PDS_VERSION_ID = PDS3
/* FILE CHARACTERISTICS DATA ELEMENTS */
RECORD_TYPE = FIXED_LENGTH
RECORD_BYTES = 2880 /* FITS standard record length */
FILE_RECORDS = 3
FILE_NAME = "RA_WAVE_003.LBL"
DATA_FORMAT = FITS
/* INSTRUMENT AND MISSION DESCRIPTIVE DATA ELEMENTS */
INSTRUMENT_ID = "ALICE"
INSTRUMENT_NAME = "ALICE"
INSTRUMENT_TYPE = "ULTRAVIOLET SPECTROMETER"
INSTRUMENT_HOST_ID = "RO"
INSTRUMENT_HOST_NAME = "ROSETTA-ORBITER"
MISSION_ID = "ROSETTA"
MISSION_NAME = "INTERNATIONAL ROSETTA MISSION"
/* DATA OBJECT POINTERS IDENTIFICATION DATA ELEMENTS */
^HEADER = ("RA_WAVE_003.FIT",1)
^WAVELENGTH_OFFSET_IMAGE = ("RA_WAVE_003.FIT",3)
/* PRODUCT, DATA SET, AND VOLUME DATA ELEMENTS */
PRODUCT_ID = "RA_WAVE_003"
PRODUCT_CREATION_TIME = 2007-04-04
DATA_SET_ID = "RO-C/CAL/X-ALICE-2-CVP1-V1.0"
PRODUCER_ID = "ROSETTA_ALICE"
PRODUCER_FULL_NAME = "ANDREW J. STEFFL"
PRODUCER_INSTITUTION_NAME = "SOUTHWEST RESEARCH INSTITUTE"
/* DATA OBJECT DEFINITIONS */
OBJECT = HEADER
BYTES = 5760 /* RECORD_BYTES x RECORDS */
HEADER_TYPE = FITS
INTERCHANGE_FORMAT = BINARY
RECORDS = 2
DESCRIPTION = "
FITS header for Rosetta-Alice Wavelength calibration file. This
header contains keywords that describe the variation of the
wavelength scale with the detector electronics temperature."
END_OBJECT = HEADER
OBJECT = WAVELENGTH_OFFSET_IMAGE
LINE_SAMPLES = 32 /* FITS NAXIS1 keyword */
LINES = 1 /* FITS NAXIS2 keyword */
SAMPLE_BITS = 32
SAMPLE_TYPE = IEEE_REAL
AXIS_ORDER_TYPE = "FIRST_INDEX_FASTEST"
LINE_DISPLAY_DIRECTION = "UP"
SAMPLE_DISPLAY_DIRECTION = "RIGHT"
DESCRIPTION = "
FITS (Flexible Image Transport System) format is defined in 'Astronomy
and Astrophysics', volume 376, page 359; bibcode 2001A&A...376..359H
This FITS file contains constants used by the IDL routine
'ralice_wavecal.pro' to determine the wavelength solution for the
Rosetta Alice UV spectrometer. Since Alice uses a delay-line
detector, the pixel location of a photon event assigned by the
electronics will vary as a function of temperature (due to the
changing resistance).
To monitor this shift, the electronics produce artificial events
(stim pulses) at two locations (near [17, 22] and [1023,12]).
Unfortunately, the second stim pulse is recorded by the detector
electronics as lying outside of the standard 1024x32 region, and
as a result, most of the counts produced by this stim are assigned
to a single pixel [1023,12]. Consequently, only the first stim pulse
can be used to determine the wavelength shift.
The average location of the stim pulse (weighted by counts) was
calculated. Gaussians were then fit to the emission lines: Lyman gamma,
Lyman beta, Lyman alpha, O I 1304, C I 1561,and C I 1657 present in
the spectra of comet C/2002 LINEAR T7 observed in April and May
2004 and the Lyman alpha in sky observations obtained in 2004 and 2005.
The wavelength scale for row 15 of the Alice data is given, by the
following equation:
lambda = m_s*X + alpha_S + beta_s*S + gamma_s*S**2 + delta_s*S**3
where X is the column number on the detector and S is the centroid
position of the stim pulse. m_s is the instrument dispersion and is
derived from comparison of the Mars dayglow observed by Rosetta Alice
with that observed by HUT (Feldman et al. 1995)
Although the stim pulses are usually on for Alice observations,
there are some observations made without stim pulses. For these, the
stim position S is derived from the detector electronics temperature
via the following equation:
S = alpha_T + beta_T*T + gamma_T*T**2 + delta_T*T**3
In addition to the temperature dependence of the wavelength scale,
some distortion is introduced by the Alice optics. This distortion
is most pronounced in rows 5-12 of the detector, where lower
wavelengths are shifted to lower column numbers, relative to the
central row (row 15, zero-indexed). The 32-element vector contains
offsets (relative to row 15 and in units of pixels) for each row of
the Alice detector, as derived from Mars dayglow observations."
END_OBJECT = WAVELENGTH_OFFSET_IMAGE
END