Vol. 5, No. 7 - July 1997
- Ron Oliversen
Our colleagues at VILSPA have screened all of the raw images taken since October 1994 in order to identify images affected by the DMU anomaly. Among the NASA images, 96 LWP and 423 SWP images were affected. We are currently implementing the NEWSIPS software to flag these images, and will begin processing them in the next week or so. (Note that some images have already been processed and archived but do not include the flagging - they will be reprocessed.)
In the NEWSIPS software, we have defined a new quality flag to indicate a
pixel that may be affected by DMU corruption. In an image identified as
corrupted by the screening process, each pixel with a value of 159 DN is
flagged as "possibly corrupted". (Since the corruption can be
identified
only on a statistical basis, it isn't possible to say which of the pixels
with 159 DN are valid and which have corrupted values.) The nu flag is set
to -8 for any pixel with 159 DN. The nu flags are then carried along in
the processing just as the other nu flags are handled. These images are
identified in the COMMENTS and in the processing history. In
the following
example, 14 pixels were found to have values of 159 DN, of which 12 pixels
are expected to be corrupted values. Please note that these pixels may or
may not affect spectral data; some corrupted pixels may fall outside the
region containing useful scientific data.
COMMENT BY RA: EXP 1 APER L C=202,B=36 COMMENT BY RA: 0 MISSING MINOR FRAMES NOTED ON SCRIPT COMMENT BY RA: 0 BAD SCAN STARTS NOTED ON SCRIPT COMMENT BY RA: EXP 1 TRACKED ON GYROS COMMENT BY RA: S PREP USED COMMENT BY RA: OFFSET 1 FROM: SAO 119431 COMMENT BY RA: OFFSET 1 COORDINATES: 12 27 37.1 +02 30 27 COMMENT BY RA: OFFSET 1 MAGNITUDE: 9.300 COMMENT BY RA: FESCOUNT 1 = 120 FES-MODE 1 = FO COMMENT BY RA: WARNING: Some LWP low dispersion spectra taken after 12 Nov 1992 COMMENT BY RA: are contaminated by scattered solar spectrum. COMMENT BY RA: WARNING: Image affected by the 159 DN anomaly COMMENT BY RA: 14 pixels with 159 DN, corrupted: 12 + 1 /- 3 HISTORY IUE-LOG STARTED 04-JUL-1997 14:43:10 HISTORY PROCESSING SYSTEM: NEWSIPS VERSION 2.5.4 HISTORY ULTRIX VERSION HISTORY LWP29832 HISTORY PROCESSED AT GODDARD SPACE FLIGHT CENTER HISTORY **************************************************************** HISTORY **************************************************************** HISTORY START RAW_SCREEN 4-JUL-1997 14:46:37 HISTORY 6 BRIGHT SPOTS DETECTED HISTORY 0 MISSING MINOR FRAMES DETECTED HISTORY *** WARNING: THIS IMAGE IDENTIFIED AS AFFECTED BY DMU CORRUPTION HISTORY ALL PIXELS WITH DN = 159 FLAGGED AS POSSIBLY ERRONEOUS HISTORY LARGE APERTURE SPECTRUM WILL BE EXTRACTED AS HISTORY POINT SOURCE HISTORY LARGE APERTURE CONTINUUM DN LEVEL = 180 HISTORY SMALL APERTURE CONTINUUM DN LEVEL = 0 HISTORY BACKGROUND DN LEVEL = 33 HISTORY END RAW_SCREEN 4-JUL-1997 14:47:58 HISTORY ****************************************************************
prolog was implemented which corrects an
error in displaying prolog information on Unix and PC platforms when the
IDL procedure resides in the user's working directory.
prolog was implemented which is
compatible with IDL search paths using VMS logicals.
platform was implemented which points to
the correct mail utility on systems running DEC Unix.
idfile was implemented which fixes a bug
which occurs when the full data path name contains the phrase
.LAB. Also, a new version of idt was implemented
which appends a 0 to image numbers less than 10,000 when
creating file names (e.g., files will be named
swp01234hlg.dat rather than swp1234hlg.dat).
are
coadd.pro, datarec.pro,
gotordaf.pro, iue3drd.pro,
iueatrd.pro, iueim.pro,
iueqictape.pro, lbl.pro,
makemelo.pro, and vicar.pro. They should be
included in the pro folder under the
iuelib folder.
In addition, there are three routines that should not be included in the
pro folder: iueqictap (not
iueqictape.pro) is just an empty file;
idb_item_info.pro is obsolete; and tvroam.pro
only belongs in the VAX distribution. All of these changes will be
incorporated in the next version of the IUEDAC
software library, to be released in the next few months.
SWP09744HLG indicates a (high
dispersion) large aperture exposure, while SWP09744HSM
indicates a small aperture exposure. The aperture is determined from
information extracted from the header record of the original GO-format
file. However, this information wasn't added to the file headers until
October, 1980.
It appears that when the aperture information is not available, the NDADS software calculates RDAF-format file names assuming the large aperture was used. Users should therefore be cautioned that small aperture images processed before 1980 may be given file names indicating large aperture data. The problem is expected to be corrected in the near future.
If it is uncertain which aperture was used, users should first check the
GO comments stored in the first 10 lines of the VICAR label
(e.g., using the IUEDAC program label). The best
source for this information, however, is still the original observing
script.
Note that the above problem does not affect NEWSIPS-processed files.
or send a postcard to:
IUE Data Analysis Center (IUEDAC)
Code 686.9, NASA-GSFC
Greenbelt, MD 20771
* IUE Data Analysis Center * IUE Project*