Data Format and Reduction
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NICI Data Format and Reduction
This page describing the NICI data format is organized as follows:
- MEF Format
- Science Detector Readout
- World Coordinate System
- NICI_FIXWCS
- Data Processing
- Example NICI MEF Header
MEF File Format
NICI data are processed by the Gemini Data-Handling System (DHS) and written in Multi-Extension FITS (MEF) format similar to other Gemini Instruments. The NICI MEF format contains a Primary Header followed by two extensions:
- Primary Header
- Extension 1: Red (holmes) channel header and data
- Extension 2: Blue (watson) channel header and data
See the bottom of this page for an example NICI header.
Primary Header
The primary header contains keywords common to both channels: date and time, telescope configuration, environment, and instrument configuration items such as the AO system and Focal Plane Mask. Due to GSA requirements, the primary header also contains channel-specific keywords such as the filter and integration times that are repeated in the extension headers.
Extensions
The two extensions contain the data for each channel, called "red" and "blue" (or "holmes" and "watson" respectively, in much of NICI's engineering documentation). Both detectors are always read out and both extensions are always written, even when one channel may not have useful data eg. when the Dichroic Wheel is set to Mirror or Open. The first extension is always the Red channel and the second the Blue channel.
Extension Headers
The header of each extension contains information specific to the channel, such as the filter, the detector integration time and coadds, and the World Coordinate System (WCS). Although separate integration parameters are specified for each channel, in NICI's current implementation the detectors are read out identically so the two sets of parameters have the save values. However, the two WCS's indicate the different reflections and a slight rotation between the two channels (see the WCS section for details).
Extension Data
The image data are written in 32-bit floating point format. The pixel in the upper left corner of each detector is the first written to its corresponding extension. Note that by default most image viewers display the first pixel in the lower left corner, so NICI images will appear flipped up-down unless the data or image are inverted.
Science Detector Readout
Each of the two science detectors is paired with an array controller which contains real-time clocking patterns programmed into firmware, and a pixel server: a rackmount computer running linux which reads and processes data from the controller.
The detectors are read out using a sample-up-ramp algorithm as follows:
- Each detector is read non-destructively by array controller every 0.38 s up to a total of N NDR's. The equivalent exposure time, which is listed as Exposure Time in the OT and ITIME_R and ITIME_B in the headers, is therefore (N-1)*0.38s.
- At the end of the ramp, the pixel server software fits a slope m to the sampled values for each pixel and computes (N-1)*m as the signal value.
- If NCOADDS > 1, the detectors are reset and another ramp begins. The successive frames are coadded in the pixel server memory.
- After the desired number of coadds are taken, the controller passes the accumulated coadds to the DHS which writes the MEF extensions. The saved signal value is represented as S = NCOADDS * (N-1) * m.
Note that the recorded values are sums, not averages, so they may have to be scaled accordingly during data reduction, eg. to compare science and calibration data possibly taken with different NCOADDs. For example: for ADU per 0.38 s frame, compute S / (NCOADDS *(N-1)) for ADU per second, compute S / (NCOADDS * (N-1) * 0.38)
World Coordinate System
Each of the two NICI extensions contains a set of World Coordinate System (WCS) records for that channel's science data array.
Related to the WCS are two parameters: Instrument Position Angle (IPA)
and Instrument Alignment Angle (IAA). The IPA is the position angle
on sky, in degrees east of north, which is up on the science detector;
i.e. IPA = 0 means that North will be up. The IAA is the rotation
between the telescope and science detector reference frames. IPA
and IAA are related by:
CassRotator Angle = IPA - Parallactic Angle - IAA + 180 deg.
For example, if a science detector is mounted exactly aligned with the telescope frame,
IAA = 0. To achieve IPA = 0 (North up on detector) on the meridian where
parallactic angle = 0, the CassRotator would be set to 180.
