We determine and tabulate A [λ] /A K , the wavelength dependence of interstellar extinction, in the Galactic plane for 1.25µm ≤ λ ≤ 8.0µm along two lines of sight: l = 42 • and l = 284 • . The first is a relatively quiescent and unremarkable region; the second contains the giant H II region RCW 49 as well as a "field" region unrelated to the cluster and nebulosity. Areas near these Galactic longitudes were imaged at J, H, and K bands by 2MASS and at 3-8µm by Spitzer for the GLIMPSE Legacy program. We measure the mean values of the color excess ratios (A [λ] − A K )/(A J − A K ) directly from the color distributions of observed stars. The extinction ratio between two of the filters, e.g. A J /A K , is required to calculate A [λ] /A K from those measured ratios. We use the apparent JHK magnitudes of giant stars along our two sightlines, and fit the reddening as a function of magnitude (distance) to determine A J /kpc, A K /kpc, and A J /A K . Our values of A [λ] /A K show a flattening across the 3-8µm wavelength range, roughly consistent with the Lutz et al. (1996) extinction measurements derived for the sightline toward the Galactic center.

GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire), a SIRTF Legacy Science Program, will be a fully sampled, confusion-limited infrared survey of the inner twothirds of the Galactic disk with a pixel resolution of ∼ 1.2 ′′ using the Infrared Array Camera (IRAC ) at 3.6, 4.5, 5.8, and 8.0 µm. The survey will cover Galactic latitudes |b| ≤ 1 • and longitudes |l| = 10 • to 65 • (both sides of the Galactic center). The survey area contains the outer ends of the Galactic bar, the Galactic molecular ring, and the inner spiral arms. The GLIMPSE team will process these data to produce a point source catalog, a point source data archive, and a set of mosaicked images. We summarize our observing strategy, give details of our data products, and summarize some of the principal science questions that will be addressed using GLIMPSE data. Up-to-date documentation, survey progress, and information on complementary datasets are available on the GLIMPSE web site: www.astro.wisc.edu/glimpse.

A visual examination of the images from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) has revealed 322 partial and closed rings that we propose represent partially or fully enclosed three-dimensional bubbles. We argue that the bubbles are primarily formed by hot young stars in massive star formation regions. We have found an average of about 1.5 bubbles per square degree. About 25% of the bubbles coincide with known radio H ii regions, and about 13% enclose known star clusters. It appears that B4-B9 stars (too cool to produce detectable radio H ii regions) probably produce about three-quarters of the bubbles in our sample, and the remainder are produced by young O-B3 stars that produce detectable radio H ii regions. Some of the bubbles may be the outer edges of H ii regions where PAH spectral features are excited and may not be dynamically formed by stellar winds. Only three of the bubbles are identified as known SNRs. No bubbles coincide with known planetary nebulae or W-R stars in the GLIMPSE survey area. The bubbles are small. The distribution of angular diameters peaks between 1 0 and 3 0 with over 98% having angular diameters less than 10 0 and 88% less than 4 0. Almost 90% have shell thicknesses between 0.2 and 0.4 of their outer radii. Bubble shell thickness increases approximately linearly with shell radius. The eccentricities are rather large, peaking between 0.6 and 0.7; about 65% have eccentricities between 0.55 and 0.85.

The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey is a new survey of Galactic 13 CO J ¼ 1 ! 0 emission. The survey used the SEQUOIA multipixel array on the Five College Radio Astronomy Observatory 14 m telescope to cover a longitude range of l ¼ 18 55N7 and a latitude range of jbj < 1 , a total of 75.4 deg 2 . Using both position-switching and On-The-Fly mapping modes, we achieved an angular sampling of 22 00 , better than half of the telescope's 46 00 angular resolution. The survey's velocity coverage is À5 to 135 km s À1 for Galactic longitudes l 40 and À5 to 85 km s À1 for Galactic longitudes l > 40 . At the velocity resolution of 0.21 km s À1 , the typical rms sensitivity is (T Ã A ) $ 0:13 K. The survey comprises a total of 1,993,522 spectra. We show integrated intensity images (zeroth moment maps), channel maps, position-velocity diagrams, and an average spectrum of the completed survey data set. We also discuss the telescope and instrumental parameters, the observing modes, the data reduction processes, and the emission and noise characteristics of the data set. The Galactic Ring Survey data are available to the community online or in DVD form by request.

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