Wisconsin Ultraviolet Photo-Polarimeter Experiment

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 (December 2 through 11). The launch GMT was 1990, day 336/06:49:01. The WUPPE was designed to measure the polarization of light in the ultraviolet. WUPPE obtained simultaneous spectra and polarization measurements from 1400 to 3300A. WUPPE consisted of a 0.5m f/10 classical Cassegrain telescope and a spectropolarimeter. The telescope fed light to a low resolution spectrometer which was equipped with various polarimetric analyzers. A magnesium flouride Wollaston polarizing beam-splitter was placed between the aperture and the relay mirror and split the beam into two orthogonally-polarized spectra. The two polarized spectra were measured simultaneously by two parallel 1024-pixel arrays of an intensified Reticon photodiode array. The cesium telluride photocathode of the microchannel plate intensifier provided a spectral coverage from 1400 to 3300 Angstroms. The WUPPE spectrometer was a modified Monk-Gilleson spectrometer: a plane grating is placed between a spherical relay mirror and the detector. The focal plane scale was 26 arcsec/mm. The dispersion was 78 A/mm, blaze at 2000 Angstroms. A set of halfwave plates at 6 different angles provided spectropolarimetric modulation with 5 Angstrom resolution on point sources through apertures from 6 to 40 arcsec. A "Lyot" analyzer was used to provide 50-100 Angstrom spectropolarimetric resolution on faint point targets and diffuse nebulae.

Because of the very high signal/noise required for polarimetry, most WUPPE targets were in the 0-8 magnitude range: readout integration times ("frames") were less than 8 seconds, so that a typical observation was the sum of many short frames. The apertures included a 40 arcsec diameter acquisition aperture and a 4.2 arcsec diameter stellar aperture, in addition to a number of aperture shapes for diffuse source, (e.g. 6x12 and 3x50 arcsec). WUPPE had the ability to offset from the other two ultraviolet instruments (HUT and UIT) by as much as 15 arcminutes by use of its articulated secondary mirror. In spectral mode the field of view was 50 arcsec perpendicular to the dispersion for a spatial resolution better than 0.7x6 arcsec. The total system quantum efficiency was about 4 percent, polarimetric efficiency about 75 percent, polarimetric stability was better than 0.04 percent, and the instrumental polarization (from in flight observations of unpolarized standard stars) was less than 0.1 percent. In the Lyot mode the polarimeter measured Stokes Q, U, V with 50-100 A resolution. In the Halfwave plate mode the Stokes Q, U were supported with 10 A resolution.

Field identification, offsetting, focussing, and pointing trim were accomplished by relaying the zero-order image of the WUPPE spectrometer grating to a blue-sensitive Zero-Order Detector (ZOD) camera. The ZOD was an intensified RCA 320x512 two-dimensional CCD array. The intensifier was an ITT 18 mm proximity-focussed channel intensifier with P-20 phosphor, quartz faceplate, and S-20 photocathode for blue-sensitivity. The array was uncooled and typically read out every second. The ZOD camera had a 3.4 x 4.4 arcmin field of view, 1 x 5 arcsec resolution, and was sensitive up to 15th magnitude for a 1 second integration. The ZOD made it possible for the experiment team to acquire and guide upon faint targets and targets in crowded fields. There were three camera modes: field, zoom and downfield. The field mode was used for identification and acquisition of the targets. Its size was 3.3 x 4.4 arcmin, 320 x 256 pixels and used a 1-bit display. The zoom mode was used for fine pointing and focus. The size of the zoom image was 24 x 32 arcsec, 30 x 40 pixels and used a 6-bit grey scale display. The downfield data was similar to the field data except it used the 6-bit grey scale display and was used to produce a more detailed picture of the field around the object of interest.

