Data Set Overview : The Midcourse Space Experiment (MSX) sampled the mid-infrared thermal emission from the zodiacal dust cloud in spectral bands centered at 8.3, 12, 15, and 21 microns, with a variety of experiments during a 9 month period in 1996. The experiments and their results are described in  Price, S.D., P.V. Noah, D. Mizuno, R.G. Walker, and S. Jayaraman 2003. Midcourse Space Experiment Mid-infrared measurements of the thermal emission from the zodiacal dust cloud. Astron. J. 125, 962-983. [PRICEETAL2003]  These observations were obtained with the MSX Spatial Infrared Imaging Telescope (SPIRIT III). Data from four different experiments are included in this data set, as described below (descriptions excerpted from [PRICEETAL2003]). Stars were removed and the detectors combined as described in Price et al. 2003. The file naming convention is as follows: The four character abbreviation for the experiment (in parentheses after each experiment below) is followed by the two digit observation number within the experiment. Following this is the letter indicating the band, A, C, D, or E. The B band observations are omitted due to non-detection. Finally a digit following the band letter is used to distinguish multiple observations in the same band.  Celestial Background Experiment 1 (CB01)  CB01 obtained five ecliptic pole-to-pole scans that came within 25-30 degrees of the sun. The scans started a few degrees behind the north ecliptic pole and scanned in ecliptic latitude at constant ecliptic longitude (epoch 1996.5) terminating at the south ecliptic pole. The CB01 scans near the sun were sandwiched between the highest priority experiments conducted after the initial commissioning phase of the mission, and mid-summer of 1996, when the spacecraft was no longer in eclipse for part of the orbit. The earth was used as an occulting disk to block the sun for these observations,  Celestial Background Experiment 4 (CB04)  CB04 simultaneously measured the zodiacal background as it covered the two gaps in sky coverage left by the IRAS survey with a set of 61 scans. Collectively, the CB04 scans sampled sun-centered longitudes between 98 and 295 degrees. The scans started a few degrees behind the north ecliptic pole, but scanned at constant 1983.5 epoch longitude and ended at 70 degrees south ecliptic latitude. Thus, the focal plane swept a swath 1 degree in longitude (at the ecliptic plane) at a nominal scan rate of 0.125 degrees/sec. The last 31 scans of CB04 were executed at half this scan rate to partially compensate for the higher noise caused by increasing focal plane temperature toward the end of the mission.  Lunar Off-Axis Response Experiment (DC32)  The DC32 experiment plan was to obtain a series of seven scans at the same Sun-centered longitude, nominally within 15 degrees of the Moon, over two and a half days; the middle scan crossed the Moon, while the other scans were on either side of it. The first and last scans in the series were programmed to be far enough away from the Moon that they can be used to define the zodiacal background for the experiment. Six such experiments were executed, four against the full Moon and two against the three-quarter Moon at solar elongations of ~180 and ~90 degrees respectively. The last experiment against the full Moon was taken late in the mission and was not included in the database because of excessive noise. Each observation consisted of a down (decreasing latitude) and up scan at an approximately constant Sun-centered longitude at a scan rate of 0.06 degrees/sec. Unlike the CB01 and CB04 experiments, these scans were executed with the columns parallel to the scan direction. Thus, a very narrow swath was swept out in longitude but with a very large number of samples within a given latitude interval.  Zodiacal observation in the Mirror Scan Mode (EM10)  This experiment scanned 170 degrees along the ecliptic plane, from a sun-centered longitude of ~160 degrees to ~330 degrees, at a rate of 0.3 degrees/sec. The sensor was repositioned to ecliptic latitude of -50 degrees and a latitude profile obtained at a sun-centered longitude of ~329 degrees. These data were taken in mirror scan mode, with the mirror scan direction perpendicular to the spacecraft motion, that is, in latitude for the scan along the plane and in longitude for the latitude scan. The amplitude of the mirror scan was 1.5 degrees. The geometry was such that contiguous coverage was obtained along the center line of the scan.

Confidence Level Overview : A number of factors influence the absolute accuracy of the measured zodiacal radiance: the absolute radiance calibration of the sensor, the uncertainty in the dark offset measurement, the biases introduced by the dark offset model, the temperature of the focal plane array, and factors external to the telescope such as the non-rejected Earth radiation (NRER). These factors are examined in detail as they apply to the present data set, in the appendix of Price et al. (2003) q.v.  The dark offset analysis of the EM10 experiment observations were based on a comparison between observations of the same ecliptic longitudes from different experiments (CB01 and CB04) coupled with a model of the zodiacal background to decouple the effects of differing observing epochs between the different experiments (section 4.1 of Price, Noah, Mizuno, Walker, and Jayaraman, AJ 125, 962-983, 2003). The dark offset calibration for the CB01 and CB04 experiments also used observations from overlapping observations, but from within each experiment, with no modifications due to the change in the relative position of the spacecraft during the epoch of the experiment. As the solar elongation changes when observing a single point near the plane of the ecliptic, the column density and temperature of interplanetary dust changes and can result in a variation in brightness background of order 1% on timescales of 12 hours (c.f., Hauser et al., Ap J Letters, 278, L15-L18, 1984).This result suggests that the dark offset matrices derived assuming a constant zodiacal background in the overlapping regions within a given CB experiment may be in error. Although the effect on the data from not taking into account this small change in the zodiacal background is probably small, this notice is included to make the user aware of the assumptions used in the dark offset data analysis procedures.