The Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) was one of three ultraviolet (UV) telescopes on the Astro-1 payload which flew aboard the space shuttle Columbia during a nine day mission in December 1990. It was reflown for 16 days in March 1995 on board Endeavour during the Astro-2 mission. WUPPE is a 0.5m f/10 Cassegrain telescope and spectropolarimeter. It obtained simultaneous spectra and polarization measurements, with a spectral resolution of about 16A, from 1450 to 3200A. A set of halfwave plates at 6 different angles provide spectropolarimetric modulation with 16A 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%. A detailed description of the instrument is given in Nordsieck et al 1994, SPIE, 2010, 2. See also the WUPPE web site for more information: http://www.sal.wisc.edu/WUPPE
Astro 1 & 2 WUPPE reduced data products include calibrated spectra and polarizations. During the Astro-2 mission WUPPE took 369 observations of 254 objects; some objects have multiple pointings. 112 pointings of 79 targets were taken of WUPPE prime targets. 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 WUPPE prime target polarization results represent the majority of the useful polarimetry obtained by WUPPE during the Astro-2 mission. There were 149 pointings of 90 objects of Hopkins Ultraviolet Telescope (HUT) prime interest and 108 pointings of 85 objects of Ultraviolet Imaging Telescope (UIT) interest. The data set given here is for the WUPPE prime pointings only. The HUT & UIT results will be submitted at a later date.
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 an Error spectrum, all consisting of 1024 32-bit data points for each array from about 1450 to 3200A.
WUPPE data analysis and software development takes place at the Univer- sity 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 rocket UV spectropolarimetric data. This software package was operating on UNIX based microVAXes for several years and is currently running on Silicon Graphics Indy machines running IRIX 6.3.
The Stokes %Q and %U, and %Error spectra and flux calibrated (Flambda- ergs/cm**2/sec/A) data along with pertinent housekeeping data and data reduction information for each of the Astro-2 WUPPE prime target halfwave mode pointings (112 pointings of 79 targets, about 2.6 Mbytes of data) have been written to FITS files and are described in this document.
The file name consists of the following:
WUPPE2_ObjectID_PointingID_HW.fits (e.g. WUPPE2_PHI-PER_220311_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 ObjectID can vary from 3 to 8 characters and may be a mix of numbers and/or alphabetic information and may contain embedded '-'s.
PointingID = a 6 digit number representing the object identification number which was assigned during the mission. Each Astro-2 shuttle pointing had a unique PointingID number. (However, the PointingID number may not be unique for both Astro missions. A small number of PointingIDs used in the Astro-1 mission were also used in Astro-2.)
HW is the Halfwave polarimeter mode.
The FITSIO package, version 4.14, written by William Pence at the Goddard Spaceflight Center, was used to generate the FITS files. They were written on a Silicon Graphics Indy running IRIX 6.3.
FITS files including the polarimetry are generally 25920 bytes in length; the size can be larger with more FITS header records. The flux-only FITS files are generally 11520 bytes.
A WUPPE2 Halfwave Level 1 FITS file looks like the following:
+-------------------+
| |
| Header |
| |
+-------------------+
+-------------------+
| |
| Data (1024 x 4) |
| Flambda |
| %Q |
| %U |
| %Error |
| |
+-------------------+
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. A set of comments giving the data reduction history is also included along with a "Special Comments" section. The exact headers of the 2 example files are given below. The primary array data (1024 x 4 32 bits per data point) consists of the Flux array in units of ergs/cm**2/sec/A (Flambda), the Stokes parameters %Q, %U, and %Error. For the fluxes, bad data have been zeroed out. For the polarization data, the bad data are when the %Error data have been zeroed out. The %Q and %U data remain (allowing inspection of those data) but should not be used.
