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Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)
Halfwave Level 1 Data FITS files
July 28, 1996
1.0 Description of the Instrument
The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) was one of three ultraviolet telescopes on the ASTRO-1 payload which flew aboard the space shuttle Columbia during a nine day mission in December 1990. WUPPE is a 0.5m f/10 Cassegrain telescope and spectropolarimeter. It obtained simultaneous spectra and polarization measurements, with a spectral resolution of about 10Å, from 1400 to 3200Å. A set of halfwave plates at 6 different angles provide spectropolarimetric modulation with 10Å resolution on point sources through apertures from 6 to 40 arcsec. Calibrations of instrumental polarimetric efficiency, residual polarization, position angle registration, and flux sensitivity were performed by a combination of preflight laboratory measures and in-flight standard star observations. The data are corrected for telemetry errors, thermal background, cosmic ray hits, second order contamination, pointing errors, and instrumental polarization, which is roughly 0.05%.
2.0 WUPPE/Astro-1 Level 1 Halfwave Data
Level 1 data products include calibrated spectra and/or polarizations of approximately 75 targets, 24 of which are WUPPE1 prime targets. Some objects have multiple pointings. (WUPPE also observed the prime targets of the other two UV instruments which yielded good spectra in many cases but generally did not have sufficient signal-to-noise for useful polarization measurements.)
The data have been processed using methods developed for the ground-based spectropolarimetric data from the Pine Bluff Observatory (PBO) of the University of Wisconsin. This involves summation of equivalent readouts on a particular object, subtraction of background scans, division by the flat field calibration spectra, flux calibration using spectra of known bright stars, polarimetric calibration using data obtained during pre-launch and in-flight observations. For halfwave mode data, the filters are differenced and a Fourier analysis, pixel-by-pixel as a function of filter angle, is done to give Stokes parameters %Q and %U spectra along with a %Error spectrum, all consisting of 1024 32-bit data points for each array from about 1400 to 3200A.
WUPPE data analysis and software development takes place at the University of Wisconsin Space Astronomy Laboratory (SAL). Much of the WUPPE reduction software is based on a FORTRAN language generalized Reticon detector/spectropolarimeter package (REDUCE) developed at SAL to support ground-based (PBO) and Aerobee Rocket UV spectropolarimeter data. This software package has been operating on UNIX based microVAXes for several years.
The Stokes %Q and %U, and %Error spectra and flux calibrated (Flambda- ergs/cm2/sec/A) data along with pertinent housekeeping data for each of the Halfwave mode pointings (43 pointings of 31 targets, about 1 Mbyte of data) have been written to FITS files and are herein described. (Note the %V data is available with the Lyot polarization mode data but not the Halfwave.) In some cases the observation was too short or data from at least 2 filter pairs were not collected to produce polarization results. We have provided only the flux calibrated data in these cases (8 of the 43 pointings). In two of the pointings the object was never in the aperture. No data is provided for these cases. See the WUPPE1 Halfwave Observation Log at the end of this document for more specific information on the Halfwave Pointings.
3.0 WUPPE1 Halfwave Level 1 Data FITS file naming convention
WUPPE1_ObjectID_PointingID_HW.FITS (e.g. WUPPE1_ALF-CAM_210720_HW.FITS)
where,
OBJECTID = The Mission Target List name. The names are common to the HUT, UIT and WUPPE instruments. The number of characters in OBJECT can vary from 3 to 8 characters. May be a mix of numbers and/or alphabetic information. May contain imbedded '-'s.
PPPPPP = The POINTING_ID is a 6 digit number representing the object identification number which was assigned during the ASTRO1 mission. Each shuttle pointing had a unique POINTING_ID number. There may be several pointings of a single object.
HW is the Halfwave polarimeter mode.
4.0 Example files and Description of Halfwave FITS files
Please note: Astro-1 WUPPE files were reformatted following the conventions followed for Astro-2 data and redelivered to MAST by the WUPPE Project. Please see WUPPE2 Halfwave Info for an up-to-date description of the FITS format for these files.
Example FITS files for the Halfwave mode data:
WUPPE1_ALF-CAM_210720_HW.FITS
WUPPE1_L2PUP_360713_HW.FITS (flux-only data)
They were written on a Digital DECstation 5000/240 using DEC Fortran for Ultrix RISC Systems, running Ultrix 4.2. The FITSIO package, version 3.2, written by William Pence at the Goddard Space Flight Center, was used to generate the FITS files.
The FITS file including the polarimetry is 28800 bytes in length (57 VMS blocks). The flux-only FITS file is 11520 bytes (23 blocks).