Because the TCS uses the IAA to position the Cass Rotator and thus the physical rotation of the instrument relative to sky, setting the IAA accurately is required to achieve the correct IPA that is requested by an observation. If NICI is dismounted from the telescope and moved to another port, or even if it is remounted on the same port, slight variances in the mounting require the IAA to be updated. After the IAA is set properly, instrument software parameters are updated to generate a correct WCS.
Image Distortion
The Gemini-standard WCS indicates the pixel scale and orientation of the data, but it does not include higher order terms such as distortion. With NICI, to measure and correct distortion the following procedure is used.
- A rectangular grid mask in the Fiber Optic Calibration Source (FOCS) is inserted into the beam, illuminated with GCAL, and imaged with the science camera. This mask is at the telescope focal plane, above the NICI AO system, so the total distortion from both the AO and science camera optics is present in the images.
- A perfectly rectilinear grid of points is fitted to the imaged mask spots over the inner ~ 512 pixels. The offset, spot separation, and rotation of the grid are adjusted to obtain the best least-squares fit. Only the inner section of the image, where distortion is small, is used for this initial step so that overall scale and rotation are not affected by the larger distortion near the edges and corners.
- The position differences between the grid points and the spots are measured and fitted to an 3rd order polynomial using the IDL routine POLY_WARP. This routine generates a set of fitting coefficients kx and ky.
- Science data are corrected by reading the files of fitting coefficients and applying them with the IDL routine POLY_2D.
- Grid mask image, Red (holmes) channel
- Grid mask image, Blue (watson) channel
- Dark image, Red channel
- Dark image, Blue channel
- kx and ky coefficients, Red channel (IDL savefile)
- kx and ky coefficients, Blue channel (IDL savefile)
Examples of the data and fitting coefficients:
A simple example of applying the distortion corrections in IDL is:
;; Open MEF file and read Red (holmes) and Blue (watson) extensions fits_open, 'S20110101_S0001.fits', fcb fits_read, fcb, imh, hdrh, exten_no=1, /no_pdu fits_read, fcb, imw, hdrw, exten_no=2, /no_pdu ;; Warp holmes channel restore, 'niciwarp_focs_2010dec_h.sav' imh_w = poly_2d(imh, kx, ky, 2, cubic=-0.5) ;; Warp watson channel restore, 'niciwarp_focs_2010dec_w.sav' imw_w = poly_2d(imw, kx, ky, 2, cubic=-0.5)
Calibrating the IAA and WCS
The following procedure is used to calibrate the IAA and WCS.
- A high-precision binary star or astrometric field is imaged with the AO loop closed.
- The images are distortion-corrected using the above procedure.
- The Red (holmes) channel position angle is measured and a new IAA value computed. (Strictly speaking, the IAA is correct for the Red channel only, due to the 1.1 degree rotation between the two detectors.)
- The new IAA is applied, the data retaken, and the cycle is repeated until the IAA is correct.
- The new WCS coefficients for both channels (including the 1.1 deg relative rotation of the Blue channel) are derived from the measured alignment and pixel scale, then applied to the instrument software which generates the WCS during observing.
During NICI's history, we have steadily upgraded these procedures in order to improve the WCS accuracy. Our goal was to achieve a rotation accuracy of about 0.1 degree (1 pixel across NICI's 1024-pixel field is equivalent to 0.056 deg). Before November 2010, the binary stars 70 Oph and HDO 171 B-C were imaged for these calibrations. Stars with very precise orbits based on speckle imaging are required to reach 0.1 deg accuracy; we found that many binary orbits are insufficiently precise, and typical star pairs and star fields suffer from significant proper motion effects. These binaries' positions appeared to be sufficiently precise, but the components spanned only about 1/2 the field and saturated slightly with the AO loop closed, which limited the NICI measurement accuracy.
Starting in November 2010 we began to use an LMC field that has been characterized for JWST calibrations. The field contains one 11 mag star for AO guiding, plus a dozen faint stars which can be detected with NICI. The distortion-corrected position data are fitted to a model which yields typical errors below 1 pixel rms.
