position angle |
|
ROTMODE |
Requested rotator mode (position or parallactic) |
|
TELMODE |
Requested telescope mode (track, guide, active, adaptive) |
- Similar data exists for the guide star and for the AO reference star as supplied to the TCS. These data should be written into the headers under a parallel naming scheme (e.g. GSNAME, GSRA, GSDEC, etc.) but the data does not need to be read back from the TCS.
- For any quantities that change during an exposure (UTC, LST, Airmass, etc.) the instrument is free to define if the values in the headers correspond to the beginning or end of an exposure as long as it is clear in the header.
General Information:
This section contains information that is of astronomical interest (e.g. UT, LST, Airmass). Some of the quantities are constantly changing during science exposures. We leave it up to the instrument teams to define if the values in the headers correspond to the beginning or end of an exposure as long as it is clear in the FITS keyword description field. Note that the RA and DEC read back from the DD below shows the current position of the telescope, even during slews, for the current date and time, after application of any proper motion and precession. These values are for an EPOCH corresponding to right then (e.g. 2010.123456) but are always EQUINOX=J2000.
DD variable name |
FITS Keyword |
Description |
S_Instrument |
|
Check the authorized instrument |
UTC |
UTC_OBS |
Current UTC (instrument can define if this is the start or end of exposures |
LST |
LST_OBS |
Current LST |
|
ZD |
Zenith distance (degrees). Calculated from (90 - TELALT)? |
AirMass |
AIRMASS |
Airmass. Calculated from 1/cos(ZD)?. |
|
HA |
Hour Angle (+East, -West). Calculated from OBSRA - LST_OBS? |
S_AchievedRAHMS |
RA |
The current RA of the telescope. Changes during slews, Epoch=NOW! |
S_AchievedDECDMS |
DEC |
The current DEC of the telescope. Changes during slews, Equinox=J2000 |
|
EPOCH |
The current EPOCH of the observation |
AZPosition |
TELAZ |
The current AZ of the telescope |
ELPosition |
TELALT |
The current ALt (EL) of the telescope |
S_FBGRPosition |
ROTANGLE |
The physical rotator angle (asec). Covers the full [-90,450] degree range |
ParAngle |
PARANGLE |
The current parallactic angle |
S_PosAngle |
POSANGLE |
The current position angle |
|
MEANFWHM |
Mean site FWHM, corrected to std Vband @ 1airmass |
|
TIME2LIM |
Time to hit a limit (whatever is first) |
|
TIME2SET |
Time to set (go below some operational EL limit) |
GCS status
DD variable name |
FITS Keyword |
Description |
S_GuideFlag |
ISGUIDED |
Boolean isGuiding flag, states if GCS is running the guide loop. Guiding could still be paused or not effective due to lost guide star |
S_GuideHotspotX |
GSKFP_X |
Guide star kernel focal plane X coordinate |
S_GuideHotspotY |
GSKFP_Y |
Guide star kernel focal plane Y coordinate |
|
IGSFWHM |
Instantaneous (last) guide star FWHM |
|
MGSFWHM |
Mean (since isCollimated) guide star FWHM |
|
MGSXRMS |
Mean (since isCollimated) guide star X rms |
|
MGSYRMS |
Mean (since isCollimated) guide star Y rms |
WFS status
DD variable name |
FITS Keyword |
Description |
S_WFSIsCollimated |
ISCOLLIM |
Boolean isCollimated flag |
S_WFSRMS |
IWFSRMS |
Instantaneous (last) WFS rms (initialized to 0.0) |
|
|
Human-readable (string) time of last transfer of Z's to PSF |
|
MWFSRMS |
Mean (since isCollimated) WFS rms |
- The boolean isCollimated flag is set to zero on all presets and any offsets exceeding a couple of arcsec. It is set back to one when a successful wfs cycle shows an rms wavefront error below some configurable threshold (currently 600nm). This is the flag to watch if you want to "wait for collimation" prior to starting science observations. The time of last update can be watched to monitor if the wfs is stale or not.
Adaptive-Optics Quantities (AO Team to define these?)