A single 4-digit ID was assigned to each astronomical target name. This ID may have RA's and declinations over a 5-arcminute range. The size of this range was chosen under the assumption that 5-arcminute precision was good enough to compute acquisition/loss times and orbiter maneuvers, and that 5 arcminutes was large enough for flexibility in, for example, choosing HUT targets within UIT galaxies. This 4-digit ID should be Astro 1 mission-independent. It was the target ID given in the Program Target List (PTL). If the ID has a solarsystem ('S') flag, it may have any RA or Dec. If a target was used both as a calibration target and a science target it was given two ID numbers, depending on the purpose of the particular acquisition. This permited more accurate time distribution measurements. Two additional numbers following the above 4 digit ID number represented the individual pointing number assigned to the observation. Thus a given target might have several pointings throughout the ASTRO 1 mission. The entire 6 digit number is equivalent to the NDADS Data Type "Pointing-ID" and the "Pointing-ID" as given in the WUPPE1 file names.

00 is science class 0.0
10 is the object itself
14 is the pointing number assigned to the observation

All Astro 1 / WUPPE file names on NDADS begin with "WUPPE1". WUPPE1 file names have one of 4 extensions; .FITS for FITS files, .PS for PostScript files, .F for Fortran 77 programs, and .DOC for ASCII document files. WUPPE1 file names are organized in two ways. One dataset is organized by the Object-ID and the file names contain both the Object-ID and the 6-digit Pointing-ID (pppppp). A second dataset is organized by the Mission elapsed time (MET) day number, which is contained within the file name. All FITS files have the Data-Type encoded within the file name. In the sample file names below the following conventions are used:

Notes:

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, alphabetic information, and/or 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.

DAYyz = The mission elapsed time (MET) day number times 10 (eg. 00, 05, 10,... 80). Files containing "DAYyz" in the file name were obtained within a given 12-hour periods. The launch GMT was 1990, day 336/06:49:01 which is defined to be MET day00, 00h:00m:00s. For example, MET DAY00 runs from a MET time of 0 day, 00h:00m:00s to llh:59m:59s; DAY05 runs from MET time of 0 day, 12h:12m:12s to 23h:59m:59s, etc.

Data-Types:

HW = Halfwave filter data,
L2 = Medium resolution Lyot filter (Not available)
L4 = Low resolution Lyot filter (Not available)
SN = SCAN data
ZM = ZOOM data
FD = FIELD data
DN = DOWNFIELD data
EG = Engineering data

4.1 Level 1 Spectropolarimeter data:

WUPPE1_OBJECTID_PPPPPP_HW.FITS
WUPPE1_OBJECTID_PPPPPP_HW.PS
WUPPE1_OBJECTID_PPPPPP_HW.DUMP

Samples:
WUPPE1_ALF-CAM_210720_HW.FITS
WUPPE1_HD25443_065823_HW.PS

4.2 Level 0 SCAN Spectrometer data:

WUPPE1_DAYyz_SN_nnnn.FITS
WUPPE1_OBJECTID_PPPPPP_SN_nnnn.FITS

Samples:
WUPPE1_BD284211_001014_SN_0001.FITS
WUPPE1_DAY05_SN_0001.FITS

nnnn = 4 digit starting SCAN number

4.3 Level 0 Zero Order Detector (ZOD) ZOOM Data:

WUPPE1_DAYyz_ZM_nnnn.FITS
WUPPE1_OBJECTID_PPPPPP_ZM_nnnn.FITS

Sample Files:
WUPPE1_DAY05_ZM_0001.FITS
WUPPE1_BD284211_001014_ZM_nnnn.FITS
WUPPE1_C-LEVY_111230_ZM_0001.FITS

nnnn = 4 digit starting ZOOM Image number

4.4 Level 0 ZOD DOWNFIELD Data:

WUPPE1_DAYyz_DN_n.FITS
WUPPE1_OBJECTID_PPPPPP_DN_n.FITS

Sample Files:
WUPPE1_NGC1068_820333_DN_1.FITS

n = 1 digit DOWNFIELD Image Number

4.5 Level 0 ZOD FIELD data:

WUPPE1_DAYyz_FD_nnnnn.FITS
WUPPE1_OBJECTID_PPPPPP_FD_nnnnn.FITS

Sample Files:
WUPPE1_DAY55_FD_00081.FITS
WUPPE1_NGC4151_FD_00081.FITS

nnnnn = 5 digit FIELD Starting Image Number

4.6.0 Level 0 Engineering Data:

WUPPE1 Level 0 Engineering data consist of General Measurement Loop (GML) data and Image Motion Compensation System (IMCS) data.