A WUPPE1 Halfwave Level 1 FITS file looks like the following:
+-------------------+
| |
| Primary header |
| |
+-------------------+
Primary data
(Flambda)
+-------------------+
| |
| Extension Header |
| |
+-------------------+
+----++----++----+
W_0 DelW | %Q || %U || %E |
| || || |
| || || |
| || || |
| || || |
| || || |
| || || |
| || || |
+----++----++----+
The set of basic header information includes the primary array keywords and keywords describing the data arrays, target information, telescope engineering data relative to the observation, and calibration information. The exact headers of the 2 example files are given below.
The primary array data consists of the Flux array (1024 integer*4 words) in units of ergs/cm2/sec/A (Flambda). The binary tables extension includes headers, the first wavelength of the data set, the bin size (# Angstroms/pixel), the Stokes parameters %Q and %U, and %Error. For the fluxes, bad data have been zeroed out. For the the polarization data, the bad data have been zeroed out in the %Q, %U and %Error arrays. There is no binary table extension for the flux-only FITS files.
4.1 Level 1 WUPPE1 Halfwave FITS file header
Example FITS File name: WUPPE1_ALF-CAM_210720_HW.FITS
Primary FITS Header:
SIMPLE = T / file does conform to FITS standard BITPIX = -32 / number of bits per data pixel NAXIS = 2 / number of data axes NAXIS1 = 1024 / length of data axis 1 NAXIS2 = 1 / length of data axis 2 EXTEND = T / FITS dataset may contain extensions CRVAL1 = 1348.00 / Wavelength in Angstroms of first pixel CDELT1 = 2.00 / Number of Angstroms/pixel CRPIX1 = 1.00 / Starting pixel number CTYPE1 = 'WAVELENGTH' / Wavelength in Angstroms CTYPE2 = 'FLAMBDA ' / Flux (ERGS/CM*2/SEC/A) ORIGIN = 'UW-Space Astronomy Lab' / Creator of FITS file DATE = '24/03/95' / FITS file creation date COMMENT = 'Fri Mar 24 16:47:56 1995' / Date FITS file was created DATE-OBS= '04/12/90' / Date of Observation (GMT) OBSERVAT= 'ASTRO-1 ' / Observatory TELESCOP= 'WUPPE ' / Telescope INSTRUME= 'SPECTROPOLARIMETER' / Instrument Used MODE = 'HW ' / Halfwave Polarimeter Mode OBJECT = 'ALF-CAM ' / Object Observed ID = '2107-20 ' / Target ID PRIME = 'WUPPE ' / Prime Instrument EQUINOX = 1950.00 / Equinox for coordinates RA = 72.2659 / Right ascension in degrees DEC = 66.2607 / Declination in degrees GMTSTART= '338/20: 3:15' / GMT start time of observation GMTSTOP = '338/20:12: 7' / GMT stop time of observation METSTART= '2/13:14:14' / Mission Elapsed Time start time METSTOP = '2/13:23: 6' / Mission Elapsed Time stop time EXPOSURE= 462.00 / Useful Exposure Time (seconds) FRAMETIM= 0.20 / Frametime for each scan (seconds) SEQ-NUM = 53 / WUPPE Sequence Number HVPS = 3.70 / High Voltage Power Supply (volts) THERM = -36.10 / Instrument temperature (Centigrade) POSANGLE= 30.00 / Spacecraft Position Angle IMCSTATU= 'ON ' / IMCS status DAYNIGHT= 'most N ' / Day/Night Status APERTURE= 8 / Aperture Used FILTER = 6 / Filter Used CALIBRAT= 'wuppe1k ' / Instrumental polarization calibration used AVE-POL = 1.1993 / Mean %Pol over entire wavelength region AVE-ERRO= 0.0058 / Mean %Error in %Pol AVE-PA = 135.59 / Mean Position Angle (degrees) REDCOMME= 'Good solid observation' / Data reduction comments Extension Header: XTENSION= 'BINTABLE' / binary table extension BITPIX = 8 / 8-bit bytes NAXIS = 2 / 2-dimensional binary table NAXIS1 = 12296 / width of table in bytes NAXIS2 = 1 / number of rows in table PCOUNT = 0 / size of special data area GCOUNT = 1 / one data group (required keyword) TFIELDS = 5 / number of fields in each row TTYPE1 = 'WAVELENGTH' / label for field 1 TFORM1 = '1E ' / data format of the field: 4-byte REAL TUNIT1 = 'ANGSTROM' / physical unit of field TTYPE2 = 'DELTA WAVELE' / label for field 2 TFORM2 = '1E ' / data format of the field: 4-byte REAL TUNIT2 = 'ANGSTROM' / physical unit of field TTYPE3 = '%Q ' / label for field 3 TFORM3 = '1024E ' / data format of the field: 4-byte REAL TTYPE4 = '%U ' / label for field 4 TFORM4 = '1024E ' / data format of the field: 4-byte REAL TTYPE5 = '%Error ' / label for field 5 TFORM5 = '1024E ' / data format of the field: 4-byte REAL EXTNAME = 'POLARIMETRY' / name of this binary table extension
