We present images of the Galactic center in the dust continuum at 31.5 and 37.7 km obtained with the Kuiper WideÐeld Infrared Camera on the Kuiper Airborne Observatory. The raw images have a spatial resolution of and cover a region roughly 10@ (R.A.) by 24@ (decl.) in extent. Here we discuss the D8A .5 innermost (6.9 ] 9.1 pc) regions roughly centered on Sagittarius A*, where the high signal-to-2@ .8 ] 3@ .6 noise ratio permits image restoration to spatial resolution at 31.5 and 37.7 km, respectively. D3A .6È5A .7 These images clearly delineate the warm dust in the "" minispiral ÏÏ but also show an elliptical structure centered on Sgr A* and intersecting the minispiral at the western arc that we identify as the photodissociated inner rim of the circumnuclear disk (CND) or ring. This is the Ðrst image of the complete disk and the Ðrst image of both the minispiral and CND in a single tracer, thereby permitting detailed studies of the intimate association between these two structures. The 31.5/37.7 km color temperature map indicates that most of the far-UV Ñux required to heat the dust grains must come from centrally located sources. The cluster of He I emission-line stars recently identiÐed near Sgr A* is sufficient to provide half the heating for the far-IR ring and minispiral structures, the balance likely being provided by O and B stars associated with the cluster. We also Ðnd D16 color temperature peaks distributed within the CND that we suggest are the locations of early type (B4 to O9) main-sequence stars. To match the observed far-IR Ñuxes from the ring, we require an unusually high 30È40 km dust grain emissivity and/or an usually high UV albedo.The far-IR morphology is reproduced by a simple model : an inclined (i D 65¡), slightly elliptical (e D 0.06) torus with one focus at Sgr A* and two streamers on parabolic orbits with foci at Sgr A*. The torus has an inner radius of 1.58 pc, is D0.4 pc thick, and consists of clumpy cloudlets with characteristic sizes less than 0.15 pc. The northern streamer is identiÐed with the northern arm, and the east-west (EW) streamer is identiÐed with the bar and eastern arm structures seen in both their [Ne II] Ðne-structure line emission and the radio continuum. The northern arm is traced in the far-IR continuum from regions D1.4 pc outside of the far-IR ring to its apparent intersection with the EW streamer. The eastern CND is not detected in the radio continuum because of extinction by the intervening northern arm, which therefore must be nearly in the plane of the CND. Extensions of the EW streamer outside of the CND are apparent to the east and especially to the northwest. The EW streamer lies D85¡ out of the plane of the CND and is on a parobolic orbit focused on Sgr A* at a distance of 0.33 pc, with its apex well in front of or behind Sgr A*.
We present first light spectra that were measured by the newly‐developed Far‐Infrared Spectroscopy of the Troposphere (FIRST) instrument during a high‐altitude balloon flight from Ft. Sumner, NM on 7 June 2005. FIRST is a Fourier Transform Spectrometer designed to measure accurately the far‐infrared (15 to 100 μm; 650 to 100 wavenumbers, cm−1) emission spectrum of the Earth and its atmosphere. The flight data successfully demonstrated the FIRST instrument's ability to observe the entire energetically significant infrared emission spectrum (50 to 2000 cm−1) at high spectral and spatial resolution on a single focal plane in an instrument with one broad spectral bandpass beamsplitter. Comparisons with radiative transfer calculations demonstrate that FIRST accurately observes the very fine spectral structure in the far‐infrared. Comparisons also show excellent agreement between the atmospheric window radiance measured by FIRST and by instruments on the NASA Aqua satellite that overflew the FIRST flight. FIRST opens a new window on the spectrum that can be used for studying atmospheric radiation and climate, cirrus clouds, and water vapor in the upper troposphere.
The far-infrared spectroscopy of the troposphere (FIRST) instrument is a Fourier transform spectrometer developed to measure the Earth's thermal emission spectrum with a particular emphasis on far-infrared (far-IR) wavelengths greater than 15 μm. FIRST was developed under NASA's Instrument Incubator Program to demonstrate technology for providing measurements from 10 to 100 μm (1000 to 100 cm(-1)) on a single focal plane with a spectral resolution finer than 1 cm(-1). Presently no spectrometers in orbit are capable of directly observing the Earth's far-IR spectrum. This fact, coupled with the fundamental importance of the far-IR to Earth's climate system, provided the impetus for the development of FIRST. In this paper the FIRST instrument is described and results of a detailed absolute laboratory calibration are presented. Specific channels in FIRST are shown to be accurate in the far-IR to better than 0.3 K at 270 K scene temperature, 0.5 K at 247 K, and 1 K at 225 K.
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