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The principal objective of the astronomy experiments onboard the MSX satellite was to complete the census of the mid-infrared (4.2-25 micron or um) sky: namely, the areas missed by the IRAS mission (about 4% of the sky was not surveyed by IRAS), and the Galactic Plane (where the sensitivity of IRAS was degraded by confusion noise in regions of high source densities or of structured extended emission). The photometry is based on co-added image plates, as opposed to single-scan data, which results in improved sensitivity and hence reliability in the fluxes. Comparison with Tycho-2 positions indicates that the astrometric accuracy of the new catalog is more than 1" better than that in Version 1.2.
The infrared instrument on MSX was named SPIRIT III; it was a 35-cm clear aperture off-axis telescope with five line scanned infrared focal-plane arrays of 18.3 arcseconds square pixels, with a high sensitivity (0.1 Jy at 8.3 um). The filter characteristics of the 6 spectral bands B1, B2, A, C, D and E are summarized below, where all wavelengths are in micron (µm):
Band Center FWHM Points ---------------------------- B1 4.29 um 4.22 - 4.36 um B2 4.35 4.24 - 4.45 A 8.28 6.8 - 10.8 C 12.13 11.1 - 13.2 D 14.65 13.5 - 15.9 E 21.34 18.2 - 25.1
The MSX catalog names of the sources have been defined according to International Astronomical Union (IAU) conventions with a unique identifier combined with the position of the source. In this case, the MSX PSC V2.3 sources are named using the convention MSX6C GLLL.llll+/-BB.bbbb, where MSX6C denotes that this is MSX data run using Version 6.0 of the CONVERT software, and GLLL.llll+/-BB.bbbb gives the Galactic coordinates of the source.
The UV instrument on MSX was named UVISI (Mill et al., 1994, Journal of Spacecraft and Rockets, 31, 900 (1994JSpRo..31..900M in ADS); Carbary et al., 1994, Applied Optics, 33, 4201 (1994ApOpt..33.4201C in ADS)). The fields-of-view for the narrow-field and wide-field UV imagers were 1.46 x 1.19 degrees (detector pixels of 20.6" x 17.5") and 13.4 x 9.2 degrees (detector pixels of 3.12' x 2.27'), respectively. Four filters were used with the narrow-field imager (IUN) with effective wavelengths centered at 2480 Angstrom (IUN3), 2310 Angstrom (IUN4), 2230 Angstrom (IUN5), and 2930 Angstrom (IUN6). Two filters were used with the wide-field imager (IUW) and centered at 1320 Angstrom (IUW3) and 1560 Angstrom (IUW6).
The HEASARC has removed from this table the parameter describing the objects' magnitude in the IUN5 filter as all of the sources had null values for this parameter. The CDS had previously made the following modifications compared to the version of the catalog as published in the reference paper:
(1) The angular distances to the SIMBAD object (column "AngDist" of file catal.dat, called 'Offset' in this HEASARC table) was recomputed at CDS, the original values looking suspect. (2) In the course of this modification, 17 SIMBAD IDs were removed due to a large offset, most likely due to a sign error in the interpretation of SIMBAD's declination for IDs: 003341+001712 063054+004539 063211+005630 063754+003151 133358+001928 142557+003939 144541+002439 155701+004808 162743+004620 185855+003355 191033+004132 193004+005316 194525+001239 195040+004101 195717+001959 202844+005149 234324+000729