4.2 Example FITS File name: WUPPE1_L2PUP_360713_HW.FITS (flux-only data)
Primary FITS Header: SIMPLE = T / file does conform to FITS standard BITPIX = -32 / number of bits per data pixel NAXIS = 2 / number of data axes NAXIS1 = 1024 / length of data axis 1 NAXIS2 = 1 / length of data axis 2 CRVAL1 = 1360.00 / Wavelength in Angstroms of first pixel CDELT1 = 2.00 / Number of Angstroms/pixel CRPIX1 = 1.00 / Starting pixel number CTYPE1 = 'WAVELENGTH' / Wavelength in Angstroms CTYPE2 = 'FLAMBDA ' / Flux (ERGS/CM*2/SEC/A) ORIGIN = 'UW-Space Astronomy Lab' / Creator of FITS file DATE = '06/10/95' / FITS file creation date COMMENT = 'Fri Oct 6 15:09:36 1995' / Date FITS file was created DATE-OBS= '08/12/90' / Date of Observation (GMT) OBSERVAT= 'ASTRO-1 ' / Observatory TELESCOP= 'WUPPE ' / Telescope INSTRUME= 'SPECTROPOLARIMETER' / Instrument Used MODE = 'HW ' / Halfwave Polarimeter Mode OBJECT = 'L2PUP ' / Object Observed ID = '3607-13 ' / Target ID PRIME = 'WUPPE ' / Prime Instrument EQUINOX = 1950.00 / Equinox for coordinates RA = 108.0029 / Right ascension in degrees DEC = -44.5573 / Declination in degrees GMTSTART= '342/ 6:12:17' / GMT start time of observation GMTSTOP = '342/ 6:35:12' / GMT stop time of observation METSTART= '5/23:23:16' / Mission Elapsed Time start time METSTOP = '5/23:46:11' / Mission Elapsed Time stop time EXPOSURE= 256.00 / Useful Exposure Time (seconds) FRAMETIM= 128.00 / Frametime for each scan (seconds) SEQ-NUM = 191 / WUPPE Sequence Number HVPS = 3.70 / High Voltage Power Supply (volts) THERM = -34.10 / Instrument temperature (Centigrade) POSANGLE= 134.00 / Spacecraft Position Angle IMCSTATU= 'ON ' / IMCS status DAYNIGHT= 'N-D ' / Day/Night Status APERTURE= 8 / Aperture Used FILTER = 8 / Filter Used REDCOMME= 'Decent spectrum;filts 8&9 only' / Data reduction comments
5.0 Software
The programs "hwfitsread.f" and "fluxfitsread.f" were written to verify the contents of the Level 1 FITS files. It also uses the GSFC FITSIO software package. These programs are available from NDADS.
6.0 PostScript files
PostScript files have been provided in which the Flux (Flambda), binned Percent Polarization and binned Position Angle (data binned to a constant error) have been plotted for the WUPPE1 Halfwave pointings. The naming convention is as above except ".FITS" has been replaced by ".ps".
e.g.
WUPPE1_ObjectID_PointingID_HW.ps (WUPPE1_ALF-CAM_210720_HW.ps)
For the spectrum-only pointings 3 postscript files are provided in which the flux of 8 objects have been plotted. The file names are:
Contains plots of:
Pointing-ID Object-name
WUPPE1_HW_SPECTRA1.PS 210210 KAP-CAS
210910 ALF-ORI
210912 ALF-ORI
WUPPE1_HW_SPECTRA2.PS 240210 ETA-HOR
241713 21VUL
350311 HR1099
WUPPE1_HW_SPECTRA3.PS 360713 L2PUP
811613 NGC4151
7.0 ASCII Dumps of Halfwave FITS files.
ASCII dumps of each for the Halfwave FITS files have also been archived on NDADS. Each ASCII Halfwave file is named:
WUPPE1_ObjectID_PointingID_HW.DUMP (WUPPE1_ALF-CAM_210720_HW.DUMP)
With the Object ID and PointingID as defined above.
8.0 WUPPE1 Halfwave Mode Target List/Observation Log
Summary:
43 Halfwave Pointings by WUPPE1 (where WUPPE went into OBS mode)
33 Pointings have polarimetric data
8 Pointings have spectra only
2 Pointings - the object was never in the aperture
The ASTRO-1 WUPPE OBSERVATION LOG has been extracted to a separate file for ease of access.