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 = 4 / length of data axis 2 COMMENT FITS (Flexible Image Transport System) format defined in Astronomy and COMMENT Astrophysics Supplement Series v44/p363, v44/p371, v73/p359, v73/p365. COMMENT Contact the NASA Science Office of Standards and Technology for the COMMENT FITS Definition document #100 and other FITS information. COMMENT FITSIO package v4.14 used CRVAL1 = 1354.00 / 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) CTYPE3 = '%Q ' / Linear Stokes %Q CTYPE4 = '%U ' / Linear Stokes %U CTYPE5 = '%Error ' / Error in %Polarization COMMENT The errors given in the error array are the statistical errors COMMENT based on the residuals of the least squared fit to the 3 COMMENT filter-pair polarimetric data (see section 2.3 of Wolff, COMMENT Nordsieck & Nook 1996 AJ 111, 856). COMMENT The instrumental polarization stability of WUPPE is +/- 0.04% COMMENT and the polarization efficiency is Pol/20. COMMENT ***IMPORTANT NOTE*** COMMENT **The ERROR array is also being used as a QUALITY array. COMMENT **For bad/contaminated data, the errors have been set to zero COMMENT **but the %Q & %U arrays for those wavelengths remain unchanged COMMENT **to allow inspection of the bad data. ORIGIN = 'UW-Space Astronomy Lab' / Creator of FITS file DATE = ' 5/02/98' / FITS file creation date COMMENT = 'Thu Feb 5 15:32:52 1998' / Date FITS file was created COMMENT = 'Silicon Graphics Indy - Irix 6.3' / Computer used to write FITS files DATE-OBS= '05/03/95' / Date of Observation (GMT) dd/mm/yy OBSERVAT= 'ASTRO-2 ' / Observatory TELESCOP= 'WUPPE ' / Telescope INSTRUME= 'SPECTROPOLARIMETER' / Instrument Used MODE = 'HW ' / Halfwave Polarimeter Mode OBJECT = 'PHI-PER ' / Object Observed NAME2 = 'HD10516 ' / Alternate Target Name ID = '2203-11 ' / Target ID PRIME = 'WUPPE ' / Prime Instrument EQUINOX = 1950.00 / Equinox for coordinates RA = 25.13 / Right ascension in degrees DEC = 50.44 / Declination in degrees GMTSTART= '64/20:54' / GMT start time of observation (dd/hh:mm) METSTART= '03/14:16' / Mission Elapsed Time start time (dd/hh:mm) EXPOSURE= 997.0 / Useful Exposure Time (seconds) FRAMETIM= 0.2 / Frametime for each scan (seconds) SEQ-NUM = 106 / WUPPE Sequence Number HVPS = 3.70 / High Voltage Power Supply (volts) GAIN = 'High ' / Spectrometer Gain (High or Low) THERM = -33.10 / Instrument temperature (Centigrade) POSANGLE= 197.20 / Observatory Position Angle IMCSTATU= '-1 ' / Image Motion Compensation System status COMMENT IMCS:-1=man disab;0=auto disab;1=enab;2=out of limits DAYNIGHT= 'Day ' / Day-Night Status COMMENT Day-Night designations: "Night", "Day" (All Night or All Day) COMMENT "MostN", "MostD" (Mostly Night or Mostly Day), "N/D" or "D/N" COMMENT (Night into Day, Day into Night, roughly half the time in each). APERTURE= 8 / Aperture Used COMMENT Ap 8=6"x12";Ap 1=40" diam;Ap 2=4.2" diam FILTER = 6 / Starting Filter Number CALIBRAT= ' wuppe2i' / Instrumental polarization calibration used AVE-POL = 0.436 / Mean %Pol over entire wavelength region AVE-ERRO= 0.004 / Mean %Error in %Pol AVE-PA = 49.4 / Mean Position Angle (degrees) COMMENT Useful data generally are from 1450A-3200A with a spectral COMMENT resolution of 16A. HISTORY Data Reduction History HISTORY Wavelength calibration using Aluminum lines (created 4/25/95) HISTORY Filter mixing fixed for 0.2 sec frametime scans HISTORY Remove cosmic ray hits & telemetry errors & deviant scans HISTORY Remove offsets & thermal background & correct for thermal drift HISTORY Remove detector background (Astro-2 dtr bkg: created 5/22/95) HISTORY Apply noise reduction & 2nd order correction(created 3/13/96) HISTORY For each scan, correct for image motion in pitch & yaw HISTORY Apply flat field for Astro-2 point source (created 3/21/96) HISTORY Apply flux calibration: used HST standards & ptg correction HISTORY (created 4/1/97) HISTORY Apply Astro-2 high gain instrumental polarization calibration: HISTORY wuppe2i (created 5/16/96) COMMENT WUPPE Astro-2 flux calibration has a relative flux accuracy COMMENT of 5% between 1700A and 3000A and 10% outside this range. COMMENT Due to pointing