A reference to the JWST LMC field is at:
Photometric and Astrometric Calibration of the JWST Instrument Complement, R. Diaz-Miller, 2006
Note that the distortion correction is incorporated into the WCS measurement; therefore in order to achieve consistent astrometric results the above distortion correction must be applied.
The following table summarizes the NICI port changes and subsequent IAA and WCS revisions.
NICI IAA and WCS Measurements | |||||||
Mounting Date | Port | WCS Revision Date | Target | IAA | Red Scale | Blue Scale | Example Dataset |
2008-07-27 | 5 | 2008-10-07 | 70 Oph | 112.3 | 17.900 | 17.900 | GS-NICI-COMM1-318 |
2009-10-24 | 1 | 2009-10-29 | HDO 171 B-C | 247.5 | 18.060 | 18.060 | Eng files 20101024 1-11 |
2010-03-20 | 5 | 2010-05-09 | 70 Oph | 111.7 | 17.800 | 17.800 | GS-CAL20100509-2 |
2010-10-20 | 5 | 2010-12-14 | LMC-11mag | 112.6 | 17.932 | 17.970 | GS-CAL20101225-2 |
2011-01-14 | 1 | 2011-02-16 | LMC-11mag | 247.5 | 17.973 | 18.009 | GS-CAL20110117-2 |
2011-03-11 | 1 | 2011-03-14 | LMC-11mag | 247.5 | 17.973 | 18.009 | GS-CAL20110314-2 |
2011-04-27 | 1 | 2011-04-15 | LMC-11mag | 247.5 | 17.973 | 18.009 | GS-CAL20110512-1 |
2011-06-08 | 5 | 2011-06-24 | HIP 62403 | 112.82 | 17.978 | 18.014 | GS-CAL20110626-3 |
2012-02-15 | 5 | 2012-02-01 | LMC-11mag | 112.64 | 17.950 | 17.986 | GS-CAL20120224-5 |
2012-07-13 | 5 | 2012-08-27 | LMC-11mag | 112.42 | 17.936 | 17.973 | -- |
Table Description:
- Mounting Date: The date NICI was mounted or remounted on the telescope.
- Port : The port on which NICI was mounted, 5 = side-looking, 1 = up-looking.
- WCS Revision Date : The date that the IAA and WCS parameters were updated for the final time after a remounting. Note that this date can be several days or weeks after the mounting date, due to delays caused by instrument problems or weather. (See below.)
- Target : Target observed for alignment measurements.
- IAA : IAA value derived from alignment, for N up at IPA=0 on distortion-corrected Red channel data.
- Red Scale : Red channel pixel scale, in mas/pixel.
- Blue Scale : Blue channel pixel scale, in mas/pixel.
- Example Data : An example astrometric data set, taken after the WCS update when possible.
Notes:
- This table does not include details of the astrometric measurement efforts between the dates of an instrument mounting and the "final" WCS. Often, multiple measurement and correction cycles over several days or weeks were required due to instrument problems or poor weather. In some cases, we were forced to take science data with an incorrect WCS before the final astrometric solution was available. Information on correcting science data taken in these intermediate periods is available on request.
- The relative rotation of the Blue channel relative to the Red is 1.1 degrees. Before 2010 Nov 22, the Blue channel WCS was incorrectly set to a relative angle of 0.8 degrees, due to a previous measurement error on one of the binary stars. Information on correcting this error is available on request.
- The Blue channel pixel scale is approximately 1.002 times the Red channel scale. Before 2010 Nov 22, this is not represented in the two WCS's (both are set to the same scale), due to the limited precision of the binary star measurements. With the LMC astrometric field, however, the difference is detectable, so the WCS's now represent the different scales.
- The uncertainty of the rotation measurement is approximately +-0.05 deg, as judged from both the precision of fitting the distortion-corrected images (typically 0.5 - 1.0 pixels), and the variation in the fitted angle between different images. Note that a 1 pixel shift across the width of the detector (1024 pixels) is equivalent to a rotation of 0.056 degrees.
