Mehrdad Moshir

Spitzer 70 and 160 μm Observations of the Extragalactic First Look Survey

We present 70 and 160 μm 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 μm sample and 49% of the 160 μm–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 μm/70 μm color temperature for the dust is T_d ≃ 30 ± 5 K, and the average 70 μm/24 μm spectral index is α ≃ 2.4 ± 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 μm are consistent within uncertainties with the models of galaxy evolution, but there are indications that the current models may require slight modifications. Deeper 70 μm observations are needed to constrain the models, and redshifts for the faint sources are required to measure the evolution of the infrared luminosity function.

Model Based Systems Engineering on the Europa mission concept study

At the start of 2011, the proposed Jupiter Europa Orbiter (JEO) mission was staffing up in expectation of becoming an official project later in the year for a launch in 2020. A unique aspect of the pre-project work was a strong emphasis and investment on the foundations of Model-Based Systems Engineering (MBSE). As so often happens in this business, plans changed: NASAs budget and science priorities were released and together fundamentally changed the course of JEO. As a result, it returned to being a study task whose objective is to propose more affordable ways to accomplish the science. As part of this transition, the question arose as to whether it could continue to afford the investment in MBSE. In short, the MBSE infusion has survived and is providing clear value to the study effort. In the process, the need to remain relevant in the new environment has brought about a wave of innovation and progress. By leveraging the existing infrastructure and a modest additional investment, striking advances in the capture and analysis of designs using MBSE were achieved. The effort has reaffirmed the importance of architecting. It has successfully harnessed the synergistic relationship of architecting to system modeling. We have found that MBSE can provide greater agility than traditional methods. We have also found that a diverse ‘ecosystem’ of modeling tools and languages (SysML, Mathematica, even Excel) is not only viable, but an important enabler of agility and adaptability. 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.

A Robust Algorithm for the Pointing Refinement and Registration of Astronomical Images

We present a generic algorithm for performing astronomical image registration and pointing refinement. The method is based on the matching of positions and fluxes of available point sources in image overlap regions. This information is used to compute a set of image offset corrections by globally minimizing a weighted sum of all matched point-source positional differences in a prespecified reference image frame. A fast linear sparse matrix solver is used for the minimization. From these corrections, the pointings and orientations of images can be refined in either a relative sense in which pointings become fixed (registered) relative to a single input image, or in an absolute sense (in the International Celestial Reference System (ICRS)) if absolute point-source information is known. The latter provides absolute pointing refinement to an accuracy that depends on the robustness of point-source extractions, match statistics, and accuracy of the astrometric catalog used. The software is currently used in the Spitzer image-processing pipelines, although it is adaptable to any astronomical imaging system that uses the FITS image format and world coordinate system (WCS) pointing standard. We test the algorithm using Monte Carlo simulations and compare them to image data acquired with the Infrared Array Camera (IRAC) onboard the Spitzer Space Telescope. We find that dispersions in matched source separations after refinement are entirely consistent with centroiding errors in source extractions, implying that systematic uncertainties due to inaccurately calibrated distortions are negligible. For these data, we predict refinements to better than ∼70 and ∼280 mas (2 j radial) for the IRAC 3.6 and 8 mm bands, respectively. These bands bracket two extremes in available source matches, and for the data under study, correspond to an average of about 55 and 8 matches per image in these two bands, respectively.

Background Consistency in Overlapping Images

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.

First Results from the ISO-IRAS Faint Galaxy Survey*

We present the first results from the ISO-IRAS Faint Galaxy Survey (IIFGS), a program designed to obtain ISO observations of the most distant and luminous galaxies in the IRAS Faint Source Survey by filling short gaps in the ISO observing schedule with pairs of 12 μm ISOCAM and 90 μm ISOPHOT observations. As of 1997 October, over 500 sources have been observed, with an ISOCAM detection rate over 80%, covering over 1.25 deg^2 of sky to an 11.5 μm point-source completeness limit of approximately 1.0 mJy (corresponding to a ~10 σ detection sensitivity). Observations are presented for nine sources detected by ISOPHOT and ISOCAM early in the survey for which we have ground-based G- and I-band images and optical spectroscopy. The ground-based data confirm that the IIFGS strategy efficiently detects moderate-redshift (z = 0.11-0.38 for this small sample) strong emission line galaxies with L_(60 μm) ≳ 10^(11) L_☉; one of our sample has L_(60 μm) > 10^(12) L_☉ (H_0 = 75 km s^(-1) Mpc^(-1), Ω = 1). The infrared-optical spectral energy distributions are comparable to those of nearby luminous infrared galaxies, which span the range from pure starburst (e.g., Arp 220) to infrared QSO (Mrk 231). Two of the systems show signs of strong interaction, and four show active galactic nucleus (AGN)-like excitation; one of the AGNs, F15390+6038, which shows a high excitation Seyfert 2 spectrum, has an unusually warm far- to mid-infrared color and may be an obscured QSO. The IIFGS sample is one of the largest and deepest samples of infrared-luminous galaxies available, promising to be a rich sample for studying infrared-luminous galaxies up to z ~ 1 and for understanding the evolution of infrared galaxies and the star formation rate in the universe.

Midcourse Space Experiment Surveys

The Midcourse Space Experiment (MSX) conducted several infrared surveys during its 10 month mission which began in April 1996. We report on the progress in the analysis of these survey observations with an initial estimate of the instrument performance parameters. Initial results indicate that the surveys are at least as sensitive as the Infrared Astronomy Satellite (IRAS) survey, and have higher spatial resolution.

Quantifying Spacecraft Failure in an Uncertain Environment: the Case of Jupiter Europa Orbiter

Study of the Outer Planets is considered as a high priority activity by the Planetary Science community. One candidate for the next Outer Planets Flagship Mission (OPFM –missions in the

The Midcourse Space Experiment Point Source Catalog, Version 1.2

2B–

The SIP Convention for Representing Distortion in FITS Image Headers

4B range) is the Jupiter Europa Orbiter (JEO) concept. In this work, we address the interplay of various types of uncertainties to probe the possibility of characterizing the reliability of a proposed mission concept. By combining the aleatory characterization of spacecraft subsystems and the epistemic uncertainties of the Jovian environment we describe an approach for quantifying possible ranges of mission durations for a potential JEO concept. The work here illustrates the potential for probabilistic representations of epistemic uncertainties by introducing temporal correlations. In addition the effects of failure correlations among similar components in a spacecraft are incorporated to assess their impact on the failure likelihood.