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:

DD variable name	FITS Keyword	Description
S_RotCenterRAHMS	CRVAL1
S_RotCenterDECDMS	CRVAL2

• 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.

DD variable name	FITS Keyword	Description

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

DD variable name	FITS Keyword	Description
AZPosition	TELAZ	Telescope mount Azimuth
ELPosition	TELALT	Telescope mount Altitude
S_DGRPosition	LDGROT/RDGROT	Raw Rotator Angle

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