- The uncertainty in the pixel scale is also around 1 pixel across the detector, or 0.1%. Variations at the 0.1 - 0.2% level are present between the individual measurements.
- The principal source of measurement error appears to be variability in PSF shape and quality across the field due to anisoplanatism in the AO correction. However, the distortion correction is also probably an important factor. We have not thoroughly investigated the sources of error at the 0.1% or 0.05 degree level.
nici_fixwcs
The IDL program
Data Processing
At present, the Gemini IRAF package does not include specific routines for processing NICI data. However, processing follows typical imaging data reduction pipeline steps (as for NIRI, for example). An experimental Python package for processing of NICI ADI/ASDI data using the LOCI algorithm is available, but it is not officially supported.
Example NICI Header
Extracted from file S20110117S0029.fits The keywords have been sorted into groups, and explanatory notes added for each group. PRIMARY HEADER -------------- # DATE-OBS and TIME-OBS are generated by the low-level Instrument # Controller and most accurately indicate the start of the integration. DATE-OBS= '2011-01-17' / UTC Date of observation (YYYY-MM-DD) TIME-OBS= '01:28:01' / UTC at array controller start of integration # Other times are generated by the higher-level software and are less accurate. UT = '01:27:58.1' / UTC at observation start MJD_OBS = 55578.0619 / MJD of start of obseration # Standard FITS keywords OBSERVAT= 'Gemini-South' / Name of telescope (Gemini-North|Gemini-South) TELESCOP= 'Gemini-South' / Gemini-South INSTRUME= 'NICI ' / Instrument used to acquire data # Observers OBSERVER= 'Lee, Hayward' / Gemini Observers SSA = 'Wenderoth' / Gemini SSAs # Gemini program, observation, and data labels OBSTYPE = 'OBJECT ' / Observation type OBSCLASS= 'partnerCal' / Observe class GEMPRGID= 'GS-CAL20110117' / Gemini Science Program ID OBSID = 'GS-CAL20110117-2' / Gemini Observation ID DATALAB = 'GS-CAL20110117-2-018' / DHS Data Label # Observing conditions as set by Observer in SeqExec at time of observation RAWIQ = '70-percentile' / Raw Image Quality RAWCC = '50-percentile' / Raw Cloud Cover RAWWV = '80-percentile' / Raw Water Vapour/Transparency RAWBG = '80-percentile' / Raw Background # Data assessment and release status RAWPIREQ= 'UNKNOWN ' / PI Requirements Met RAWGEMQA= 'UNKNOWN ' / Gemini Quality Assessment RELEASE = '2011-01-17' / End of proprietary period YYYY-MM-DD # Target and Pointing data from the TCS # Not to be confused with the WCS in the extensions OBJECT = 'f606w_11.341' / Object Name FRAME = 'FK5 ' / Target coordinate system EQUINOX = 2000. / Equinox of coordinate system EPOCH = 2000. / Target Coordinate Epoch RA = 80.48629583 / Target Right Ascension DEC = -69.44843889 / Target Declination PMRA = 0. / Target Proper Motion in RA PMDEC = 0. / Target Proper Motion in Declination PARALLAX= 0. / Target Parallax RADVEL = 0. / Target Heliocentric Radial Velocity RATRGOFF= 0. / Target offset in RA in arcsec DECTRGOF= 0. / Target