instabilities, fluxes are not absolute. COMMENT WUPPE Astro-2 instrumental polarization is Q=-0.04% and COMMENT U=-0.08% (which has been removed). COMMENT Special Comments COMMENT *2400A "Glitch"* COMMENT The data between about 2380A and 2420A are bad (& therefore the COMMENT error array has been set to zero) due to a detector flaw in COMMENT the "A" polarimetric array. ========================================================================================= FITS File header (flux only data): WUPPE2_GAM2VEL_220410_HW.fits 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 COMMENT FITS (Flexible Image Transport System) format defined in Astronomy and COMMENT Astrophysics Supplement Series v44/p363, v44/p371, v73/p359, v73/p365. COMMENT Contact the NASA Science Office of Standards and Technology for the COMMENT FITS Definition document #100 and other FITS information. COMMENT FITSIO package v4.14 used CRVAL1 = 1364.00 / 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 = ' 5/02/98' / FITS file creation date COMMENT = 'Thu Feb 5 17:45:06 1998' / Date FITS file was created COMMENT = 'Silicon Graphics Indy - Irix 6.3' / Computer used to write FITS files DATE-OBS= '17/03/95' / Date of Observation (GMT) dd/mm/yy OBSERVAT= 'ASTRO-2 ' / Observatory TELESCOP= 'WUPPE ' / Telescope INSTRUME= 'SPECTROPOLARIMETER' / Instrument Used MODE = 'HW ' / Halfwave Polarimeter Mode OBJECT = 'GAM2VEL ' / Object Observed NAME2 = 'HD68273 ' / Alternate Target Name ID = '2204-10 ' / Target ID PRIME = 'WUPPE ' / Prime Instrument EQUINOX = 1950.00 / Equinox for coordinates RA = 122.01 / Right ascension in degrees DEC = -47.20 / Declination in degrees GMTSTART= '76/01:42' / GMT start time of observation (dd/hh:mm) METSTART= '14/19:30' / Mission Elapsed Time start time (dd/hh:mm) EXPOSURE= 214.0 / Useful Exposure Time (seconds) FRAMETIM= 0.2 / Frametime for each scan (seconds) SEQ-NUM = 433 / WUPPE Sequence Number HVPS = 3.10 / High Voltage Power Supply (volts) GAIN = 'Low ' / Spectrometer Gain (High or Low) THERM = -33.10 / Instrument temperature (Centigrade) POSANGLE= 161.70 / Observatory Position Angle IMCSTATU= '1 ' / Image Motion Compensation System status COMMENT IMCS:-1=man disab;0=auto disab;1=enab;2=out of limits DAYNIGHT= 'Night ' / Day-Night Status COMMENT Day-Night designations: "Night", "Day" (All Night or All Day) COMMENT "MostN", "MostD" (Mostly Night or Mostly Day), "N/D" or "D/N" COMMENT (Night into Day, Day into Night, roughly half the time in each). APERTURE= 8 / Aperture Used COMMENT Ap 8=6"x12";Ap 1=40" diam;Ap 2=4.2" diam FILTER = 6 / Starting Filter Number COMMENT Useful data generally are from 1450A-3175A with a spectral COMMENT resolution of 16A. HISTORY Data Reduction History HISTORY Wavelength calibration using Aluminum lines (created 4/25/95) HISTORY Filter mixing fixed for 0.2 sec frametime scans HISTORY Remove cosmic ray hits & telemetry errors & deviant scans HISTORY Remove offsets & thermal background & correct for thermal drift HISTORY Remove detector background (Astro-2 dtr bkg: created 5/22/95) HISTORY Apply noise reduction & 2nd order correction(created 3/13/96) HISTORY NO correction for image motion in pitch & yaw HISTORY Apply flat field for Astro-2 diffuse source (created 3/28/96) HISTORY Apply flux calibration: used HST standards & NO ptg correction HISTORY (created 4/1/97) COMMENT WUPPE Astro-2 flux calibration has a relative flux accuracy COMMENT of 5% between 1700A and 3000A and 10% outside this range. COMMENT Due to pointing instabilities, fluxes are not absolute. COMMENT Special Comments COMMENT Very bright object;Defocussed Image
The programs wfitsread.f and wfluxfitsread.f were written to verify the contents of the Astro-2 WUPPE Level1 FITS files. They also use the FITSIO v4.14 software package. These programs create ASCII dump files.
WUPPE Reference List
see www.sal.wisc.edu/WUPPE/pubswuppe.html for the latest list of WUPPE
references.
To request copies of relevant WUPPE documents, preprints/reprints, bibliography, or general questions, please email Marilyn Meade at the UW Space Astronomy Laboratory. See also the WUPPE Web site: http://www.sal.wisc.edu/WUPPE