4.6.1 GML Engineering data:

WUPPE1_DAYyz_EG_cnn.PS
WUPPE1_OBJECTID_PPPPPP_EG_cnn.PS

Sample Files:
WUPPE1_DAY70_EG_A01.PS -> WUPPE1_DAY70_EG_A40.PS
WUPPE1_DAY70_EG_M01.PS -> WUPPE1_DAY70_EG_M40.PS
WUPPE1_DAY70_EG_D01.PS -> WUPPE1_DAY70_EG_D46.PS

WUPPE1_G70D8247_260911_EG_A01.PS -> WUPPE1_G70D8247_260911_EG_A40.PS

cnn = 1 character + 2 digit number indicating which engineering value is contained in the file. Analog data = A01 -> A32; Serial Message data = M01 ->M40; Digital Data = D01 -> D46.

4.6.2 Image Motion Compensation System (IMCS) data:

WUPPE1_DAYyz_ISTATUS.PS (Only available ordered by DAYyz)

4.6.3 Documentation:

All documentation is in plain ASCII format.

WUPPE1_GENINFO.DOC
WUPPE1_OBSLOG.DOC
WUPPE1_HALFWAVE.DOC
WUPPE1_SCAN.DOC
WUPPE1_ZOOM.DOC
WUPPE1_DOWNFIELD.DOC
WUPPE1_FIELD.DOC
WUPPE1_ENGINEERING.DOC

4.6.4 Software:

All software is Fortran and uses FITSIO 3.2. It was written with DEC fortran for ULTRIX RISC Systems (Ultrix 4.2) and is F77. Software files are available from NDADS.

SPECFITSREAD.F - Read FITS header and primary data array of the Level 0 spectrometer (SCAN) data.

ZOOMFITSREAD.F - Read FITS header and primary data array of the Level 0 ZOD Zoom camera data.

HWFITSREAD.F - Read FITS header, primary data array (flux), and Binary table extension (%P, and P.A.) of the Level 1 Halfwave Filter Spectropolarimetry data

FLUXFITSREAD.F - Read FITS header and primary data array (flux) of the Level 1 Halfwave Filter Spectropolarimetry data

DFLDFITSREAD.F - Read FITS header and primary data array of the Level 0 ZOD Downfield camera data.

FLDFITSREAD.F - Read FITS header and primary data array of the Level 0 ZOD Field camera data.

The following list of WUPPE 1 filters and apertures are referred to in the WUPPE1 FITS data files.

5.1 WUPPE Filter List:

5.2 WUPPE Aperture Wheel:

NOTES: (a) Launch stow position (b) Rochon prism, mounted with plane of splitting at PA 22.5 (c) Apertures 10 and 11 have occulting disks in the center of their slits of 3 and 12 arc-sec, respectively. (d) PA measured clockwise from radius vector of wheel to optic axis.

When using these data in any publication or presentation, please include the following statements in your acknowledgements:

"The WUPPE datasets were developed by the WUPPE project, University of Wisconsin-Madison, supported by NASA contract NAS5-26777".

Postscript version is coming soon from the project. WUPPE Project will also have HTML version on their web site soon. The WUPPE Operations Requirements/Procedures Manual - Volume 1 is available on microfiche upon request from the NSSDC CRUSO office (see address below). Ask for document TRF B43054.

NSSDC / Coordinated Request and User Support Services Office
NASA/Goddard Space Flight Center
Code 633.4
Greenbelt, Maryland 20771
Phone (301) 286-6695