We present 70 and 160 m observations from the Spitzer extragalactic First Look Survey (xFLS). The data reduction techniques and the methods for producing co-added mosaics and source catalogs are discussed. Currently, 26% of the 70 m sample and 49% of the 160 m-selected sources have redshifts. The majority of sources with redshifts are star-forming galaxies at z < 0:5, while about 5% have infrared colors consistent with active galactic nuclei. The observed infrared colors agree with the spectral energy distributions (SEDs) of local galaxies previously determined from IRAS and Infrared Space Observatory data. The average 160 m/70 m color temperature for the dust is T d ' 30 AE 5 K, and the average 70 m/24 m spectral index is ' 2:4 AE 0:4. The observed infrared-to-radio correlation varies with redshift as expected out to z $ 1 based on the SEDs of local galaxies. The xFLS number counts at 70 and 160 m are consistent within uncertainties with the models of galaxy evolution, but there are indications that the current models may require slight modifications. Deeper 70 m observations are needed to constrain the models, and redshifts for the faint sources are required to measure the evolution of the infrared luminosity function.

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By leveraging the existing Model‐Based Systems Engineering (MBSE) infrastructure at JPL and adding a modest investment, the Europa Mission Concept Study made striking advances in mission concept capture and analysis. This effort has reaffirmed the importance of architecting and successfully harnessed the synergistic relationship of system modeling to mission architecting. It clearly demonstrated that MBSE can provide greater agility than traditional systems engineering methods. This paper will describe the successful application of MBSE in the dynamic environment of early mission formulation, the significant results produced and lessons learned in the process.

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We present an algorithm for achieving background consistency in overlapping images. The algorithm consists of two main steps. First, the images are interpolated to a common grid. Second, the cumulative pixel-by-pixel difference between the overlapping areas of all pairs of images is minimized with respect to the unknown constant offsets of the input images. The images are corrected by adding the computed offsets. Optionally, detection and masking of bright objects in the images can be performed prior to minimization. This option is especially useful for images with a high density of cosmic-ray hits. We use simulated data to optimize the algorithm in order to achieve a trade-off between the speed of execution and the quality of the background matching. We also show several examples of the application of this algorithm to real Spitzer data. The algorithm has been implemented and successfully used by the Spitzer image processing package MOPEX (Makovoz & Khan) and deployed by the Spitzer automated pipeline.