S_AOLoopOn |
AOCLOSED |
Boolean: Is the AO loop closed |
WCS data:
- The same quantities for RA and DEC are also available as radians in S_RotCenterRA and S_RotCenterDEC.
- The pointing kernel can provide a complete WCS for the image. It gives the position of the pointing origin in the telescope focal plane and the coordinates (e.g. on-sky for the RADEC coordinate system) corresponding to that position. This is not yet implemented in the TCS, but it is the correct way to define a WCS for the data. LUCIFER currently implements the WCS by retrieving the coordinates of the rotator center from the DD and writing a fixed CRPIX1/2 value corresponding to the last measurement of the rotator center position on the detector.
Telescope Collimation data:
DD variable name |
FITS Keyword |
Description |
S_M1CollX |
M1_POSX |
Primary mirror position in X |
S_M1CollY |
M1_POSY |
Primary mirror position in Y |
S_M1CollZ |
M1_POSZ |
Primary mirror position in Z |
S_M1CollRx |
M1_ROTX |
Primary mirror rotation around X |
S_M1CollRy |
M1_ROTY |
Primary mirror rotation around Y |
S_M1CollRz |
M1_ROTZ |
Primary mirror rotation around Z |
S_M1CollTemp |
M1CTEMP |
Primary mirror glass temperature (Collimation Temp) |
S_M1AirTemp |
M1ATEMP |
Primary mirror air temperature |
S_M2CollX |
M2_POSX |
Secondary mirror position in X |
S_M2CollY |
M2_POSY |
Secondary mirror position in Y |
S_M2CollZ |
M2_POSZ |
Secondary mirror position in Z |
S_M2CollRx |
M2_ROTX |
Secondary mirror rotation around X |
S_M2CollRy |
M2_ROTY |
Secondary mirror rotation around Y |
S_M2CollRz |
M2_ROTZ |
Secondary mirror rotation around Z |
S_M2CollTemp |
M2CTEMP |
Secondary mirror glass temperature. Is there no glass temp sensor at M2? |
|
M2ATEMP |
Secondary mirror air temperature. Is there no air temp sensor at M2? |
S_M3CollTip |
M3__TIP |
Tertiary mirror tip |
S_M3CollTilt |
M3_TILT |
Tertiary mirror tilt |
S_M3CollPiston |
M3_PSTN |
Tertiary mirror piston |
S_M3CollSel |
M3_ZROT |
Tertiary mirror rotation around Z axis |
S_M3CollTemp |
M3CTEMP |
Tertiary mirror glass temperature. Is there no glass temp sensor at M3? |
|
M3ATEMP |
Tertiary mirror air temperature. Is there no air temp sensor at M3? |
Telescope Temperature Sensors
DD variable name |
FITS Keyword |
Description |
Temp201 |
TTEMP201 |
Middle C ring steel |
Temp202 |
TTEMP202 |
Middle C ring air |
Temp203 |
TTEMP203 |
Upper C ring steel |
Temp204 |
TTEMP204 |
Upper C ring air |
Temp205 |
TTEMP205 |
Lower C ring steel |
Temp206 |
TTEMP206 |
Lower C ring air |
Temp207 |
TTEMP207 |
Right lower wind brace steel |
Temp208 |
TTEMP208 |
Right lower wind brace air |
Temp209 |
TTEMP209 |
Right mirror cell brace steel |
Temp210 |
TTEMP210 |
Right mirror cell brace air |
Temp301 |
TTEMP301 |
Right C ring extension steel |
Temp302 |
TTEMP302 |
Right C ring extension air |
Temp303 |
TTEMP303 |
Left C ring extension steel |
Temp304 |
TTEMP304 |
Left C ring extension air |
Temp305 |
TTEMP305 |
Upper wind brace steel |
Temp306 |
TTEMP306 |
Upper wind brace air |
Temp307 |
TTEMP307 |
Right middle wind brace steel |
Temp308 |
TTEMP308 |
Right middle wind brace air |
Temp309 |
TTEMP309 |
Left middle wind brace steel |
Temp310 |
TTEMP310 |
Left middle wind brace air |
Weather information
DD variable name |
FITS Keyword |
Description |
SMTPressure |
SMTPRESA |
SMT Ambient air pressure (units) |
SMTTemp |
SMTTEMPA |
SMT Ambient temperature (C) |
SMTHumidity |
SMTHUMID |
SMT Relative humidity (%) |
SMTDewPoint |
SMTDEWPT |
SMT Dew point (C) |
LBTPressure |
LBTPRESA |
LBT Ambient air pressure (units) |
LBTTemp |
LBTTEMPA |
LBT Ambient temperature (C) |
LBTHumidity |
LBTHUMID |
LBT Relative humidity (%) |
LBTDewPoint |
LBTDEWPT |
LBT Dew point (C) |
LBTWIndSpeed |
WINDSPD |
LBT Wind speed |
LBTWindDir |
WINDDIR |
LBT Wind direction (AZ) |
LBC:
The information in this section has yet to be formatted for the wiki. It covers the current (March 2010) state of the LBC cameras and the telescope information written into the headers.