offset in DEC in arcsec RATRACK = 0. / Differential tracking rate RA DECTRACK= 0. / Differential tracking rate Dec WAVELENG= 16520. / Effective Target Wavelength TRKFRAME= 'FK5 ' / Tracking co-ordinate TRKEQUIN= 2000. / Tracking equinox XOFFSET = -3.53700546226 / Telescope offset in x in arcsec YOFFSET = 0.699708767922 / Telescope offset in y in arcsec POFFSET = -2. / Telescope offset in p in arcsec QOFFSET = -3. / Telescope offset in q in arcsec RAOFFSET= 2. / Telescope offset in RA in arcsec DECOFFSE= 3. / Telescope offset in DEC in arcsec # Additional Pointing Data HA = '-00:52:22.05' / Telescope hour angle ELEVATIO= 50.1760388888889 / Current Elevation AZIMUTH = 172.835761111111 / Current Azimuth AIRMASS = 1.301 / Mean airmass for the observation AMSTART = 1.301 / Airmass at start of exposure AMEND = 1.301 / Airmass at end of exposure PA = 0. / Sky Position Angle at start of exposure # Telescope Configuration INPORT = 1 / Number of ISS port where instrument is located CRPA = -49.5685362028393 / Current Cass Rotator Position Angle CRMODE = 'FOLLOW ' / Cass Rotator Mode CGUIDMOD= 'Basic ' / Carousel Mode M2BAFFLE= 'RETRACTED' / Position of M2 baffle M2CENBAF= 'OPEN ' / Position of M2 central hole baffle IAA = 247.5 / Instrument Alignment Angle SFRT2 = -0.373 / Science fold rotation angle (degrees) SFTILT = 3.17 / Science fold tilt angle (degrees) SFLINEAR= -357.15 / Science fold linear position (mm) AOFOLD = 'park-pos.' / AO Pick-Off Mirror Position PWFS1_ST= 'parked ' / PWFS1 probe state (frozen,guiding,parked) PWFS2_ST= 'guiding ' / PWFS2 probe state (frozen,guiding,parked) OIWFS_ST= 'guiding ' / OIWFS probe state (frozen,guiding,parked) AOWFS_ST= 'parked ' / AOWFS probe state (frozen,guiding,parked) P2FOCUS = -0.06 / PWFS2 Focus Offset (mm) # Peripheral Wavefront Sensor pointing data OBSEPOCH= 0. / Epoch at start of exposure P2AOBJEC= 'GSC0916200265' / Object Name for PWFS 2, Chop A P2AFRAME= 'FK5 ' / PWFS2 Target co-ordinate system P2AEQUIN= 2000. / Equinox for PWFS2 guide star coordinates P2AEPOCH= 2000. / Epoch for PWFS2 guide star coordinates P2ARA = 80.57442917 / RA of PWFS2 guide star P2ADEC = -69.35331111 / Declination of PWFS2 guide star P2APMRA = 0. / PWFS2 Proper Motion in RA P2APMDEC= 0. / PWFS2 Proper Motion in Declination P2ARV = 0. / PWFS2 Heliocentric Radial Velocity P2APARAL= 0. / PWFS2 Parallax of Target P2AWAVEL= 6500. / PWFS2 Effective Target Wavelength # On-Instrument Wavefront Sensor (i.e. the NICI AO System) pointing data OIAOBJEC= 'f606w_11.341' / Object Name for OIWFS, Chop A OIAFRAME= 'FK5 ' / OIWFS Target co-ordinate system OIAEQUIN= 2000. / Equinox for OIWFS guide star coordinates OIAEPOCH= 2000. / Epoch for OIWFS guide star coordinates OIARA = 80.48629583 / RA of OIWFS guide star OIADEC = -69.44843889 / Declination of OIWFS guide star OIAPMRA = 0. / OIWFS Proper Motion in RA OIAPMDEC= 0. / OIWFS Proper Motion in Declination OIARV = 0. / OIWFS Heliocentric Radial Velocity OIAPARAL= 0. / OIWFS Parallax of Target OIAWAVEL= 7000. / OIWFS Effective Target Wavelength # Telescope environment # Also provided in