-------------------------------------------------------------------------------------
WUPPE-1 Selected Reference List
1 1991 M. Taylor, A. D. Code, K. H. Nordsieck, C. M. Anderson, B. L. Babler, K. S.
Bjorkman, G. C. Clayton, A. M. Magalhaes, M. R. Meade, R. E. Schulte-Ladbeck,
and B. A. Whitney, Ap. J. Letters, 382, L85-L88. "First Ultraviolet
Spectropolarimetry of Hot Supergiants"
2 1991 K. S. Bjorkman, K. H. Nordsieck, A. D. Code, C. M. Anderson, B. L. Babler,
G. C. Clayton, A. M. Magalhaes, M. R. Meade, M. A. Nook, R. E. Schulte-Ladbeck,
M. Taylor, and B. A. Whitney, Ap. J. Letters, 383, L67-L70. "First Ultraviolet
Spectropolarimetry of Be Stars from WUPPE"
3 1992 G. C. Clayton, C. M. Anderson, A. M. Magalhaes, A. D. Code, K. H. Nordsieck,
M. R. Meade, M. J. Wolff, B. L. Babler, K. S. Bjorkman, R.E. Schulte-Ladbeck,
M. Taylor, and B. A. Whitney, Ap. J. Letters, 385, L53-L57. "The First
Spectropolarimetric Study of the Wavelength Dependence of Interstellar
Polarization in the Ultraviolet"
4 1992 R. E. Schulte-Ladbeck, K. H. Nordsieck, A. D. Code, C. M. Anderson, B. L.
Babler, K. S. Bjorkman, G. C. Clayton, A. M. Magalhaes, M. R. Meade, D.
Shepherd, M. Taylor, and B. A. Whitney, Ap. J. Letters, 391, L37-L40.
"The First Linear Polarization Spectra of Wolf-Rayet Stars in the
Ultraviolet: EZ Canis Majoris and Theta Muscae"
5 1992 R. E. Schulte-Ladbeck, D. S. Shepherd, K. H. Nordsieck, A. D. Code, C. M.
Anderson, B. L. Babler, K. S. Bjorkman, G. C. Clayton, A. M. Magalhaes,
M. R. Meade, M. Taylor, and B. A. Whitney, Ap. J. Letters, 401, L105-L108.
"Evidence for a Bipolar Nebula Around the Peculiar B[e] star HD45677 from
Ultraviolet Spectropolarimetry"
6 1993 A. D. Code, M. R. Meade, C. M. Anderson, K. H. Nordsieck, G. C. Clayton,
B. A. Whitney, A. M. Magalhaes, B. L. Babler, K. S. Bjorkman, R. E. Schulte-
Ladbeck, and M. Taylor, Ap. J. Letters, 403, L63-L65.
"The First Ultraviolet Spectropolarimetric Study of NGC1068"
7 1993 K. S. Bjorkman, M. R. Meade, K. H. Nordsieck, C. M. Anderson, B. L. Babler,
G. C. Clayton, A. D. Code, A. M. Magalhaes, R. E. Schulte-Ladbeck, M. Taylor,
and B. A. Whitney, Ap. J., 412, 810-813.
"Ultraviolet Spectropolarimetry of the Be Star PP Carinae with WUPPE"
8 1993 K. H. Nordsieck, A. D. Code, C. M. Anderson, M. R. Meade, B. L. Babler,
D. E. Michalski, R. H. Pfeifer, and T. E. Jones, Wisconsin Astrophysics 477,
(appeared in the proceedings of the SPIE symposium on X-Ray and UV
Polarimetry held in July 1993 in San Diego, CA).
"Exploring Ultraviolet Astronomical Polarimetry: Results from the
Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE)"
9 1994 K. H. Nordsieck, L. Rao, M. R. Meade, C. M. Anderson, B. L. Babler,
K. S. Bjorkman, A. D. Code, M. Taylor, N. E. Zellner, A. M. Magalhaes,
G. C. Clayton, R. E. Schulte-Ladbeck, B. A. Whitney, B.A.A.S.,26,864.
"Ultraviolet/Visible Spectropolarimetry of Alpha Orionis"
9.0 Further Information
Additional information on WUPPE can be found in the WUPPE1_GENINFO.DOC For further information send mail to archive@stsci.edu for help from the MAST staff.
OR
Ms. Marilyn Meade
UW Space Astronomy Laboratory
Chamberlin Hall
1150 University Avenue
Madison, WI 53706
Phone (608) 263-4678
meade@sal.wisc.edu
The information on this page came from the WUPPE project via the Astrophysics Data Center at Goddard Space Flight Center.
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