OBJNAME name of the Target
OBJECT Identifier observation title
OBJRA commanded R.A. in hours (given by OB)
OBJDEC commanded Dec. in degree (given by OB)
PMRA Proper motion for R.A. in arcsec/hour Change to OBJPMRA
PMDEC Proper motion for DEC. in arcsec/hour Change to OBJPMDE
OBJEPOCH coordinates epoch of OBJRA and OBJDEC
POSANGLE Requested position angle Need to add this
### Include ROTMODE (position or parallactic) and TELMODE (track, guide, active)
### For POSANGLE, PARANGLE, and ROTANGLE, I would prefer these keywords be used for the value in effect at the time the data were taken,
### and use OBJPA to specify the requested position (or parallactic) angle.
### The OBJRA and OBJDEC
can be read back from the telescope as noted above, but this information is supplied by the
### instrument and therefore should not need to be read back (unless it is for a sanity check).
### NB: OBJRA, OBJDEC are only written into headers when coming from a preset in an OB! For example, they are
### missing for observations taken with the DEC=-90 flag (take image here).
### DD variable name FITS Kwd Description Notes/Change/Add:
#===========================================================================================================================================================================
ParAngle PARANGLE Parallactic Angle [deg] Current parallactic angle
PA_PNT Position Angle of the pointing [deg] call this "Acheived PA"
ROTANGLE Rotator Angle [deg]
LST LST_OBS ST at start
UTC UTC_OBS UT at start
S_AchievedRA TELRA actual R.A. in radians (from TCS) = OBSRA ?
S_AchievedDEC TELDEC actual DEC. in radians (from TCS) = OBSDEC ?
OBSEPOCH coordinates epoch of OBSRA and OBSDEC Should be e.g.: 2010.123 (today's decimal date)
### The quantities read back for TELRA and TELDEC are proper-motion and precession corrected Equinox J2000 coordinates, so
### OBSEPOCH should actually reflect the epoch of the observation, not the epoch of the specified source coordinates!
S_AchievedAZ TELAZ Az angle at start N=0,E=+90 (from TCS) Change to mcs.azDrive.position
S_AchievedALT TELALT Alt angle at start (from TCS) Change to mcs.elDrive.position
LBTPRessure LBTPRES Ambient air pressure [mbar] (from TCS)
LBTHumidity LBTRHUM Ambient relative humidity [%] (from TCS)
LBTTemp LBTTEMP Ambient temperature [Celsius] (from TCS)
LBTWindDir LBTWNDIR Ambient wind direction [deg] (from TCS)
LBTWindSpeed LBTWNSPD Ambient wind speed [m/s] (from TCS)
LBTDewPoint LBTDEWPT Not found in LBC header[0]