furlongs per fortnight and other imperial units (not shown) HUMIDITY= 14. / The relative humidity (fraction, 0..101). TAMBIENT= 13.1 / The ambient temp (C). DEWPOINT= -13.7 / The dew point (C). PRESSURE= 547.7044 / The atmospheric pressure (mm Hg). WINDSPEE= 4.5 / The wind speed (m/s). WINDDIRE= 349. / The wind direction (degrees). # NICI AO System Configuration FOCS = 'Open ' / Fiber Optic Calib. Src. FOCS_OFF= -4. / Fiber Optic Calib. Src. Offset FOCSLASR= F / Laser calibration source on FOCSIR = F / IR calibration source on TTSM = '{7105 -8301}' / TipTilt Position NDFW = 'Open ' / Neutral Density Filter Wheel LPSTATE = 'feedback' / AO loop state: idle | feedback | pr.imat | ttdm PRSERVO = 'pr ' / AO primary servo state: off | pr TTSERVO = 'off ' / AO secondary (TT) servo state: off | dm PRGAIN = 0.11 / AO pr.gain EFD = 0.565087 / AO extra focal distance DMFRNTEL= 0.26 / AO DM Front electrode (UH DM only) CNTLMAT = 'uhdm_20110107_3500BCDavg.inv.' / AO Control Matrix HVAPS = T / AO DM HVA Power Supply State APD1PS = T / AO APD1 Power Supply State APD2PS = T / AO APD2 Power Supply State HVACHAS = T / AO HVA Chassis State CNTRCHAS= T / AO Counter Chassis State LPOPTON = F / AO Loop Optimizer running AOCHNGD = F / AO parameters changed during capture FOCOFFEN= F / AO Focus offload to telescope enable TTOFFEN = F / AO TT offload to telescope enable TTGSIGN = -1. / AO tt.sign APDTEMP = 1.7 / AO APD temperature sensor (deg C) MEMSTK = 3501 / AO membrane stroke LP_SEC = 197332 / AO Loop Counter status (seconds since boot) TTGAIN = 0. / AO tt.gain MEMPHA = 67000 / AO membrane phase MEMFRQ = 1300 / AO membrane frequency DCFLOOR = 0.0001 / AO DC threshold/floor PRGSIGN = -1. / AO pr.sign LPCOADDS= 1 / AO loop Coadds LOOPFRQ = 1300 / AO Loop Update Rate LPCOUNT = 256526878 / AO Loop Counter at capture start (cycles since # NICI Science Camera Configuration -- elements common to both channels FPMW = 'Clear_G5710' / Focal Plane Mask Wheel FPMW_OFF= 0.02 / Focal Plane Mask Offset (deg) PMW = '95_G5731' / Pupil Mask Wheel SMR = 16.01 / Spider Mask Rotator angle (deg) SMRMODE = 'FIXED ' / Spider Mask Mode DICHROIC= 'H-50/50_G5701' / Dichroic Wheel # Red Channel Configuration (records duplicated in Ext 1 header) BIAS_R = 'mid ' / Red detector bias MODE_R = 'sur ' / Red exposure mode SLOWCT_R= 24 / Red detector slow counts ITIME_R = 30.02 / Red integration time NDR_R = 80 / Red non-destructive reads NCOADD_R= 1 / Red number of co-adds FILTER_R= 'CH4-H4%L_G0740' / Red Filter Wheel PI = 'Open ' / Pupil Imager # Blue Channel Configuration (records duplicated in Ext 2 header) BIAS_B = 'mid ' / Blue detector bias MODE_B = 'sur ' / Blue exposure mode SLOWCT_B= 24 / Blue detector slow counts ITIME_B = 30.02 / Blue integration time NDR_B = 80 / Blue non-destructive reads NCOADD_B= 1 / Blue number of co-adds FILTER_B= 'CH4-H4%S_G0743' / Blue Filter Wheel Extension 1: Red (holmes) Channel --------------------------------- # Required FITS keywords XTENSION= 'IMAGE ' / IMAGE extension BITPIX = -32 / number of bits per data pixel NAXIS = 2 / number of data axes