PDS_VERSION_ID = PDS3 RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 OBJECT = DATA_SET DATA_SET_ID = "HST-C-FOS-3-RSA-WIRTANEN-V1.0" OBJECT = DATA_SET_INFORMATION ARCHIVE_STATUS = "PRE PEER REVIEW" ABSTRACT_DESC = "The HST-C-FOS-3-RSA-WIRTANEN-V1.0 data set contains the spectra from the Faint Object Spectrograph (FOS) of the Hubble Space Telescope spacecraft. The comet WIRTANEN observations were obtained during July 1996 and January 1997." CITATION_DESC = "Stern, A. et al, Calibrated spectral data obtained from the FOS instrument on the Hubble Space Telescope of comet Wirtanen during July 1996 and January 1997. ESA Planetary Science Archive and NASA Planetary Data System, 2004." DATA_SET_COLLECTION_MEMBER_FLG = "NULL" DATA_SET_TERSE_DESC = "NULL" DATA_SET_NAME = "HST FOS COMET WIRTANEN DATA V1.0" DATA_OBJECT_TYPE = SPECTRUM START_TIME = 1996-07-22T17:18:31.000 STOP_TIME = 1997-01-15T04:09:20.000 DATA_SET_RELEASE_DATE = 2004-07-01 PRODUCER_FULL_NAME = "Ed Grayzeck" DETAILED_CATALOG_FLAG = "N" DATA_SET_DESC = " Data Set Overview ================= [STERNETAL1998] Three observations of 46P/Wirtanen were obtained between 22 July 1996 and 15 January 1997. All these observations were ob- tained using the HST Faint Object Spectrograph (FOS). Data were collected using the largest (i.e., A-1) aperture aboard the FOS in order to maximize sensitivity to faint emissions; this aperture has an effective size of 3.66 x 1.29 arcsec. Each of the three FOS observations of Wirtanen was allocated 1 orbit of spacecraft time. The spacecraft sequence for the observations was to maneuver to the comet, conduct an acquisition of Wirtanen in the F0S aperture, and then obtain the data spectrum. To accomplish the acquisition and centering of the comet's center of brightness in the aperture, HST acquired Wirtanen using a blind maneuver to its calculated apparent position as seen from the spacecraft, obtained a fine acquisition image using the flat mirror, and then conducted an F0S peak up using A- 1/BIN mode. This complete, the flat mirror was replaced in the FOS optical train by grating G270H, and an exposure of approximately 1300 s across the spectral region 2222-—3277 A was then obtained. These data were accesed via the HST archive system (http://archive.stsci.edu/cgi-bin/stdads_retrieval_options) Parameters ========== [BAUM1994] Page 197-290 allows interpretation of FITS header parameters, describes the instrument, the Routine Science Data Processing (RSDP), and calibration problems. The 0.86 arc sec circular aperture {B-3} was used. The red Digicon {amber} (detector F12) was combined with one grating: the 2200-3200 angstrom interval was obtained with the FOS G270H grating Effective spectral resolution is 3.3 angstroms full width at half maximum of 4.6 angstroms for the FOS G270H grating, assuming the aperture was filled with an extended source of uniform brightness. Data ==== [excerpts for the FOS manual] We are most interested in the contents of the .c1*, .c0*, and .c2* files as these contain the flux-calibrated data, wavelengths and errors for an exposure. The easiest way to get a quick glance at your spectra is by using the routine splot or fwplot if you want to plot wavelength vs. flux (see FOS and GHRS Spectra on page 3-17). We recommend that you generate the FOS paper products for your data with the STSDAS routine pp_dads and obtain a variety of displays and tables which, as we shall see in FOS Paper Products on page 30-15, can facilitate the assessment of your data quality. ___________________________________________________________________________ Suffix File Contents Suffix File Contents Raw Data Files Calibrated Data Files (input for calfos) (output from calfos) .d0h/.d0d Science data image .c0h/.c0d Calibrated wavelengths .q0h/.q0d Science data quality .c1h/.c1d Calibrated fluxes .shh/.shd Standard header packet .c2h/.c2d Propagated statistical Additional Files .jih/.jit Jitter files (.cmh, .cmj, .trl Trailer file .cmi) .pdq/.ocx PODPS/OPUS data quality files _________________________________________________________________________ Calibrated Data Files Several types of calibrated output files are produced by calfos. These are listed in Table 30.1. More extensive descriptions of each type of file are provided below. Calibrated Wavelength Files (.c0h/.c0d) These files contain single-precision floating point calibrated vacuum wavelengths corresponding to the center of each pixel of the science data. All FOS wavelength solutions assume the first pixel is pixel 0. Calibrated Flux Files (.c1h/.c1d) These files contain single-precision floating point calibrated fluxes (in ergs sec-1 cm-2 Å-1) corresponding to each pixel of the science data. Calibrated Statistical Error Files (.c2h/.c2d) These files contain the statistical errors of the original data. These files are calibrated in lock-step with the science data files. Errors caused by sky and background subtraction, flatfields, and sensitivity are not included in the error estimates. Headers, Keywords, and Group Parameters Header files provide much of the information needed to reduce FOS data. A description of each keyword is generally provided in the header itself. Some important header parameters, such as exposure timing information, background correction, or scattered light correction, have different values for each group of data within the file. Such parameters are termed group parameters. Table 30.4 is a description of the different topics covered in the various header files. The header files used most often are the standard header packet (.shh), the science data header file (.d0h), and the calibrated science data header file (.c1h). Most of the information needed to understand the data is found among the header keyword types that describe general information (Table 30.4a) and among the processing and calibration information (Table 30.4c) sections of the headers. Table 30.5 lists many important header keywords used to interpret FOS data. IRAF tasks such as imhead or hselect can be used to list the various header keywords. Values of group parameters, on the other hand, can be obtained only with imhead. Table 30.6 provides a listing of all FOS group parameters, with typical values and explanatory comments for each. ___________________________________________________________________________ Keyword Type Information in Keywords Source =========================================================================== a) General Information =========================================================================== General Data General structure of information for All headers data file in standard FITS style Group Parameters: Acquisition data description, All headers OSS including time of acquisition (modified Julian date), maximum and minimum data values, and axes information Group Parameters: Observation type and ground-based GIM Calibrated PODPS correction values from GIMP_CORR header files Generic Existence of science trailer line and .d0h Conversion reject array Keywords: FOS Descriptor Description of FOS file and GIM All headers Keywords: correction COSTAR Keywords: Positions of the COSTAR FOS M1 mirror .shh Coordinate System ========== ====== Observational constraints led to blind pointing of the telescope. In addition the HST pipeline headers are not optimized for planetary data. The FITS headers contain Right Ascension and Declination pointing " CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= See manuals for information concerning wavelength calibration and scattered light. Limitations =========== " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "46P/WIRTANEN" TARGET_TYPE = COMET END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "HST" INSTRUMENT_ID = "FOS" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BAUM1994" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END