### You can also read SMT* and write parallel information to keywords starting with SMT* as above.
### The env.weather.* entries are active now, please change LBC to using these as soon as possible.
S_M1CollX MIRRORX Primary mirror X position [mm]
S_M1CollY MIRRORY Primary mirror Y position [mm]
S_M1CollZ MIRRORZ Primary mirror Z position [mm]
S_M1CollRx MIRRORRX Primary mirror RX rotation [arcsec]
S_M1CollRy MIRRORRY Primary mirror RY rotation [arcsec]
S_M1CollRz MIRRORRZ Primary mirror RZ rotation [arcsec]
S_M1CollTemp M1CTEMP Primary Mirror glass temperature
S_M1AirTemp M1ATEMP Primary mirror air temperature
### LBC Collimation models have apparently been made to date using the SMT temperatures! It would be much better to use
### the temperature that the primary mirror uses to do the temperature corrections to the collimation models. Add at least
### M1CTEMP (M1 collimation temperature) to the LBC headers, adding M1ATEMP is optional.
* Generalize anything that contains 'LBC' in the keyword if possible:*
LBCOBNAM Observing Block ID Change to OBNAME (supplied by observer)
LBCOBFIL [no fits comment] Change to OBARCH (as written to archive)
LBCOBID Observing Block ID ?
LBCUSER P.I. Name Change to PI_NAME
OBSERVER Observer Name Change to PARTNER
Use OBSERVER for the person at the telescope taking data
LBCPIPEC Command to be executed on the image
LBCNCHIP Number of active chips in LBC camera
LBCCHIP1 1st chip status (1=on 0=off)
LBCCHIP2 2nd chip status (1=on 0=off)
LBCCHIP3 3rd chip status (1=on 0=off)
LBCCHIP4 4th chip status (1=on 0=off)
LBCBIN Binning of the Pixels
LBCSPRED Pixel reading speed (0=normal, 1=fast)
LBCBACK Background from technical chips [ADU]
LUCIFER:
The information in this section has yet to be formatted for the wiki. It covers the current (March 2010) state of LUCIFER and the telescope information written into the headers. Only listed here are things currently retrieved from the DD that LBTO would prefer be changed to match the list above.
S_AGWHappy Torsten said do not rely on these
S_AGWState Torsten said do not rely on these
S_GuideRA Supplied by observer - no need to read these back
S_GuideDEC Supplied by observer - no need to read these back
S_GuideBadCount See first section for update/suggestions
S_RotAngle The computed rotator angle from the pcs subsystem
S_Instrument The authorized instrument
MODS:
These are particular additional DD entries used by MODS image FITS headers and
their corresponding header keywords.
Rotation Angles
All units are in degrees in the FITS header
DD variable name |
FITS Keyword |
Description |
S_ParAngle |
PARANGLE |
Parallactic Angle |
S_PosAngle |
POSANGLE |
Celestial/Parallactic Position Angle |
S_RotAngle |
ROTANGLE |
Rotator Angle |
S_RotMode |
ROTMODE |
Rotator Mode (Position or Parallactic) |
GCS- and PCS-based AGw and Guide-Star Parameters
All units are in millimeters
DD variable name |
FITS Keyword |
Description |
S_AGWKFPReqX |
GPREQ_X |
Requested Guide Probe X |
S_AGWKFPReqY |
GPREQ_Y |
Requested Guide Probe Y |
S_AGWKFPPosX |
GPACT_X |
Achieved Guide Probe X |
S_AGWKFPposY |
GPACT_Y |
Achieved Guide Probe Y |
S_GSXPredicted |
GSPRED_X |
Predicted guide star X |
S_GSYPredicted |
GSPRED_Y |
Predicted guide star Y |
S_GSXMeasured |
GSMEAS_X |
Measured guide star X |
S_GSYMeasured |
GSMEAS_Y |
Measured guide star Y |
S_GSCumXPredmMeas |
GSDELTAX |
difference in X |
S_GSCumYPredmMeas |
GSDELTAY |
difference in Y |
MCS-based Telescope Alt/El and raw Rotator parameters
All are in units of decimal degrees in the FITS headers
MODS uses the raw rotator angle to define various instrument servicer rotations (e.g., for
loading masks, servicing cameras, entering the service hatch) etc. via the rotServicePosition() calls
in the IIF.
--
DavidThompson - 29 Mar 2010
Converted to external names
ChrisBiddick 3 Nov 2016