NAXIS1 = 1024 / length of data axis 1 NAXIS2 = 1024 / length of data axis 2 # Gemini keywords FRMNAME = 'dhsPut-nici-data1' / Name assigned to a frame of data. FRAMEID = '2 ' / Gemini frame identifier DATATYPE= ' ' EXTNAME = 'SCI ' / Extension Name EXTVER = -1 / Number assigned to a FITS extension. PCOUNT = 0 / required keyword; must = 0 GCOUNT = 1 / required keyword; must = 1 # Channel and Detector CHANNEL = 'RED ' / Science Camera Channel DETNAME = 'SCA-47814' / Sensor Chip Assembly Number # Red Channel Configuration SUBARRAY= ' { 0 0 512 512 } ' / Region of interest BIAS_R = 'mid ' / Red detector bias MODE_R = 'sur ' / Red exposure mode SLOWCT_R= 24 / Red detector slow counts ITIME_R = 30.02 / Red integration time NDR_R = 80 / Red non-destructive reads NCOADD_R= 1 / Red number of co-adds FILTER_R= 'CH4-H4%L_G0740' / Red Filter Wheel PI = 'Open ' / Pupil Imager # WCS for Red Channel RADECSYS= 'FK5 ' / R.A./DEC. coordinate system reference CTYPE1 = 'RA---TAN' / R.A. in tangent plane projection CTYPE2 = 'DEC--TAN' / DEC. in tangent plane projection CRVAL1 = 80.4883844 / RA at Ref pix in decimal degrees CRVAL2 = -69.4482734 / DEC at Ref pix in decimal degrees CRPIX1 = 413.999522 / Ref pix of axis 1 CRPIX2 = 594.997314 / Ref pix of axis 2 CD1_1 = 5.01646534E-06 / WCS matrix element 1 1 CD1_2 = 8.26096075E-11 / WCS matrix element 1 2 CD2_1 = -3.29874171E-10 / WCS matrix element 2 1 CD2_2 = -5.01703714E-06 / WCS matrix element 2 2 Extension 2: Blue (watson) Channel ---------------------------------- # Required FITS keywords XTENSION= 'IMAGE ' / IMAGE extension BITPIX = -32 / number of bits per data pixel NAXIS = 2 / number of data axes NAXIS1 = 1024 / length of data axis 1 NAXIS2 = 1024 / length of data axis 2 # Gemini keywords FRMNAME = 'dhsPut-nici-data2' / Name assigned to a frame of data. FRAMEID = '3 ' / Gemini frame identifier DATATYPE= ' ' EXTNAME = 'SCI ' / Extension Name EXTVER = -1 / Number assigned to a FITS extension. PCOUNT = 0 / required keyword; must = 0 GCOUNT = 1 / required keyword; must = 1 # Channel and Detector CHANNEL = 'BLUE ' / Science Camera Channel DETNAME = 'SCA-47815' / Sensor Chip Assembly Number # Blue Channel Configuration SUBARRAY= ' { 0 0 512 512 } ' / Region of interest BIAS_B = 'mid ' / Blue detector bias MODE_B = 'sur ' / Blue exposure mode SLOWCT_B= 24 / Blue detector slow counts ITIME_B = 30.02 / Blue integration time NDR_B = 80 / Blue non-destructive reads NCOADD_B= 1 / Blue number of co-adds FILTER_B= 'CH4-H4%S_G0743' / Blue Filter Wheel # WCS for Blue Channel RADECSYS= 'FK5 ' / R.A./DEC. coordinate system reference CTYPE1 = 'RA---TAN' / R.A. in tangent plane projection CTYPE2 = 'DEC--TAN' / DEC. in tangent plane projection CRVAL1 = 80.4883844 / RA at Ref pix in decimal degrees CRVAL2 = -69.4482734 / DEC at Ref pix in decimal degrees CRPIX1 = 570.000515 / Ref pix of axis 1 CRPIX2 = 650.997321 / Ref pix of axis 2 CD1_1 = -5.0159887E-06 / WCS matrix element 1 1 CD1_2 = -6.99793144E-08 / WCS matrix element 1 2 CD2_1 = 7.03997325E-08 / WCS matrix element 2 1 CD2_2 = -5.01655469E-06 / WCS matrix element 2 2